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Articoli di riviste sul tema "AQUEOUS PRECIPITATION METHOD"
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Zhu, Qing Xia, Wei Hui Jiang, Hong Da Wang e Chuan Shao. "Preparing Fluorhydroxyapatite by Aqueous Precipitation Method". Advanced Materials Research 412 (novembre 2011): 167–70. http://dx.doi.org/10.4028/www.scientific.net/amr.412.167.
Testo completoAbstract (sommario):
The nanosized fluorhydroxyapatite (FHA) had been synthesized by aqueous precipitation method. The effects of synthesis temperature,fluoride ion concentration and pH value on the fluoride substitution were investigated.The phase composition and the change of crystal structure were characterized by X-ray diffraction and fourier transform infrared spectroscopy. The results show that crystal lattice parameters and bond energy make changes by incorporation of F in the structure.The size of FHA crystals increase as the precipitation temperature. The phase composition of FHA is mainly controlled by the pH value.
2
Shi, He Bin, Hong Zhong, Yu Liu, Jin Yan Gu e Chang Sheng Yang. "Effect of Precipitation Method on Stoichiometry and Morphology of Hydroxyapatite Nanoparticles". Key Engineering Materials 330-332 (febbraio 2007): 271–74. http://dx.doi.org/10.4028/www.scientific.net/kem.330-332.271.
Testo completoAbstract (sommario):
This paper reports synthesis of hydroxyapatite nanoparticles by three precipitation methods. Homogeneous aqueous solution of Ca(NO3)2 and H3PO4 was used as precursor solution, and NH3•H2O was precipitator. Calcium deficient hydroxyapatite nanorods were obtained by adding the precipitator into precursor solution, near stoichiometric hydroxyapatite nanoparticles were derived from adding precursor solution into the precipitator, and smaller hydroxyapatite nanoparticles were prepared by adding precipitator and precursor solution simultaneously into a reaction vessel. The stoichiometry of hydroxyapatite was mainly affected by pH at precipitation reaction process. The crystal size and shape of hydroxyapatite particles was related to Ostwald ripening. The stoichiometry and morphology of hydroxyapatite nanoparticles can be controllable by selecting suitable coprecipitation process.
3
Varshosaz, Jaleh, Saeedeh Ahmadipour, Majid Tabbakhian e Shokoufeh Ahmadipour. "Nanocrystalization of Pioglitazone by Precipitation Method". Drug Research 68, n. 10 (9 aprile 2018): 576–83. http://dx.doi.org/10.1055/a-0591-2506.
Testo completoAbstract (sommario):
Abstract Background Poor solubility in aqueous medium limits the use of many drugs. Different methods have been adopted to promote the rate of dissolution of slightly water soluble drugs. Crystallization improves solubility, and bioavailability by increasing the surface area of slightly water soluble drugs. Pioglitazone (PGZ), which is a class II Biopharmaceutical Classification System drug has a slight solubility in water and a slow rate of dissolution, which may have a negative effect on its metabolism leading to a therapeutic failure. Aim The aim of this study was to improve the solubility of PGZ-HCl; an antidiabetic drug using precipitation method. Materials and Methods Formulations were prepared with polyethylene glycol 6000 and isomalt using different speed of homogenizer and quantity of solvent by precipitation method. Drug-polymer interactions were examined using differential scanning calorimetry (DSC), and Powder X-Ray Diffraction (PXRD). Surface structure were shown by SEM photographs. Results The particle size was significantly decreased and solubility was enhanced with increase speed, ethanol solvent and increase stabilizer, however very high amount of stabilizer resulted in a decrease in solubility. Conclusion This result however showed that solid dispersion technique is a potential method for increasing dissolution profile of a poorly aqueous soluble agent.
4
Sun, Yi, Xiao Yi Shen e Yu Chun Zhai. "Preparation of Ultrafine ZnO Powder by Precipitation Method". Advanced Materials Research 284-286 (luglio 2011): 880–83. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.880.
Testo completoAbstract (sommario):
Ultrafine ZnO powder was synthesized by precipitation method, using zinc sulfate and aqueous ammonium carbonate as raw material and precipitant, respectively. The influence of the concentration of aqueous ammonium carbonate on the precipitation rate of Zn2+ was discussed and their relationship was also illustrated. The precipitation rate of Zn2+ increased gradually with the mol ratio of CO32-to Zn2+, which reached up to more than 96% when the mol ratio was 1.2. In addition, the crystal structure and morphology of the precursor and ZnO powder were also characterized using XRD and SEM. The results indicated that ZnO powder was hexagon wurtzite structure and spherical figure with high purity and regular crystal form.
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Harden, F. J., Iain R. Gibson e J. M. S. Skakle. "Simplification of the Synthesis Method for Silicon-Substituted Hydroxyapatite: A Raman Spectroscopy Study". Key Engineering Materials 529-530 (novembre 2012): 94–99. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.94.
Testo completoAbstract (sommario):
The addition of silicon ions to hydroxyapatite (HA) provides a more inorganic bone-like chemical composition compared to stoichiometric HA. It is known to aid the bioactivity of the material and to improve the rates of osseointegration, osteoconduction and bone mineralisation. The literature, however, lacks detailed information regarding each step of the aqueous precipitation procedure to produce silicon-substituted HA (Si-HA). The current work utilised Raman spectroscopy at each stage of the aqueous precipitation method to determine how the silicate is incorporated into the HA structure when producing Si-HA. Raman spectra indicated that at the initial stages of the reaction the disilicate ion (Si2O76-) formed with the orthosilicate (SiO44-) ion becoming more dominant after sintering. The results demonstrated that the form of silicate in the Si-HA aqueous precipitation method can be tracked using Raman spectroscopy.
