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1
Whiting, Gareth Thomas. "Metal phosphate and precious metal catalysts for selective oxidation." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/34002/.
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The main objective researched in this thesis involves the selective oxidation of methanol to formaldehyde, using metal phosphate based catalysts. Molybdenum and vanadium phosphate based catalysts have been prepared, thoroughly characterised and tested as active catalysts for the selective oxidation of methanol to formaldehyde. Initial investigations highlighted the relatively low activity of both metal phosphate catalysts, however, significant enhancements in the catalytic activity and formaldehyde selectivity of both materials have been achieved in this research, primarily by supporting molybdenum phosphate catalysts using a range of supports, and also promoting both molybdenum and vanadium pyrophosphates with transition metals. It was discovered that a catalyst of 10 wt% (MoO2)2P2O7 supported on SiO2 containing 1 mol% vanadium (as a promoter) achieved significantly higher formaldehyde per pass yields (>20 %) than MoO3 supported on SiO2 (reported in the literature) and comparable activity to that of the commercial iron molybdate catalyst. Due to the promotional effect of vanadium, and the known activity of V2O5 catalysts for the oxidation of methanol to formaldehyde, molybdenum promoted (VO2)2P2O7 catalysts were tested for this reaction and reported for the first time. Catalytic studies revealed that there is a direct correlation between molybdenum content and catalytic activity, indicating a synergistic effect of the two transition metals. The penultimate chapter of this thesis involves the use of supported mono- and bi-metallic gold(palladium) catalysts and their use in both CO oxidation and selective methanol oxidation. A novel method of maintaining considerably small Au(Pd) nanoparticle size (unlike the standard thermal treatment method) has been discovered by the Hutchings group at Cardiff Catalysis Institute, involving the removal of stabilising IV ligands with a solvent extraction method. Using high resolution microscopy and a range of characterization techniques, the nanoparticle size was attributed to the surprisingly high activity achieved for both CO oxidation and methanol oxidation to methyl formate, at low temperatures which, particularly in the case of methanol oxidation, is a remarkable discovery.
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Young, Mary Jane. "Phosphate diester cleavage mediated by transition metal complexes." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40473.
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Two independent studies have been developed in this thesis. In the first study, the reactivities of metal-alkoxide and metal-hydroxide nucleophiles are compared for cleaving phosphate diesters. In the second study, the reactivity of a dinuclear metal complex is compared to a mononuclear metal complex for hydrolyzing RNA.Copper(II) complexes of bis(2-pyridylmethyl)amine (Cu(II)bpa), N-(2-hydroxyethyl)bis(2-pyridylmethyl)amine (Cu(II)hebpa) and N-(3-hydroxypropyl)bis(2-pyridylmethyl)amine (Cu(II)hpbpa) have been synthesized and their reactivities and mechanisms for cleaving bis(2,4-dinitrophenyl) phosphate (BDNPP) have been investigated. Cu(II)hpbpa is observed to be the most reactive (k = 7.2 $ times$ 10$ sp{-1}$ M$ sp{-1}$ s$ sp{-1}$ at 25$ sp circ$C, pH 8.8) for cleaving BDNPP followed by Cu(II)bpa (k = 2.0 $ times$ 10$ sp{-2}$ M$ sp{-1}$ s$ sp{-1}$) and Cu(II)hebpa (k = 2.0 $ times$ 10$ sp{-2}$ s$ sp{-1}$). HPLC product analyses indicated that Cu(II)hpbpa cleaves BDNPP mostly through transesterification while the complexes Cu(II)bpa and Cu(II)hebpa cleave BDNPP predominantly by hydrolysis. The differences in the mechanisms and the reactivities are explained in terms of the differences in the structures of the three copper(II) complexes.
Copper(II) complexes of 1,8-bis(1,4,7-triazacyclononyl-N-methyl)naphthalene (tntn), 1,4,7-triazacyclononane (tacn), and N-benzyl-1,4,7-triazacyclononane (btacn) have been prepared and their reactivities compared for cleaving RNA. The novel dinuclear copper(II) complex, Cu(II)$ sb2$tntn, is observed to be 200-500 fold faster per metal center than the mononuclear copper(II)complexes, Cu(II)tacn and Cu(II)btacn, for cleaving a diribonucleotide, ApA, and its cyclic phosphate intermediate, $2 sp prime3 sp prime$-cAMP. Cu(II)$ sb2$tntn (2.0 mM) reduces the half life of ApA (0.05 mM) to 50 minutes (pH 6, 50$ sp circ$C); this represents a rate acceleration of approximately 10$ sp5$ fold over the background hydroxide rate. The half life of $2 sp prime3 sp prime$-cAMP (0.05 mM) is decreased to 4 minutes in the presence of Cu(II)$ sb2$tntn (2.0 mM, pH 6, 25$ sp circ$C); this represents a rate acceleration of about 10$ sp8$ fold over the background hydroxide rate.
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Chernobryva, Mariya. "Development of metal-based catalysts for phosphate ester hydrolysis." Thesis, Queen Mary, University of London, 2016. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24631.
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The development of artificial metal-based catalytic systems for phosphate ester hydrolysis is the central focus of this work. Currently, significant efforts are concentrated in this field of research as phosphate esters are remarkably stable linkages and are found in the molecules of life DNA and RNA, as well as in toxic compounds, such as nerve agents, pesticides and herbicides. The thesis describes the design and synthesis of a series of N-functionalised azamacrocyclic ligands suitable for metal chelation. An efficient strategy is described, where an aminal precursor is used for the selective N-alkylation of a cyclen moiety, in order to obtain non-bridged and ethylene-bridged cyclen-based ligands. Thereafter, the synthesis of the tetraamine Co(III) and Zn(II) aqua-hydroxo complexes is detailed, followed by a study of the coordination chemistry of Co(III)-based cyclen complexes. Moreover, the redox behaviour of such complexes is investigated by means of cyclic voltammetry. The hydrolytic activity of these complexes towards phosphate ester substrates is then presented. The hydrolytic activity of the cyclen-based Co(III) complexes is shown to be extremely sensitive to modest changes in the ligand structures, even though they do not affect the coordination geometry. Cyclen-based Zn(II) complexes appear to have no appreciable activity towards hydrolysis of phosphate mono- and di-esters under the same experimental conditions. The effect of incorporating polymerisable tetraamine Co(III) complexes into the nanogels on their hydrolytic efficiency is also investigated using molecular imprinting technique. The design and synthesis of structurally similar tripodal 'click' ligands, suitable for the preparation of a range of d-block metal complexes is then presented. The coordination chemistry of the complexes of these structurally similar ligands is explored using a range of techniques including single crystal X-ray crystallography, EPR and UV-Vis spectroscopies and cyclic voltammetry. Due to their poor aqueous solubility various ways to improve this are also examined. Future developments of the metal-based catalysts are then discussed including key issues to be addressed to achieve their potential applications in biological systems.
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Simmons, Jane. "The structure and function of amorphous calcium phosphate biominerals." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339520.
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Montague, William. "The suitability of magnesium phosphate cement for uranium metal encapsulation." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/44117.
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Nuclear waste streams consist of a diversity of physical and chemical forms, requiring a toolbox approach in the application of materials to their disposal. Solid uranium metal wastes constitute a disposal challenge due to their tendency to oxidise, making encapsulation within cementitious waste packages for storage potentially troublesome. MKPC (Magnesium Potassium Phosphate Cement) is being considered as an alternative to Portland cement for U-metal encapsulation due to the potential for lower free water content, lower internal pH and the micro-encapsulation of radioactive isotopes as low-solubility phosphate minerals. In this work the development and characterisation of MKPCs optimised for U-metal encapsulation was undertaken. This included the investigation of MKPC property development under both near ambient and elevated temperature conditions, the performance of MKPC/U-metal wasteform corrosion trials utilising temperature elevation (to 30, 40 and 50 °C) for the acceleration of chemical kinetics, and assessment of the impact of dehydration treatments (at 50, 80 and 110 °C) on the cement properties. In general MKPC exhibited excellent processing and mechanical properties. Other significant outcomes of the work include, firstly, the determination that uranium corrosion rate dependencies in MKPC are dominated heavily by the presence of water over other chemical effects, with an anoxic activation energy of 68 ± 6 kJ/mol. Secondly, the development of a methodology for determining the bound water content of MKPC, which allowed the calculation of the extent of reaction. This enabled analysis yielding empirical strength-porosity and kinetic models of the material, capable of facilitating improved mix design for the tailoring of MKPC properties. Finally, the instability of the K-struvite matrix toward dehydration at temperatures of ≥ 72 °C has been recorded. The work concluded that MKPC has many properties which make it suitable as a general encapsulant, whilst being ultimately unsuitable for U-metal storage without further development around the reduction of water availability.
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Robson, P. "Structural studies of phosphates and molybdophosphates formed in nitric acid : Vibrational spectroscopic, isotopic-tracer and plutonium/americium absorption studies on zirconium phosphate and ammonium/caesium/rubidium molybdophosphates formed in nitric ac." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379904.
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Williams, Daniel M. "Phosphate ester hydrolysis promoted by lanthanide (III) and transition metal complexes." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35551.
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Phosphate ester linkages are omnipresent in nature and are found in many biologically important molecules such as DNA, RNA and ATP. Many enzymes that hydrolyze phosphate esters are activated by metal ions. Since the structure of biological enzymes can be quite complicated, it is often useful to work with simpler artificial metalloenzymes to help elucidate the mechanisms by which phosphate ester hydrolysis is activated by metals.In principle, simple dinuclear metal complexes could hydrolyze phosphate esters by double Lewis acid activation or by a combination of single Lewis acid activation and metal-hydroxide activation. These two mechanisms are kinetically indistinguishable. In this study, two different phosphate substrates are used to distinguish these mechanisms.
