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.