6
Suwanboon, Sumetha, e Pongsaton Amornpitoksuk. "Structural, Optical and Photocatalytic Properties of ZnO Nanoparticles Prepared by Precipitation Method". Advanced Materials Research 979 (giugno 2014): 163–66. http://dx.doi.org/10.4028/www.scientific.net/amr.979.163.
Testo completoAbstract (sommario):
ZnO nanoparticles were synthesized from PEG600 diacid modified-Zn (CH3COO)2.2H2O solution by precipitation method and an aqueous NaOH solution was used as precipitating agent. The crystal structure, morphology and optical property of ZnO nanoparticles were characterized by XRD, SEM and UV-Vis spectrophotometer, respectively. The crystallinity increased while the Eg value decreased as a function of PEG600 diacid concentrations. The ZnO nanoparticles that had the highest crystallinity and lowest Eg value exhibited the highest efficiency of photocatalytic degradation of about 90% when irradiating with a UV light for 3 h.
7
Wang, Li Qin, Xiang Ni Yang, Yang Han, Rui Jun Zhang e Yu Lin Yang. "Synthesis and Characterization of ZnO Nanoparticles in the Method of Precipitation". Key Engineering Materials 474-476 (aprile 2011): 1725–29. http://dx.doi.org/10.4028/www.scientific.net/kem.474-476.1725.
Testo completoAbstract (sommario):
ZnO nanoparticles were synthesized in the method of precipitation, and they were characterized by the means of the transmission electron microscopy (TEM), the X-ray powder diffraction (XRD), the thermogravimetric analysis and differential thermal analysis (TG-DTA), and the Fourier transform infrared spectroscopy (FT-IR). Also their photocatalytic and degradation performance for the methyl orange aqueous solution were studied. The research results showed as-prepared ZnO nanoparticles were spherical crystals in hexagonal crystal system, and their size distribution was mainly in the range of 20-30 nm. The annealing temperature was about 390 °C, and a few organics remained, which may be helpful for the formation of ZnO particles. They had integrated crystal form, high crystallinity and thermal stability. Moreover, the obtained ZnO nanoparticles had excellent photocatalytic and degradation performance for the methyl orange aqueous solution. When reacted for 3.5 h, the degradation rate of the methyl orange aqueous solution was up to about 97%.
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Hsueh, Hui Chung, Zue Chin Chang, Chang Ching You e C. B. Lin. "A Novel Method to Fabricate Silver Chloride Films". Applied Mechanics and Materials 117-119 (ottobre 2011): 652–55. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.652.
Testo completoAbstract (sommario):
Abstract: This investigation develops a novel method for fabricating silver chloride films by the heterogeneous precipitation of sodium chloride from aqueous solution and supersaturated solid-state silver nitrate out of aqueous solution. The morphology of the bottom surface of the silver chloride film thus obtained comprises numerous porous stick structures. The top surface comprises equiaxed grains, and columnar grains are observed in the cross-section.
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Chang, Yajing, Xiaopeng Cheng, Jinhua Zhang e Dabin Yu. "Highly stable CdTe quantum dots hosted in gypsum via a flocculation–precipitation method". Journal of Materials Chemistry C 7, n. 39 (2019): 12336–42. http://dx.doi.org/10.1039/c9tc04412d.
Testo completo
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Ding, Jie Feng, Jian Fen Li, Wei Yi Dan, Qiang Sheng Wang e Han Fen Zhou. "Process Optimization and Preparation of Ferric Oxide Nanoparticles by Homogeneous Precipitation Method". Applied Mechanics and Materials 401-403 (settembre 2013): 683–87. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.683.
Testo completoAbstract (sommario):
For the purpose of developing an effective Fe2O3-doped nickel-based catalysts to be used in biomass gasification, Fe2O3nanoparticles were prepared by homogeneous precipitation method involving an aqueous solution of Fe (NO3)3·9H2O and urea as precipitator. Different approaches, such as XRD and SEM, were used to characterize the products. Meanwhile, the effects of various technical parameters in preparation process on the yield of products were investigated, and optimal conditions for preparing Fe2O3nanoparticles were found as follows: the molar ratio of urea to Fe (NO3)3·9H2O for 5:1, temperature of precipitation reaction for 125°C, concentration of iron salt for 0.20mol/L. The Fe2O3nanoparticles prepared under the optimal conditions were spherical in shape and well dispersed; they had high purity and a fine crystal phase of cubic syngony with a mean particle size of about 28nm.
Tesi sul tema "AQUEOUS PRECIPITATION METHOD"
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Ramli, Muhd Harris Bin. "Dynamic Effects on Migration of Light Non-Aqueous Phase Liquids in Subsurface". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189380.
Testo completo
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SINGH, GYAN PRAKASH. "SYNTHESIS OF YELLOWISH GREEN BIOCOMPATIBLE HYDROXYAPATITE PHOSPHOR VIA SURFACTANT ASSISTED AQUEOUS PRECIPITATION METHOD". Thesis, 2013. http://dspace.dtu.ac.in:8080/jspui/handle/repository/16130.