Lanthanide (iii) salts have proven extraordinarily effective in accelerating the rate of phosphate ester hydrolysis by several orders of magnitude. Consequently, there has been much effort in recent years to develop a ligand that would bind lanthanides so as to further improve their ability to hydrolyze phosphates. These efforts have met with limited success. Reported here is a dinuclear lanthanide (iii) complex which hydrolyzes BNPP (bis p-nitrophenyl phosphate) with unprecedented reactivity at pH 7.0 and 25°C.
A mononuclear copper (ii) 6,6'-diamino-2,2 '-bipyridyl complex is synthesized which gives one of the fastest rate accelerations reported for hydrolyzing 2',3 '-cAMP. A hydrogen bonding mechanism is proposed for the acceleration of the rate of hydrolysis of the cyclic phosphate.
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Williams, Daniel M. "Phosphate ester hydrolysis promoted by lanthanide (III) and transition metal complexes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0015/NQ55393.pdf.
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Ho, Mui Yen. "Transition metal oxide and phosphate-based/carbon composites as supercapacitor electrodes." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/40274/.
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Electrochemical capacitors, also known as supercapacitors, have attracted considerable attention over the past decades owing to their higher power density, long cycle life and moderate energy density compared. A high-performance supercapacitor integrates innovative electrode materials with desirable properties coupled with low cost and sustainability. In this thesis, a series of low cost transition metal oxide-activated carbon composite materials, lithium iron phosphate-activated carbon composite materials as well as metal oxide-graphene composite materials were prepared, characterized and evaluated as supercapacitor electrodes. Iron oxide (Fe3O4) – activated carbon (AC), zinc oxide (ZnO) – AC and titanium oxide (TiO2) – AC nanocomposites were prepared by using simple mechanical mixing method. The charge storage capabilities of these metal oxide-based composites with different loading ratios were evaluated in both mild aqueous 1 M Na2SO3 and 1 M Na2SO4 electrolytes. The incorporation of small amount of metal oxides onto AC could effectively enhance the capacitive performance of pure AC electrodes. It is believed that the presence of metal oxide nanoparticles can provide favourable surface adsorption sites for sulphite anions (SO32-). Nevertheless, bulk increasing of the metal oxide content is found to distort the capacitive performance and deteriorate the specific surface area of the electrode, mainly due to the aggregation of the metal oxide particles within the composite. On the other hand, composite materials consisting of lithium iron phosphate (LiFePO4) and AC exhibit high specific capacitance of 112.41 F/g in 1 M Na2SO3 with the incorporation of 40 wt % of LiFePO4. The synergistic effect between the faradaic battery type materials and the EDLC-based materials is greatly demonstrated. The intercalation and extraction of Li+ ions in LiFePO4 lattices are responsible for the reversible Faradaic reaction on top of the adsorption and de-adsorption of SO32- anions from Na2SO3 electrolyte. In the preparation of SnO2-graphene and MoO3-graphene nanocomposites, low-temperature solvothermal method using mild reducing agents was adopted. The preparation steps do not require high pressure or extreme synthetic condition and do not involve the usage of hazardous reactants. The electrochemical results of SnO2-graphene composite electrodes demonstrate that the composite electrodes possess a high specific energy (14 Wh/kg) with 93 % capacitive retention after 1500 cycles while MoO3-graphene composite electrodes yield an enhanced specific energy (16.3 Wh/kg) which is 28 % higher than that of pure MoO3 (11.8 Wh/kg). A maximum specific capacitance of 99 F/g was obtained from the optimized SnO2-graphene composite electrodes while a high average specific capacitance of 148 F/g was achieved for MoO3-graphene composites at a scan rate of 5mV/s in neural 1 M Na2SO3 electrolyte. The incorporation of graphene onto both SnO2 and MoO3 respectively, can promote the electrochemical utilization of metal oxides as well as the electrical conductivity of the electrodes. The graphene sheet serves as a good support in promoting effective charge transfer for redox reactions of MoO3. Additionally, deposition of metal oxides on graphene sheets prevents the graphene sheets from agglomeration, resulting in facile ion transportation pathway for electrolyte to access the surface of active material.
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Thompson, Natalie A. "Comparative Study of Metal Carbonate Based Adsorbents Recovering Phosphate from Water." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535633479315897.
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Nimmagadda, Sri Krishna. "Asymmetric Transformations Catalyzed By Chiral BINOL Alkaline Earth Metal Phosphate Complexes." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6554.
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Small molecule hydrogen bond donors have emerged as versatile catalysts in asymmetric synthesis. Within this class, chiral BINOL phosphoric acid is regarded as one of the pioneer catalysts used in several asymmetric transformations. The ability of the catalyst to activate the substrates could be controlled in two different ways. (1) Dual activation/bifunctional activation of substrate by hydrogen bond interactions or ion pairing with phosphoric acid or (2) By forming chiral BINOL phosphate metal complex that could significantly alter the interactions in chiral space. In particular, chiral alkaline earth metal phosphate complexes have unique advantages as catalysts owing to the ubiquitous availability of alkaline earth metals, strong Brønsted basicity of their counterions, mild but significant Lewis acidity of the metal and their ability to coordinate at multiple reactive sites due to large ionic radius.
Chapter 1 summarizes the recent development of alkaline earth metal complexes in asymmetric catalysis. My thesis dissertation is focused on the application of chiral alkaline earth metal phosphate complexes in novel asymmetric reactions.
In Chapter 2, we disclosed an efficient asymmetric one-pot synthesis of chiral 1,3-oxazolidines and chiral 1,3-oxazinanes. Chiral oxazolidines and oxazinanes are widely used as auxiliaries in asymmetric transition metal catalysis and also key structural motifs in natural products with biological activities. We developed a new synthetic method for chiral 1,3-oxazolidines which follows the enantioselective addition of alcohols to imines catalyzed by chiral 3,3’-(triisopropylphenyl)-derived BINOL magnesium phosphate to form hemiaminal intermediate, which then undergoes mild base mediated intramolecular nucleophilic substitution to afford highly enantioselective 1,3-oxazolidines and 1,3-oxazinanes in good yields.
In Chapter 3, we developed the first catalytic enantioselective desymmetrization process for the synthesis of novel axially chiral cyclohexylidene oxime ethers. Even though these molecules were found to be optically active in 1910, methods to synthesize these molecules are scarce. We have developed an efficient desymmetrization process of 4-phenyl cyclohexanones with phenoxyamines catalyzed by chiral BINOL strontium phosphate complex to afford highly enantioselective products. We then extended this methodology to the dynamic kinetic resolution of 2-substituted cyclohexanones to form chiral 2-substituted cyclohexyl oximes in good enantioselectivities, as demonstrated in Chapter 4. We further demonstrated the utility of these compounds by converting them to chiral 2-aryl cyclohexylamines which are important synthetic intermediates.
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Anantharaman, Ganapathi. "Synthesis and structural studies of group 12 metallasiloxane and phosphonate aggregates precursors for metal silicate and phosphate assemblies /." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=97033754X.
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Lu, Ling. "Synthesis and properties of pillared and non-pillared metal organo-phosphates and phosphonates." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385318.
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Atuah, Laura. "In situ remediation of metal contaminated soil : Phosphate treatment and earthworm toxicity." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529981.
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Zhao, Yue. "Preparation and investigation of group 13 metal organo-phosphate hybrid-framework materials." Winston-Salem, NC : Wake Forest University, 2009. http://dspace.zsr.wfu.edu/jspui/handle/10339/42608.
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Thesis (Ph.D.)--Wake Forest University. Dept. of Chemistry, 2009.Title from electronic thesis title page. Thesis advisor: Abdessadek Lachgar. Vita. Includes bibliographical references (p. 140-156).
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Fry, Fiona Helen 1972. "Metal complexes based on macrocyclic ligands and their ability to hydrolyse phosphate esters." Monash University, School of Chemistry, 2002. http://arrow.monash.edu.au/hdl/1959.1/8279.
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Harani, R. "Studies of electronic properties of mixed transition metal oxide and lanthanide phosphate glasses." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353991.
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Moss, Rob M. "Structural studies of metal doped phosphate glasses and computational developments in diffraction analysis." Thesis, University of Kent, 2009. https://kar.kent.ac.uk/38807/.
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The thesis focuses on the analysis and determination of the structure of various metal doped phosphate glasses, which are of interest for their potential biomedical properties. The structures have been determined principally by X-ray and neutron diffraction but are also supported by complimentary X-ray absorption spectroscopy measurements and computational modelling. Such studies contribute to about half of the work presented in this thesis. Among the glasses of interest are silver-doped calcium sodium phosphates, which exhibit antimicrobial properties when the Ag+ ions are released over time in an aqueous environment. The advanced probe technique of neutron diffraction with isotropic substitution (NDIS) has been applied to elucidate the structural role of silver in these glasses. The results revealed that silver occupies a highly distorted octahedral environment analogous to that in crystalline Ag2SO4. Another glass study herein is associated with zinc titanium calcium sodium phosphate, which is biomedically interesting since the release of Zn2+ ions is shown to enhance cell attachment and proliferation. Structural analysis of multi-component glasses such as these tends to be difficult, but diffraction techniques and X-ray absorption spectroscopy have been used together to reveal the cation first neighbour coordination environments. The other significant element of the work presented here has been the development of data analysis techniques, with the emphasis on the creation of a program, which allows co-fitting of X-ray and neutron diffraction data of amorphous (and potentially crystalline) data. The code is written in MATLAB and makes use of the Nelder-Mead simplex method to minimise a set of “best guess” structural parameters supplied by the user. Extrema bound constraints are implemented by means of a sinusoidal parameter transform. Ultimately, the code is to be compiled and made available to users via the ISIS Pulsed Neutron Facility, UK.
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Kilgour, Douglas William. "Potential negative effects of adding phosphate-based fertilizers to lead in metal-contaminated soils." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/KILGOUR_DOUGLAS_2.pdf.
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Zhu, Hongyan. "The development and in vitro evaluation of mixed metal hydroxy-carbonate compounds as phosphate binders." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403216.
