Cr(Ⅵ)污染地下水修复的PRB填料实验研究

Experimental Study on the Remediation of Chromium Contaminated Groundwater with PRB Media

Fe0与Cr(Ⅵ)发生表层反应使Fe0-渗透反应墙(PRB)利用率极低且易板结、堵塞.针对Fe0利用率低,易板结、堵塞问题,研究了不同高分子材料包裹铁粉对受污染地下水中Cr(Ⅵ)的去除影响;实验结果表明,海藻酸钠(SA)作为包裹材料效果最好.FEI电镜扫描及EDX能谱分析结果表明,SA跟2价金属阳离子Ca2+交联形成孔隙结构,不仅为零价铁的附着提供了大量的吸附点位,还可使Cr(Ⅵ)进入到内部与铁粉反应.考察了SA包裹零价铸铁粉(SAC)和包裹还原铁粉(SAR)对Cr(Ⅵ)的去除影响;实验结果表明,SAC除铬性能是SAR的2倍.SAC填料工艺参数优化后,符合一级反应动力学;采用SAC填料进行动态实验,反应完全后铬/铁比高达32.25 mg.g-1,且填料仍然保持较高的渗透系数(2.38 cm.s-1);对SAC填料进行成本分析发现,SAC填料具有明显的价格优势,相比零价铸铁粉混砂填料节约成本76.56%.采用SAC填料治理Cr(Ⅵ)污染地下水是可行的.

Due to the surface reaction between zero-valent iron and Cr（Ⅵ）, iron cannot be fully utilized in the Fe0-Permeable Reactive Barrier（PRB）, and the PRB is prone to compaction and blockage. In order to resolve these problems, iron powder coated with different polymer was tested in the treatment of chromium-polluted groundwater. Experimental results demonstrated that sodium alginate （SA） was the best package materials. According to analysis with FEI and EDX, pore structures were created by cross-linking of SA with Ca2＋, in which a lot of attaching points exist, and through which Cr（Ⅵ） could react with interior iron powder. SA coating cast iron （SAC） and reduced iron （SAR） were tested in the treatment of chromium-polluted groundwater individually; the results showed that the removal efficiency of Cr（Ⅵ） by SAC was double that by SAR. After optimization of technology parameters of SAC, the Cr（Ⅵ） removal process follows the pseudo first-order kinetics. Based on dynamic experiments with SAC, Cr（Ⅵ）/Fe0 was up to 32.25 mg·g-1 and the PRB maintained high permeability coefficient （2.38 cm·s-1） after complete reaction. Compared with cast iron mixed with sand, SAC has the distinct advantage of price, and the media cost can be reduced by 76.56%. Using SAC as the PRB media is feasible in the remediation of chromium contaminated groundwater.