Testo completoAbstract (sommario):
Terbium doped hydroxyapatite (THA), Tb:Ca10(PO4)6(OH)2 phosphors synthesized via
surfactant (CTAB) assisted aqueous precipitation method. It is basically a room
temperature synthesis excluding the sintering at 550o C, which was performed just for the
removal of residual organic template. The phase, morphology, luminescent properties of
THA powders were examined by usingX-ray diffraction, scanning electron microscopy
(SEM), excitation and emission spectra. XRD analysis reveals the nanocrystalline nature
of THA with crystallite size 48 nm. SEM images indicate the formationof ‘micro-cubes’
with uniform size distribution. Excitation spectra measured for THA samples by
monitoring 541nm emission wavelength. Emission spectra measured for the THA samples
by exciting the samples at 377 nm wavelength.The intensities of the emission peaks were
found to be increasing with the increase ofterbium concentration. The Commission
Internationale deI’Eclairage (CIE) chromaticity coordinates calculated for the synthesized
THA phosphor, which indicate thatthe terbium doped hydroxyapatitephosphor exhibits
yellowish green emission under 377 nm excitation.
3
Yang, Zhi-Feng, e 楊志鋒. "Preparation of Magnetic Fe3O4/Carbon Nanocomposites by Co-precipitation Method for Removal of Copper Ions from Aqueous Solution". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/09366709340664966772.
Testo completoAbstract (sommario):
碩士元智大學
化學工程與材料科學學系
105
With the rapid development of semiconductor manufacturing, the treatment of liquid waste in the production process cause increasingly the attention of the enterprises. In this reaserch, the magnetic Fe3O4/Carbon nanocomposites prepared by co-precipitation method was used as absorbent for the absorption of copper ions. The efficient separation of the absorbent and absorbate and the recycling of absorbent were realized by the magnetic propert. In this reaserch, XRD, XPS, FTIR, TEM and SEM were used to analyze the micromorphology and component of the pruducts. Using the isotherm models of Langmuir, Freundlich and Dubinin-Radushkevich were to analyze the adsorption equilibrium datas of diffrenet proportion of carbon and Fe3O4 in order to study mechanism of adsorption. The results of XRD and XPS indicate the high purity of products and the results of SEM and TEM indicate the size of Fe3O4 nanoparticles is approximately 20 nm with a highly dispersed. The theoretical maximum adsorbing capacity of CNT@Fe3O4 and GO@Fe3O4 for copper ions was calculated by Langmuir isothermal equation is between 9.32 and 9.48 mg g-1, 15.43 and 32.49 mg g-1 respectively, which indicate a slight adding of Fe3O4 can enhance adsorbing capacity of GO. The type of adsorption of them is belong to ino-exchange type and belong to endothermic process. In this study, the alkaline solution was succeedly used to desorb the Cu2+ from magnetic Fe3O4/Carbon nanocomposites, and it work best when pH is 11.
Libri sul tema "AQUEOUS PRECIPITATION METHOD"
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Araújo, Ana Cláudia Vaz de. Síntese de nanopartículas de óxido de ferro e nanocompósitos com polianilina. Brazil Publishing, 2021. http://dx.doi.org/10.31012/978-65-5861-120-2.
Testo completoAbstract (sommario):
In this work magnetic Fe3O4 nanoparticles were synthesized through the precipitation method from an aqueous ferrous sulfate solution under ultrasound. A 23 factorial design in duplicate was carried out to determine the best synthesis conditions and to obtain the smallest crystallite sizes. Selected conditions were ultrasound frequency of 593 kHz for 40 min in 1.0 mol L-1 NaOH medium. Average crystallite sizes were of the order of 25 nm. The phase obtained was identified by X-ray diffractometry (XRD) as magnetite. Scanning electron microscopy (SEM) showed polydisperse particles with dimensions around 57 nm, while transmission electron microscopy (TEM) revealed average particle diameters around 29 nm, in the same order of magnitude of the crystallite size determined with Scherrer’s equation. These magnetic nanoparticles were used to obtain nanocomposites with polyaniline (PAni). The material was prepared under exposure to ultraviolet light (UV) or under heating, from dispersions of the nanoparticles in an acidic solution of aniline. Unlike other synthetic routes reported elsewhere, this new route does not utilize any additional oxidizing agent. XRD analysis showed the appearance of a second crystalline phase in all the PAni-Fe3O4 composites, which was indexed as goethite. Furthermore, the crystallite size decreases nearly 50 % with the increase in the synthesis time. This size decrease suggests that the nanoparticles are consumed during the synthesis. Thermogravimetric analysis showed that the amount of polyaniline increases with synthesis time. The nanocomposite electric conductivity was around 10-5 S cm-1, nearly one order of magnitude higher than for pure magnetite. Conductivity varied with the amount of PAni in the system, suggesting that the electric properties of the nanocomposites can be tuned according to their composition. Under an external magnetic field the nanocomposites showed hysteresis behavior at room temperature, characteristic of ferromagnetic materials. Saturation magnetization (MS) for pure magnetite was ~ 74 emu g-1. For the PAni-Fe3O4 nanocomposites, MS ranged from ~ 2 to 70 emu g-1, depending on the synthesis conditions. This suggests that composition can also be used to control the magnetic properties of the material.
Capitoli di libri sul tema "AQUEOUS PRECIPITATION METHOD"
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Rathore, Anurag S., e R. Bhambure. "Aqueous Two-Phase-Assisted Precipitation of Proteins: A Platform for Isolation of Process-Related Impurities from Therapeutic Proteins". In Methods in Molecular Biology, 81–91. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0775-6_8.
Testo completo
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Rathore, Anurag S., e Rahul Bhambure. "Aqueous Two-Phase-Assisted Precipitation of Proteins: A Platform for Isolation of Process-Related Impurities from Therapeutic Proteins". In Methods in Molecular Biology, 101–10. Totowa, NJ: Humana Press, 2014. http://dx.doi.org/10.1007/978-1-62703-977-2_10.
Testo completo
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Schweitzer, George K., e Lester L. Pesterfield. "Precipitation and Complexation". In The Aqueous Chemistry of the Elements. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393354.003.0006.
