改性生物炭负载nZVI对土壤Cr(VI)的修复差异研究

Effects of the remediation of Cr(VI) in soil by nanoscale zero-valent iron(nZVI) with modified biochar

考察了生物炭(BC)、酸洗生物炭(HCl-BC)和纳米零价铁负载生物炭(n ZVI-HCl-BC)对土壤中Cr(VI)还原和总Cr形态转化的影响.结果表明,生物炭对Cr(VI)还原率随土壤含水率的升高而显著提高.在较高土壤含水率(70%)条件下,各生物炭对Cr(VI)的最高还原率排序为:HCl-BC(97.26%)>n ZVI-HCl-BC(88.36%)>BC(87.61%).在不同Cr(VI)污染水平下(150、300、600和900 mg·kg^(-1)),HCl-BC对土壤中Cr(VI)的还原率最高.随Cr(VI)含量升高,BC和HCl-BC对Cr(VI)的还原率呈降低趋势,而n ZVI-HCl-BC对Cr(VI)的还原率为先降低后升高.形态分析表明,生物炭在不同程度上增加了土壤中Cr残渣态的比例:n ZVI-HCl-BC(11.58%)>HCl-BC(9.53%)>BC(1.42%),表明生物炭对土壤Cr起到稳定作用.综上,改性生物炭显著促进Cr(VI)还原及总Cr向残渣态转化,表明其具有修复Cr污染土壤的潜力.

In this study,raw biochar（BC）,and two kinds of modified biochars（HCl-BC and n ZVI-HCl-BC）were assessed in terms of immobilisation efficiency of Cr（VI）and Cr species transformation in Cr-contaminated soil.The results showed that the immobilisation efficiency of three kinds of biochars increased significantly with the growing moisture content.Under a high moisture content（70%）,the maximum immobilisation efficiency of Cr（VI）in the biochars were sequenced as follow：HCl-BC（97.26%）n ZVI-HCl-BC（88.36%）BC（87.61%）.The immobilisation efficiency of Cr（VI）was the highest in HCl-BC with different Cr（VI）pollution levels（150,300,600 and 900 mg·kg^（-1））.With the content of Cr increasing,the immobilisation efficiency of Cr（VI）rose in BC and HCl-BC.While it decreased and then increased in n ZVI-HCl-BC.Results of the Cr species analysis showed that residual fraction increased to different degrees after biochar treatment.The increase of residual fraction in percentage were ranked as follow：n ZVI-HCl-BC（11.58%）HCl-BC（9.53%）BC（1.42%）,indicating that biochars promoted stabilization of Cr in soil.The modified biochars enhance the immobilisation of Cr（VI）and convert available Cr to residual effectively.Consequently,the modified biochars can be used as an amendment for Crcontaminated soil.