Arsenic Incorporation in Synthetic Struvite (NH4MgPO4路6H2O): A Synchrotron XAS and Single-Crystal EPR Study

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• 作者：Jinru Lin ; Ning Chen ; Yuanming Pan
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：November 19, 2013
• 年：2013
• 卷：47
• 期：22
• 页码：12728-12735
• 全文大小：372K
• 年卷期：v.47,no.22(November 19, 2013)
• ISSN：1520-5851

文摘

Struvite, a common biomineral and increasingly important fertilizer recovered from wastewater treatment plants, is capable of sequestering a wide range of heavy metals and metalloids, including arsenic. Inductively coupled plasma mass spectrometric (ICPMS) analyses and microbeam synchrotron X-ray fluororescence (渭-SXRF) mapping show that struvite formed under ambient conditions contains up to 547 卤 15 ppm As and that the uptake of As is controlled by pH. Synchrotron As K-edge XANES spectra measured at 20 K show that As⁵⁺ is the predominant oxidation state in struvite, irrespective of Na₂HAsO₄路7H₂O or NaAsO₂ as the source for As. Modeling of As K-edge EXAFS data suggest that local structural distortion associated with the substitution of As⁵⁺ for P⁵⁺ in struvite reaches up to 3.75 脜. Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated struvite disclose five [AsO₃]^{2鈥?/sup> radicals and one [AsO₄]2鈥?/sup> radical. These arsenic-centered oxyradicals are all readily attributed to form from diamagnetic [AsO₄]3鈥?/sup> precursors during irradiation, providing further support for exclusive incorporation and local structural expansion beyond the first shell of As5+ at the P site in struvite.}