Testo completoAbstract (sommario):
In Chapter 2, a method for the construction of single-element E–pH diagrams has been presented. No agent which could produce an insoluble compound nor any agent which could complex with any of the simple ions in the single-element diagrams except OH− has been included. However, it is of interest in many cases to derive E–pH diagrams for systems which involve the precipitation or complexation of one or more of the simple ions present in the single-element diagram. One method of deriving such diagrams is to recognize that precipitation or complexation of a simple cation or anion reduces the concentration of the simple ion in solution considerably. If this reduced simple-ion concentration is calculated, it can then be used to construct a new E–pH diagram for the simple ion. Therefore, since the predominant species in the region labeled as the simple ion is no longer the simple cation or anion due to the precipitation or complexation, the region is re-labeled with the precipitated compound or the complex. E–pH diagrams which involve the precipitation or complexation of one or more of the simple ions present in the single-element diagram may also be obtained using one of the available computer programs. For complicated systems, the hand calculations become time consuming and it is often better to employ a computer program. In order to determine the changes in a single element E–pH diagram that occur due to the addition of a precipitating species and the resulting formation of an insoluble compound, the following five steps may be followed. (1) Select an element of interest showing a simple cation or anion and construct the E–pH diagram for the element at a soluble species equilibrium concentration of 10−4.0 M. (2) Select a precipitating agent which will form an insoluble compound with a simple cation or anion of the element of interest. In order to determine which species will form insoluble compounds with the simple ions of an element, it is often useful to consult a list of solubility rules.
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Dahlan, Irvan, e Sariyah Mahdzir. "Adsorption of Dyes in Aqueous Medium Using RHA and CFA". In Handbook of Research on Resource Management for Pollution and Waste Treatment, 458–75. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-0369-0.ch019.
Testo completoAbstract (sommario):
The preparation of adsorbent from the mixture of rice husk ash (RHA) and coal fly ash (CFA) has been investigated for adsorption of acid violet 7 (AV7) and brilliant green (BG) dyes. The RHA-CFA adsorbents were prepared using three different methods, i.e. reflux, magnetic co-precipitation, and magnetic template. Five different additives were used in reflux method. The results showed that RHA-CFA adsorbent prepared through reflux methods using NaOH and Na2CO3 shows higher dyes adsorption removal as compared to other methods. From zeta potential analysis, the electric charge of the outer layer of prepared adsorbent shows no effect towards adsorption of AV7 and BG dyes. By using a 3-factor, 3-level factorial design, the relationship between all variables was studied. From the response surface models, the optimum adsorbent preparation variables could be obtained by using RHA-CFA adsorbent prepared by refluxing 3:1 ratio of RHA to CFA in 1.21 M NaOH solution. The results indicated that the optimized values agree reasonably well with the validated experimental results.
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Harris, E. L. V. "Concentration of the extract". In Protein Purification Techniques. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780199636747.003.0010.
Testo completoAbstract (sommario):
A concentration step is frequently required after a clarified solution of the protein has been obtained, in order to aid subsequent purification steps. This is particularly important when the protein is obtained in culture medium from cells (e.g. bacteria or tissue culture cells). Concentration of the protein solution results in a decreased volume, as well as a higher protein concentration. Clearly a smaller volume of solution is easier to handle in subsequent steps, such as precipitation or loading onto a chromatography column. Higher protein concentration minimize protein losses by non-specific adsorption to container walls or column matrices. In addition many subsequent purification steps require a minimum protein concentration to be effective, for example, precipitation is more efficient at concentrations above 100 μg/ml, whilst for adsorption chromatography (e.g. ion exchange or affinity) the concentration of protein must be greater than the dissociation constant. Concentration is achieved by removal of water and other small molecules: (a) By addition of a dry matrix polymer with pores that are too small to allow entry of the large protein molecules (Section 2). (b) By removal of the small molecules through a semi-permeable membrane which will not allow the large molecules through (i.e. ultrafiltration, Section 3). (c) By removal of water in vacua (i.e. lyophilization, Section 4). Precipitation can also be used to concentrate proteins if the pellet is redissolved in a smaller volume, and in addition often results in some degree of purification of the protein of interest. However, as mentioned above precipitation is more effective if the total protein concentration is above 100 μg/ml (see Section 6). Two-phase aqueous extraction can also be used to concentrate the protein, with an associated degree of purification (see Section 7). This is one of the simplest and quickest methods of concentrating solutions of proteins, requiring minimal apparatus. A dry matrix polymer, such as Sephadex, is added to the protein solution and allowed to absorb the water and other small molecules; the pores within the matrix are too small to allow the protein to be absorbed.
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Khosroupour Arabi, Mostafa, e Morteza Ghorbanzadeh Ahangari. "Heavy Metals Adsorption by Nanosheet: Mechanism and Effective Parameters". In Advances in Nanosheets [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.1001599.
Testo completoAbstract (sommario):
Nowadays, scientists are working on removing heavy metals from the environment. Among the methods for heavy metals removal such as precipitation, evaporation, electroplating and ion exchange, which have many disadvantages, adsorption is the cost effective and environmental friendly technique. Using nanosheets as the base materials for the adsorption because of their large surface area and high adsorption capacity is broadened. Carbon products (Graphene), boron nitride materials (BNM), transition metal dichalcogenides (TMDs), layered double hydroxiades (LDHs) and MXene are most well-known nanosheets, which have used for heavy metal ions removal from aqueous solutions. In this review, experimental and simulation studies on nanosheet adsorbents are presented to pinpoint the importance of this group of nano-materials on water/wastewater treatment technology. Molecular dynamics (MD) and density functional theory (DFT) are the most common simulation methods for demonstration of adsorption mechanism of nanosheets. In addition, synthesis methods, adsorption mechanism, adsorption performance, and effective parameters of nanosheets and novel techniques to improve the adsorption capability and regeneration of adsorbents are introducing. This study indicate that nanosheets can regenerate over a number of adsorption/desorption cycles. With all the advantages of nanosheets, it should be noted that their use in larger industrial scales should be further investigated.
