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1
Kasmiyati, Sri, Santosa S, Irfan Dwidja Priyambada, Kumala Dewi, and Rintawati Sandradewi. "Perkecambahan Biji Dan Pertumbuhan Kecambah Varietas Sorgum (Sorghum bicolor L.) Pada Cekaman Krom Heksavalen." Bioma : Berkala Ilmiah Biologi 17, no. 1 (June 17, 2015): 41. http://dx.doi.org/10.14710/bioma.17.1.41-54.
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In contrast to other toxic trace metals, Cr has received little attention. Since valence level of chromium determines its toxicity, chromium is categorized as unique heavy metal. Chromium hexavalent (Cr6+) has the biggest toxicity among other valence levels. Seed germination and seedling growth are sensitive to heavy metal stresses. This research aimed to find out the responses of seed germination and seedling growth of 12 sorghum varieties toward Cr6+. Seed germination and seedling growth experiment was done on 12 sorghum varieties (Badik, UPCA-1, Keris, Keris M3, hegari Genjah, Gambela, Selayer, Sangkur, Mandau, Batari, Kawali, dan Numbu), planted in petridishes with Cr6+ treatment in form of chromate (K2CrO4) and dichromate (K2Cr2O7) compounds with 0, 50 and 500 mg of Cr/l concentration for a week. The parameters measured were the number of seeds germinate each day; the length of radicle and plumule, and fresh and dry weight at the end of experiment. The results showed that higher concentration of Cr6+ both in form of dichromate and chromate, significantly decreased the length of radicle and plumule, fresh and dry weight, and SVI (seedling vigor index) value. However, index germination (GI) value and percentage of germination of the 12 varieties sorgum significantly increased in the treatment of 50 mg Cr/l Cr6+ in form of dichromate and chromate. The treatment of dichromate compound showed bigger effect than chromate toward variables of seed germination and seedling growth of sorghum. It was noticed that 12 sorghum varieties possessed an integrated complex of adaptation to cope with the range of form of compound and concentration of Cr6+. Based on the responses of seed germination and seedling growth, Kawali, Hegari, Keris, Keris M3, Mandau, and Selayer varieties was more susceptible toward Cr6+ toxicity, and Sangkur, Selayer, Batari, and Numbu was more tolerant than other varieties. Keywords : chromate, dichromate, Sorghum bicolor, seedling, hexavalent chromium
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Averina, Yu M., G. E. Kalyakina, V. V. Menshikov, Yu I. Kapustin, and V. S. Boldyrev. "Neutralisation Process Design for Electroplating Industry Wastewater Containing Chromium and Cyanides." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 84 (June 2019): 70–80. http://dx.doi.org/10.18698/1812-3368-2019-3-70-80.
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Manufacturing processes in the electroplating industry employ hazardous chemicals and generate hazardous waste, including hexavalent chromium compounds and heavy metal cyanides. We designed a reagent-based treatment technology that can remove these contaminants and is relatively simple to implement and maintain. The technology features low reagent consumption but high treatment efficiency and simplifies separating precipitates from the treated effluent. The paper presents a detailed description of how to neutralise electroplating shop wastewater. We propose a system of organizational and technological measures to improve chemical safety.
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Marcus, Maria Iuliana, Mihaela Andreea Mitiu, Maria Vlad, Mariana Mincu, Gina Ghita, and Ana Maria Anghel. "Influence of Different Electroplating Sludge Types on the Iron Ions Recovery Yield." Revista de Chimie 69, no. 3 (April 15, 2018): 618–20. http://dx.doi.org/10.37358/rc.18.3.6161.