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Liang, Tao. "Chiral Phosphoric Acids and Alkaline Earth Metal Phosphates Chemistry." Thesis, University of South Florida, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3632228.
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Asymmetric synthesis and catalysis is one of the leading research areas in chemistry society, for its versatility and efficiency in obtaining chiral molecules that found the vast majority in natural active compounds and synthetic drugs. Developing asymmetric catalytic methodology is at the frontier in both industrial and academic research laboratories. Enantioselective organocatalysis has emerged as a powerful synthetic tool that is complementary to metal-catalyzed transformations. The development of chiral phosphoric acid and metal phosphate as catalysts has been a breakthrough in recent years. Chiral phosphoric acids have been shown to be powerful catalysts in many organic transformations. Moreover, chiral metal phosphates, which formed by simply replacing the proton in phosphoric acid with metals, have introduced new catalytic activations and broaden the scope of phosphoric acids. This thesis details new highly enantioselective chiral phosphoric acid-catalyzed Pinacol rearrangement and robust alkaline phosphates catalytic system, which utilizes novel carbonyl activation.
The Pinacol rearrangement has long been known to be difficult to control in terms of regioselectivity and stereoselectivity. The initial studies found that indolyl-diol compounds can be treated with chiral phosphoric acids to afford the Pinacol rearrangement with high regio- and enantioselectivity. Over 16 chiral phosphoric acids were screened, and it was found an H8-BINOL-phosphoric acid variant with 1-naphthyl groups at 3 and 3' position was the excellent catalyst. This asymmetric transformation is tolerant toward variety of substituents both on the indole ring and migrating groups.
During the study, it was found that different ways to generate the catalyst had critical effect on this catalytic transformation. Only those phosphoric acids washed with HCl after column chromatography afforded the rearrangement products with high enantioselectivity. And those without treating with HCl were found contaminated by alkaline metals. These "contamination" catalysts were also found active with carbonyl activations.
A highly enantioselective catalytic hetero-Diels-Alder reaction of alpha-keto esters has been developed with chiral alkaline metal phosphates. A calcium 1-naphthyl-BINOL phosphate was found to be the optimum catalyst. A large range of alpha-keto esters as well as isatins can be applied in this alkaline phosphates catalytic system with high efficiency and selectivity. The structure of the catalyst is detailed for the first time by X-ray crystal structure analysis. A proposed Transition state model is provided based on the catalyst crystal structure and Raman spectroscopy analysis.
This methodology was further developed with an asymmetric Mukaiyama-Michael addition of beta,gamma-unsaturated alpha-keto ester. The best catalyst was found to be a magnesium chiral phosphate. And the transformation was found capable of tolerating a wide variety of beta,gamma-unsaturated alpha-keto esters.
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Woinaroschy, Kristina Michaela. "Cyclen transition metal complexes as biomimetic catalysts, phosphate anion sensors and building-blocks in supramolecular assemblies." kostenfrei, 2007. http://www.opus-bayern.de/uni-regensburg/volltexte/2009/890/.
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Schirndinger, von Schirnding Constantin [Verfasser], and Thomas [Akademischer Betreuer] Bein. "Mesoporous metal phosphate-citrate nanoparticles as anti-cancer agents / Constantin Schirndinger von Schirnding ; Betreuer: Thomas Bein." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1238518540/34.
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Xu, Chunbao. "Continuous and batch hydrothermal synthesis of metal oxide nanoparticles and metal oxide-activated carbon nanocomposites." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07302006-231517/.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.Teja, Amyn, Committee Chair ; Kohl, Paul, Committee Member ; Liu, Meilin, Committee Member ; Nair,Sankar, Committee Member ; Rousseau, Ronald, Committee Member.
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Gcanga, Esihle. "Methylgyoxal signalling in Phaseolus vulgaris under phosphate deficiency." UWC, 2020. http://hdl.handle.net/11394/7364.
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Masters of ScienceIn this study, we observed that phosphate (P) deficiency stunted plant growth and produced plants with poor morphological characteristics (yellow and small leaves). Furthermore, we treated plants with 0.8 mM (control) and 0.02 mM P (deficient) in addition to 6 μM methylglyoxal (MG) and we observed that the plants treated with MG had a higher germination, and better morphological characteristics (the leaves were more dark green and bigger in size) compared to the P deficient plants. However, we also observed that the P deficient plants treated with MG had low levels of both O2- and H2O2 and this could be a possible reason for the improved growth and morphological characteristics. In contrast, the P deficient plants not treated with MG had high levels of O2- and H2O2 which could be the possible reason for the observed cell death. We also performed biochemical assays including superoxide dismutase, ascorbate peroxidase, malondialdehyde content, ascorbic acid content, catalase, and most of the assays showed high levels of reactive oxygen species (ROS) and low levels of antioxidant activities in plants not treated with MG while high levels of antioxidant activities and low levels of ROS were observed in plants treated with exogenous MG. Since nitric oxide (NO) is also known to be a signalling molecule, we did a NO assay and observed that NO content increased under low exogenous doses of MG. From our findings we came to a hypothesis that MG modulates P deficiency stress in P. vulgaris through NO signalling or it might be that NO and MG work in tandem to modulate signalling pathways under P deficiency. Finally, we looked at the nutrient profile and the results showed that while there was a poor nutrient profile generally under P deficiency, there was an improvement in nutrient profile when MG was administered at low doses.
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Ohira, Koji. "Systematic survey of phosphate materials for lithium-ion batteries by first principle calculations." Master's thesis, 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180500.
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SILVA, Fernando Bruno Vieira da. "Inputs of heavy metals and rare earth elements in soils via phosphate fertilizers and correctives." Universidade Federal Rural de Pernambuco, 2018. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/7319.
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Phosphate fertilizers and corrective are significant sources of soil contamination by heavy metals and rare earth elements, and long-term cultivated soils can accumulate heavy metals above the maximum permissible limits. In this sense, the objectives of the study were (i) to evaluate the potential contamination of Brazilian soils by heavy metals and rare earth via phosphate fertilizers and corrective; (ii) to evaluate the accumulation of heavy metals in soils intensively cultivated with sugarcane, as well as to identify the possible sources of contamination. Initially, were performed total digests of 53 representative samples of P-containing fertilizers and commercialized in Brazil. Concentrations of As, Cd, Cr, Hg and Pb were investigated in fertilizers, which are elements regulated by national legislation. Also the additions of these metals to Brazilian soils were estimated based on the annual consumption and the average concentrations verified in each product. Subsequently, 60 samples of surface soils from areas cultivated with sugarcane were collected, these areas had a long history of use. In the soils, the environmentally available metals (Cd, Cr, Cu, Ni, Pb and Zn) were evaluated, as well as the physico-chemical characterization. The contents of metals in the soils were compared with the guiding values of quality; correlated with soil properties and; subjected to multivariate statistical analyzes to trace the origin of the metals. Finally, the total and soluble concentrations of Ce, La, Nd, Pr, Sm, Sc, Eu, Y, Dy, Gd, Yb, Er, Tb, Ho and Lu were investigated in 60 supplies samples (phosphate fertilizer, and limestone) used in Brazilian agriculture. In addition, the contributions of these elements to Brazilian soils were estimated through the use of phosphate fertilizers and soil correctives. The results of the study showed that Cd in phosphate rocks are the most worrisome, and that in the medium term the heavy metals present in fertilizers containing P do not represent environmental risk. However, the intensive application of phosphate fertilizers in soils cultivated with sugarcane promoted the accumulation of Cd above the guiding values of quality, and in some cases the soils represented a potential risk to human health. With regard to rare earths, it was observed that the solubility of these elements in phosphate fertilizers is dependent on the raw material used in industry (igneous or sedimentary). The annual additions of these elements to Brazilian soils are > 4000 t year-1 and that Ce, La, Nd and Y are the most worrisome. Limestone proved to be a significant source of Gd for agricultural soils. Therefore, soils that continuously receive high doses of these inputs are probably enriched with ETRs.
Fertilizantes fosfatados e corretivos são fontes significativas de contaminação do solo por metais pesados e elementos terras raras, e, solos cultivados por um longo tempo podem acumular metais pesados acima dos limites máximos permissíveis. Nesse sentido, o estudo teve por objetivos (i) avaliar o potencial de contaminação dos solos brasileiros por metais pesados e terras raras via fertilizantes fosfatados e corretivos; (ii) avaliar o acúmulo de metais pesados em solos intensivamente cultivados com cana-de-açúcar, como também identificar as possíveis fontes de contaminação. Inicialmente, foram realizadas digestões totais de 53 amostras representativas de fertilizantes contendo P e comercializadas no Brasil. As concentrações de As, Cd, Cr, Hg e Pb foram investigadas nos fertilizantes, que são os elementos regulamentados pela legislação nacional. Adicionalmente, as adições destes metais aos solos brasileiros foram estimadas baseadas no consumo anual e nas concentrações médias verificadas em cada produto. Posteriormente, 60 amostras de solos superficiais de áreas cultivadas com cana-de-açúcar foram coletadas, estas áreas tinham um longo histórico de uso. Nos solos, os teores ambientalmente disponíveis dos metais (Cd, Cr, Cu, Ni, Pb e Zn) foram avaliados, assim como as caracterizações físico-químicas. Os teores dos metais nos solos foram comparados com os valores orientadores de qualidade; correlacionados com as propriedades dos solos e; submetidos às análises estatísticas multivariadas para traçar a origem dos metais. Por fim, as concentrações totais e solúveis de Ce, La, Nd, Pr, Sm, Sc, Eu, Y, Dy, Gd, Yb, Er, Tb, Ho e Lu foram investigadas em 60 amostras de insumos (fertilizante fosfatado, gesso e calcário) utilizados na agricultura brasileira. Além disso, os aportes destes elementos aos solos brasileiros foram estimados através do uso de fertilizantes fosfatados e corretivos do solo. Os resultados do estudo demonstraram que Cd em rochas fosfatadas são os mais preocupantes, e, que em médio prazo os metais pesados presentes nos fertilizantes contendo P não representam risco ambiental. Contudo, a aplicação intensiva de fertilizantes fosfatados nos solos cultivados com cana-de-açúcar promoveu o acúmulo de Cd acima dos valores orientadores de qualidade, e em alguns casos os solos representaram potencial risco à saúde humana. Com relação aos terras raras, observou-se que a solubilidade destes elementos nos fertilizantes fosfatados é dependente da matéria prima utilizada na indústria (ígnea ou sedimentar). As adições anuais destes elementos aos solos brasileiros são > 4000 t ano-1 e que Ce, La, Nd e Y são os mais preocupantes. O calcário se mostrou uma fonte significativa de Gd para os solos agrícolas. Desta forma, os solos que recebem continuamente elevadas doses destes insumos, provavelmente, estão enriquecidos com ETRs.
