Jia Yongfeng, Xu Liying, Fang Zhen, Demopoulos George P
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
Environ Sci Technol. 2006 May 15;40(10):3248-53. doi: 10.1021/es051872+.
X-ray diffraction and Raman spectroscopy were used in this study to characterize arsenate phases in the arsenate-ferrihydrite sorption system. Evidence has been obtained for surface precipitation of ferric arsenate on synthetic ferrihydrite at acidic pH (3-5) underthe following experimental conditions: sorption density of As/Fe approximately 0.125-0.49 and arsenic equilibrium concentration of <0.02-440 mg/L. Surface precipitation occurred under apparently undersaturated (in the bulk solution phase) conditions, and probably involved initial uptake of arsenate by surface complexation followed by transition to ferric arsenate formation on the surface as indicated by XRD analysis. At basic pH (i.e., pH 8), however, no ferric arsenate was observed in arsenate-ferrihydrite samples at a sorption density of As/Fe approximately 0.125-0.30 and an arsenic equilibrium concentration of 2.0-1100 mg/ L. At pH 8, arsenate is sorbed on ferrihydrite predominantly via surface adsorption, and the XRD patterns resemble basically that of ferrihydrite.
本研究采用X射线衍射和拉曼光谱对砷酸盐-水铁矿吸附体系中的砷酸盐相进行表征。在以下实验条件下，已获得酸性pH值（3 - 5）时合成水铁矿上砷酸铁表面沉淀的证据：As/Fe吸附密度约为0.125 - 0.49，砷平衡浓度<0.02 - 440 mg/L。表面沉淀在明显不饱和（在本体溶液相中）的条件下发生，可能涉及砷酸盐首先通过表面络合作用被吸附，随后如XRD分析所示，在表面转变为砷酸铁的形成。然而，在碱性pH值（即pH 8）时，在As/Fe吸附密度约为0.125 - 0.30且砷平衡浓度为2.0 - 1100 mg/L的砷酸盐-水铁矿样品中未观察到砷酸铁。在pH 8时，砷酸盐主要通过表面吸附作用吸附在水铁矿上，XRD图谱基本类似于水铁矿的图谱。