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Sposito, Garrison. "Soil Adsorption Phenomena". In The Chemistry of Soils. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780190630881.003.0012.
Testo completoAbstract (sommario):
Adsorption experiments involving soil particles typically are performed in a sequence of three steps: (1) reactio of an adsorptive (ion or molecule) with a soil contacting an aqueous solution of known composition under controlled temperature and applied pressure for a prescribed period of time, (2) separationof the wet soil slurry from the supernatant aqueous solution, and (3) quantitationof the ion or molecule of interest, both in the aqueous solution and in the separated soil slurry along with its entrained soil solution. The reaction step can be performed in either a closed system (batch reactor) or an open system (flow-through reactor), and it can proceed over a time period that is either relatively short (to investigate adsorption kinetics) or very long (to investigate adsorption equilibration). The separation step is similarly open to choice, with centrifugation, filtration, or gravitational settling being conventional methods to achieve separation. The quantitation step, in principle, should be designed not only to determine the moles of adsorbate and unreacted adsorptive, but also to verify whether unwanted side reactions, such as precipitation of the adsorptive or dissolution of the adsorbent, have influenced the experiment. After reaction between an adsorptive i and a soil adsorbent, the moles of i adsorbed per kilogram of dry soil is calculated with the standard equation ni ≡ niT − Mwmi where niT is the total moles of species i per kilogram dry soil in a slurry (batch process) or a soil column (flow-through process), Mw is the gravimetric water content of the slurry or soil column (measured in kilograms water per kilogram dry soil), and mi is the molality (moles per kilogram water) of species i in the supernatant solution (batch process) or effluent solution (flow-through process). Equation 8.1 defines the surface exces, ni, of an ion or molecule adsorptive that has become an adsorbate. Formally, ni is the excess number of moles of i per kilogram soil relative to its molality in the supernatant solution. As mentioned in Section 7.2, this surface excess may be a positive, zero, or negative quantity.
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Kumar, Ashok, Kaman Singh, Utkarsh Dixit, Rayees Ahmad Bhat e Satya Prakash Gupta. "Removal of Arsenic -¨A Silent Killer¨ in the Environment by Adsorption Methods". In Arsenic [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98985.
Testo completoAbstract (sommario):
Water is one of the most essential requirements for living being to survive because 70–80% of the mass of most living bodies consists of water and various mineral and organic salts . Water is also most important component of our environment. Large amount of water is used in various industries or commercial level or domestic level and finally effluent water is loaded with large amount of pollutants such as organic chemicals (surfactants, dyes, phenols etc.), inorganic hazardous heavy metals (As in present case) microbes (bacteria, fungi etc.) pollutants particulate etc. Arsenic is a natural metalloid chemical that may be present in groundwater and surface water gets polluted, hence, aquatic life of plants and animals is disturbed and cause abnormal growth and various diseases, hence, short term or long term changes occurs in ecosystem. Hence, treatment of wastewater is essentially required before discharge effluent wastewater into ponds or lagoons, drains and rivers. Arsenic is one such element that contaminates the environment as reported in several countries. The largest population at risk is in Bangladesh followed by India (West Bengal). Arsenic is familiar as silent killer because dissolved in water, it is colorless, odorless, and tasteless, yet consumption of relatively small doses of this element in its most toxic forms can cause rapid and violent death. It is a human carcinogen in water over a wide range of pH values, having harmful effects on both human health and environment, even at low concentration. Because of this effect, the World Health Organization (WHO) and the US Environmental Protection Agency (USEPA) set the arsenic standard for drinking water at .010 ppm to protect consumers served by public water systems. Ingestion only poses health problems if a dangerous amount of arsenic enters the body. Then, it can lead to cancer, liver disease, coma, and death. There is no effective treatment for arsenic toxicity. Only the removal of arsenic from aqueous system can prevent the toxicity. A great deal of research over recent decades has been done to lower the concentration of arsenic in drinking water and still there is a need to develop ecofriendly techniques. Existing major arsenic removal technologies include oxidation, adsorption, precipitation, coagulation and membrane separation. This book chapter presents a systematic description of current status of research in the area of arsenic removal from contaminated water and comparison of all technologies available with more emphasis on adsorption.
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Bethke, Craig M. "Mass Transfer". In Geochemical Reaction Modeling. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195094756.003.0015.
Testo completoAbstract (sommario):
In previous chapters we have discussed the nature of the equilibrium state in geochemical systems: how we can define it mathematically, what numerical methods we can use to solve for it, and what it means conceptually. With this chapter we begin to consider questions of process rather than state. How does a fluid respond to changes in composition as minerals dissolve into it, or as it mixes with other fluids? How does a fluid evolve in response to changing temperature or variations in the fugacity of a coexisting gas? In short, we begin to consider reaction modeling. In this chapter we consider how to construct reactions paths that account for the effects of simple reactants, a name given to reactants that are added to or removed from a system at constant rates. We take on other types of mass transfer in later chapters. Chapter 12 treats the mass transfer implicit in setting a species’ activity or gas’ fugacity over a reaction path. In Chapter 14 we develop reaction models in which the rates of mineral precipitation and dissolution are governed by kinetic rate laws. Simple reactants are those added to (or removed from) the system at constant rates over the reaction path. As noted in Chapter 2, we commonly refer to such a path as a titration model, because at each step in the process, much like in a laboratory titration, the model adds an aliquot of reactant mass to the system. Each reactant Ar is added at a rate nr, expressed in moles per unit reaction progress, ξ. Negative values of nr, of course, describe the removal rather than the addition of the reactant. Since ξ is unitless and varies from zero at the start of the path to one at the end, we can just as well think of nr as the number of moles of the reactant to be added over the reaction path. A simple reactant may be an aqueous species (including water), a mineral, a gas, or any entity of known composition.