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Electroplating sludge resulting from wastewater (washing wastewater and technological solutions) treatment is considered to be a hazardous waste, being a mixture of hydroxides of many heavy metals such us: iron, chromium, copper, nickel, cadmium or zinc. The metal compounds from electroplating sludge have a great economic value, thus, a number of techniques have been investigated in order to recover them. This paper presents the results of the research activity in the laboratory in order to recover Fe (II, III, VI) from two types of electroplating sludge: a fresh sludge from wastewaters treatment and an old sludge, stabilized by disposal for many years. Iron recovery was performed by the solubilization of the sludge in several stages, to yield hydroxides or metal salts of chromium, iron, or zinc. The iron recovery has been performed from the cake obtained after the chromium recovery. In this cake, the iron is present in the form of divalent, trivalent and hexavalent iron. The iron recovery yield was 98.50% from fresh sludge (recovery in one stage) and 96.80% from old sludge (recovery in two stages).
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Abrashov, Aleksey, Nelya Grigoryan, Tigran Vagramyan, and Naum Asnis. "On the Mechanism of Formation of Conversion Titanium-Containing Coatings." Coatings 10, no. 4 (March 29, 2020): 328. http://dx.doi.org/10.3390/coatings10040328.
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The present work is devoted to the study of the mechanism of the process of formation of adhesive oxide-titanium coatings on steel, zinc, and aluminum surfaces. For the first time, the following hypothesis has been confirmed experimentally, namely, that nickel, being the first metal to be deposited on a steel substrate, creates active centers on which titanium oxides are formed, because the hydrolysis of hexafluorotitanic acid is adsorbed, which then form a continuous film. The data obtained, regarding the dependence of the coating thickness on the linear rate of the solution flow along the treated surface, indirectly confirm that the formation of insoluble titanium oxides occurs because of the alkalization of the solution adjacent to the surface. It has been established that in the presence of hexavalent molybdenum compounds in the solution as oxidizers, molybdenum is included in the coating in the form of oxides. It has been revealed that in the lower layers of the coating, molybdenum is contained in the form of compounds of molybdenum (V) and (VI), while in the upper layers, it is contained only in the form of the compound of molybdenum (VI).
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Abdul Salam, Femina, and Anantharaman Narayanan. "Leached compounds from the extracts of pomegranate peel, green coconut shell, and karuvelam wood for the removal of hexavalent chromium." Green Processing and Synthesis 8, no. 1 (January 28, 2019): 281–87. http://dx.doi.org/10.1515/gps-2018-0085.
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Abstract During biosorption, the biosorbent releases many organic compounds to the medium. In the present study, extracts of pomegranate peel (PP), green coconut shell (GCS), and karuvelam wood (KW) were prepared at three different conditions, namely 12 h, 3 h, and 3 h at pH 2, for the removal of hexavalent chromium [Cr(VI)]. The amount of organic compounds, mainly the leached organic compounds in the extract before and after treatment with Cr(VI) solution, was determined by chemical oxygen demand analysis. The total phenolic content, antioxidant activity, and total flavonoid content were used to estimate the chromium reduction potential of the extracts. The PP extract is the richest in all the three factors, followed by GCS and KW. The disappearance rate of Cr(VI) in the presence of PP extract reached 99.63% for the 50 mg/l concentration within 3 min, while it was 12% and 10% for GCS and KW, respectively, for the same concentration and time. Reaction mechanisms were formulated with the help of Fourier transform infrared spectroscopy to confirm the role of leached compounds from natural materials for the removal of heavy metal.
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Kumar, Dinesh, and Amit Kumar. "Syntheses, Characterization, and Biological Activities of Metal Complexes of N-(2-Carbamoylthienyl)-C-(3′-carboxy-2′-hydroxyphenyl) Azetidin-2-one with Some Di-, Tetra-, and Hexavalent Metal Ions." Journal of Chemistry 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/124790.
