硫酸盐还原菌介导水铁矿相转化特征及其产物对Cr(Ⅵ)固存的影响

Phase transition characteristics of ferrihydrite mediated by sulfate-reducing bacteria and the effect of its products on Cr(Ⅵ)fixation

硫酸盐还原菌(SRB)广泛存在于酸性矿山废水(AMD)污染的土壤中,其介导的铁矿物转化过程及其相转化产物影响着重金属的迁移转化行为.选取土壤中的典型铁氧矿物水铁矿作为研究对象,探究了SRB(Desulfovibrio vulgaris ATCC 7757)介导水铁矿的矿相转化,分析了水铁矿相转化产物对Cr(Ⅵ)的固存能力,揭示了不同相转化阶段产物对六价铬(Cr(Ⅵ))的固存能力及作用机制.结果表明,SRB介导下矿物的相转化路径为水铁矿-马基诺矿-磁铁矿,反应过程的相转化产物对Cr(Ⅵ)的固存能力呈先增加后降低的趋势:反应第5 d水铁矿相转化的产物主要为马基诺矿,此阶段相转化矿物对Cr(Ⅵ)的固存能力达到141.06 mg·g^(-1),固存方式以还原作用为主;14 d时相转化矿物主要以马基诺矿和磁铁矿复合形式存在,复合产物对Cr(Ⅵ)的固存能力仅为79.59 mg·g^(-1),其对Cr(Ⅵ)的固存方式包括还原和吸附作用,还原和吸附对Cr(Ⅵ)固存的贡献占比分别为78.82%和21.17%.由此可见,水铁矿相转化产物组成的差异是导致其对Cr(Ⅵ)固存能力及作用机制变化的关键因素.

Sulfate-reducing bacteria are widespread in soil contaminated with acid mine drainage,and their mediated transformation of iron minerals and phase transformation products influence the migration and transformation behavior of heavy metals.Mineral phase transformation of ferrihydrite mediated by SRB(Desulfovibrio vulgaris ATCC 7757)was explored,and the retention of Cr(Ⅵ)by ferrihydrite phase transformation products was analyzed.The results revealed the retention ability and mechanism of Cr(Ⅵ)in different phase transformation products.It was found that the pathway of SRB-mediated phase transformation was ferrihydrite-mackinawite-magnetite,and the retention of Cr(Ⅵ)was initially increased and then decreased:On the 5th day of the reaction,the main transformation product was mackinawite.The retention of Cr(Ⅵ)by the transformation minerals reached 141.06 mg·g^(-1).The phase-transformed minerals mainly exist in the composite form of mackinawite and magnetite after 14 days,and the storage capacity of the composite product for Cr(VI)is only 79.59 mg·g^(-1).The retention of Cr(Ⅵ)by the composite product involves reduction and adsorption.Thus,the contribution of reduction and adsorption to Cr(Ⅵ)retention was 78.82%and 21.17%,respectively.In summary,the difference in phase transformation products of ferrihydrite is the key factor leading to the change of Cr(Ⅵ)retention ability and mechanism.The research can provide a theoretical basis to study the behavior of biogeochemistry and the development of microbial remediation of heavy metal pollution.