Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions.
Adsorption of arsenic with struvite and hydroxylapatite in phosphate-bearing solutions.
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DOI：
10.1016/j.chemosphere.2015.12.061
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发表时间：
2016-03
期刊：
影响因子：
8.8
通讯作者：
A. Rouff;N. Ma;Adam B Kustka
中科院分区：
文献类型：
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作者：
A. Rouff;N. Ma;Adam B Kustka
当考虑碱性含磷废水中的污染物迁移性时，砷在中性 pH 值以上的吸附是相关的，并且在存在磷酸盐矿物质的情况下可能是可行的。在 pH 8-11 条件下，从含有 2.7–0.125 mM 磷酸盐和 0.05 mM As(III) 或 As(V) 的溶液中评估鸟粪石 (MgNH4PO4·6H2O, MAP) 和羟基磷灰石 (Ca5(PO4)3OH, HAP) 上的砷吸附。 7 天内，As(III) 从溶液中的去除量极小，但 As(V) 的去除量随着 pH 值的增加而增加，并且在 MAP 存在的情况下去除率高于 HAP，在 pH 11 的 MAP 溶液中去除率最高为 74%。对从 pH 10-11 溶液中回收的固体进行 X 射线吸收精细结构光谱 (XAFS) 分析揭示了 MAP 和 HAP 吸附 As(V) 的不同机制。砷通过形成 Mg-O-As 键与 MAP 形成单齿单核表面配合物，但并入 HAP 的近表面，形成约翰铝石状 (Ca5(AsO4)3OH) 结构。在 pH 10-11 下使用放射性 33 P 进行的实验表明，HAP 表面的 P 交换速度更快，这可以促进更容易的 As 掺入。与 MAP 形成的表面吸附物相比，HAP 中近表面掺入的 As 可能不太容易再活化。总体而言，在磷酸盐存在的情况下，MAP 和 HAP 都可以在高 pH 值下吸附 As。这与砷在与磷酸盐矿物相接触的碱性污染水中的命运有关。
Arsenic sorption at above neutral pH is relevant when considering contaminant mobility in alkaline, phosphorus-bearing wastewaters, and may be viable in the presence phosphate minerals. Arsenic adsorption on struvite (MgNH4PO4·6H2O, MAP) and hydroxylapatite (Ca5(PO4)3OH, HAP) was evaluated at pH 8–11 from solutions with 2.7–0.125 mM phosphate and 0.05 mM As(III) or As(V). Over 7 d, As(III) removal from solution was minimal, but As(V) removal increased with pH, and was higher in the presence of MAP compared to HAP with a maximum of 74% removal in pH 11 MAP-bearing solutions. X-ray absorption fine structure spectroscopy (XAFS) analysis of solids recovered from pH 10–11 solutions revealed different mechanisms of As(V) sorption with MAP and HAP. Arsenic forms monodentate mononuclear surface complexes with MAP through the formation of a Mg–O–As bond, but is incorporated at the near-surface of HAP forming a johnbaumite-like (Ca5(AsO4)3OH) structure. Experiments using radioactive33P at pH 10–11 revealed faster exchange of P at the HAP surface, which could promote more facile As incorporation. Near-surface incorporated As in HAP may be less susceptible to remobilization compared to surface adsorbates formed with MAP. Overall, both MAP and HAP may sorb As at high pH in the presence of phosphate. This is relevant to the fate of As in alkaline contaminated waters in contact with phosphate mineral phases.