胞外聚合物对MR-1还原含镉水铁矿过程中相转化特征和镉迁移的影响  

The impact of extracellular polymeric substances on the phase transformation characteristics and cadmium migration during the reduction of cadmiumloaded ferrihydrite by MR-1

作　　者：董灼 郝鑫瑞 王衡 黄雅婧 汪小尧 易筱筠 DONG Zhuo;HAO Xinrui;WANG Heng;HUANG Yajing;WANG Xiaoyao;YI Xiaoyun(School of Environment and Energy,South China University of Technology,Guangzhou 510006;PowerChina Huadong Engineering Corporation Limited,Hangzhou 311122;Huadong Eco-Environmental Engineering Research Institute of Zhejiang Province,Hangzhou 311122;GH Water Supply(Holdings)Limited,Guangzhou 510006)

机构地区：[1]华南理工大学环境与能源学院,广州510006 [2]中国电建集团华东勘测设计研究院有限公司,杭州311122 [3]浙江省华东生态环境工程研究院,杭州311122 [4]广东粤港供水有限公司,广州510006

出　　处：《环境科学学报》2025年第3期416-426,共11页Acta Scientiae Circumstantiae

摘　　要：异化铁还原菌(DIRB)在土壤环境中广泛存在,因介导铁氧化物的相转变过程而对其负载重金属的迁移产生影响.胞外聚合物(Extracellular polymers EPS)是异化铁还原菌在生长过程中分泌出的生物活性物质,构成细胞周围的微环境,对次生矿物的形成以及重金属的迁移有重要影响.本文探讨了EPS对含镉水铁矿异化铁还原过程(希瓦氏菌Shewanella oneidensis MR-1介导)中相转化和Cd迁移的影响.结果表明,EPS能促进水铁矿的还原溶解,在无磷培养基中,EPS可以诱导蓝铁矿的生成,且该过程受pH值的影响.pH值在6.5的条件下,EPS可以促进水铁矿相转变为蓝铁矿,pH值在7.2的条件下,次生矿物均为未定形矿物.MR-1还原水铁矿的过程中,矿物中的镉先释放至溶液中,再被生成的次生矿物固定.其中形成的次生矿物与溶液中Cd通过形成Cd−O键,加强了对Cd的固定.通过形态提取发现,在pH值为6.5的条件下,矿物中的Cd主要以铁氧化物表面结合态形式存在,显著降低了Cd的迁移性.而对于pH值在7.2的条件下,固相中存在更多可交换态Cd,虽然降低了Cd的迁移性,但存在一定的释放风险.本研究为理解土壤环境中Fe、P和Cd等元素的地球化学循环过程提供了新的视角.Dissimilatory iron-reducing bacteria(DIRB)are widespread in the soil environment,which affect the migration of heavy metals by mediating the phase transition process of iron oxides.Extracellular polymers(EPS)are bioactive substances secreted by dissimilatory iron-reducing bacteria during the growth process,which constitute the microenvironment around the cells.It has an important influence on the formation of secondary minerals and the migration of heavy metals.In this paper,the effects of EPS on the phase transformation and Cd migration in the dissimilatory iron reduction process of cadmium-containing ferrihydrite(mediated by Shewanella oneidensis MR-1)were discussed.The results showed that EPS could promote the reduction and dissolution of ferrihydrite.In a phosphorus-free medium,EPS can induce the formation of vivianite,and the process was affected by pH value.Under the condition of pH 6.5,EPS could promote the transformation of ferrihydrite phase into vivianite,and under the condition of pH 7.2.The secondary minerals are all amorphous minerals.During the reduction of ferrihydrite by MR-1,cadmium in the minerals is first released into the solution and then immobilized by the generated secondary minerals.The formed secondary minerals and Cd in the solution strengthen the fixation of Cd by forming Cd−O bonds.through morphological extraction,it was found that under the condition of pH 6.5,Cd in minerals mainly existed in the form of iron oxide surface binding state,which significantly reduced the mobility of Cd.Under the condition of pH 7.2,there were more exchangeable Cd in the solid phase,which reduced the mobility of Cd,but there was a certain risk of release.This study provides a new perspective for understanding the geochemical cycle processes of Fe,P and Cd in soil environment.

关 键 词：胞外聚合物 异化铁还原 水铁矿 镉 蓝铁矿 

分 类 号：X131.3[环境科学与工程—环境科学]