黄原胶对微米铁修复地下水氯代脂肪烃污染的影响机制

Effect of xanthan gum on remediation of chlorinated aliphatic hydrocarbons-contaminated groundwater by microscale zero-valent iron particles

利用微米零价铁材料构建地下水原位反应带是一项具有广泛应用前景的地下水修复技术。目前,该技术应用的主要瓶颈是铁颗粒在地下迁移过程中的重力沉降和活性降低问题。选取3种不同粒径的市售微米零价铁,通过批次试验筛选出对地下水中典型氯代脂肪烃(CAHs)去除效能最优的微米铁。用黄原胶对筛选出的微米铁进行稳定化改性,依托去除动力学实验,对比改性前后反应体系还原脱氯量/吸附量、pH、Eh、Fe^(2+)质量浓度的动态变化过程。实验结果表明,黄原胶的稳定化改性虽抑制了微米铁对CAHs的吸附,但其缓冲了反应体系的pH的变化,抑制了微米铁的表面钝化,从而促进了对CAHs的还原过程,整体上提高了微米铁对CAHs的去除效能。

Using microscale zero-valent iron(mZVI)as the reducing agent to build in-situ reaction zone is a promising approach for groundwater remediation.At present,the main bottleneck of this approach is gravity sedimentation and activity reduction of mZVI particles during underground transport.In the present work,batch experiments are conducted with three types of mZVI with different particle sizes to identify the one with the best removal efficiency for typical chlorinated aliphatic hydrocarbons(CAHs)in groundwater.For the target mZVI,xanthan gum(XG)is used to prepare stabilized XG-coated mZVI.The dynamic change process of CAHs reductive dechlorination/adsorption capacity and pH,Eh,Fe^(2+)concentration within the reaction system before and after mZVI stabilization is compared based on removal kinetics tests.The results indicate that the stabilized modification by XG inhibits the adsorption of CAHs onto mZVI particle surface.However,XG can buffer the change of pH in solution so as to inhibit iron surface passivation,thus promoting CAHs reduction,resulting in improvement of CAHs removal efficiency as a whole.