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The cyclization of the Schiff base, N-(2-carbamoylthienyl)-3′-carboxy-2′-hydroxybenzylideneimine with ClCH2COCl in dioxane, in the presence of triethylamine (Et3N) forms N-(2-carbamoylthienyl)-C-(3′-carboxy-2′-hydroxyphenyl) azetidin-2-one, LH3(I). A methanolic solution ofIreacts with Co(II), Cu(II), Zn(II), Zr(OH)2(IV), and MoO2(VI) ions and forms the coordination compounds, [Co(LH)(MeOH)]2(II), [Cu(LH)]2(III), [Zn(LH)(MeOH)2] (IV), [Zr(OH)2(LH)(MeOH)] (V), and [MoO2(LH)(MeOH)2] (VI). The compounds have been characterized on the basis of elemental analyses, molar conductance, molecular weight, spectral (IR, NMR, reflectance, and ESR) studies, and magnetic susceptibility measurements. All the coordination compounds are nonelectrolytes (ΛM=3.1-9.2 mho cm2mol−1) in DMF.Ibehaves as a dibasic tridentate OON donor ligand inV; a dibasic tetradentate OONO donor ligand inII,III, andVI; and a dibasic tetradentate OONS donor ligand inIV.IIandIIIare dimers, while others are monomers in diphenyl.IIIexhibits subnormal magnetic moment (1.55 B.M.) and is involved in antiferromagnetic exchange, while the other complexes are magnetically dilute. A square-pyramidal structure forIIIand an octahedral structure forII,IV, andVare suggested.VIexhibits an eight-coordinate structure. The ligand (I) and its compounds show antibacterial activities towardsE. coli(gram negative) andS. aureus(gram positive).
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Daoud, Waseem, Taghi Ebadi, and Ahmad Fahimifar. "Removal of hexavalent chromium from aqueous solutions using micro zero-valent iron supported by bentonite layer." Water Science and Technology 71, no. 5 (December 17, 2014): 667–74. http://dx.doi.org/10.2166/wst.2014.493.
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Hexavalent chromium Cr(VI) is of particular environmental concern due to its toxicity, mobility, and challenging removal from industrial wastewater. It is a strong oxidizing agent that is carcinogenic and mutagenic and diffuses quickly through soil and aquatic environments. Moreover, it does not form insoluble compounds in aqueous solutions; therefore, separation by precipitation is not feasible. While Cr(VI) oxyanions are very mobile and toxic in the environment, trivalent Cr(III) cations are the opposite and, like many metal cations, Cr(III) forms insoluble precipitates. Thus, reducing Cr(VI)–Cr(III) simplifies its removal from effluent and also reduces its toxicity and mobility. Permeable reactive barriers (PRBs) with zero-valent iron (ZVI) have been used to remediate contaminated groundwater with metals, but using ZVI in remediation of contaminated groundwater or wastewater is limited due to its lack of stability, easy aggregation, and difficulty in separation of iron from the treated solution. Thus, the technology used in the present study is developed to address these problems by placing a layer of bentonite after the PRB layer to remove iron from the treated water. The removal rates of Cr(VI) under different values of pH were investigated, and the results indicated the highest adsorption capacity at low pH.
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Daulton, Tyrone L., Brenda J. Little, Kristine Lowe, and Joanne Jones-Meehan. "Microbial Reduction of Chromium(VI): In-Situ Environmental Cell Transmission Electron Microscopy Study Using Electron Energy Loss Spectroscopy." Microscopy and Microanalysis 7, S2 (August 2001): 134–35. http://dx.doi.org/10.1017/s143192760002674x.
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The geochemistry and toxicity of chromium is controlled by its valence state. Chromium is a redox active 3d transition metal with a wide range (− to +6) of possible oxidation states; however only Cr(III) and Cr(VI) are stable. Hexavalent Cr(VI) can be readily reduced to the trivalent state by Fe2+, S2−, organic compounds, wetland plants, and several species of microorganisms. The associated mechanisms of Cr(VI) reduction are technologically and biologically important because they convert a toxic, mobile element into a less toxic, immobile form.Reduction of Cr(VI) by the bacterium, Shewanella oneidensis (previously classified Shewanella putrefaciens strain MR-1), was studied by absorption spectrophotometry and in-situ, environmental cell (EC) - transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS). Shewanella oneidensis (S. oneidensis), a gram-negative, facultative bacterium is capable of respiring aerobically and anaerobically using a variety of compounds, including O2, Fe(III), Mn(IV), NO2−, NO3−, SO2, SO32−, thiosulfate (S2O32−), trimethyamine oxide, fumarate, U(VI), and Cr(VI) as terminal electron acceptors.
