Cheng Hefa, Hu Yuanan, Luo Jian, Xu Bin, Zhao Jianfu
State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, PR China.
J Hazard Mater. 2009 Jun 15;165(1-3):13-26. doi: 10.1016/j.jhazmat.2008.10.070. Epub 2008 Oct 25.
Acid mine drainage (AMD) is often accompanied with elevated concentrations of arsenic, in the forms of arsenite, As(III), and/or arsenate, As(V), due to the high affinity of arsenic for sulfide mineral ores. This review summarizes the major geochemical processes controlling the release, speciation, fate, and distribution of inorganic arsenic in mine drainage and natural systems. Arsenic speciation depends highly on redox potential and pH of the solution, and arsenite can be oxidized to the less toxic arsenate form. Homogeneous oxidation of arsenite occurs rather slowly while its heterogeneous oxidation on mineral surfaces can greatly enhance the reaction rates. Little evidence suggests that precipitation reaction limits the concentrations of arsenic in natural water, while co-precipitation may lead to rapid arsenic removal when large amount of iron hydroxides precipitate out of the aqueous phase upon neutralization of the mine drainage. Both arsenate and arsenite adsorb on common metal oxides and clay minerals through formation of inner-sphere and/or outer-sphere complexes, controlling arsenic concentration in natural water bodies. Arsenite adsorbs less strongly than arsenate in the typical pH range of natural water and is more mobile. Part of the adsorbed arsenic species can be exchanged by common anions (e.g., PO(4)(3-) and SO(4)(2-)), especially phosphate, which leads to their re-mobilization. Understanding the geochemistry of arsenic is helpful for predicting its mobility and fate in AMD and natural systems, and for designing of cost-effective remediation/treatment strategies to reduce the occurrence and risk of arsenic contamination.
由于砷对硫化矿物矿石具有高亲和力，酸性矿山排水（AMD）中常伴有高浓度的砷，其形态为亚砷酸盐（As(III)）和/或砷酸盐（As(V)）。本综述总结了控制矿山排水和自然系统中无机砷的释放、形态、归宿和分布的主要地球化学过程。砷的形态高度依赖于溶液的氧化还原电位和pH值，亚砷酸盐可被氧化为毒性较小的砷酸盐形式。亚砷酸盐的均相氧化相当缓慢，而其在矿物表面的非均相氧化可大大提高反应速率。几乎没有证据表明沉淀反应会限制天然水中砷的浓度，而当中和矿山排水时大量氢氧化铁从水相中沉淀出来时，共沉淀可能会导致砷的快速去除。砷酸盐和亚砷酸盐都通过形成内球和/或外球络合物吸附在常见的金属氧化物和粘土矿物上，从而控制天然水体中的砷浓度。在天然水的典型pH范围内，亚砷酸盐的吸附强度低于砷酸盐，且其流动性更强。部分吸附的砷物种可被常见阴离子（如PO(4)(3-)和SO(4)(2-)），尤其是磷酸盐交换，这会导致它们重新迁移。了解砷的地球化学有助于预测其在AMD和自然系统中的迁移性和归宿，以及设计具有成本效益的修复/处理策略，以减少砷污染的发生和风险。
