Department of Earth and Environmental Sciences and Research Institute of Natural Science (RINS), Gyeongsang National University, Jinju 660-701, Republic of Korea.
School of Environmental Science and Engineering, Gwangju Institute of Science and Technology(GIST), Gwangju 500-712, Republic of Korea.
Environ Technol. 2014 Jan-Feb;35(1-4):251-61. doi: 10.1080/09593330.2013.824508.
Arsenite sorption from aqueous solutions was investigated using two-line ferrihydrite at room temperature, as a function of solution pH and arsenite loading. The isotherms, pH envelopes, and kinetics of arsenite sorption were characterized and its mechanism was elucidated via X-ray absorption spectroscopic studies. Arsenite sorption showed only slight pH dependence with a sorption maximum centered around pH 8.0. The Langmuir isotherm is most appropriate for arsenite sorption over the wide range of pH, indicating the homogenous and monolayer sorption of arsenite. The kinetic study demonstrated that arsenite sorption onto two-line ferrihydrite is considerably fast and the equilibrium is achieved within the reaction time of 3 h. X-ray absorption near-edge structure spectroscopy elucidated a slight change in oxidation state of arsenite for the initial concentration of 13.35 mM at pH 4. The extended X-ray absorption fine structure (EXAFS) spectroscopy results indicate that types of surface complexes of arsenite appeared to be very similar to those proposed by the previous studies in that the bidentate binuclear corner-sharing (2C) complex is predominant at all the surface loadings. However, our EXAFS results suggest that regardless ofpH, the mixed complexes of2C and bidentate mononuclear edge-sharing surface complex (2E) as well as the 2C complex are favoured at low and intermediate surface loadings, but only the 2C complex is dominant at high surface loading. Overall, the EXAFS results support the efficient removal of arsenite by the two-line ferrihydrite through the formation of highly stable inner-sphere surface complexes, such as 2C complex.
采用室温下的双线型水铁矿研究了水溶液中砷酸盐的吸附，作为溶液 pH 和砷酸盐负载的函数。通过 X 射线吸收光谱研究，对吸附等温线、pH 包络线和砷酸盐吸附动力学进行了特征描述，并阐明了其机制。砷酸盐的吸附仅表现出轻微的 pH 依赖性，吸附最大值集中在 pH 8.0 左右。Langmuir 等温线最适合在宽 pH 范围内吸附砷酸盐，表明砷酸盐的均匀单层吸附。动力学研究表明，砷酸盐在双线型水铁矿上的吸附相当快，在 3 小时的反应时间内达到平衡。X 射线吸收近边结构光谱阐明了在 pH 4 时初始浓度为 13.35mM 的砷酸盐的氧化态略有变化。扩展 X 射线吸收精细结构（EXAFS）光谱结果表明，砷酸盐的表面络合物类型似乎与先前研究中提出的非常相似，即在所有表面负载下，双齿双核角共享（2C）络合物占主导地位。然而，我们的 EXAFS 结果表明，无论 pH 值如何，在低和中等表面负载下，混合 2C 和双齿单核边缘共享表面络合物（2E）以及 2C 络合物都很有利，但在高表面负载下，只有 2C 络合物占主导地位。总体而言，EXAFS 结果支持通过形成高度稳定的内球表面络合物（如 2C 络合物），由双线型水铁矿有效去除砷酸盐。