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G. Saiz, Paula, Ainara Valverde, Bárbara Gonzalez-Navarrete, Maibelin Rosales, Yurieth Marcela Quintero, Arkaitz Fidalgo-Marijuan, Joseba Orive, et al. "Modulation of the Bifunctional CrVI to CrIII Photoreduction and Adsorption Capacity in ZrIV and TiIV Benchmark Metal-Organic Frameworks." Catalysts 11, no. 1 (January 1, 2021): 51. http://dx.doi.org/10.3390/catal11010051.
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The presence of hexavalent chromium water pollution is a growing global concern. Among the currently applied technologies to remove CrVI, its adsorption and photocatalytic reduction to CrIII less mobile and toxic forms are the most appealing because of their simplicity, reusability, and low energy consumption. However, little attention has been paid to bifunctional catalysts, that is, materials that can reduce CrVI to CrIII and retain both hexavalent and trivalent chromium species at the same time. In this work, the dual CrVI adsorption–reduction capacity of two iconic photoactive water-stable zirconium and titanium-based metal–organic frameworks (MOFs) has been investigated: UiO-66-NH2 and MIL-125. The bifunctionality of photoactive MOFs depends on different parameters, such as the particle size in MIL-125 or organic linker functionalization/defective positions in UiO-66 type sorbents. For instance, the presence of organic linker defects in UiO-66 has shown to be detrimental for the chromium photoreduction but beneficial for the retention of the CrIII phototransformed species. Both compounds are able to retain from 90 to 98% of the initial chromium present at acidic solutions as well as immobilize the reduced CrIII species, demonstrating the suitability of the materials for CrVI environmental remediation. In addition, it has been demonstrated that adsorption can be carried out also in a continuous flux mode through a diluted photoactive MOF/sand chromatographic column. The obtained results open the perspective to assess the bifunctional sorption and photoreduction ability of a plethora of MOF materials that have been applied for chromium capture and photoreduction purposes. In parallel, this work opens the perspective to develop specific chemical encoding strategies within MOFs to transfer this bifunctionality to other related water remediation applications.
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Tumolo, Marina, Valeria Ancona, Domenico De Paola, Daniela Losacco, Claudia Campanale, Carmine Massarelli, and Vito Felice Uricchio. "Chromium Pollution in European Water, Sources, Health Risk, and Remediation Strategies: An Overview." International Journal of Environmental Research and Public Health 17, no. 15 (July 28, 2020): 5438. http://dx.doi.org/10.3390/ijerph17155438.
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Chromium is a potentially toxic metal occurring in water and groundwater as a result of natural and anthropogenic sources. Microbial interaction with mafic and ultramafic rocks together with geogenic processes release Cr (VI) in natural environment by chromite oxidation. Moreover, Cr (VI) pollution is largely related to several Cr (VI) industrial applications in the field of energy production, manufacturing of metals and chemicals, and subsequent waste and wastewater management. Chromium discharge in European Union (EU) waters is subjected to nationwide recommendations, which vary depending on the type of industry and receiving water body. Once in water, chromium mainly occurs in two oxidation states Cr (III) and Cr (VI) and related ion forms depending on pH values, redox potential, and presence of natural reducing agents. Public concerns with chromium are primarily related to hexavalent compounds owing to their toxic effects on humans, animals, plants, and microorganisms. Risks for human health range from skin irritation to DNA damages and cancer development, depending on dose, exposure level, and duration. Remediation strategies commonly used for Cr (VI) removal include physico-chemical and biological methods. This work critically presents their advantages and disadvantages, suggesting a site-specific and accurate evaluation for choosing the best available recovering technology.