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Ingle, Gajendrasingh. "Chiral BINOL Metal Phosphate/Phosphoric Acid Catalyzed Enantioselective Addition of Phosphorus and Sulfur Nucleophiles to Imines and Epoxides." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4339.
Full textAbstract:
The research presented in this dissertation focuses on chiral BINOL metal phosphatephosphoric acid catalyzed enantioselective additions of phosphorus and sulfur nucleophiles to imines and epoxides. In chapter 2, we reported a new method to synthesize chiral amino phosphine oxides. The reaction combines N-substituted imines and diphenylphosphine oxide catalyzed by chiral magnesium 9-antryl phosphate. A wide variety of aliphatic and aromatic aldimines substituted by electron neutral benzhydryl or dibenzocycloheptene groups were excellent substrates for the addition reaction. The imines protected with dibenzocycloheptene protecting group provided better enantioselectivity than those protected with benzhydryl group, while both imines gave comparable yields. Also, the substituted diphenylphosphine oxides were excellent nucleophiles obtaining chiral α-amino phosphine oxides in good yields and enantioselectivities.
In chapter 3, we reported the first catalytic asymmetric method to prepare enantioenriched N,S-acetals catalyzed TRIP phosphoric acids. The reaction combined N-acyl imines with thiols to generate products in excellent yield and enantioselectivity. Electron-rich and electron-deficient aromatic N-acyl imines were excellent substrate for the addition reaction. A wide range of aliphatic and aromatic thiols obtained the N,S-acetals in excellent yields and enantioselectivities.
The TRIP phosphoric acid was found to be an extremely efficient catalyst for the transformation, resulting in asymmetric induction at extremely low catalyst loading.
In chapter 4, a highly enantioselective method for desymmetrization of meso-epoxides using thiols catalyzed by substituted BINOL lithium phosphate is reported. This is the first example of epoxide activation using metal phosphate is reported. Various five and six membered aliphatic cyclic meso-epoxides were excellent substrates for the desymmetrization reaction; aromatic acyclic epoxides also reacted with excellent yield and asymmetric induction. Similarly electron rich and electron deficient aromatic thiols obtained the β-hydroxyl sulfides in excellent yields and enantioselectivities.
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Belaiche, Mohammed. "Correlations entre structure et proprietes magnetiques des systemes unidimensionnels a empilements exotiques d'ions cu**(2+) et (vo)**(2+)." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13041.
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Correlations entre structure et proprietes magnetiques de systemes unidimensionnels caracterises par des empilements exotiques de metaux de transition tels des phosphates et des sulfates de vanadium et de cuivre. Les chaines ferro ou antiferromagnetiques se sont revelees adaptees a l'etude des correlations magnetostructurales. L'influence de la competition entre diverses interactions est traitee en particulier dans le cas de la frustration 1d. Un traitement quantique est developpe pour l'analyse des proprietes thermodynamiques de composes nouveaux de formule voh(po::(4)), 4h::(2)o; cu::(2)oso::(4), acu::(3)(po::(4))::(4), avec a=ca, sr et cu::(3)(po::(4))::(2)
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Guaya, Caraguay Diana Elizabeth. "Evaluation of phosphate and ammonium removal and valorization from urban waste waters by impregnated metal hydrated oxides inorganic natural zeolites." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461091.
Full textAbstract:
Phosphate and ammonium removal from waste water by adsorption using inorganic natural sorbents has been identified as a promising technology. The advantages of this methodology are associated with its availability and effective low cost.
Some natural and synthetic zeolite materials have been used for the individual phosphate and ammonium removal from aqueous solutions. The zeolites revealed high affinity for ammonium removal. However, some modifications stages are indispensable to enhance their oxyanionic sorption capacity to achieve high phosphate removal ratios. So, it is highly desirable to obtain a single sorbent for both cation and anion removal capacity from aqueous solutions. For this purpose, a natural zeolite with clinoptilolite as major mineral phase, was impregnated with metallic oxyhydroxides after conversion to the sodium form. As a result, hydrated metal oxides (HMO) of Al, Fe and Mn were immobilized on the zeolite surface structure.
The efficiency of aluminium, iron and manganese hydrated metal oxides was individually evaluated for the simultaneous phosphate and ammonium removal from aqueous solutions through batch and continuous mode assays using a granular natural zeolite sample. High selectivity was developed by modified zeolites towards these species in the presence of competing ions commonly present in urban and industrial waste waters. The regeneration assays demonstrated the limited use of modified zeolites in operational cycles as losses of the hydrated metal oxide along within the operation cycles will require re-impregnation stages. Then, an alternative option for final valorization of ammonium and phosphate is the use of the loaded zeolites as soil amendment for agricultural and forestry purposes or for environmental rehabilitation of degraded soils.
Therefore, a second approach could be to use the impregnated zeolites as nutrients carriers, improving their fertilizing properties by including potassium. For this purpose, powder samples of the natural zeolite in the potassium form were impregnated with the metallic oxyhydroxides and were enriched on nutrients (N,P,K) by using treated waters from the secondary effluent from "El Prat" Waste Water Treatment Plant using batch mode assays. The N-P-K release rates of the enriched zeolite samples were determined by column test using mixtures with three different types of agricultural soils.La recuperación de fosfato y amonio de agua residual mediante adsorción usando adsorbentes inorgánicos naturales ha sido identificado como una tecnología muy prometedora. Las ventajas de esta metodología se asocian a la amplia disponibilidad de adsorbentes de este tipo y su bajo costo. Algunos materiales zeolíticos naturales y sintéticos han sido usados para la adsorción individual de fosfato y amonio de soluciones acuosas. Las zeolitas revelan alta afinidad para la adsorción de amonio. Sin embargo, algunas etapas de modificación son indispensables para incrementar la capacidad de adsorción oxianiónica y conseguir altas tasas de adsorción de fosfato. Entonces, resulta conveniente obtener un solo adsorbente para la adsorción simultánea de cationes y aniones de soluciones acuosas. Con este propósito, una zeolita natural que contiene clinoptilolita como mayor fase mineralógica, se impregnó con hidróxidos metálicos después de su conversión a la forma sódica. Como resultado, los óxidos metálicos hidratados (HMO) de Al, Fe and Mn fueron inmovilizados en la superficie de la estructura zeolítica. La eficiencia de los óxidos metálicos hidratados de aluminio, hierro y manganeso fue evaluada individualmente para la adsorción simultánea de fosfatos y amonio de soluciones acuosas mediante ensayos por lotes y en continuo usando una zeolita en forma granular. Una alta selectividad fue demostrada por parte de las zeolitas modificadas respecto a la adsorción de estas especies en presencial de iones competidores comúnmente existentes en aguas residuales urbanas e industriales. Los ensayos de regeneración demostraron el uso limitado de las zeolitas modificadas en continuo así como también la pérdida de los óxidos metálicos hidratados con cada ciclo de operación puesto que requiere de una nueva impregnación en cada etapa. Entonces, una opción alternativa para la final valorización de fosfato y amonio es el uso de las zeolitas saturadas como material de mejoramiento de suelos con propósitos agrícolas o también para la rehabilitación de suelos degradados. Es así que se evidencia una oportunidad en el uso de zeolitas impregnadas como transportadores de nutrientes, de tal forma que mejoren las propiedades fertilizantes mediante la inclusión de potasio. Para cumplir con este objetivo, la zeolita natural en polvo se impregnaron con oxihidróxidos metálicos que fueron enriquecidos con nutrientes esenciales (N, P, K) usándolas para tratar aguas residuales provenientes de efluentes secundarios, específicamente de la Planta de Tratamiento de Agua Residual "El Prat" usando ensayos por lotes. Las tasas de liberación de N-P-K de las zeolitas enriquecidas se determinaron mediante pruebas en columna usándolas como aditivos en tres tipos diferentes de suelos agrícolas.
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Bernhardt, Anne, Martha Schamel, Uwe Gbureck, and Michael Gelinsky. "Osteoclastic differentiation and resorption is modulated by bioactive metal ions Co2+, Cu2+ and Cr3+ incorporated into calcium phosphate bone cements." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-230765.
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Biologically active metal ions in low doses have the potential to accelerate bone defect healing. For successful remodelling the interaction of bone graft materials with both bone-forming osteoblasts and bone resorbing osteoclasts is crucial. In the present study brushite forming calcium phosphate cements (CPC) were doped with Co2+, Cu2+ and Cr3+ and the influence of these materials on osteoclast differentiation and activity was examined. Human osteoclasts were differentiated from human peripheral blood mononuclear cells (PBMC) both on the surface and in indirect contact to the materials on dentin discs. Release of calcium, phosphate and bioactive metal ions was determined using ICP-MS both in the presence and absence of the cells. While Co2+ and Cu2+ showed a burst release, Cr3+ was released steadily at very low concentrations (below 1 μM) and both calcium and phosphate release of the cements was considerably changed in the Cr3+ modified samples. Direct cultivation of PBMC/osteoclasts on Co2+ cements showed lower attached cell number compared to the reference but high activity of osteoclast specific enzymes tartrate resistant acid phosphatase (TRAP), carbonic anhydrase II (CAII) and cathepsin K (CTSK) and significantly increased gene expression of vitronectin receptor. Indirect cultivation with diluted Co2+ cement extracts revealed highest resorbed area compared to all other modifications and the reference. Cu2+ cements had cytotoxic effect on PBMC/osteoclasts during direct cultivation, while indirect cultivation with diluted extracts from Cu2+ cements did not provoke cytotoxic effects but a strictly inhibited resorption. Cr3+ doped cements did not show cytotoxic effects at all. Gene expression and enzyme activity of CTSK was significantly increased in direct culture. Indirect cultivation with Cr3+ doped cements revealed significantly higher resorbed area compared to the reference. In conclusion Cr3+ doped calcium phosphate cements are an innovative cement modification because of their high cytocompatibility and support of active resorption by osteoclasts.
