Degradation Rule Of Various Kinds Of Organic Dye By Thermally Activated Sodium Persulfate

Activated persulfate oxidation technique is a new type of AOPs,which developed in the area of environmental pollution treatment in recent years.Persulfate is very stable at room temperature which is required to be activated by light,heat,sound or transition metals etc.,to generate SO^4-·from S₂O₈^2-.The oxidation reduction potential of SO^4-·is 2.6V,closing to hydroxyl radicals?OH·,E⁰=2.7V?.In theory,most organic pollutants in water can be degraded in this way.To study the degradation rules of organic compounds under different pH conditions,29 kinds of organic compounds including metanil yellow,methylene blue,bromophenol blue etc.were selected.The thermal activated temperature of sodium was set to 60?.Visible spectrophotometer and total organic carbon?TOC?were selected to analyze the organic compounds removal efficiency.Additionally,the relativity of quantum chemical descriptors of organic compounds and the kinetic constants of color removal and TOC removal ratio were studied.The results as followed:?1?The experiments showed that after thermally activated persulfate oxidation of organic compounds for about 1h,almost all compounds'color removal ratio reached above 80%in three pH conditions.Color removal ratio under acidic condition was superior,followed by that in alkaline condition,and that in neutral condition was the smallest.The degradationrule conformed to the first order kinetics equation in the first few minutes.Color removal rate increased by 40%and 12%in acidic condition when compared with that in neutral and alkaline condition,respectively.?2?TOC removal ratio under acidic condition was superior,followed by that in alkaline condition,and that in neutral condition was the smallest.TOC removal ratio of different substances had a much difference.For example,TOC removal ratio of metanil yellow was up to 99%under alkaline conditions,but the removal rate of bromophenol blue is only 7%under acidic conditions.Initial removal of TOC is complex,which showed thermally activated persulfate to the nature and structure of the material had strong selectivity.?3?17 quantum chemical parameters were calculated by Gaussian09/DFT/B3LYP/6-311g?d,p?and the relationships between kinetic constants of organic pollutants and their quantum chemical parameters were analyzed.Fukui?+?max and E?B3LYP?had negative correlation with color removal rate in alkaline and neutral conditions.Bond order under the three conditions of pH effects TOC removal rate,and was negatively correlated with KTOC,in the contrary of Fukui indexes.?4?We got three QSAR models in three pH values after multiple linear regression polynomial fitting.Such models had good coherence and stability with real data and high quality of predictability.