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Brandi, Giorgio, Giuditta Fiorella Schiavano, Amedeo Albano, Flaminio Cattabeni, and Orazio Cantoni. "Growth delay and filamentation of Escherichia coli wild-type and Rec A cells in response to hexavalent chromium and other metal compounds." Mutation Research Letters 245, no. 3 (November 1990): 201–4. http://dx.doi.org/10.1016/0165-7992(90)90050-t.
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Tian, Xuerui, Xing Xin, Yuanzhe Gao, Dandan Dai, Jinjin Huang, and Zhangang Han. "Crystal structures of hybrid completely reduced phosphomolybdates and catalytic performance applied as molecular catalysts for the reduction of chromium(VI)." Acta Crystallographica Section C Structural Chemistry 74, no. 11 (October 18, 2018): 1310–24. http://dx.doi.org/10.1107/s2053229618013025.
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The exploration of highly efficient and low-cost catalysts for the treatment of hexavalent chromium CrVI in environmental remediation is currently one of the most challenging topics. Here, three phosphomolybdate hybrid compounds have been successfully isolated by the hydrothermal method and been applied as supramolecular catalysts for the reduction of CrVI. Single-crystal X-ray diffraction revealed their formulae as (H2bpp)2[Fe(H2O)][Sr(H2O)4]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·5H2O (1), (H2bpp)2[Na(H2O)(OC2H5)][Fe(H2O)2][Ca(H2O)2]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·4H2O (2) and (H2bpe)3{Fe[Mo6O12(OH)3(HPO4)3(H2PO4)]2}·8H2O (3) [bpp is 1,3-bis(pyridin-4-yl)propane (C13H14N2) and bpe is trans-1,2-bis(pyridin-4-yl)ethylene (C12H10N2)]. The three hybrids consist of supramolecular networks built up by noncovalent interactions between {Fe[P4Mo6 VO31]2}22− polyanions and protonated organic cations. This kind of hybrid polyoxometalate could be applied as heterogeneous molecular catalysts for the reduction of CrVI. It was found that the organic moiety plays a vital role in influencing the catalytic activity of the polyanions. Organic bpp-containing hybrids 1 and 2 are highly active in the catalytic reduction of heavy metal CrVI ions using HCOOH as reductant, while bpe-containing hybrid 3 is inactive to this reaction. This work is significant for the design of new catalysts, as well as the exploration of reaction mechanisms at a molecular level.
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Sterns, M., RL Withers, P. Midgeley, and R. Vincent. "Preparation and Partial Characterization of Two New Hexavalent Uranium Metal Uranates." Australian Journal of Chemistry 49, no. 7 (1996): 817. http://dx.doi.org/10.1071/ch9960817.
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The preparation, chemical characterization and structural investigation by X-ray and electron diffraction of two uranates (VI), namely Sr5U3O14 and of Pb11U5O26, are reported. The strontium compound, the unit cell of which is metrically tetragonal with a = 11.248(5), c = 11.086(5) Ǻ, Z = 4, was shown by electron diffraction to be orthorhombic, space group Pbca with a = b. Crystals of Sr5U3O14 are invariably submicroscopically twinned and, because of the identity of a and b, mimic tetragonal symmetry. The lead uranate , Pb11U5O26, was shown to be a long-period superstructure with unit cell dimensions a = 44.54, b = 15.586, c = 8.241 Ǻ, Z = 8.
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Tian, Feng, Yan Rong Ni, Kai Tuo Zhang, and Chao Hua Su. "Study on the Formula of the Environmental Friendly High Temperature Type PVC Sheathing Compound." Advanced Materials Research 557-559 (July 2012): 1602–6. http://dx.doi.org/10.4028/www.scientific.net/amr.557-559.1602.
