含铁黏土矿物与电子传递体强化生物还原固定地下水中Cr(Ⅵ)的过程和机理分析

Enhancing process and mechanism of Cr(Ⅵ)bioreduction and fixation in groundwater by Fe(Ⅲ)-bearing clay mineral and electron shuttle

为了提高微生物还原固定Cr(Ⅵ)的速率,实现地下水Cr(Ⅵ)污染物的快速有效去除,采用添加黏土矿物与电子传递体的方法,考察了含铁黏土矿物NAu-2和电子传递体AQDS单独/共存条件下对希瓦氏菌Shewanella oneidensis MR-1还原固定地下水中不同浓度Cr(Ⅵ)(0.1~2.0 mmol·L^−1)的影响。结果表明:单独添加NAu-2对不同浓度Cr(Ⅵ)生物还原过程均无促进作用;单独添加AQDS对不同浓度Cr(Ⅵ)(0.2~2.0 mmol·L^−1)生物还原过程均产生强化作用,强化系数达到1.33~3.90;同时添加NAu-2和AQDS时,不同浓度Cr(Ⅵ)(0.2~2.0 mmol·L^−1)生物还原时的强化作用均得到明显提升,强化系数达到2.02~10.49。此外,对比NAu-2和AQDS共存时对MR-1还原不同浓度Cr(Ⅵ)的协同促进作用,发现在低浓度Cr(Ⅵ)(0.1~0.5 mmol·L^−1)体系中未产生协同作用(协同系数<1.0),中、高浓度Cr(Ⅵ)(0.8~2.0 mmol·L^−1)体系中产生了明显的协同作用(SF>1.0),且在Cr(Ⅵ)浓度为1.2 mmol·L^−1时,协同效果最为明显(协同系数为2.98),说明NAu-2和AQDS对中、高浓度Cr(Ⅵ)(0.8~2.0 mmol·L^−1)还原过程的协同促进作用差异较大。通过对不同Cr(Ⅵ)浓度条件下NAu-2、AQDS与MR-1共存的复杂体系中Cr(Ⅵ)迁移转化过程和机理进行研究,可为实际Cr(Ⅵ)污染场地修复提供新的修复思路及参考数据。

In order to improve the efficiency of Cr(Ⅵ)bioreduction and fixation and to achieve rapid and effective removal of Cr(Ⅵ)pollutants in groundwater,the method of adding clay minerals and electron shuttle was adopted.The effects of iron-bearing clay mineral NAu-2 alone,electron shuttle AQDS alone and their both on the bioreduction and fixation of Cr(Ⅵ)with different concentrations of 0.1~2.0 mmol·L^−1 in groundwater by metal-reducing bacteria Shewanella oneidensis MR-1 were explored.The results showed that NAu-2 alone addition have no effect on the promotion of Cr(Ⅵ)bioreduction,while AQDS alone addition could promote the bioreduction of Cr(Ⅵ)with different concentrations of 0.1~2.0 mmol·L^−1,and the enhancement factor reached 1.33~3.90.With simultaneous addition of NAu-2 and AQDS,the enhancement of bioreduction was significantly elevated for Cr(Ⅵ)with different concentrations,and the enhancement factor reached 2.02~10.49.In addition,compared with the synergistic effects for bioreduction of Cr(Ⅵ)with different concentrations by MR-1 under the coexistence of AQDS and NAu-2,synergistic effect didn’t occur at low Cr(Ⅵ)contents of 0.1~0.5 mmol·L^−1 with the synergistic factor lower than 1.0;while a significant synergistic effect occurred at medium and high Cr(Ⅵ)contenta of 0.8~2.0 mmol·L^−1 with the synergistic factor higher than 1.0,and at the concentration of 1.2 mmol·L^−1,the most significant synergistic effect occurred with the synergistic factor=2.98.This indicated that there were big differences in synergistic effect for the bioreduction of Cr(Ⅵ)among the medium and high concentrations.This study provides new remediation thought and reference data for the Cr(Ⅵ)contaminated sites through investigating the process and mechanism of Cr(Ⅵ)migration and transformation in the NAu-2,AQDS and MR-1 coexisting complex system under different concentrations of Cr(Ⅵ).