研究了纳米氧化铁吸附Cr（Ⅵ）反应特征及其对柠檬酸还原Cr（Ⅵ）的催化作用，并探讨了该作用的土壤环境意义。结果表明，纳米氧化铁对Cr （Ⅵ）的吸附能力较强；提高pH和离子强度对吸附过程有抑制作用；吸附速率可区分为快、慢阶段，5 min内吸附量可占总吸附量80％以上。纳米氧化铁可加速柠檬酸还原Cr（Ⅵ），且还原过程主要发生在溶液相，部分机理是柠檬酸与Fe（Ⅲ）相互作用生成的Fe（Ⅱ）将Cr（Ⅵ）还原。同时，体系pH越低，上述催化作用越明显。此外，砖红壤?柠檬酸体系Cr（Ⅵ）还原转化为Cr（Ⅲ）的比例较低，但加入纳米氧化铁后则明显提高，说明后者将有助于消除土壤环境中Cr（Ⅵ）污染风险。
Adsorption of Cr(Ⅵ) by nano iron oxide and the surface?catalyzed Cr(Ⅵ) reduction by citric acid were examined together with their significance in soil environments. As the results showed, nano iron oxide had high capacity for Cr(Ⅵ) adsorption, which was unfavorable when pH and ionic strength were increased. The Cr(Ⅵ) adsorption was characterized by an initial fast phase followed by a slow phase, evidenced by the adsorbed Cr(Ⅵ) accounting for 80%of the total amount within 5 min. Cr(Ⅵ) reduction by citric acid was accelerated in the presence of nano iron oxide, especially at low pH. Fe (Ⅱ) generated from the interaction between citric acid and aqueous Fe(Ⅲ) partly contributed to the catalytic effect. Moreover, Cr(Ⅵ) reduction in the oxisol?citric acid system was relatively low, and was promoted with the addition of nano iron oxide. The result suggest that nano iron oxides in soil environments are helpful to alleviate the risk posed by Cr(Ⅵ) .
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