微米炭介导下4-硝基氯苯的还原-氧化耦合修复

针对土壤和地下水中难以去除的污染物4-硝基氯苯(4CNB),本文提出了微米级活性炭(MAC)介导的先还原后氧化的耦合修复工艺.通过序批实验、密度泛函分析、电子顺磁共振分析等手段研究了MAC表面性质、温度对强化硫化物还原4CNB的影响,探究了4CNB还原-氧化反应机理.结果表明在MAC介导下,4CNB可能发生了热力学有利的双电子还原过程,并且MAC对污染物的吸附富集作用减轻硫化物对过硫酸盐氧化过程的影响,高效去除了难以被硫化物还原和过硫酸盐氧化的4CNB.MAC强化下,4CNB还原速率相比单独硫化物作还原剂时提高8～82倍,35℃以上反应4h其降解率超99%.当4CNB还原为4-氯苯胺(CAN)后在炭表面经自由基氧化和过硫酸盐直接氧化去除.本研究提出了一种新的微米炭介导的4CNB还原-氧化耦合修复路线,为利用热处理工艺余热,实现低能耗、低成本修复4CNB污染土壤和地下水提供了新的思路.

Micro carbon mediated reduction-oxidation coupling process for 4-nitrochlorobenzene remediation

Acoupling remediation process mediated by micron-activated carbon (MAC) was proposed for the degradation of 4-nitrochlorobenzene (4CNB), a pollutant that is difficult to remove from soil and groundwater. The effect of MAC surface properties and temperature on the reductive degradation of 4CNB by sulfide and the mechanism of 4CNB reduction-oxidation reaction mediated by MAC were studied by batch experiments, density functional theory analysis, and electron paramagnetic resonance analysis. The results showed that MAC could change the reduction of 4CNB into a thermodynamically favorable two-electron transfer process, and reduce the effect of sulfides on persulfate oxidation through pollutant adsorption and enrichment. Then 4CNB, which was difficult to be reduced and oxidized by sulfides and persulfates alone, was effectively removed. Under MAC intensification, the reduction rate of 4CNB was 8~82 times higher than that of single sulfide as a reducing agent, and the degradation of 4CNB exceeded 99% in 4hours at above 35℃. When 4CNB was reduced to 4-Chloroaniline (CAN), it was removed by free radical oxidation and persulfate oxidation on the surface of the carbon. In this study, a new micron carbon mediated reduction-oxidation coupling route for 4CNB remediation was proposed, which provided a new insight for developing low energy consumption and low-cost remediation strategies for 4CNB-contaminated soil and groundwater by using waste heat.