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Harrison, Roger G., Paul W. Todd, Scott R. Rudge e Demetri P. Petrides. "Drying". In Bioseparations Science and Engineering. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780195391817.003.0014.
Testo completoAbstract (sommario):
The last step in the separation process for a biological product is usually drying, which is the process of thermally removing volatile substances (often water) to yield a solid. In the step preceding drying, the desired product is generally in an aqueous solution and at the desired final level of purity. The most common reason for drying a biological product is that it is susceptible to chemical (e.g., deamidation or oxidation) and/or physical (e.g., aggregation and precipitation) degradation during storage in a liquid formulation. Another common reason for drying is for convenience in the final use of the product. For example, it is often desirable that pharmaceutical drugs be in tablet form. Additionally, drying may be necessary to remove undesirable volatile substances. Also, although many bioproducts are stable when frozen, it is more economical and convenient to store them in dry form rather than frozen. Drying is now an established unit operation in the process industries. However, because most biological products are thermally labile, only those drying processes that minimize or eliminate thermal product degradation are actually used to dry biological products. This chapter focuses on the types of dryer that have generally found the greatest use in the drying of biological products: vacuum-shelf dryers, batch vacuum rotary dryers, freeze dryers, and spray dryers [1]. The principles discussed, however, will apply to other types of dryers as well. We begin with the fundamental principles of drying, followed by a description of the types of dryer most used for biological products. Then we present scale-up and design methods for these dryers. After completing this chapter, the reader should be able to do the following: • Do drying calculations involving relative humidity using the psychrometric moisture chart and the equilibrium moisture curve for the material being dried. • Calculate the relative amounts of bound and unbound water in wet solids before drying. • Model heat transfer in conductive drying and calculate conductive drying times. • Interpret drying rate curves. • Calculate convective drying times of nonporous solids based on mass transfer.
Atti di convegni sul tema "AQUEOUS PRECIPITATION METHOD"
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Zhao, Bin, e Geng yan Xing. "Synthesis of beta-Tricalciumphosphate Powder through Aqueous Precipitation Method". In 2009 2nd International Conference on Biomedical Engineering and Informatics. IEEE, 2009. http://dx.doi.org/10.1109/bmei.2009.5305604.
Testo completo
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Qifeng, Qin, e Li Xiaoyan. "Study on Active Magnesium Oxide Adsorption Properties of Sr (II) in Aqueous Solution". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67917.
Testo completoAbstract (sommario):
The active magnesium oxide (AMO) was synthesized by homogeneous precipitation method with microwave and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). Adsorption of Sr(II) by AMO was investigated under the effect of AMO dosages, pH of solution, temperature and contact time and analyzed the kinetics and thermodynamics characteristics. The results showed that AMO has very good adsorption capacity on Sr(II) in aqueous solution,When pH of solution is 8.0, the solid-liquid ratio is 0.25 g·L−1, initial Sr(II) concentration is 50mg·L−1, the contact time is 80 min at 298K, the removal rate and adsorption capacity reached 98.29% and 187.5 mg·g−1, respectively. Kinetic and thermodynamic results indicate that adsorption behavior of Sr(II) by AMO fitted well with pseudo-second-order model and the Freundlich isothermal model. Adsorption thermodynamic parameters showed that the process of adsorption is spontaneous and endothermic.
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Lamsal, Buddhi, e Md Mahfuzur Rahman. "Conventional and novel technologies for extraction of protein and their impact on structure and functionality as ingredient". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/dhxf1174.
Testo completoAbstract (sommario):
Proteins possess their techno-functionalities by virtues of their state of being, i.e., their molecular makeup and structure, which in turn, is affected by the technologies employed to extract them from the matrices they belong to. This is true for both plant proteins and cell-based proteins. While pH-modulated solubility based aqueous extraction, followed by isolation, is the overwhelming method for plant protein preparations, other technologies, for example dry fractionation (separation based on density, air drag or electrostatic charges), enzyme-, microwave-, ultrasound-, pulsed electric energy- and high pressure-assisted extraction, subcritical water, reverse micelles extraction, and aqueous two-phase systems extraction have been researched for better yields and functionality. Physical separation or dry fractionation preserves the molecular structure and protein possesses better techno-functional and sensory properties than conventional alkaline and acid-based methods. However, dry fractionation can produce only protein concentrate, not isolate. Although alkaline and acid-based methods can prepare to isolate efficiently, subsequent acid precipitation and drying methods form insoluble aggregates and enhance oxidation, which in turn, affect solubility and related functional properties as well as contribute to off-flavor. This presentation will summarize such technologies for extraction, potential for sustainability and their impact on protein's structure and techno-functionalities such as solubility, foaming/emulsion, gelation etc. It will also present authors' recent research on ultrasound-assisted extraction of soy protein and changes in major isolate structure/ function.
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Bai, Qiang, e V. K. Dhir. "Numerical Simulation of Bubble Dynamics in the Presence of Boron in the Liquid". In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24186.
