Arsenic Speciation in Newberyite (MgHPO4路3H2O) Determined by Synchrotron X-ray Absorption and Electron Paramagnetic Resonance Spectroscopies: Implications for the Fate of Arsenic

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• 作者：Jinru Lin ; Ning Chen ; Yuanming Pan
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：June 17, 2014
• 年：2014
• 卷：48
• 期：12
• 页码：6938-6946
• 全文大小：380K
• 年卷期：v.48,no.12(June 17, 2014)
• ISSN：1520-5851

文摘

Newberyite (MgHPO₄路3H₂O), a biomineral and common constituent in guano deposits, is an important decomposition product of struvite that is an increasingly popular green fertilizer recovered from wastewaters. Two samples of newberyite containing 1099 and 25 ppm As have been obtained at pH = 6.4, by using Na₂HAsO₄路7H₂O and NaAsO₂ as the dopant, respectively (i.e., Synthesis 1 and Synthesis 2). Synchrotron arsenic K-edge X-ray absorption spectroscopic data of newberyite from Synthesis 1 show that As⁵⁺ is dominant and has a local environment typical of the arsenate species. Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated newberyite from Synthesis 1 contain two arsenic-associated oxyradicals: [AsO₃]^{2鈥?/sup> and [AsO₂]2鈥?/sup> derived from As5+ and As3+, respectively, at the P site. Quantitative analyses of powder EPR spectra allow determinations of the As5+ and As3+ contents in newberyite from Synthesis 1 and Synthesis 2. Elevated concentrations of arsenic also occur in natural newberyite transformed from struvite in guano deposits and record the accumulation of this metalloid in the food chain. Therefore, newberyite, which sequesters As during crystallization and retains this metalloid during the transformation from struvite, can attenuate arsenic contamination from green fertilizers in moderately acidic soils. Also, the capacity for accommodating both As5+ and As3+ in the crystal lattice coupled with simple chemistry and easy crystallization at ambient conditions makes newberyite an attractive material for remediation of arsenic contamination in aqueous environments.}