Rongrong Ding,Guannan Zhou,Chuanshu He,Wenqiang Li,Yiran Wang,Xiaocheng Liu,Bo Lai,Yang Mu
The process of FeS oxygenation is intrinsically associated with the fate of contaminants in heterogeneous aquifers, whereas the impacts of common heavy metals are poorly understood. In this study, we found that the introduction of Co 2+ and Ni 2+ (Me 2+ ) resulted in a remarkable 3–10-fold enhancement in the degradation of bisphenol A , which stemmed from the significant increase in the generation of •OH and SO 4 •− . The improved production of reactive species was primarily attributed to the accelerated regeneration of Fe(II); the introduction of Me 2+ manipulated the electronic structure of FeS and consequently facilitated electron transfer from S 2- to Fe(III), as revealed by experimental evidence and density functional theory calculations. This study represents the first endeavor to underscore the influence of coexisting heavy metals on contaminant degradation during FeS oxygenation.
Dong Cheng,Haoran Ding,Yuansen Tan,Dezhi Yang,Ying Pan,Wenjuan Liao,Feng He
Oxidizing potential of FeS for organic contaminants degradation due to hydroxyl radicals (•OH) production has been recently documented, but the oxidizing efficiency was limited. Here, we revealed that low-molecular-weight organic acids (LMWOAs) can immensely enhance phenol degradation during FeS oxygenation due to increased utilization efficiency of FeS electron for •OH production. Upon oxygenation of 0.5 g/L FeS, phenol degradation boosted from 7.1% without LMWOAs to 91.5%, 84.6% and 95.0% with the addition of 1 mM oxalate, citrate and EDTA, respectively. Electron utilization efficiency of Fe(II) for •OH production dramatically rose from 0.3% with FeS alone to respective 2.0%, 2.5% and 2.7% in the LMWOAs systems. An increase in oxalate concentrations benefited •OH formation and phenol degradation. Coexisting oxalate led to an additional •OH production pathway from Fe(II)-oxalate oxidation , which expanded the O 2 reduction to H 2 O 2 from a two- to one-electron transfer process. Meanwhile, electron transfer from FeS to dissolved Fe(III)-oxalate promoted the redox cycling of Fe(III)/Fe(II), thus supplying the Fe(II) oxidation for •OH production. Moreover, the presence of oxalate decreased the crystallinity and particles size of lepidocrocite generated from FeS oxidation. Consequently, this study shed lights on the LMWOAs-enhanced contaminant degradation in either natural or engineered FeS oxidation systems.
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