零价铁去除废水中的汞

Removal of Hg in Wastewater by Zero-Valent Iron

研究了零价铁(zero-valent iron,ZVI)去除废水中Hg2+的动力学特征及其影响因素,初步探讨了ZVI与Hg2+的作用机制.结果表明,ZVI对废水中Hg2+的最佳去除条件:Hg2+的初始浓度为0.10 mg·L-1、pH为5、ZVI用量为0.050 g、温度为25℃,获得Hg2+的去除率为94.5%.ZVI对废水中Hg2+有一个快速的去除过程,可用准一级反应动力学方程描述,速率常数为0.010 min-1.ZVI去除废水中Hg2+的机制主要是氧化还原反应、铁氧化物和氢氧化物的吸附和共沉淀作用,ZVI表面钝化是降低Hg2+去除率的主要原因,其钝化成分主要是FeOOH和Fe2O3-Fe3O4.胡敏酸可与ZVI还原产生的Fe2+、Fe3+结合形成Fe-HA复合物,增加可溶性铁的比例,缓解ZVI的钝化,对细铁氧化物和铁氢氧化物胶体具有稳定作用,增强对废水中Hg2+的吸附作用.

Kinetic characteristics of mercury ion （Hg2＋ ） removal in wastewater by zero-valent iron （ZVI） and the influence factors were studied, and the reaction mechanism of ZVI and Hg2＋ was preliminarily discussed. The removal rate of Hg2＋ in wastewater reached 94. 5% under the optimal removal conditions, i. e. the initial concentration of Hg2＋ was 0. 10 mg. L-1 , the initial pH was 5, the ZVI dosage was 0. 050 g, and the temperature was 25℃. There was a rapid removal process for Hg2＋ in wastewater by ZVI, which could be described by the pseudo first-order reaction kinetic equation, and the rate constant was 0. 010 min -1 The removal mechanism of Hg2 ＋ may mainly be attributed to the oxidation-reduction of ZVI, and the adsorption and flocculation precipitation of iron oxides and hydroxides. However, the passivation of FeOOH and Fe2O3-Fe3O4 on ZVI surface may be the main reason for the decrease in the removal rate of Hg2 ＋ . Humic acid （HA） in wastewater could not only form Fe-HA complex with the Fe2 ＋ and Fe3 ＋ produced by ZVI reduction, which increased the ratio of soluble iron and relieved ZVI passivation, but also stabilize fine iron oxide and iron hydroxide colloid, and thus enhance the adsorption of Hg2 ＋ in wastewater.