A collaborative strategy for enhanced reduction of Cr(Ⅵ) by Fe(0) in the presence of oxalate under sunlight:Performance and mechanism  

作　　者：Qi Zhou Yang Li Heng Yang Yun Gao 

机构地区：[1]College of Chemistry and Chemical Engineering,Anhui University,Hefei 230601,China [2]Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control,School of Environmental Science and Engineering,Institute of Environmental Health and Pollution Control,Guangdong University of Technology,Guangzhou 510006,China [3]Chengdu Integrated Testing Center of Rocks and Ores,Sichuan Geology and Mineral Exploration and Development Bureau,Chengdu 610081,China [4]Anhui Electric Power Construction Second Engineering Co.Ltd.,China Energy Construction Group,Hefei 230000,China

出　　处：《Journal of Environmental Sciences》2020年第4期385-394,共10页环境科学学报（英文版）

基　　金：supported by Project funded by China Postdoctoral Science Foundation(No.2017M611533)

摘　　要：Nanometer-size zero-valent iron(NZVI)is an efficient reducing agent,but its surface is easily passivated with an oxide layer,leading to reaction inefficiency.In our study,oxalate(OA)was introduced into this heterogeneous system of NZVI,which could form ferrioxalate complexes with the NZVI surface-bound Fe3+and dissolved Fe3+in the solution.Photolysis of ferrioxalate complexes can facilitate the generation of Fe2+from Fe3+and CO2·-radical,both species have strong reduction capacity.Hence,a"photo-oxalate-Fe(0)"system through sunlight induction was established,which not only prohibited the formation of a surface passivation layer,but also displayed a synergetic mechanism of ferrioxalate photolysis to enhance reduction,exhibiting remarkably higher degradation activity(several times faster)toward the model pollutant Cr(Ⅵ)than the mechanism with NZVI alone.Factor tests suggested that both NZVI dosage and OA content markedly affected the reduction rate.Low pH was beneficial to the reduction efficiency.Moreover,recyclability experiment showed that the reduction rate decreased from 0.21706 to 0.03977 min-1 after three cycles of reuse due to the NZVI losing reaction activity generally,but the system still maintained considerable reduction capacity.Finally,a mechanism was revealed whereby NZVI would transform to Fe oxides after the exhaustion of its reductive power,and the photolysis of ferrioxalate to promote the cycling of iron species played the predominant role in providing extra reduction ability.These features confirm that introduction of OA into Cr(Ⅵ)reduction by NZVI through sunlight induction is advantageous and promising.

关 键 词：Nanometer-size zero-valent iron OXALATE Sun irradiation Photolysis of ferrioxalate Cycling of surface iron Synergetic mechanism 

分 类 号：X703[环境科学与工程—环境工程]