Liu Guo J, Zhang Xiang R, McWilliams L, Talley J W, Neal C R
Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Mar;43(4):430-6. doi: 10.1080/10934520701795749.
As(V) adsorption onto a commercially available TiO2 (Degussa P25) in NaCl or NaClO4 at various concentrations (0.001-0.1 M) was investigated. The effect of natural organic matter (NOM) on As(V) removal through the adsorption by TiO2 was also examined. In either electrolyte, As(V) adsorption onto TiO2 increased with the increase of ionic strength under alkaline conditions (pH 7.0-11.0). Under acidic conditions (pH 4.0-6.0), the adsorption of As(V) onto TiO2 was insensitive to ionic strength in NaClO4 electrolyte but decreased with increasing ionic strength in NaCl electrolyte. The presence of 2-15 mg/L NOM as C significantly decreased the fraction of As(V) adsorbed onto TiO2 at pH 6.0 regardless of the initial As(V) concentration (1-15 microM). The measurement of zeta potential of TiO2 with and without As(V) suggests that the presence of As(V) can shift the point of zero charge (pH(pzc)) of TiO2 to a lower pH value. The overall data presented in this study suggest that As(V) can form both inner-sphere and outer-sphere complexes on TiO2 surface, and NOM is an important factor controlling As(V) adsorption onto TiO2.
研究了在不同浓度（0.001 - 0.1 M）的NaCl或NaClO₄溶液中，五价砷（As(V)）在市售二氧化钛（Degussa P25）上的吸附情况。还考察了天然有机物（NOM）对通过二氧化钛吸附去除As(V)的影响。在碱性条件（pH 7.0 - 11.0）下，在任何一种电解质中，As(V)在二氧化钛上的吸附都随离子强度的增加而增加。在酸性条件（pH 4.0 - 6.0）下，在NaClO₄电解质中，As(V)在二氧化钛上的吸附对离子强度不敏感，但在NaCl电解质中，其吸附随离子强度的增加而降低。无论初始As(V)浓度（1 - 15 μM）如何，2 - 15 mg/L以碳计的NOM的存在都会显著降低在pH 6.0时吸附在二氧化钛上的As(V)的比例。对有和没有As(V)时二氧化钛的zeta电位测量表明As(V)的存在可使二氧化钛的零电荷点（pH(pzc)）向较低的pH值移动。本研究给出的数据表明As(V)可在二氧化钛表面形成内球络合物和外球络合物，且NOM是控制As(V)在二氧化钛上吸附的一个重要因素。
