Department of Energy, Environmental and Chemical Engineering, and ‡Department of Earth and Planetary Sciences, Washington University in St. Louis , St. Louis, Missouri 63130, United States.
Environ Sci Technol. 2016 Dec 20;50(24):13502-13510. doi: 10.1021/acs.est.6b03637. Epub 2016 Dec 6.
The potential for new U.S. regulations for Cr(VI) in drinking water have spurred strong interests in improving technologies for Cr(VI) removal. This study examined iron electrocoagulation for Cr(VI) removal at conditions directly relevant to drinking water treatment. Cr(VI) is chemically reduced to less soluble Cr(III) species by the Fe(II) produced from an iron anode, and XANES spectra indicate that the Cr is entirely Cr(III) in solid-phases produced in electrocoagulation. The dynamics of Cr(VI) removal in electrocoagulation at pH 6 and pH 8 at both oxic and anoxic conditions can be described by a new model that incorporates Fe(II) release from the anode and heterogeneous and homogeneous reduction of Cr(VI) by Fe(II). Heterogeneous Cr(VI) reduction by adsorbed Fe(II) was critical to interpreting Cr(VI) removal at pH 6, and the Fe- and Cr-containing EC product was found to catalyze the redox reaction. Dissolved oxygen (DO) did not observably inhibit Cr(VI) removal because Fe(II) reacts with DO more slowly than it does with Cr(VI), and Cr(VI) removal was faster at higher pH. Even in the presence of common groundwater solutes, iron electrocoagulation lowered Cr(VI) concentrations to levels well below California's 10 μg/L.
美国可能对饮用水中的六价铬(Cr(VI))进行新的规定，这促使人们强烈关注改进去除 Cr(VI)的技术。本研究考察了铁电化学混凝法在直接与饮用水处理相关的条件下去除 Cr(VI)的效果。通过铁阳极产生的 Fe(II)，Cr(VI)被化学还原为更难溶的 Cr(III)物种，XANES 光谱表明，在电混凝中生成的固体相中 Cr 完全为 Cr(III)。在 pH 值为 6 和 8 以及有氧和无氧条件下，电混凝中 Cr(VI)的去除动力学可以用一个新模型来描述，该模型包含了阳极释放的 Fe(II)以及 Fe(II)对 Cr(VI)的异质和均相还原。吸附态 Fe(II)对 Cr(VI)的异质还原对于解释 pH 值为 6 时的 Cr(VI)去除至关重要，并且发现含有 Fe 和 Cr 的 EC 产物能够催化该氧化还原反应。溶解氧 (DO) 没有明显抑制 Cr(VI)的去除，因为 Fe(II)与 DO 的反应速度比与 Cr(VI)的反应速度慢，并且在较高 pH 值下 Cr(VI)的去除速度更快。即使在常见的地下水溶质存在下，铁电化学混凝也能将 Cr(VI)浓度降低到远低于加利福尼亚州 10μg/L 的水平。
