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Electron-transfer-dominated non-radical activation of peroxydisulfate for efficient removal of chlorophenol contaminants by one-pot synthesized nitrogen and sulfur codoped mesoporous carbon
Environmental Research ( IF 7.7 ) Pub Date : 2020-11-18 , DOI: 10.1016/j.envres.2020.110496
Juan Yang , Xiaoqian He , Jun Dai , Yumei Chen , Yingjie Li , Xuefeng Hu

Synergistic adsorption and oxidative degradation (via persulfate activation) on metal-free carbonaceous materials are expected to be environmentally friendly and highly efficient approach toward contaminants removal. Herein, nitrogen and sulfur codoped mesoporous carbon (NSDMC) were firstly synthesized via co-carbonization of calcium citrate and thiourea without any templates. NSDMC samples exhibit remarkably enhanced adsorption capacity and oxidative degradation (by activating PDS) for chlorophenols elimination. Increased SBET and introduced N-containing functional groups are beneficial for chlorophenols adsorption, PDS accessibility and successive activation. Doped sulfur species (especially for thiophenic S) can enhance the electron-transport performance of NSDMC, further promoting PDS activation and chlorophenols degradation. It can be ascribed to the synergistic effect of N and S codoping. NSDMC-30 (containing 5.83 at.% nitrogen and 2.15 at.% sulfur, and possessing SBET of 1935.9 m2·g-1) exhibits the optimal adsorption and catalytic oxidation capability for 4-CP removal. Degradation rate constant of NSDMC-30 is 0.125 min-1, which is 3.0 times and 7.8 times higher than nitrogen-doped MC and pristine MC, respectively. Radicals quenching experiments and EPR tests demonstrate that non-radical pathways play dominant role for PDS activation and chlorophenols degradation. Based on the influences of catalyst loading, initial 4-CP concentration, and PDS dosage on degradation kinetics of 4-CP, the pre-adsorption is unveiled to be the critical step determining oxidation rate of chlorophenols. More importantly, the results of in-situ Raman and electrochemical tests show that the surface-confined and activated PDS complex (carbon-PDS*) and continuous electron transfer from co-adsorbed 4-CP are mainly responsible for the oxidative degradation of chlorophenols. The intermediate products and TOC removal indicate that chlorophenols can be efficiently degraded and mineralized by as-synthesized NSDMC via activating PDS. Besides, the present NSDMC/PDS system is also applicable for purification of actual polluted water samples. This work provides in-depth knowledge of carbon-driven nonradical process for PDS activation and contaminants remediation.



中文翻译:

电子转移为主的过氧二硫酸盐的非自由基活化,通过一锅合成氮和硫共掺杂的介孔碳有效去除氯酚污染物

不含金属的碳质材料上的协同吸附和氧化降解(通过过硫酸盐活化)有望成为环保且高效的污染物去除方法。在此,首先通过柠檬酸钙和硫脲的共碳化,无需任何模板,即可合成氮和硫共掺杂的中孔碳(NSDMC)。NSDMC样品显示出显着增强的吸附能力和氧化降解(通过激活PDS)以消除氯酚。S BET增加引入的含氮官能团有利于氯酚的吸附,PDS可及性和连续活化。掺杂的硫(尤其是噻吩S)可以增强NSDMC的电子传输性能,从而进一步促进PDS活化和氯酚的降解。这可以归因于N和S共掺杂的协同作用。NSDMC-30(含5.83 at。%的氮和2.15 at。%的硫,S BET为1935.9 m 2 ·g -1)对4-CP去除具有最佳的吸附和催化氧化能力。NSDMC-30的降解速率常数为0.125 min -1分别比掺氮MC和原始MC高3.0倍和7.8倍。自由基淬灭实验和EPR测试表明,非自由基途径在PDS活化和氯酚降解中起主要作用。基于催化剂负载量,4-CP初始浓度和PDS用量对4-CP降解动力学的影响,预吸附是决定氯酚氧化速率的关键步骤。更重要的是,原位拉曼光谱和电化学测试结果表明,表面受限和活化的PDS络合物(carbon-PDS *)和来自共吸附的4-CP的连续电子转移是造成氯酚氧化降解的主要原因。中间产物和TOC的去除表明,通过活化的PDS,合成的NSDMC可以有效地降解和矿化氯酚。此外,本发明的NSDMC / PDS系统也可用于纯化实际的污水样品。这项工作为PDS活化和污染物修复提供了碳驱动的非自由基过程的深入知识。

更新日期:2020-11-18
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