Humic acid promoted activation of peroxymonosulfate by Fe3S4 for degradation of 2,4,6-trichlorophenol: An experimental and theoretical study

Chlorophenols are difficult to degrade and biohazardous in the natural environment. This study demonstrated that humic acid (HA) could promote Fe3S4 activation of peroxymonosulfate (PMS) to degrade 2,4,6-trichlorophenol (TCP), the degradation efficiency of TCP was increased by 33%. The system of Fe3S4-HA/PMS produced more reactive oxygen species, and •OH was the dominant ROS. The genealogy of iron oxides together with S0 on the Fe3S4 surface inhibited PMS activation leading to the significant reduction of TCP degraded (< 70%). These problems could be solved successfully through introducing HA, which facilitated electron transfer and increased the continuous release of iron ions by 2 times. In accordance with the determined density functional theory (DFT), the degradation pathway was put forward, which indicated that TCP dechlorination and oxidation to 2,6-dichloro-1,4-benzoquinone constituted the main degradation pathway. Furthermore, the intermediates that were produced in the main degradation processes of TCP showed lower toxicity than TCP according to results that were obtained utilizing the calculations of quantitative structure-activity relationship (QSAR) together with Toxicity Estimation Software Tool (TEST). Thus, the Fe3S4-HA/PMS system was demonstrated to be an efficient and safe technology for organic pollutant degradation in contaminated groundwater and surface water environments.