Arsenic immobilization by calcium arsenate formation
Arsenic immobilization by calcium arsenate formation
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DOI：
10.1021/es980998m
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发表时间：
1999-11-01
影响因子：
11.4
通讯作者：
Brown, PW
中科院分区：
文献类型：
--
作者：
Bothe, JV;Brown, PW
向含砷废物中添加石灰已被证明有利于减少溶解的砷的流动性，可能是通过形成低溶解度的砷酸钙。然而，砷酸钙形成在降低溶解砷浓度方面的作用尚未得到很好的确定。因此，平衡具有不同Ca/As比率的浆料，并且建立在升高的pH值下形成的化合物。与文献相反，未观察到Ca-3（AsO 4）（2），而是Ca-4（OH）（2）（AsO 4）（2）。4 H（2）O、Ca-5（阿索（4））（3）OH（砷酸盐磷灰石）和Ca-3（AsO 4）（2）。形成32/3 H（2）O。砷的平衡浓度在高pH值时最低。与Ca-4（OH）（2）（AsO 4）（2）平衡时的最低砷浓度。4 H（2）O和Ca-5（阿索（4））（3）OH分别为0.01和0.5 mg/L。由于砷酸盐磷灰石在近中性pH值下稳定，因此测定了其与Ca-5（PO 4）（3）OH的固溶度。这样做是为了评估磷酸根离子对砷酸根离子可能释放的影响。虽然平衡砷酸根离子浓度随pH值降低而增加，但在环境条件下不会发生固溶体形成。相反，砷酸盐磷灰石以Ca-5（PO 4）（3）OH为代价形成。
Lime additions to arsenic-containing wastes have been proven to be beneficial in reducing the mobility of dissolved arsenic, presumably through the formation of low-solubility calcium arsenates. However, the role of calcium arsenate formation in reducing the concentrations of dissolved arsenic has not been well established. Therefore, slurries with varying Ca/As ratios were equilibrated, and the compounds that formed at elevated pH values were established. In contrast to the literature, Ca-3(AsO4)(2) was not observed, rather Ca-4(OH)(2)(AsO4)(2). 4H(2)O, Ca-5(ASO(4))(3)OH (arsenate apatite), and Ca-3(AsO4)(2). 32/3H(2)O had formed. The equilibrium concentrations of arsenic were found to be the lowest at high pH. Minimum arsenic concentrations in equilibrium with Ca-4(OH)(2)(AsO4)(2). 4H(2)O and Ca-5(ASO(4))(3)OH were 0.01 and 0.5 mg/L, respectively. Because arsenate apatite is stable to near-neutral pH values, the extent of its solid solubility with Ca-5(PO4)(3)OH was determined. This was done to assess the effects of phosphate ion on the possible release of arsenate ion. Although equilibrium arsenate ion concentrations increased with decreasing pH, solid solution formation did not occur under ambient conditions. Rather, the arsenate apatite formed at the expense of Ca-5(PO4)(3)OH.