Experimental study on the remediation of chromium contaminated groundwater with PRB media

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.