Testo completoAbstract (sommario):
Abstract Deposition of boron on the fuel rod cladding during boiling of water containing boron can depress the neutron flux and lead to a decrease in nuclear reactor power output. There is practically little precise information on the temperature field, the gradients of chemical concentration and deposition of boron on the cladding surface. The objective of the present work is to simulate the nucleate boiling process along with velocity, temperature and concentration fields of aqueous boron in the vicinity of the cladding of a fuel rod. As a first step in solving the complete problem, two-dimensional numerical simulation of a bubble growth on a horizontal surface is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy and species concentration. The calculation domain is divided into macro and micro regions. In macro-region, the governing equations are used to calculate the distributions of velocity, temperature, and concentration. The Level Set method is used to capture the evolving liquid-vapor interface. For micro-region, lubrication theory is used, which includes the disjoining pressure in the thin liquid film. The solutions for micro-region and macro-region are matched at the outer edge of the micro-layer. A dilute aqueous Boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 0.003.
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Duddu, Ravindra, Nithyanand Kota e Siddiq Qidwai. "An Extended Finite Element Model of Crevice and Pitting Corrosion". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50423.
Testo completoAbstract (sommario):
A sharp interface model formulation is developed for simulating the electrochemical environment in crevices/pits due to galvanic corrosion in aqueous media. The concentration of ionic species and the electrical potential in the crevice is established using the non-dimensionalized Nernst-Planck equations along with the assumption of local electro-neutrality. The crevice/pit interface fluxes are defined in terms of the cathodic and anodic current densities using Butler-Volmer kinetics. The extended finite element method is used to discretize the governing equations and the level set function to describe the interface morphology independent of the underlying finite element mesh. The advantage of this formulation is that it eliminates the need for cumbersome mesh generation and remeshing when the interface morphology changes. Numerical investigations of steady-state intergranular crevice corrosion in idealized Al-Mg alloy microstructures in two-dimensions are conducted to establish the viability of the formulation. Simulation results predict large pH and chloride concentration within the crevice environment, which leads us to the conclusion that chemical reactions and precipitation play a prominent role during crevice corrosion.
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Kalantari Meybodi, Mahdi, Ken S. Sorbie, Oscar Vazquez, Khosro Jarrahian e Eric J. Mackay. "A Coupled Model of Phosphonate Scale Inhibitor Interactions with Carbonate Formations". In SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213819-ms.
Testo completoAbstract (sommario):
Abstract In this study, a chemical model has been developed for the simulation of the scale inhibitor (SI) interactions with carbonate systems (calcite), where the aqueous phase may contain free calcium and magnesium ions. The resulting model couples together the equations of (i) the carbonate system, (ii) the speciation of the SI, modelled as a weak polyacid, HnA, (iii) the metal (Ca2+, Mg2+) binding – SI chelant interactions and (iv) the subsequent precipitation of SI-Ca-Mg complex. These reactions are considered in conjunction with the charge balance and mass balances for calcium, magnesium, scale inhibitor and "carbon" (i.e. the carbonate system aqeous components HCO3-, CO32- and CO2 and solid CaCO3). This full equation set, with suitable reduction, results in a system of 3 non-linear equations which can be solved by the Newton-Raphson method to find the final equilibrium state of the system. The experimental results for the DETPMP/Calcite/Ca-Mg brine system from a previous study were used to check the reliability of the proposed model. The model calculates the equilibrium concentrations of all species (SI, Ca2+, Mg2+, HCO3-, CO32-, CO2, H+, and the components of the SI-Ca-Mg complexes etc.) based on their initial values and reaction constants, i.e. equilibrium constants, stability constants and solubility constants. The model can be applied either assuming a closed chemical system, or an open system and simuilation conditions were chosen in order to match the actual experiments which were matched. The model results show good quantitative agreement with the experimental results, although some assumptions must be made on the system input constants. To elucidate the precise effects that these various parameters are having in this very complex coupled system, an extensive sensitivity analysis was performed. This is especially important for uncertain parameters like stability constants of the complexes of scale inhibitor with calcium and magnesium, which are not reported in the literature. In future, this model be coupled with the adsorption model (based on the isothermal adsorption curve) and the coupled model will be incorporated into a transport model to develop a complete coupled adsorption/precipitation squeeze treatments simulation model. To our knowledge, no such model currently exists.
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Bandyopadhyay, Madhurima, Supratim Ghosh e Michael Nickerson. "Extraction and Characterization of Minimally Processed Native Faba Bean (Vicia Faba) Protein Using Mild Fractionation". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/fyfw1292.
Testo completoAbstract (sommario):
Pulse proteins are known to be high in protein and have good emulsifying properties. However, to optimize their performance as an emulsifier, the proteins need to be isolated in a manner to preserve their functional attributes. The most common commercial process to extract protein isolates from pulses such as faba bean (Vicia faba) is by alkaline extraction followed by isoelectric precipitation. However, this method relies on high pH (9-10) and spray drying, which can potentially denature the protein to alter its functionality. The present research aimed to extract native faba bean proteins from the flour using a mild aqueous fractionation and then characterize their structure, composition and functionality. The mild process will extract most likely more water-soluble albumin proteins, which would give different functionality. Faba bean flour (10% w/w) was dissolved in deionized water and centrifuged at different conditions by varying the speed (3000 and 4000 rpm) and duration (1.5 – 3.5 min). The extraction yield and purity of the proteins could be tailored by controlling centrifugal forces. Protein yield was found to decrease with an increase in time at a constant centrifugation speed. The soluble fraction obtained by centrifugation at 3000 rpm showed significantly lower interfacial tension for the samples centrifuged for a longer time duration. SDS PAGE analysis of the mildly fractionated soluble fraction revealed the presence of more albumin proteins compared to the globulin proteins. The data obtained in terms of protein composition, yield, purity, denaturation enthalpies and interfacial tension paved the way to understand the effect of the mild fractionation process on the efficiency of the minimally processed protein-rich fraction in emulsion stabilization.
