title: pH-dependent degradation of p-nitrophenol by sulfidated nanoscale zerovalent iron under aerobic or anoxic conditions.
abstract: Sulfidated nanoscale zerovalent iron (S-NZVI) is attracting considerable attention due to its easy production and high reactivity to pollutants. We studied the reactivity of optimized S-NZVI (Fe/S molar ratio 6.9), comparing with pristine nanoscale zerovalent iron (NZVI), at various pH solutions (6.77-9.11) towards p-nitrophenol (PNP) under aerobic and anoxic conditions. Studies showed that the optimized extent of sulfidation could utterly enhance PNP degradation compared to NZVI. Batch experiments indicated that in anoxic S-NZVI systems the degradation rate constant increased with increasing pH up to 7.60, and then declined. However, in aerobic S-NZVI, and in anoxic or aerobic NZVI systems, it decreased as pH increased. It was manifested that anoxic S-NZVI systems preferred to weaker alkaline solutions, whereas aerobic S-NZVI systems performed better in acidic solutions. The highest TOC removal efficiency of PNP (17.59%) was achieved in the aerobic S-NZVI system at pH 6.77, revealing that oxygen improved the degradation of PNP by excessive amounts of hydroxyl radicals in slightly acidic conditions, and the TOC removal efficiency was supposed to be further improved in moderate acidic solutions. Acetic acid, a nontoxic ring opening by-product, confirms that the S-NZVI system could be a promising process for industrial wastewater containing sulfide ions.
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Jing
authors: J
authors: Tang
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China. Electronic address: tanglin@hnu.edu.cn.
authors: Lin
authors: L
authors: Tang
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Haopeng
authors: H
authors: Feng
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China. Electronic address: zgming@hnu.edu.cn.
authors: Guangming
authors: G
authors: Zeng
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Haoran
authors: H
authors: Dong
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Chang
authors: C
authors: Zhang
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Binbin
authors: B
authors: Huang
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Yaocheng
authors: Y
authors: Deng
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Jiajia
authors: J
authors: Wang
authors: College of Environmental Science and Engineering, Hunan University, Changsha 410082, China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, China.
authors: Yaoyu
authors: Y
authors: Zhou
keywords: Aerobic conditions; Nanoscale zerovalent iron; Sulfidation; p-Nitrophenol; pH-dependent degradation