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BAKRY, AYYOB MOHAMMED A. "Applications of Chemically Modified Nitrogen Doped Carbon, Zirconium Phosphate, Metal Organic Frameworks, and Functionalized Graphene Oxide Nanostructured Adsorbents in Water Treatment." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6105.
Full textAbstract:
Water contaminations by many pollutants, especially heavy metals such as Pb(II), Hg(II), Cu(II), Cd(II), and Cr(VI) pose many public health and environmental concerns as reported in the list of hazardous substances compiled by the US Environmental Protection Agency due to their high toxicity, refractory degradation, and ease of entering food chain. Adsorption by chelating resins is proven to be the most effective method for the extraction of metal ions from polluted and wastewater. However, traditional absorbents such as activated carbon, activated alumina, clay, zeolite, etc., show limited adsorption abilities for these heavy metal ions. The major goal of this thesis is to develop efficient and cost-effective adsorbents for the extraction of heavy metals from wastewater. This dissertation will focus on the development of four chemically modified high surface area adsorbents with accessible chelating sites for capturing and retaining toxic metal ions from polluted water.
The first adsorbent, Nitrogen Doped Carboxylated Activated Carbon (ND-CAC), is prepared by a polymerization reaction between melamine and formaldehyde to form the melamine formaldehyde resin (MF-R) followed by carbonization at 800 oC under nitrogen atmosphere to form nitrogen doped carbon (ND-C), and finally oxidation to form the ND-CAC adsorbent. The ND-CAC adsorbent shows high adsorption capacities of 750.5, 250.5, 98.2 mg/g for the extraction of Pb(II), Hg(II), and Cr(VI), respectively from aqueous solutions with a high selectivity to Pb(II).
The second adsorbent, Melamine Zirconium Phosphate (M-ZrP) is prepared by a precipitation reaction between Melamine Phosphate (MP) and ZrCl4 in an aqueous solution. The M-ZrP adsorbent is used for the removal of Pb(II), Hg(II), and Cd(II) with maximum adsorption capacities of 680.4, 119.0, and 60.0 mg/g, respectively with a high selectivity to Pb(II).
The third adsorbent is chemically functionalized metal organic framework (UIO-66-IT) was prepared by post-synthetic modification using the chelating ligand 2-Imino-4-Thioburit. The adsorbent was used to extract Hg(II) and (HPO4)- ions from aqueous solutions and the results revealed exceptionally high adsorption capacities toward mercury and phosphate ions of 700 and 160 mg/g, placing it among the top functionalized MOF known for the high capacity of Hg(II) removal from aqueous solutions.
The fourth adsorbent, Melamine Thiourea Partially Reduced Graphene Oxide (MT-PRGO) prepared by the amidation reaction between chemically modified graphene oxide and melamine thiourea, is used for the effective extraction of Hg(II), Co(II) and Cu(II) from polluted water. The MT-PRGO adsorbent shows exceptional selectivity for the extraction of Hg(II) with a capacity of 651 mg/g, placing it among the top of carbon-based materials known for the high capacity of Hg(II) removal from aqueous solutions.
Desorption studies demonstrate that the new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are easily regenerated with the desorption of the heavy metal ions Hg(II), Pb(II), Cd(II), and Cr(VI) reaching 99 % - 100 % recovery from their maximum sorption capacities using different eluents. Moreover, all prepared adsorbents showed tremendous abilities to clean contaminated water from toxic heavy metals at trace concentrations. That prove the ability of using them at water contamination level when the concentration of heavy metals is very low. The new adsorbents ND-CAC, M-ZrP, UIO-66-IT, and MT-PRGO are proposed as top performing remediation adsorbents for the extraction of the heavy metals Pb(II), Hg(II), Cd(II), Cr(VI), and (HPO4)- from waste and polluted water.
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Oyetola, Samuel. "Synthese et etude des composes a**(i)m**(v)p::(2)o::(8) (a = k, rb, cs; m = sb, nb, mo, ta) et des acides echangeurs ioniques hm**(v)(po::(4))::(2),xh::(2)o (m = sb, ta), nouveaux types de luminophores potentiels : les phases (m'**(iii)::(1/2)m**(v)::(1/2))p::(2)o::(7) (m'=sb, bi, ln; m=sb, nb, ta)." Nantes, 1988. http://www.theses.fr/1988NANT2008.
Full textAbstract:
Premilere partie: la plupart des phases du titre ont une structure en couches voisine de celle de zrp-alpha. Le traitement en milieu acide des phases en couches km**(i)(po::(4))::(2), m=sb, ta permet d'obtenir les acides correspondant hm**(v)(po::(4))::(2)xh::(2)o. Un autre acide, hta(po::(4))::(2) 3d, peut etre obtenu directement par voie seche, description de sa structure tridimensionnelle. Determination de la teneur en eau, de la structure et du comportement thermique de ces differents acides dont la thermolyse conduit a des phases originales qui sont etudiees. Seconde partie: dans la premiere famille, les phases (m'**(iii)::(1/2)m**(v)::(3/2)) (po::(4))::(3) sont de type nasicon ou sc::(2)(no::(4))::(3) ou d'un nouveau type structural, dans la seconde, les phases m'**(iii)::(1/2)m**(v)::(1/2))p::(2)o::(7) presentent des structures voisines de celle de zrp::(2)o::(7)
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Tuncel, Selcan. "Synthesis Of Iron Borophosphates And Phosphates With Zeo-type Structures." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/1260460/index.pdf.
Full textAbstract:
New iron phosphate and borophosphate compounds were synthesized and characterized by single crystal/powder X-ray diffraction, infrared spectroscopy, raman spectroscopy, thermogravimetric analysis, electron microscopy and elemental analysis.
Using several compositions, Fey B(PO4)x type of compounds were attempted to be prepared by solid state reactions. The solid state reactions of boron compounds with a phosphating agent has been completed at 950oC. A new product Fe2BP3O12 is synthesized and indexed in this work which is isostructural with Cr2 BP3O12
A single crystal of iron ammonium phosphate, (NH4)3-xHxFeP3O12, was synthesized by a hydrothermal method and characterized. Its X-ray powder diffraction
pattern was indexed in orthorhombic system. The unit cell parameters were found to be as a = 7.775 (Å), b = 7.445(Å
), c = 14.331(Å
) The compound with the formula NH4FeBP2O8OH was synthesized by hydrothermal method. Its X-ray powder diffraction pattern was indexed in monoclinic system. The unit cell parameters were found to be a = 9.336, b = 8.278, c =9.642Å
, and &
#946
= 101.60o, which are good agreement with the literature values. Ferro-axinite type of compound was discovered as single crystals resembling the axinite mineral. The compound was indexed in triclinic system with the unit cell parameters of a = 7.167, b = 8.840 , c = 9.455Å
, &
#945
= 64.83o, &
#946
= 64.83o, &
#947
= 69.42o. A zeotype Fe(H2O)2BP2O8.H2O, which was obtained by hydrothermal methods before, was synthesized by a precipitation method using different initial reactant. In this case, instead of Fe+2, Fe+3 compound was used as a reactant. All the compounds have been investigated by FTIR spectroscopy and the assignments of the functional BO3, BO4 and PO4 groups have been done.
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Lazareva, Olesya. "Detailed geochemical and mineralogical analyses of naturally occurring arsenic in the Hawthorn Group." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000521.
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Gaskell, Karen J. "Core level and valence band XPS investigations of phosphorus oxygen compounds and the formation of thin oxide-free phosphate films on metal surfaces /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Liu, Jun-Yao. "Synthesis and catalytic activity of metal phosphates, phosphites and phosphonates." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366368.
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Zou, Yongkun. "Corrosion Inhibition of Al Alloy with CaSiO3 /Gluconate Based Pigments in Aggressive Gluconic Acid/Saline Media." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1461593856.
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JAYASINGHE, MANORI I. "HEAVY-METAL-ION TRANSPORT IN NANOPOROUS SELECTIVE-MEMBRANES: THEORY AND EXPERIMENT." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186764159.
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Raii, Mohamed. "Formulation, caractérisation et mise en œuvre des barrières perméables réactives à base de phosphate de calcium, utilisation pour la fixation de polluants." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/9123/1/raii.pdf.
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L'objectif principal de cette thèse est la formulation des mélanges stables contenant l'hydroxyapatite gel synthétisée (Ca-HAGel). Le comportement rhéologique des mélanges Eau/(sulfate de calcium) et hydroxyapatite/(sulfate de calcium) a été étudié. Les résultats ont montré que tout les mélanges sont caractérisés par un comportement rhéologique rhefluidifiant et thixotrope. Le potentiel zeta a été utilisé dans cette étude pour mieux appréhender les interactions entre les particules et leur effet sur le comportement des mélanges. La fixation de sulfate sur la surface de Ca- HA favorise la stabilité de la structure du Ca-HAGel. Les analyses de caractérisation effectuées sur les formulations ont montré la formation de nouveaux composés tels que le sulfate-phosphate de calcium hydrate et l'Ardealite. Les tests de lixiviation et de percolation ont révélé que le taux de relargage de soufre et strontium à partir des sous-produits de gypse était négligeable pour les mélanges contenant Ca-HAGel. Ca- HAGel stabilise les métaux lourds relargués à partir du gypse et plâtre. Les particules du gypse améliorent les performances hydrauliques de Ca-HAGel et le plâtre hydraté stabilise la structure de Ca-HAGel par la formation des particules agglomérées. Le test colonne effectué sur la formulation AWPG2 a montré une grande performance à retenir le plomb et le cadmium avec des capacités de rétention de plus de 99% et 88% respectivement. Le traitement des métaux lourds était lié aux particules de Ca-HA et aux phosphate et calcium libres. La formulation AWPG2 peut être utilisée dans les barrières perméables réactives pour traiter les eaux souterraines contaminées.