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The formula of the environmental protection PVC sheathing compound used for wires and cables contains: the base resin, composite stabilizer, plasticizer, filler, antioxidant and lubricant. Each component’s effects on the performance of the sheathing compound were studied. The optimized formula was established as: 100.00 phr PVC , 6.80 phr Ca/Zn stabilizer, 36.30 phr TOTM, 14.0.80phr DIDP, and 30.50 phr heavy calcium carbonate agent. The product properties were demonstrated by a series of experimental means. The results indicate that this formula system contain neither heavy metals such as lead, cadmium, hexavalent chromium and mercury, nor polybrominated biphenyls and their ethers, which can cause significant damage to people and the environment. The product property completely meets the performance standards set for the environmental protection 105 °C PVC sheathing compound.
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Tian, Feng, Kai Tuo Zhang, Yan Rong Ni, and Chao Hua Su. "Study on the Formula of the Environmental Friendly 90 °C PVC Sheathing Compound." Advanced Materials Research 518-523 (May 2012): 828–32. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.828.
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The formula of the environmental protection PVC sheathing compound used for wires and cables contains: the base resin, composite stabilizer, plasticizer, filler, antioxidant and lubricant. In this paper, each component’s effects on the performance of the sheathing compound were studied. The optimized formula was established as: 100.00 phr PVC SG-3, 7.80 phr Ca/Zn stabilizer, 38.00 phr DIDP, 11.00phr DOTP, 34.50 phr ground calcium carbonate, 0.40 phr Bisphenol A, 0.70 phr lubricants, and 1.50phr coloring agent. The product properties were tested. The results indicate that this formula system contain neither heavy metals such as lead, cadmium, hexavalent chromium and mercury, nor polybrominated biphenyls and their ethers, which can cause significant damage to people and the environment. The product property completely meets the performance standards set for the environmental protection 90 °C PVC sheathing compound.
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Sun, Xinzhe, Peng Guo, Yuanyuan Sun, and Yuqian Cui. "Adsorption of Hexavalent Chromium by Sodium Alginate Fiber Biochar Loaded with Lanthanum." Materials 14, no. 9 (April 26, 2021): 2224. http://dx.doi.org/10.3390/ma14092224.
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Lanthanun oxide (La2O3) is a lanthanum chemical compound incorporates a sensible anionic complexing ability; however, it lacks stability at a low pH scale. Biochar fibers will give the benefit of their massive space and plethoric uses on the surface to support a metal chemical compound. Herein, wet spinning technology was used to load La3+ onto sodium alginate fiber, and to convert La3+ into La2O3 through carbonization. The La2O3-modified biochar (La-BC) fiber was characterized by SEM, XRD and XPS, etc. An adsorption experiment proved that La-BC showed an excellent adsorption capacity for chromates, and its saturation adsorption capacity was about 104.9 mg/g. The information suggested that the adsorption was in step with both the Langmuir and Freundlich models, following pseudo-second-order surface assimilation mechanics, which showed that the Cr (VI) adsorption was characterized by single-phase and polyphase adsorption, mainly chemical adsorption. The thermodynamic parameters proved that the adsorption process was spontaneous and endothermic. The mechanistic investigation revealed that the mechanism of the adsorption of Cr (VI) by La-BC may include electrostatic interaction, ligand exchange, or complexation. Moreover, the co-existing anions and regeneration experiments proved that the La-BC is recyclable and has good prospects in the field of chrome-containing wastewater removal.
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Husien, Sh, A. Labena, E. F. El-Belely, Hamada M. Mahmoud, and Asmaa S. Hamouda. "Absorption of hexavalent chromium by green micro algae Chlorella sorokiniana: live planktonic cells." Water Practice and Technology 14, no. 3 (May 13, 2019): 515–29. http://dx.doi.org/10.2166/wpt.2019.034.