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Solomon, Alvin A., Sean M. McDeavitt, V. Chandramouli, S. Anthonysamy, S. Kuchibhotla e T. J. Downar. "Thoria-Based Cermet Nuclear Fuel: Sintered Microsphere Fabrication by Spray Drying". In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22445.
Testo completoAbstract (sommario):
Spray drying is a physical process of granulating fine powders that is used widely in the chemical, pharmaceutical, ceramic, and food industries. It is generally used to produce flowable fine powders for mechanized processing. Occasionally it is used to fabricate sintered bodies like cemented carbides, and has been used to produce sintered fuel and actinide microspheres [1]. As a physical process, it can be adapted to many powder types and mixtures and thus, has appeal for dispersion nuclear fuels, and waste forms of various compositions. It also permits easy recycling of unused powders, and generates minimal chemical waste streams that can arise in chemical sol/gel processing. On the other hand, the containment of the radioactive powders, present safety challenges that need to be addressed [2]. Detailed formal procedures and methods for characterizing and processing UO2/ThO2 mixtures have been established and approved by the Purdue Radiological Control Committee for (1) ball-milling, (2) viscosity and rheology measurements on slurries, (3) sintering, (4) co-precipitation, (5) particle size analysis using laser scattering, (6) surface area analysis using the BET technique, (7) X-ray diffraction, (8) stoichiometry measurement, (9) zeta potential measurements and (10) ceramographic preparation. The spray drying procedures represented a particular challenge since they deal with the handling of loose powders. Studies were carried out to formulate suitable stable, dense and homogeneous aqueous slurries of urania and thoria powders for the production of urania-thoria microspheres by the spray drying method. The studies included (a) particle size distribution after ball-milling, (b) viscosity, (c) zeta potential, (d) slurry flowability, stability and cleanability, (e) microsphere green strength, and f) effects of organic dispersants on the above properties. After formulating the slurry, U,ThO2 microspheres were produced using a commercial, laboratory-scale spray dryer modified for handling these radioactive materials. The microspheres thus obtained were dried at 473 K for 4 hours, presintered at 1173 K for 2 hours and sintered at 1923 K for 10 hours.
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Liu, Qingqing, e Xiaoyan Li. "Study on Adsorption of U(VI) From Aqueous Solution by Activated MgO". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67922.
Testo completoAbstract (sommario):
The activated MgO was synthesized by microwave homo-precipitator method and characterized by SEM, EDS and FT-IR methods. It was used to adsorption of U(VI) from aqueous solution with batch system. The paper discussed the effect of pH, temperature, contact time, adsorbent dose and initial U(VI) concentration on the adsorption. The results showed that activated MgO has good adsorption capacity for U(VI), the removal rate and equilibrium adsorption capacity reached 83.5% and 84.04mg·g−1 at pH 5.0, 15mg dose and 313K,respectively. The adsorption kinetics of U(VI) onto activated MgO were better fitted with pseudo-second-order kinetic.The adsorption isotherm data were fitted well to Freundlich isotherm model.The thermodynamic parameters showed that the adsorption process is endothermic and spontaneous.
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Cheng, Ming, Matthew Hodges, Kenny Kwan, Hsuan-Tsung Hsieh, Yitung Chen, George Vandegrift, Jackie Copple e James Laidler. "An Object-Oriented Systems Engineering Model Design for Integrating Spent Fuel Treatment Facility and Chemical Separation Processes". In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15885.
Testo completoAbstract (sommario):
The mission of the Transmutation Research Program (TRP) at University of Nevada, Las Vegas (UNLV) is to establish a nuclear engineering test bed that can carry out effective transmutation and advanced reactor research and development effort. TRPSEMPro package, developed from previous project period, integrated a chemical separation code from the Argonne National Laboratories (ANL). Current research focus has two folds: development of simulation system processes applied to Spent Fuel Treatment Facility (SFTF) using ASPEN-plus and further interaction of ASPEN+ program from TRPSEMPro interface. More details will be discussed below. ANL has identified three processes simulations using their separation technologies. The first process is to separate aqueous acid streams of acetic acid, nitric acid, water and a variety of fission product nitric salts. Distillation separation method is used to remove the desired components from the streams. The second simulation is to convert plutonium nitrate to plutonium metal. Steps used for the process simulation are precipitation, calcinations, fluorination and reduction. The third process currently under development is vitrification of fission product of raffinate streams. During the process, various waste streams from the plant are mixed and fed to a process that converts them to a solid state glass phase. The vitrification process used by the Hanford and Savannah River facilities was selected as a guideline to develop the prototype simulation process using ASPEN-Plus. Current research is focusing on identifying unit operations required to perform the vitrification of the waste streams. The first two processes are near completion stage. Microsoft Visual Basic (MS VB) has been used to develop the entire system engineering model package, TRPSEMPro. Currently a user friendly interface is under development to facilitate direct execution of ASPEN-plus within TRPSEMPro. The major purpose for the implementation is to create iterative interaction among system engineering modeling, ANL separation model and ASPEN-Plus process that outputs optimized separation/process simulation results. The ASPEN-plus access interface from TRPSEMPro allows users to modify and execute process parameters derived from the ASPEN Plus simulations without navigating through ASPEN-Plus. All ASPEN-plus simulation results can be also accessible by the interface. Such integration provide a single interaction gateway for researchers interested in SFTF process simulation without struggling with complicate data manipulation and joggling among various software packages.