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Allison, Timothy Murray. "Substrate specificity and mutational studies of KDO8PS." Thesis, University of Canterbury. Chemistry, 2012. http://hdl.handle.net/10092/6684.
Full textAbstract:
The enzyme 3-deoxy-D-manno-octulosonate 8-phosphate synthase (KDO8PS) catalyses the stereospecific aldol-like condensation between phosphoenolpyruvate (PEP) and the five-carbon sugar D-arabinose 5-phosphate (A5P). This is the first biosynthetic step in the formation of 3-deoxy-D-manno-octulosonate (KDO), an essential lipopolysaccharide component of all Gram-negative bacteria. KDO8PS is evolutionarily related to the shikimate pathway enzyme 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS), which catalyses a similar condensation reaction between PEP and the four-carbon sugar D-erythrose 4-phosphate (E4P), in the first step of the shikimate pathway to aromatic compounds in plants and microorganisms. As well as being a one-carbon shorter substrate, E4P has the opposite C2-OH configuration to A5P. While there are both metal-dependent and metal-independent forms of KDO8PS, in contrast, all DAH7PS are metal-dependent enzymes.
Little is understood about the key sequence features that distinguish KDO8PS and DAH7PS. These features, particularly those that contribute to A5P or E4P binding, are thought to be responsible for the differences in substrate specificity between the two enzymes. This thesis describes the functional and structural studies of KDO8PS mutants to examine the roles of these residues, using the metal-dependent KDO8PS from Acidithiobacillus ferrooxidans and the metal-independent KDO8PS from Neisseria meningitidis.
In Chapter 2 an extensive KDO8PS and DAH7PS sequence analysis is presented. The results, which identify sequence conservation in both enzymes, are discussed in the context of the (β/α)8 TIM-barrel structure. Some of the differences in conservation between the two enzymes were highlighted as being obvious in having a role or contributing to the different substrate selection preferences of the two enzymes, such as an extended β7α7 loop in KDO8PS, and motif differences on the β2α2 and β4α4 loops. A similar analysis was also used to compare metal-dependent and metal-independent KDO8PSs, and it was found the two forms differ in the conservation of only three residues.
Chapter 3 describes the characterisation of A. ferrooxidans KDO8PS (AfeKDO8PS) and investigates aspects of metal dependency in KDO8PS. The enzyme was found to be metal dependent, and like all other KDO8PS enzymes, to possess a tetrameric quaternary structure, and display tight substrate specificity. The β8α8 loop was found to have a critical role in binding and positioning the substrates, and AfeKDO8PS could not be engineered to be a metal-independent enzyme.
The role of the KDO8PS-conserved KANRS motif, present on the β2α2 loop and one of the main contributors to the A5P binding site, is probed in Chapter 4. Individual residues of the motif were mutated to investigate function, and the motif was converted to the equivalent motif found in DAH7PS (KPRS). It was found that the Lys plays a critical role in enzymatic catalysis, and is likely intimately involved in the enzyme mechanism. The Asn residue of the motif in KDO8PS was found to be an important contributor to KDO8PS stereospecificity.
The work described in Chapter 5 investigates the role of the β7α7 loop in KDO8PS. This long active-site loop, which exists in a shorter version in DAH7PS, was found not to be essential for catalysis in KDO8PS, but was necessary for efficient catalysis. The two conserved residues on the loop provide interactions to A5P, but the presence of the extended loop as a whole was found to be most important for catalytic efficiency.
In Chapter 6 a conserved residue on the re face of PEP is investigated. In KDO8PS the residue is conserved as Asp, and in DAH7PS the same residue is conserved as a Glu. Mutational analysis found that in KDO8PS the Asp residue appears to be important for enzyme activity but unimportant for PEP binding. Mutating this Asp in KDO8PS to Glu was accommodated by KDO8PS, but it was found its introduction could potentially be optimised by coupling the change with mutation to other conserved differences.
In KDO8PS, one of the interfaces between adjacent subunits in the tetrameric structure is partially composed of a conserved sequence motif, PAFLxR. In Chapter 7, the roles of the residues in this motif are explored. The Arg of the motif was found to be important for A5P binding. The equivalent (and also conserved) motif in DAH7PS is GARNxQ, and mutation of residues in the KDO8PS motif to the equivalent residues in DAH7PS was tolerated by KDO8PS, but negatively impacted upon the enzyme kinetic parameters. The sequence features investigated in the other chapters were combined with those to the subunit interface to create a DAH7PS-like protein. This extensively engineered protein lost all KDO8PS activity, but nor did it gain DAH7PS activity.
Lastly, in Chapter 8 the results from all chapters are reviewed and ideas are discussed for advancing the research presented in this thesis.
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Othman, Mohamad. "Characterisation and Control of 3-Deoxy-D-arabino-heptulosonate 7-phosphate Synthase from Geobacillus sp." Thesis, University of Canterbury. Department of chemisty, 2014. http://hdl.handle.net/10092/10113.
Full textAbstract:
3-Deoxy-D-arabino heptulosonate 7-phosphate synthase (DAH7PS) catalyses the first step of the shikimate pathway, responsible for the biosynthesis of aromatic amino acids. This pathway is found in microorganisms, plants and apicomplexan parasites and its absence in mammals makes it a viable target for antimicrobial drug design. DAH7PS enzymes differ in the regulatory machinery that decorates the catalytic (β/α)8 barrel. Some DAH7PS enzymes are fused to chorismate mutase (CM), another enzyme in the shikimate pathway. This fusion protein is allosterically regulated by chorismate (CA) or prephenate (PA), the precursor of tyrosine and phenylalanine. It has been suggested that DAH7PS enzymes evolved these extensions to the core barrel for the sole purpose of regulation.
Geobacillus sp DAH7PS (GspDAH7PSWT) is a thermophilic type Iβ DAH7PS enzyme with an N-terminal CM domain fused through a linker region. This thesis describes the functional characterisation work carried out on GspDAH7PSWT, in attempt to help determine how DAH7PS enzymes evolved such diverse methods of regulation.
Chapter 2 describes the functional characterisation work carried out on the catalytic and regulatory domains of GspDAH7PSWT. The enzyme demonstrated both DAH7PS and CM activities with the DAH7PS domain determined to be metal dependent and most activated by Cd2+. PA completely inhibited the catalytic activity of GspDAH7PSWT, and AUC demonstrated an equilibrium exists between the dimeric and tetrameric quaternary states of the enzyme in solution.
Chapter 3 describes the domain truncation of GspDAH7PSWT carried out at the linker region in order to obtain two separate protein domains, the catalytic domain lacking the N-terminal domain (GspDAH7PSDAH7PS) and the regulatory domain without the catalytic domain (GspDAH7PSCM). Both variants were fully characterised, and information obtained from each domain was compared to the respective catalytic and regulatory domains of the wild-type enzyme, which was also characterised. Like GspDAH7PSWT, GspDAH7PSDAH7PS showed greatest activation in the presence of Cd2+, with other metals having varying effects on activation rates and stability of the enzyme. Both truncated variants followed Michaelis-Menten kinetics where GspDAH7PSDAH7PS was found to be more active than GspDAH7PSWT and unaffected by PA, whereas GspDAH7PSCM was a less efficient catalyst than the CM domain of GspDAH7PSWT. AUC demonstrated that in solution an equilibrium occurs between the monomeric and tetrameric oligomeric states of GspDAH7PSDAH7PS.
Chapter 4 summarises the findings of the thesis along with future directions of this research, combining the results obtained and expanding upon them. It is concluded that the catalytic regulatory CM domain supports both protein structure and allosteric regulation of GspDAH7PSWT
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Casasnovas, Perera Rodrigo. "Theoretical studies on pyridoxal 5’-phosphate-catalyzed reactions of biological relevance." Doctoral thesis, Universitat de les Illes Balears, 2014. http://hdl.handle.net/10803/133519.
Full textAbstract:
El piridoxal fosfato (PLP) es cofactor de más de un centenar de enzimas que catalizan reacciones sobre aminoácidos como racemizaciones, transaminaciones o descarboxilaciones entre otras. Todas las reacciones catalizadas por PLP implican al menos una etapa de protonacion/desprotonación del carbono C del aminoácido o C4’ del PLP. El estudio experimental de la acidez de estos carbonos presenta muchas dificultades. En este trabajo se han diseñado estrategias computacionales para la determinación de pKas, obteniendo una metodología que proporciona pKas con incertidumbres equivalentes a las experimentales. Sehan calculado las energías de activación de la protonación/reprotonación de C por diversos residuos enzimáticos, así como simulaciones de metadinámica en la enzima Ornitina descarboxilasa que han permitido entender cómo se consigue una buena especificidad de reacción en las enzimas PLP-dependientes. Los resultados indican que las enzimas PLP-dependientes controlan la especificidad de la reacción deseada favoreciendo estados de protonación específicos para el cofactor PLP.El piridoxal fosfat (PLP) és cofactor de més d’un centenar d’enzims que catalitzen reaccions d’aminoàcids com ara racemitzacions, transaminacions o descarboxilacions entre altres. Totes les reaccions catalitzades per PLP impliquen al menys una etapa de protonació/desprotonació del carboni C de l’aminoàcid o C4’ del PLP. L’estudi experimental d’acidesa de carbonis presenten molta dificultat. En aquest treball s’han dissenyat estratègies computacionals per la determinació de pKas, obtenint una metodologia que proporciona pKas amb una incertesa equivalent a la experimental. S’han calculat les energies d’activació de la protonació/ desprotonació de C per diversos residus enzimàtics, així com simulacions de metadinàmiques de l’enzim Ornitina descarboxilasa que han permès entendre com s’aconsegueix una bona especificitat de reacció als enzims PLP-dependents. Els resultats indiquen que aquests enzims controlen l’especificitat de la reacció desitjada afavorint estats de protonació específics del cofactor PLP.
