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| Arsenite immobilization capacity and stability of iron-loaded biochar under an iron-reducing environment |
| Received:May 15, 2020 |
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| KeyWord:iron-loaded biochar;redox property;arsenite;iron reduction;microbial extracellular electron transfer |
| Author Name | Affiliation | E-mail | | ZHU Xiao-dong | School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China | | | YANG Min | Nanjing Institute of Environmental Science, Ministry of Ecology and Environment, Nanjing 210042, China
State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Nanjing 210042, China | | | WU Song | State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China | | | SHI Wei-lin | School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China | weilin-shi@163.com | | ZHOU Dong-mei | State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, China | dmzhou@nju.edu.cn |
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| Abstract: |
| In an aerobic environment, iron-loaded biochar has the capacity to adsorb arsenic, which makes it a promising material for tackling arsenic pollution in water and soil environments. In an anaerobic environment, redox-active biochar accelerated the microbial extracellular electron transfer for iron-oxide reduction, which led to the dissolution and release of arsenite[As(Ⅲ)]. However, the capacity and stability of iron-loaded biochar for immobilization of As(Ⅲ)under a reducing environment were not evaluated. Herein, the effect of iron-loaded biochar on Fe(Ⅲ)reduction and As(Ⅲ)release or immobilization during the microbial reduction of arsenite-bearing ferrihydrite[As(Ⅲ) -FH] was studied. Additionally, the stability of immobilized As(Ⅲ)and the loaded iron-oxides were evaluated under an iron-reducing environment created by Shewanella oneidensis MR-1. Magnetite-loaded biochar was synthesized by pyrolysis of iron pre-sorbed sawdust char at 400~700℃, and these iron-loaded biochars had As(Ⅲ)adsorption capacities of 0.94~1.63 mg·g-1. The iron-loaded biochar facilitated the reduction of Fe(Ⅲ)and release of As(Ⅲ)from 0 to 400 h, and the higher preparation temperature of iron-loaded biochar facilitated the faster rates of Fe(Ⅲ)reduction and As(Ⅲ)release. By prolonging the bio-reduction time to 646 h, the Fe2+ ions were precipitated to form vivianite and siderite and the presence of iron-loaded biochar promoted the immobilization of As(Ⅲ) (0.211~0.676 mg·g-1)compared to the control. On the other hand, the reduction of iron-loaded biochar by S. oneidensis MR-1 led to the transformation of magnetite to vivianite and siderite, but the As(Ⅲ)immobilization capacity was enhanced to 2.16~2.29 mg·g-1. In contrast to the aerobic environment, an iron-reducing environment led to an improvement of As(Ⅲ)immobilization capacity within 342 h, but it decreased when the incubation time was further increased to 646 h. The evaluation method will help in screening of materials suitable for the control of arsenic contamination in paddy soils. |
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