Study On Phenol Wastewater Treatment By Active Persulfate Oxidation Method

Heterogeneous Fenton-like reaction has achieved continuous attention for its adaption of wide range of p H,less volum of sludge,and enhanced reaction efficiency,as structural iron was act as catalyst.As one of the most important catalyst of heterogeneous Fenton-like reaction,natural iron mineral contain structral ferrous,and have a wide distribution.Previous research has shown that natural iron mineral has a good efficiency in catalyzing heterogeneous Fenton-like reaction.However,there has not been a unified mechanism of catalyzed heterogeneous Fenton-like reaction.In this study,heat,nano Fe₃O₄ and natural iron mineral was used as a catalyst to active Na2S2O8.Differences between in reaction p H range,radical species and organic degradation paths were analyzed.The initial concentration of 250 mg/L phenol wastewater was chosen as the target compound to investigate the degradation efficiency of an oxidation process by heat activated persulfate.The optimal reaction condition was determined to be 50℃,PDS to phenol mole ratio was 60:1,p H was 3,and acidic condition was more beneficial for the phenol degradation than alkaline condition;And the optimum reaction conditions of nano-Fe₃O₄ activated persulfate were obtained as follows: PDS and nano-Fe₃O₄ dosing quantity was 12.5 m M,the initial p H was 6.18,the temperature was 50℃,the removal rate can reach 94.97% under this condition.The rate limiting step was chemical reaction on nano-Fe₃O₄ surface;The optimum reaction conditions of natural iron mineral activated persulfate were obtained as follows: PDS and natural iron mineral dosing quantity was 0.4g/L,the initial p H was 6.18,the temperature was 50℃,the removal rate can reach 89.96% under this condition.The rate limiting step was chemical reaction on natural iron mineral surface;Radical scavenger test indicated that ·OH was the predominant radical species at alkaline condition while SO4-· played a critical role at neutral and acidic conditions in three different catalytic systems.Both of washed nano Fe₃O₄ and washed natural iron mineral maintained a high activity after four times repeated use.Heterogeneous Fenton-like reaction could adapt to a wider range of p H,compared to heterogeneous Fenton-like reaction.In p H=3⁹ the removal rate can reach 86.65%⁹6.53% in nano Fe₃O₄ catalyst system and 82.61%⁹4.41% in natural iron mineral in 180 min.Intermediates of phenol were hydroquinone,catechol and butene compounds,and the result shows that the reaction process effective degradation of phenol in wastewater.