Pyridoxal phosphate (PLP) is a cofactor of more than a hundred enzymes that catalyze amino acid reactions like racemizations, transaminations and decarboxylations amongst others. All the PLP-catalyzed reactions entail, at least, one step of protonation/deprotonation of the C carbon of the amino acid or C4’ of the PLP. The experimental study of carbon acidities involves significant difficulties. Several computational strategies for pKa predictions were designed in this work, obtaining a methodology that provides pKas with uncertainties equivalent to experiment. The activation energies of protonation/deprotonation of C by diverse enzymatic residues were calculated and the metadynamics simulations on Ornithine decarboxylase allowed understanding how PLP-dependent enzymes achieve good reaction specificities. The results indicate that PLP-dependent enzymes control the specificity of the desired reaction by favoring certain protonation states of the PLP cofactor.
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Bauer, Caroline. "Metal ion extractant in microemulsion : where solvent extraction and surfactant science meet." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20041/document.
Full textAbstract:
Le but du travail est d'étudier la structure supramoléculaire de mélanges de tensioactif hydrophile, n-octyl-beta-glucoside (C8G1), et d'un extractant d'ions métalliques hydrophobe, le tributyl-n-phosphate (TBP), en présence d'eau, d'huile et de sels. Les systèmes classiques d'extraction ionique (composés d'une phase aqueuse, d'huile et d'extractant dont le but est d'extraire un soluté de la phase polaire sont passés en revue. L'aspect colloïdal et les transitions de phases que l'on retrouve dans ces systèmes sont souvent décrits singulièrement. Nous avons transposé l'approche « diagramme de phases » issue de la physico-chimie des systèmes moléculaires organisés à ces systèmes d'extractant afin d'orienter globalement l'analyse de ces systèmes complexes. La discussion est basée sur des considérations géométriques. Un modèle thermodynamique a été développé en considérant les contraintes d'empilement des ces extractants dans le film moléculaire formant les micelles inverses d'extractant dans l'huile. Ce modèle a permis de prédire la solubilité de l'eau au sein de ces micelles inverses ainsi que leurs tailles obtenues expérimentalement. Dans une deuxième partie, le comportement physico-chimique des phases aqueuses et organiques composées respectivement d'eau/C8G1 et de TBP/huile/eau ont été étudiées, en s'intéressant particulièrement aux effets de sels, par des techniques de diffusion de rayons X aux petits angles, diffusion dynamique de la lumière et de spectroscopie UV-visible. Dans la dernière partie la description complète de la microémulsion en faisant varier la balance hydrophile-hydrophobe du mélange C8G1 et TBP a été obtenue en combinant des mesures de diffusion de neutrons aux petits angles et d'analyse chimique (Karl-Fischer, Carbone Organique Total, ICP-OES…). Le comportement co-surfactant du TBP a été déterminé par comparaison aux co-surfactants classiques que sont les n-alcools (4The presented work describes the supramolecular structure of mixtures of a hydrophilic surfactant n-octyl-beta-glucoside (C8G1), and the hydrophobic metal ion extractant tributylphosphate (TBP) in n-dodecane/water as well as in the presence of salts.In the first part, basic solvent extraction system, composed of water, oil and extractant, will be introduced. The focus, however, lies on the extraction of multivalent metal ions from the aqueous phase. During this extraction process and in the following thermodynamic equilibrium, aggregation and phase transition in supramolecular assemblies occur, which are already described in literature. Notably, these reports rest on individual studies and specific conclusions, while a general concept is still missing. We therefore suggest the use of generalized phase diagrams to present the physico-chemical behaviour of (amphiphilic) extractant systems. These phase diagrams facilitated the development of a thermodynamic model based on molecular geometry and packing of the extractant molecules in the oil phase. As a result, we are now in the position to predict size and water content of extractant aggregates and, thus, verify the experimental results by calculation.Consequently, the second part presents a systematic study of the aqueous and organic phase of water/C8G1 and water/oil/TBP mixtures. The focus lies on understanding the interaction between metal ions and both amphiphilic molecules by means of small angle x-ray scattering (SAXS), dynamic light scattering (DLS) and UV-Vis spectroscopy. We confirmed the assumption that extraction of metal ions is driven by TBP, while C8G1 remains passive. In the third and last part, microemulsions of C8G1, TBP, water (and salt) and n-dodecane are characterized by small angle neutron scattering (SANS), and chemical analytics (Karl Fischer, total organic carbon, ICP-OES,...). The co-surfactant behaviour of TBP was highlighted by comparison to the classical n-alcohol (4
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Ewald, Bastian. "Borophosphate der Haupt- und Nebengruppenmetalle: Synthese, Charakterisierung und Strukturchemische Klassifizierung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1165332117390-21543.
Full textAbstract:
Es werden neue Erkenntnisse über Borphosphat und Borophosphate der Haupt- und Nebengruppenmetalle vorgestellt. Neben Hydrothermalsynthesen und Feststoffreationen, die üblicherweise zur Synthese von Borophosphaten angewendet werden, haben insbesondere die solvothermalen Experimente mit Alkoholen bzw. Alkohol-Wasser-Mischungen zu neuen Ergebnissen geführt. Es wurden neue Borophosphate und Borat-Phosphate in den Systemen MxOy–B2O3–P2O5(–H2O) (M = K+, Rb+, Mg2+, Sc3+, Pr3+, Sm3+, In3+) dargestellt, weitere Verbindungen enthalten neben Mg2+ weitere Kationen der Haupt- und Nebengruppenmetalle (Ca, Sr, Ba, Mn, Fe, Co, Zn). Darüberhinaus gelang die Darstellung bislang unbekannter Scandium- und Lanthanphosphate(III) sowie von sauren Alkalimetall-Scandiumphosphaten(V). Aus Synthesen in Gegenwart von Ethylendiamin und Diazabizyklooktan wurden ferner zwei neue templatierte Scandiumphosphate mit porösen Gerüststrukturen erhalten. Die Kristallstrukturen aller Verbindungem wurden rötgenographisch anhand von Einkristallaufnahmen oder Pulverdaten aufgeklärt. Die Charakterisierung der Präparate erfolgte mit Röntgenpulverdiffraktometrie, EDX- und Elementaranalysen sowie durch Schwingungsspektroskopie und thermische Stabilitätsuntersuchungen. Zur Klassifizierung von (Metallo)borophosphaten wird eine Struktursystematik vorgeschlagen, welche Borophosphate und Metalloborophosphate entsprechend ihrer anionischen Teilstrukturen hierarchisch klassifiziert und in Analogie zur Terminologie der Silikate (nach Liebau) beschreibt. In Anlehnung an bestehende Konzepte für Boratminerale geht das Klassifizierungsschema dabei von einfachen Oligomeren aus. In einer struktursystematischen Übersicht wurden alle bis dato bekannten (Metallo)Borophosphate hierarchisch klassifiziert und sind in einer Übersicht vorgestellt. Beobachtete Verknüpfungsregeln und der Einfluss der Zusammensetzung B:P auf die Dimensionalität und die Verknüpfungsmuster der anionischen Teilstruktur werden diskutiert.
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Gu, Qingyi. "Biomass reactions on heterogeneous catalysts : computational studies on surface determination and reactivity." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEN011.
Full textAbstract:
Dans le contexte de la valorisation de la biomasse par catalyse hétérogène, la chimie théorique est essentielle pour guider la détermination de la nature des sites actifs en combinaison avec des caractérisations expérimentales. Ensuite, le mécanisme de réaction peut être étudié pour déterminer l’état de transition et intermédiaire déterminant la vitesse et ensuite concevoir de meilleurs catalyseurs in silico. Nous avons mis en œuvre cette approche dans plusieurs réactions impliquant des alcools qui jouent un rôle clé dans le passage du pétrole à la biomasse comme source de matière première pour les produits chimiques de commodités ou spécialités. Tout d'abord, nous nous sommes concentrés sur l'oxydation des alcools en phase liquide par l'oxygène, une réaction qui nécessite généralement un environnement alcalin, ce qui nuit à l'économie d’atomes du processus car il génère le sel carboxylate au lieu de l'acide carboxylique. Nous avons proposé un modèle d'interface métal / eau basique incluant l'adsorption d'anion hydroxyde. Cet anion charge la surface métallique et modifie son activité catalytique. Ce modèle a tout d’abord été validé en comparant l’activité prédite de Au et de Pt en présence et en l’absence de base, puis a été utilisé pour étudier l’oxydation d’éthoxylates d’alcool par des bimétalliques. Ensuite, nous sommes passés à la déshydratation en phase gazeuse d’alcools en C3 et C4 en utilisant des catalyseurs à base de phosphate. La modélisation des surfaces s’est basée sur des caractérisations expérimentales. La couverture moléculaire de l'eau à la surface en fonction de la pression et de la température a été établie à l'aide de la thermodynamique ab initio. Les simulations de spectres infrarouges d'adsorption de CO, NH3 et C2H2 nous ont permis d'identifier les sites acido-basiques qui jouent un rôle important dans l'investigation du mécanisme de réaction qui a suiviIn the context of biomass valorization by heterogeneous catalysis, computational chemistry is key to provide guidance to establish the nature of the active sites in combination with experimental characterizations. Then, the reaction mechanism can be studied to determine the rate determining transition state and intermediate and further design in silico better catalysts. We implemented this approach in several reactions involving alcohols that are key in the shift from a petroleum chemical feedstock to a biomass-based feedstock. Firstly, we focused on liquid phase alcohol oxidation by oxygen, a reaction that generally requires an alkaline environment, which is detrimental to the atom economy of the process since it generates the carboxylate salt instead of the carboxylic acid. We proposed a model of metal/basic water interface that includes the adsorption of hydroxide anion. It charges the metallic surface and modifies its catalytic activity. This model was first validated comparing the predicted activity of Au and Pt in presence and in absence of a base, and then used oxidation of alcohol ethoxylates by bimetals. Then, we switched to gas phase dehydration of C3 and C4 alcohols using phosphate-based catalysts. The modeling of the surfaces was based on experimental characterizations. The molecular coverage of water on the surface in function of the pressure and temperature was established using ab initio thermodynamic. The simulations of infrared spectra of CO, NH3 and C2H2 adsorption allowed us to identify the acido-basic sites which play an important role in the reaction mechanism investigation that followed
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Midrier, Camille. "Synthèse de nouveaux analogues de la Fosmidomycine : inhibiteurs potentiels de l'enzyme 1-Deoxy-D-Xylulose-5-Phosphate Reductoisomerase (DXR)." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2010. http://www.theses.fr/2010ENCM0009.
