【作者】 武甲；

【导师】 田秀君；

【作者基本信息】 北京交通大学 ， 环境工程， 2010， 硕士

【摘要】 研究了实验室自制的纳米零价铁处理模拟含Cr(Ⅵ)无氧地下水的影响因素、吸附动力学,并结合体系中Fe2+浓度、氧化还原电位、Zeta电位和理论计算得到的pe-pH图对纳米零价铁去除Cr(Ⅵ)的机制进行了探讨。实验结果表明,纳米零价铁对Cr(Ⅵ)的去除率随着初始Cr(Ⅵ)／Fe质量比的升高而降低。当溶液的pH为7.0,初始Cr(Ⅵ)／Fe质量比为0.025、0.050、0.075和0.100时,相应的Cr(Ⅵ)的去除率分别为100.0%、85.6%、72.7%和39.6%。酸性条件更有利于纳米零价铁对Cr(Ⅵ)的去除,当初始Cr(Ⅵ)／Fe质量比为0.100,溶液的pH为3.0、5.0、7.0、9.0和11.0时,体系中Cr(Ⅵ)的去除率分别为73.4%、57.6%、39.6%、44.1%和41.2%。纳米零价铁去除Cr(Ⅵ)的过程符合拟二级动力学方程。当溶液的pH为7.0,初始Cr(Ⅵ)／Fe质量比为0.025时,吸附速率常数(k)最大,为9.76×10-3g·(mg·min)-1。通过Fe-Cr体系形态分布图,Fe(Ⅱ)浓度分析以及反应过程中的氧化还原电位可知,Cr2072-吸附到纳米零价铁表面后被迅速地还原为Cr3+,生成的Cr3+与纳米零价铁表面的FeOOH结合生成Cr-Fe膜。而Cr-Fe膜将阻断电子在纳米零价铁与Cr2072-之间的传输,Cr(Ⅵ)得不到还原,从而纳米零价铁对Cr2072-的去除以吸附为主。应用该纳米零价铁处理实际铬渣,结果表明,应用纳米零价铁处理铬渣萃取液,当萃取液中Cr(Ⅵ)／Fe=0.017时,Cr(Ⅵ)的去除率可达100%；应用纳米零价铁同铬渣直接混合,当纳米零价铁同铬渣的质量比为4%时,铬渣中Cr(Ⅵ)的含量在一天内由16 g·kg-1降至0.01 g·kg-1以下；应用纳米零价铁和水泥处理铬渣,铬渣中的六价铬并不能被有效地去除。更多还原

【Abstract】 Laboratory experiments and theoretical modeling studies were performed to investigate the mechanisms of Cr (Ⅵ) removal from deoxygenated simulated groundwater using nanoscale zero-valent iron, and to evaluate influencing factors and kinetics based on zeta potential, redox potential, ferrous concentrations, and the pe-pH diagram of Fe-Cr-H2O system.Experimental results demonstrate that the removal efficiency of Cr (Ⅵ) decreases with the increasing Cr (VI)/Fe mass ratio. When the Cr (Ⅵ)/nZVI mass ratio is 0.025, 0.050,0.075, and 0.100, the corresponding Cr (Ⅵ) removal rate is 100.0%,85.6%, 72.7% and 39.6%, respectively. The Cr (Ⅵ) removal is favorable at acidic pH with fixed Cr(Ⅵ)/Fe mass ratio of 0.100. When pH is 3.0,5.0,7.0,9.0 and 11.0, the Cr (Ⅵ) removal rate is 73.4%,57.6%,39.6%,44.1%, and 41.2%, accordingly. The Cr(Ⅵ) removal follows the pseudo second-order kinetics. When pH is 7.0 and Cr (Ⅵ)/nZVI mass ratio is 0.025, the rate of Cr (Ⅵ) removal is the highest with the rate constant at 9.76×10-3g·(mg·min)-1.The following conclusion could be inferred by analyzing pe-pH diagram of Fe-Cr-H2O system, redox potential and the concentration of ferrous. The conversion from Cr2O72- to Cr3+ should be instantaneous when Cr2O72- is absorbed on the surface of Fe. The Cr (Ⅵ) was reduced to Cr (Ⅲ), which was subsequently incorporated into the FeOOH shell and formed a Cr-Fe film. The film once formed could further inhibit the electron transfer between Cr2O72- and Fe. Then Cr (Ⅵ) removal was primary controlled by the adsorption process.Deoxygenated COPR extract was treated with nZVI at the mass ratio of Cr (Ⅵ)/nZVI=0.017, and 100% Cr (Ⅵ) was removed; The ZVI could reduce the Cr(Ⅵ) content in COPR from 16 g·kg-1 to less than 0.01 g·kg-1 within 1 d of treatment at nZVI/COPR mass ratio of 4%; the Cr(Ⅵ) in COPR cannot be reduced efficiently with the S/S treatment.更多还原