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Arsenic Removal (arsenic + removal)
Selected AbstractsOptimization of an Iron Intercalated Montmorillonite Preparation for the Removal of Arsenic at Low Concentrations,ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 1 2007D. Masih Abstract A series of iron intercalated montmorillonites (Fe-Monts) were prepared using (i) ion exchange of native sodium and calcium ions with iron ions, (ii) base hydrolysis of inserted iron ions in montmorillonite suspension, and (iii) insertion of pre-hydrolyzed iron colloid in montmorillonite. The materials were characterized by X-ray diffraction and gas adsorption-desorption techniques. The basal d(001)-spacing and BET specific surface area increased after the intercalation of iron species in montmorillonite. Local iron structure studied by X-ray absorption fine structure (XAFS) spectroscopy showed an unsaturation of the Fe···Fe coordination number (N 2.5) of the intercalated iron species as compared to the bulk iron oxyhydroxides (N 6). The Fe-Monts were employed for arsenic removal from aqueous solutions at low concentration (0.2,16 mg/L). Among the Fe-Monts, the one prepared by the hydrolysis of inserted iron ions, was the best in performance. The saturation adsorption amount of the optimized iron-montmorillonite was 4 and 28 times higher for the removal of arsenite and arsenate, respectively, as compared to bulk iron oxyhydroxide (goethite). Compared with bulk iron oxyhydroxide, the Fe-Monts were superior for arsenate uptake and comparable for arsenite. In addition, arsenite adsorbed on the Fe-Monts was found to be oxidized to arsenate based on XAFS spectroscopy. [source] Growth of three bacteria in arsenic solution and their application for arsenic removal from wastewaterJOURNAL OF BASIC MICROBIOLOGY, Issue 6 2008P. Mondal Abstract The present paper compares the arsenic removal capacities of three bacterial strains namely, Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 form wastewater (simulated acid mine drainage) containing arsenic (As(III):As(V)::1:1), Fe, Mn, Cu and Zn in the concentration of 15 mg/l, 10 mg/l, 2 mg/l, 5 mg/l and 10 mg/l respectively, in bulk liquid phase. Growth patterns of these bacteria in presence of arsenic in solution as well as under starvation have also been investigated as the acid mine drainage normally does not contain organic carbon and also contains high arsenic. At the nutrient broth concentration of 1.25 g/l and in presence of 15 mg/l arsenic sufficient growth of these strains have been observed. However, growth of Ralstonia eutropha MTCC 2487 has been found slightly more than Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374. Arsenic removal capacities of Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 from simulated acid mine drainage are ,67%, 60% and 61% respectively. It has also been observed that arsenic concentration of 15 mg/l prolongs the stationary phase of these strains. pH and temperature for the above studies have been maintained at 7.1 ± 0.1 and 29 ± 1 °C, respectively. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Systematic engineering for efficient arsenic removalBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Article first published online: 20 JAN 2010 No abstract is available for this article. [source] Enhanced arsenic accumulation by engineered yeast cells expressing Arabidopsis thaliana phytochelatin synthase,BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2008Shailendra Singh Abstract Phytochelatins (PCs) are naturally occurring peptides with high-binding capabilities for a wide range of heavy metals including arsenic (As). PCs are enzymatically synthesized by phytochelatin synthases and contain a (,-Glu-Cys)n moiety terminated by a Gly residue that makes them relatively proteolysis resistant. In this study, PCs were introduced by expressing Arabidopsis thaliana Phytochelatin Synthase (AtPCS) in the yeast Saccharomyces cerevisiae for enhanced As accumulation and removal. PCs production in yeast resulted in six times higher As accumulation as compared to the control strain under a wide range of As concentrations. For the high-arsenic concentration, PCs production led to a substantial decrease in levels of PC precursors such as glutathione (GSH) and ,-glutamyl cysteine (,-EC). The levels of As(III) accumulation were found to be similar between AtPCS-expressing wild type strain and AtPCS-expressing acr3, strain lacking the arsenic efflux system, suggesting that the arsenic uptake may become limiting. This is further supported by the roughly 1:3 stoichiometric ratio between arsenic and PC2 (n,=,2) level (comparing with a theoretical value of 1:2), indicating an excess availability of PCs inside the cells. However, at lower As(III) concentration, PC production became limiting and an additive effect on arsenic accumulation was observed for strain lacking the efflux system. More importantly, even resting cells expressing AtPCS pre-cultured in Zn2+ enriched media showed PCs production and two times higher arsenic removal than the control strain. These results open up the possibility of using cells expressing AtPCS as an inexpensive sorbent for the removal of toxic arsenic. Biotechnol. Bioeng. 2008;99: 333,340. © 2007 Wiley Periodicals, Inc. [source] | ||||||||||