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Abstract Hexavalent chromium Cr (VI) is a toxic heavy metal that discharged by many industries into the water streams. It is the most toxic form of chromium compound, which causes significant damage to receiving ecosystems. A microalgal species, Chlorella sp., was used as a biosorbent material to remove Cr (VI) from Cr-contaminated effluents. Furthermore, different variables: pH, temperature, contact time, Cr (VI) concentration and algal dose, were optimized in order to determine the optimum conditions that achieve the highest removal efficiency. The optimization process was achieved through two steps: one factor at a time (OFAT) experiments followed by 25 general full factorial. Moreover, molecular identification was performed using 18S rRNA in order to demonstrate the species of Chlorella, and it was identified as Chlorella sorokiniana. The highest chromium removal efficiency of 99.6793% was achieved at 100 ppm Cr (VI) after three days' contact time. Chlorophyll ‘a’ estimation as a growth indicator stated that Chlorella sorokiniana can tolerate 100 ppm Cr (VI) for three days' exposure. The results suggested that Chlorella sorokiniana is a good biosorbent material and it distinguished by its high ability to uptake Cr (VI) from solutions.
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Husain, Nazim, and Riaz Mahmood. "Hexavalent chromium induces reactive oxygen species and impairs the antioxidant power of human erythrocytes and lymphocytes: Decreased metal reducing and free radical quenching ability of the cells." Toxicology and Industrial Health 33, no. 8 (May 15, 2017): 623–35. http://dx.doi.org/10.1177/0748233717703892.
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The toxicity of hexavalent chromium [Cr(VI)] in biological systems is thought to be closely associated with the generation of free radicals and reactive oxygen species. These species are produced when Cr(VI) is reduced to its trivalent form in the cell. This process results in oxidative stress due to an imbalance between the detoxifying ability of the cell and the production of free radicals. We have studied the effect of potassium dichromate (K2Cr2O7), a [Cr(VI)] compound, on the antioxidant power of human erythrocytes and lymphocytes under in vitro conditions. Incubation of erythrocytes and lymphocytes with different concentrations of K2Cr2O7 resulted in a marked dose-dependent decrease in reduced glutathione and an increase in oxidized glutathione and reactive oxygen species levels. The antioxidant power of the cells was decreased, as determined by metal reducing and free radical quenching assays. These results show that [Cr(VI)] upregulates the generation of reactive oxygen species and, as a consequence, the cellular antioxidant defences are compromised. The resulting oxidative stress may contribute to Cr(VI)-induced cellular damage.
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Khomko, Natalia. "ASSESSMENT OF THE IMPACT OF THE PAPER ENTERPRISE ON THE ENVIRONMENT." Environmental Problems 5, no. 4 (2020): 185–90. http://dx.doi.org/10.23939/ep2020.04.185.
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Pulp and paper enterprises are of great importance for sustainable economic and environmental development of certain regions and the economy of Ukraine. Man uses many natural resources during the lifetime, creating a burden on nature. As the world's population increases, this load increases, leading to a shortage of resources and deterioration in the environment. The main activity of Kokhavynska Paper Mill PJSC is the production of sanitary products for the domestic market and export. Rational use of secondary raw materials helps to cut the use of forest resources and reduce the amount of waste paper utilized in landfills. 15291.76 t of pollutants from the sources of the enterprise emissions enter the air each year. A total of 9 standardized and 3 non-standardized substances (greenhouse gases) are released into the atmosphere, namely nitrogen oxides, carbon monoxide, nitrogen (1) oxide (N 2 O) (greenhouse gas), carbon dioxide (greenhouse gas), methane (greenhouse gas), iron and its compounds, manganese and its compounds, hexavalent chromium (expressed in terms of chromium trioxide), gaseous fluorides, hydrogen sulfide, saturated hydrocarbons C12- C19. There is no excess of the established maximum concentration limits at all emission sources at this enterprise. To assess the impact of the enterprise on soils, the content of heavy metals Zn, Cr (VI), Co, Cu, Pb, Mn, and Fe at the border of the sanitary protection zone of the enterprise was determined and the maximum multi plicity of the excess of MPC of heavy metals was calculated. The content of heavy metals in the selected soil samples was determined using a spectrophotometer atomic absorption C-115-M1. Evaluation of soils for heavy metals showed that the soils at the border of the sanitary protection zone of the enterprise are contaminated with heavy metals. The maximum multiplicity of the excess of the MPC of heavy metals in the soil is 1.04 times for lead; 0.43 times for zinc; 0.37 times for chromium; 0.93 times for copper; 1.85 times for manganese; 0.35 times for cobalt. Maximum concentrations of heavy metals exceed their background content: 1.6 times for lead; 1.8 times for zinc; 1.16 times for chromium; 0.77 times for copper; 3.9 times for manganese; 9.7 times for iron; 1.2 times for cobalt.
