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Abstract: Infrared absorption spectra of xCaO(1− x − z)SiO2 zP2O5 glass system with a CaO:SiO2 molar ratio 3:2 and with 0.0⩽ z ⩽0.5 are examined in the region 4000–400cm−1, together with XRD. Deconvoluted spectra were analyzed to determine the position and relative amounts of the IR bands responsible for the different silicate and phosphate units. Bonding mechanism such as Si–O–Si, Si–O–Ca, P–O–P, O–P–O, P13;O− etc. is suggested for random arrangement. A variation in the band positions and the relative amounts of various bonds with P2O5 is also shown. The result indicates that P5+ occupies the network position and forms the linkage Si–O–P in the glass for higher amount of P2O5. This Si–O–P bond may lead to the formation of five and six coordinated silicon in the glass matrix. The bands related to bending mode of H2O molecules and the stretching mode of P–O–H groups forming hydrogen bonding are shown to result in several bands in the 1521–1700 and 1758–3059cm−1 range, respectively. X-ray diffraction pattern of the base samples, within the detection limit, shows that all are homogeneous glasses and on optical inspection they did not show any evidence of phase separation. [Copyright &y& Elsevier]

Selenium (Se) nanoparticles are often synthesized by anaerobes. However, anaerobic bacteria cannot be directly applied for bioremediation of contaminated top soil which is generally aerobic. In this study, a selenite-reducing bacterium, Citrobacter freundii Y9, demonstrated high selenite reducing power and produced elemental nano-selenium nanoparticles (nano-Se 0 ) under both aerobic and anaerobic conditions. The biogenic nano-Se 0 converted 45.8–57.1% and 39.1–48.6% of elemental mercury (Hg 0 ) in the contaminated soil to insoluble mercuric selenide (HgSe) under anaerobic and aerobic conditions, respectively. Addition of sodium dodecyl sulfonate enhanced Hg 0 remediation, probably owing to the release of intracellular nano-Se 0 from the bacterial cells for Hg fixation. The reaction product after remediation was identified as non-reactive HgSe that was formed by amalgamation of nano-Se 0 and Hg 0 . Biosynthesis of nano-Se 0 both aerobically and anaerobically therefore provides a versatile and cost-effective remediation approach for Hg 0 -contaminated surface and subsurface soils, where the redox potential often changes dramatically. [ABSTRACT FROM AUTHOR]

Nitrate and arsenic are common pollutants in groundwater. However, we are still lacking technologies that can remove nitrate and arsenic simultaneously using a single species of microorganism. In the present study, the potential of synchronous removal of nitrate and arsenite from water by a single anaerobic nitrate-reducing Fe(II) oxidizing Citrobacter freundii strain PXL1 was assessed. The strain PXL1 could grow well in arsenite concentration of 2.85–13.65 μM and efficiently oxidize Fe(II), reduce nitrate and remove As(III) from water. Scanning electron microscopy, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy analysis showed that the strain PXL1 produced poorly crystalline Fe(III) oxides. As(III) was removed mainly by adsorption and co-precipitation of the biogenic Fe(III) oxides. The anaerobic nitrate-dependent Fe(II) oxidizing bacteria including C. freundii PXL1 are promising microbes for in situ remediation of nitrate and arsenite contaminated groundwater. [ABSTRACT FROM AUTHOR]