Full textAbstract:
La synthèse enzymatique de terpénoides chez les mammifères provient de la voie mevalonique. Récemment une voie différente a été découverte et s'est révélée être prépondérante pour de nombreux organismes comme les plantes et bactéries. L'identification d'un inhibiteur de cette cascade enzymatique permettrait le développement d'une nouvelle famille d'herbicide. Les caractéristiques de la 1-déoxy-D-xylulose 5-phosphate réductoisomérase (DXR) font de cette enzyme très spécifique une cible pour la synthèse de nouveaux composés. La Fosmidomycine ainsi que son analogue acétylé le plus proche, FR-900098 restent des références pour l'inhibition de la DXR. Dans ce contexte, l'ensemble des molécules décrites dans la littérature en tant qu'inhibiteurs a été classé en fonction des modifications apportées sur le substrat naturel ou la Fosmidomycine. A partir de l'ensemble de ces informations, cinq familles ont été synthétisées pour trouver un nouveau motif complexant. Pour deux d'entre elles, le squelette de base contient un acide phosphonique et un acide phosphinique sur lequel a été introduit la diversité moléculaire grâce aux réactions de Pudovik et de couplage pallado-catalysé. Les autres motifs complexant originaux sont constitués d'une fonction carbonyle et d'un hétérocycle en α ou β. Après optimisation de la synthèse des précurseurs, la diversité a été introduite à l'aide, par exemple, d'une réaction de trois composantes permettant la préparation d'hétérocycle. Enfin, deux modifications ont été faites sur le bras espaceur : l'introduction d'atomes de fluor pour modifier les propriétés physicochimiques ou d'un atome d'azote, point d'attache de nouveaux groupementsThe non-mevalonate pathway is widely found in higher plants and in many eubacteria, including pathogenic ones, but not in mammals. Identifying a non-mevalonate pathway inhibitor would greatly contribute to the search for new herbicides. The unique properties of 1-Deoxy-D-xylulose 5-phosphate reductoisomerase make it remarkable and rational target for drug design. The phosphonohydroxamic acid Fosmidomycin, which acts through inhibition of DXR, is a natural compound produced in the fermentation of Streptomyces and still remains, with its N-acetyl homologue FR900098, one of the most active compounds. First of all, the enzyme and all the potential inhibitors tested in literature were classified in order to understand the global quest for therapeutically useful compounds. In this context, we designed and synthesized five different families of Fosmidomycin analogues containing a new chelating unit. Two targets molecules families bearing a phosphinophonic acid as common core were imagined. Divergent approach allowed the introduction of the chemical diversity thank to powerful pallado-catalyzed coupling reaction. The other families containing carbonyl group and heterocycle in α‐ and β‐position were regarded as highly potent complexing units. Chemical diversity was introduced mainly at the end of the synthesis. For one of them convergent ring formation using three-components reaction was developed. Finally two modifications of the Fosmidomycin linker were performed by the introduction of fluorine atoms on the parent structure as well as the replacement of a carbon by a nitrogen atom in order to create a new point of modifications
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Stone, Erica. "EFFECTS OF ORTHOPHOSPHATE CORROSION INHIBITOR IN BLENDED WATER QUALITY ENVIRONMENTS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2961.
Full textAbstract:
This study evaluated the effects of orthophosphate (OP) inhibitor addition on iron, copper, and lead corrosion on coupons exposed to different blends of groundwater, surface water, and desalinated seawater. The effectiveness of OP inhibitor addition on iron, copper, and lead release was analyzed by statistical comparison between OP treated and untreated pilot distribution systems (PDS). Four different doses of OP inhibitor, ranging from zero (control) to 2 mg/L as P, were investigated and non-linear empirical models were developed to predict iron, copper, and lead release from the water quality and OP doses. Surface characterization evaluations were conducted using X-ray Photoelectron Spectroscopy (XPS) analyses for each iron, galvanized steel, copper, and lead/tin coupon tested. Also, a theoretical thermodynamic model was developed and used to validate the controlling solid phases determined by XPS. A comparison of the effects of phosphate-based corrosion inhibitor addition on iron, copper, and lead release from the PDSs exposed to the different blends was also conducted. Three phosphate-based corrosion inhibitors were employed; blended orthophosphate (BOP), orthophosphate (OP), and zinc orthophosphate (ZOP). Non-linear empirical models were developed to predict iron, copper, and lead release from each PDS treated with different doses of inhibitor ranging from zero (control) to 2 mg/L as P. The predictive models were developed using water quality parameters as well as the inhibitor dose. Using these empirical models, simulation of the water quality of different blends with varying alkalinity and pH were used to compare the inhibitors performance for remaining in compliance for iron, copper and lead release. OP inhibitor addition was found to offer limited improvement of iron release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus, pH, and alkalinity reduced iron release while increased silica, chloride, sulfate, and temperature contributed to iron release. Thermodynamic modeling suggested that FePO4 is the controlling solid that forms on iron and galvanized steel surfaces, regardless of blend, when OP inhibitor is added for corrosion control. While FePO4 does not offer much control of the iron release from the cast iron surfaces, it does offer protection of the galvanized steel surfaces reducing zinc release. OP inhibitor addition was found to reduce copper release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increases in total phosphorus, silica, and pH reduced copper release while increased alkalinity and chloride contributed to copper release. Thermodynamic modeling suggested that Cu3(PO4)2•2H2O is the controlling solid that forms on copper surfaces, regardless of blend, when OP inhibitor is added for corrosion control. OP inhibitor addition was found to reduce lead release for the OP dosages evaluated for the water blends evaluated compared to pH adjustment alone. Empirical models showed increased total phosphorus and pH reduced lead release while increased alkalinity, chloride, and temperature contributed to lead release. Thermodynamic modeling suggested that hydroxypyromorphite is the controlling solid that forms on lead surfaces, regardless of blend, when OP inhibitor is added for corrosion control. The comparison of phosphate-based inhibitors found increasing pH to reduce iron, copper, and lead metal release, while increasing alkalinity was shown to reduce iron release but increase copper and lead release. The ZOP inhibitor was not predicted by the empirical models to perform as well as BOP and OP at the low dose of 0.5 mg/L as P for iron control, and the OP inhibitor was not predicted to perform as well as BOP and ZOP at the low dose of 0.5 mg/L as P for lead control. The three inhibitors evaluated performed similarly for copper control. Therefore, BOP inhibitor showed the lowest metal release at the low dose of 0.5 mg/L as P for control of iron, copper, and lead corrosion.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering PhD
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Del, Pilar Albaladejo Joselyn. "Zeolite-supported Cobalt Catalysts for Water Oxidation in Artificial Photosynthetic Systems." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313603462.
Full text
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Baydemir, Tuncay. "Investigations On The Properties And Drug Releases Of Biodegradable Polymer Coatings On Metal Substrates As Drug Carriers." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611140/index.pdf.
Full textAbstract:
The use of various biodegradable polymers for the improvement of different controlled and long-lasting drug release systems is an active research area in recent years. The application of different metal prostheses, especially titanium based ones,
to the human body is also very common. A most important disadvantage of these prostheses is the risk of infection at the application areas that necessitates the removing of the prosthesis with a second surgical operation and reapplication of it after recovery. One of the best ways to solve this problem is to render metal prostheses infection free with controlled and sustainable drug (antibiotic) release systems.
The long term sustained release of relevant antibiotics from the various biodegradable polymer coated metal implants is studied in this thesis. Virtual fatigue analysis and drug loading capacities of titanium and stainless steel samples with different surface pattern and modifications were studied. Various biodegradable
polymer and drug combinations were examined and used for coating of metal prosthesis. The aim is to design polymer-drug coated metal implants that are capable of releasing a feasible amount of drug up to a period of at least 1 month. Various
coating techniques and surface modifications were also employed to improve the adhesional properties of the drug containing polymers. Their adhesion abilities on the metal substrates were tested by Lap-shear and T-peel tests. Polymer degradation
kinetics was followed by viscosity studies. Calibration lines for different drugs were obtained and drug releases on different systems were followed by using UV spectroscopy and microbial antibiotic sensitivity tests.
Among the techniques applied to prevent fast release of drugs initially, the coatings of Vancomycin absorbed β
-TCP (&
#946
-tricalcium phosphate) homogeneously distributed in poly(D,L-lactide-co-glycolide) solution in chloroform followed by an inert coating with poly(L-lactide) system proved to be feasible. By this technique, initial burst release was minimized and drug release from implants lasted nearly 2 months. Multiple coatings on polymer plus drug coating layer also gave promising results. In vivo studies on dorsal muscles of native rabbits with antibiotic loaded implants gave no negative effect on the surrounding tissues with high compatibility free of infection.