Weiss Associates, 5801 Christie Ave., Suite 600, Emeryville, CA 94608, USA.
Chemosphere. 2010 Feb;78(8):1028-35. doi: 10.1016/j.chemosphere.2009.11.034. Epub 2010 Jan 13.
Drinking-water treatment residual (WTR) have been proposed as a low-cost alternative sorbent for arsenic (As) - contaminated aquatic and soil systems. However, limited information exists regarding the effect of solution chemistry on As sorption by WTR. A batch incubation study was carried out to investigate the effect of solution pH (3-9) on As(V) sorption by Al- and Fe-based WTR as a function of solid: solution ratio (SSR) and initial As concentration. The effect of competing ligands (phosphate-P(V) and sulfate), and complexing metal (calcium) on As(V) sorption envelopes at the optimum SSR (200gL(-1)) was also evaluated. At 200gL(-1) SSR, maximum As(V) sorption ( approximately 100%) exhibited by the Fe-WTR was limited at the pH range of 3-7, whereas, the Al-WTR demonstrated approximately 100% As(V) sorption in the entire pH range. The negative pH effect on As(V) sorption became more pronounced with increasing initial As concentrations and decreasing SSR. Sorption of As(V) by surfaces of both WTR decreased in the presence of P(V), exhibiting strong pH dependence. Only for the Fe-WTR, increased dissolved iron concentrations at pH>7 supported a Fe-hydroxide reductive dissolution mechanism to account for the enhanced As sorption at alkaline pH. Addition of sulfate did not influence As(V) sorption by both WTR. A cooperative effect of calcium on As(V) sorption was observed at alkaline pH due to the formation of a calcium-arsenate phase. The constant capacitance model provided reasonable fits to the sorption envelope data for both single ion and binary ion (As and P) systems, but it was unable to explain the enhanced As sorption by the Fe-WTR at pH>7.
饮用水处理残留（WTR）已被提议作为一种低成本的替代吸附剂，用于处理受砷（As）污染的水和土壤系统。然而，关于溶液化学对 WTR 吸附砷的影响的信息有限。进行了一项批式孵育研究，以调查溶液 pH（3-9）对 Al 和 Fe 基 WTR 吸附 As(V)的影响，其函数为固液比（SSR）和初始 As 浓度。还评估了竞争配体（磷酸盐-P(V)和硫酸盐）和络合金属（钙）对最佳 SSR（200gL(-1)）下 As(V)吸附包络线的影响。在 200gL(-1)SSR 下，Fe-WTR 表现出的最大 As(V)吸附（约 100%）在 pH 范围为 3-7 时受到限制，而 Al-WTR 在整个 pH 范围内表现出约 100%的 As(V)吸附。随着初始 As 浓度的增加和 SSR 的降低，负 pH 对 As(V)吸附的影响变得更加明显。在存在 P(V)的情况下，两种 WTR 的表面对 As(V)的吸附减少，表现出强烈的 pH 依赖性。仅对于 Fe-WTR，在 pH>7 时增加的溶解铁浓度支持 Fe-氢氧化物还原溶解机制，以解释在碱性 pH 下增强的 As 吸附。硫酸盐的添加对两种 WTR 的 As(V)吸附没有影响。在碱性 pH 下，由于形成钙-砷酸盐相，观察到钙对 As(V)吸附的协同效应。恒电容模型对单离子和二元离子（As 和 P）系统的吸附包络线数据提供了合理的拟合，但无法解释在 pH>7 时 Fe-WTR 增强的 As 吸附。
