黄铁矿强化零价铁去除Orange Ⅱ研究

The Roles of Pyrite on Enhancing Orange Ⅱ Removal by ZVI

零价铁(ZVI)具有价廉易得、安全无毒、还原性较强等特点,能用于去除环境中众多污染物.但其反应活性会随着介质pH值的升高、表面钝化产物的形成而降低,而且反应介质的pH值适用范围较窄.将价廉的黄铁矿(pyrite)与零价铁混合,用于处理合成废水中的偶氮染料Orange Ⅱ,研究了介质的pH值、pyrite/ZVI质量比对Orange Ⅱ去除率的影响,并对协同反应机理进行了初步探讨.结果表明:在相同实验条件下,pyrite协同ZVI对Orange Ⅱ的去除率远高于相同剂量pyrite和ZVI分别对Orange Ⅱ去除率的加和.当初始pH=7.0、pyrite/ZVI质量比为1～4时,与Orange Ⅱ反应的表观速率常数是相应零价铁的9.36～28.0倍.此外,在初始pH值为5.0～10.0时,pyrite/ZVI对Orange Ⅱ均显示了良好的去除效果.机理研究表明:在零价铁去除Orange Ⅱ时,pyrite的存在导致了反应介质pH值的降低,并能将ZVI表面钝化产物转化为高还原活性Fe(Ⅱ),从而显示出显著的强化作用.

Zero valent iron(ZVI)has been widely applied to the removal of diversified contaminants in the environment due to its lower cost, nontoxicity and high reductivity. However, the reactivity of ZVI will decrease quickly due to the pH rise of reaction medium and surface passivation along with the reaction and narrow working pH. In this work, a combination of pyrite with zero valent iron(ZVI)was used to enhance the removal of azo dye Orange II, the effects of pH and the mass ratio of pyrite/ZVI on the removal of Orange II were investigated, and the synergetic reaction mechanism was also studied. The results show that under the same reaction condition, the removal efficiency of Orange II by pyrite/ZVI is much higher than the sum of that by pyrite and ZVI respectively with the same addition. At initial pH 7.0, the rate constant( k obs )of pyrite/ZVI with the mass ratio ranging from 1.0 to 4.0 is enhanced by 9.36~28.0 folds compared with that of ZVI alone. Moreover, at the pH ranging from 5.0~10.0, pyrite/ZVI also shows better efficiency for the removal of Orange II. The mechanism study reveals that the presence of pyrite could decrease the pH of reaction medium, and prompt the transformation of passive products on ZVI surface to highly reactive Fe(II).