Characteristic And Degradation Mechanism Of P-chlorophenol Using Potassium Persulfate/zero-valent Iron System In Simulation Wastewater

As an important chemical material, chlorophenols have been widely used in production and in daily life since the twenty-first century. And the environmental problems become more serious than before. A new advanced oxidation technology was described in this study. As the target pollutant, the 4-chlorophenol(4-CP) was degraded by potassium persulfate(KPS) activated with zero valent iron(ZVI). And some aspects which influenced the removal of 4-CP were researched, as well as the degradation reaction mechanism.Major influence factors were analysed in the experiment. The results showed that4-CP in the wastewater could be easily remote in the ZVI/KPS system. More than 90%removal of 4-CP was observed in1 h of reaction time while keeping the reaction temperature at 30℃, pH value at 5, 4-CP concentration of 20 mg/L, ZVI concentration of0.3g/L and KPS constant of 1.6mmol/L. Further experiment indicated that the removal of4-CP would be enhance by batch throwing the KPS. Moreover, the process followed the pseudo-first-order kinetics.The feature analysis of the system suggested that the pH value in the solution decreased with the reaction, which indicating the formation of acid compound.Furthermore, the variation of ferrous iron concentration proved that the removal efficiency of 4-CP depended directly on the concentration of ferrous ion of the system. In contrast to the ZVI/KPS system, the reaction was terminated rapidly in the ZVI or KPS system. It showed that the degradation of 4-CP wasn’t the separate effect of some reactant, but the combined function of the system. After injected with methanol and tert butyl alcohol, the degradation of 4-CP reduced by 70% and 30%. A conclusion can be drawn from this phenomenon that sulfate radicals and hydroxyl radicals were generated in the system, and the former radicals played a major role on the degradation of 4-CP. Similar results were also shown in the experiment in iodometry.By using TOC analysis, a slow mineralization process was detected. The mineralization rate is far lower than the removal rate of 4-CP at the same time. Besides,the increase concentration of chloride ion indicated the occurrence of dechlorination reaction. Considering the conclusions above, the degradation of 4-CP could be inferred as follows. Firstly, the dechlorination and oxidation process of 4-CP was accompanied by the formation of hydroquinone and p-benzoquinone. Secondly, the intermediate products were attacked by sulfate radical and then turned into small molecule organic acide. At last,carbon dioxide and water were detected in the final system.