Oxidative Degradation Of2,4,6-Trichlorophenol Induced By Sulfate Radical

2,4,6-Trichlorophenol(TCP), with high toxicity, easy bioaccumulation and poor biodegradation, is frequently detected in water and landfill. Therefore, it is of great significance to develop the technology on the degradation and removal of2,4,6-TCP. In the present study, Co(II)-mediated decomposition of peroxymonosulfate(KHSO5, PMS)was used to produce sulfate radical for the degradation of2.4,6-TCP. The kinetics and mechanisms were discussed in Co/PMS/2,4,6-TCP, CI/Co/PMS/2,4,6-TCP, Cl/PMS/2,4,6-TCP, respectively.The results of Co/PMS/2,4,6-TCP reaction system indicated reducing the initial concentration of2,4,6-TCP, increasing Co2+concentration and PMS concentration as well as adjusting pH after PMS addition could accelerate the degradation of2,4,6-TCP. Besides, different pH adjustment orders led to different degradation rate. The order of Co2+â†'PMSâ†'pHâ†'TCP showed the fastest degradation rate. Increase in pH, as well as the concentration of Co2+and PMS, could increase the TOC removal of2,4,6-TCP. The maximum mineralization rate after4h reaction was up to54.94%. The intermediates identified by GC-MS included dichlorophenol, chlorinated hydroquinone, quinone and small molecular products. Sulfate radical attacked2,4,6-TCP to produced chloride ions, which could be oxidized to active chlorine radical and was involved the degradation of2,4,6-TCP with sulfate radical.The results of Cl/Co/PMS/2,4.6-TCP system showed the additional chloride ions could inhibit or promote the reaction significantly as the Cl-concentration was<5mmol/L or>50mmol/L. With the increase of chloride ions concentrations, the mineralization of2,4,6-TCP was inhibited gradually. But the increase in pH could promote the mineralization of2,4,6-TCP. The intermediates identified in2.4,6-TCP degradation in the presence of chloride ions were main polychlorinated compounds and trichlorophenol. It was proposed that the chloride ions added in the solution were oxidized to Cl2·-by sulfate radical, and then substituted H atom to form the polychlorinated compounds. In Cl/PMS/2,4,6-TCP system, the chloride ions and PMS could react with each other to form active species HOCl/Cl2. These active species could decompose2,4.6-TCP directly, but the degradation rate was still lower than that in Co/PMS/2,4,6-TCP system. The degradation rate and mineralization of2,4,6-TCP depended on the concentrations of chloride ions. When the concentrations of chloride ions were above100mmol/L,2,4,6-TCP could be removed completely within1h. With the increase of chloride ions concentration, TOC removal increased, but lower than that in the presence of Co2+catalyst.