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Leombruni, Alberto, Federica Morlacchi, Linda Collina, Daniel Leigh, and Mike Mueller. "Full-scale application of ELS® microemulsion Technology for the Treatment of an Aquifer Contaminated with perchloroethylene and trichloroethylene via Ehnanced Reductive Dechlorination." Acque Sotterranee - Italian Journal of Groundwater, March 30, 2020. http://dx.doi.org/10.7343/as-2020-434.
Full textAbstract:
Mixed plumes of chlorinated organics and oxidized metals are a common contaminant at many sites. The oxidized metals can be mediated by the establishment of moderately reducing conditions. The chlorinated organics have been demonstrated to be degradable by specific dechlorinating microrganisms in anaerobic environment such as Dehalococcoides sp. Enhanced biological dechlorination requires the presence of an effective electron donor to provide molecular hydrogen (H2) to completely degrade chlorinated ethenes. Distribution of the electron donor results in the biologically mediated establishment of highly reducing conditions in the treatment zone. This process also results in the reduction and precipitation of the oxidized metals via sulphate-reducing conditions. Peroxychem LLC has developed an innovative electron donor, ELS® Microemulsion Reagent (ELS) for in situ treatment of chlorinated organics and metals. This substrate has been successfully applied at numerous sites to address a variety of contaminants. ELS® is an organic electron donor composed of an easily fermentable organic substrate based on lecithin, and designed to enhance in situ anaerobic bioremediation aquifers contaminated by organochlorine compounds and heavy metals such as hexavalent chromium Cr[VI]. The product is easy to mix, dilute and inject into the subsurface. Once in the groundwater, indigenous microorganisms utilize ELS to rapidly generate highly reducing conditions, favoring biotic dechlorination reactions and the reduction of oxidized metals such as Cr[VI]. This innovative technology was successfully applied to a former manufacturing site in the center of Italy, where groundwater was historically contaminated with Tetrachloroethylene (PCE > 5.5 milligrams per Liter; mg/L), Trichloroethylene (TCE > 2 mg/L), 1,2-Dichloroethene (1,2-DCE > 1 mg/L) and, to a lesser extent, Vinyl Chloride (VC) and 1,2-Dichloropropane (DP). A pump-and-treat system (P&T) installed in the source was active as a source containment measure and to speed up the overall groundwater remediation. However, there was concern that the pumping could affect the ELS treatment effectiveness because of the increased groundwater flow velocity and the potential for removal of the injected bioremediation substrate. To mitigate this potential some wells were switched off the flow rates of others was adjusted to ensure compatibility with the planned product injection. In particular, an upstream low-flow-rate pump and treat system was maintained over the ELS® treatment period, primarily to delay the fast-downstream diffusion of the amendments in the aquifer, thus enhancing the source treatment. Following the calibration of the P&T system, approximately 4,900 kg of ELS® concentration was injected under high pressure at 51 locations into the source area. In about 12 months from injection of ELS® Microemulsion into the groundwater in the main source area, concentrations of PCE, TCE and the recognized catabolites, such as DCE and VC, rapidly reduced, compared to the pre-treatment concentrations, until they reached the statutory national limits (CSC D.lgs 152/06) in the main monitoring piezometers of the area, also highlighting the establishment of clear and enhanced biotic reducing conditions. No rebound effects have been observed in the next three years of monitoring.