Distinct roles of pH and organic ligands in the dissolution of goethite by cysteine  

作　　者：Ji Li Chenlu Shi Wenbin Zeng Yaru Wang Zebin Hong Yibing Ma Liping Fang 

机构地区：[1]Faculty of Material Sciences and Chemistry,China University of Geosciences,Wuhan 430074,China [2]Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management,Institute of Eco-environmental and Soil Sciences,Guangdong Academy of Sciences,Guangzhou 510650,China [3]National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China,Guangzhou 520650,China [4]Macao Environmental Research Institute,Macao University of Science and Technology,Taipa 999078,Machao,China

出　　处：《Journal of Environmental Sciences》2022年第3期260-268,共9页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos.42077301,21876161);the National Key Research and Development Project of China (No.2020YFC1808702);Guangdong Academy of Sciences’Project (No.2019GDASYL-0102006).

摘　　要：Electron shuttles such cysteine play an important role in Fe cycle and its availability in soils,while the roles of pH and organic ligands in this process are poorly understood.Herein,the reductive dissolution process of goethite by cysteine were explored in the presence of organic ligands.Our results showed that cysteine exhibited a strong reactivity towards goethite-a typical iron minerals in paddy soils with a rate constant ranging from 0.01 to0.1 hr^(-1).However,a large portion of Fe(Ⅱ) appeared to be "structural species" retained on the surface.The decline of pH was favorable to generate more Fe(Ⅱ) ions and enhancing tendency of Fe(Ⅱ) release to solution.The decline of generation of Fe(Ⅱ) by increasing pH was likely to be caused by a lower redox potential and the nature of cysteine pH-dependent adsorption towards goethite.Interestingly,the co-existence of oxalate and citrate ligands also enhanced the rate constant of Fe(Ⅱ) release from 0.09 to 0.15 hr-1;nevertheless,they negligibly affected the overall generation of Fe(Ⅱ) in opposition to the pH effect.Further spectroscopic evidence demonstrated that two molecules of cysteine could form disulfide bonds(S-S) to generate cystine through oxidative dehydration,and subsequently,inducing electron transfer from cysteine to the structural Fe(Ⅲ) on goethite;meanwhile,those organic ligands act as Fe(Ⅱ) "strippers".The findings of this work provide new insights into the understanding of the different roles of pH and organic ligands on the generation and release of Fe induced by electron shuttles in soils.

关 键 词：Electron transfer Reductive dissolution Iron cycling Organic ligands 

分 类 号：X13[环境科学与工程—环境科学]