Removal of herbicide atrazine by a novel biochar based iron composite coupling with peroxymonosulfate process from soil: Synergistic effect and mechanism

Over the past decade, herbicides contaminated soil poses a serious threat to humans and environment. In this study, a novel biochar supported zero valent iron (BC-nZVI) was used as a heterogeneous catalyst activating peroxymonosulfate (PMS) for the removal of herbicide atrazine (ATZ) from soil. The results revealed that the removal of ATZ by BC-nZVI/PMS process was superior to that of BC/PMS or nZVI/PMS process. A synergistic effect between BC/PMS and nZVI/PMS processes has been successfully achieved in BC-nZVI/PMS process, and nearly 96% of ATZ removal was obtained at optimum reaction conditions. BC-nZVI/PMS process exhibited an excellent performace on ATZ removal compared with BC-nZVI/H2O2 or BC-nZVI/persulfate (PS) process. PMS decomposition by BC-nZVI/PMS process was higher than the sum of BC/PMS and nZVI/PMS processes. A low Cu concentration accelerated ATZ removal, and Cu was also effectively immobilized. SO4− was the predominant reactive oxygen species responsible for ATZ degradation, and OH and 1O2 also took part in reaction. Four kinds of ATZ degradation products were identified, and ATZ degradation could be achieved through de-alkylation, dechlorination and hydroxylation processes. A reaction mechanism of PMS activation by BC-nZVI was proposed based on the synergistic effect of BC and nZVI. In addition to ATZ, coexisting pollutants such as 2,4-dichlorophenol (2,4-DCP), Cu and Cd were also simultaneously removed from soil.