A Study On Oxidation Mechanism Of Fenton Its Application In Laboratory Wastewater Treatment

As the advantages in the treatment of bio-refractory organic wastewater,Fenton attracts a lot of attention,employed widely.In this paper,the study was conducted on Fe?III?hydrolysis distribution,Fe?II?concentration variation,H₂O₂ decomposition,formation of hydroxyl radical and effect of inorganic anions for the purpose of better understanding the Fenton mechanism systematically in Fenton processes.Based on the above studies,Fenton was used to treat laboratory wastewater.They are briefly as follows:?1?In Fenton processes,hydrolysis rate of Fe?III?was increased markedly with the increase in pH,and decreased rapidly with the increase either Fe?II?concentration or H₂O₂ concentration.Fe?III?hydrolysis rate was inhibited significantly by inorganic anions,the kind of organic and the concentration of organic,respectively.The results followed the order of Aniline>phenol>nitrobenzene>prometryn,PO₄^3-?29?F^-?29?SO₄^2-?29?Cl^-?29?CO₃^2-?29?NO₃^-,respectively.Fe?III?hydrolysis rate in Fenton process was markedly higher than that in the Fenton-like.?2?The oxidation ability of Fenton and Fenton-like were effected by initial pH,initial Fe?II?/Fe?III?concentration and initial H₂O₂ concentration.The oxidation ability of Fenton was significantly higher than Fenton-like,as residual Fe?II?was significantly high in Fenton process.?3?Inorganic anions inhibited X-GN decomposition in Fenton processes,following the order ofH₂PO₄^-?29?SO₄^2-?29?Cl^-?29?CO₃^2-?29?NO₃^-.After Fe?II?concentration was optimized,the inhibition was decreased remarkably,and following the order of Cl^-?29?SO₄^2-?29?CO₃^2-?29?H₂PO₄^-?29?NO₃^-.The inhibition of inorganic anions was stronger in Fenton-like than in Fenon process.?4?The optimization of Fenton pretreatment as SBR and coagulation was evaluated by COD removal rate,H₂O₂ efficiency,AOS and BOD₅/COD.The optimum condition was determined as initial pH=2.98,initial Fe?II?=5mmol/L,initial H₂O₂=45mmol/L,reaction time=120min.pH adjustment before SBR can decreased significantly the concentration of Cu and Cr,but a little influence on COD and NO₃^--N.After the treatment by Fenton—SBR,the residual COD,Cu and Cr reach comprehensive discharge standard I of wastewater,butNO₃^--Nconcentration is very high.However,after adjusting the rate of BOD₅/NO^--N,theNO^--N concentration is decreased to about 10mg/L.The optimum coagulation condition is determined as PAC 2.5g/L and pH8.0,after Fenton-coagulation,the residual COD,Cu and Cr also reach comprehensive discharge standard I of wastewater,however,NO₃^--Nwas removed only a little.?5?Fenton-SBR was studied on the treatment of 2-CP wastewater,the optimization of Fenton pretreatment as SBR was evaluated by dechlorination,The optimal Fenton condition was determined at pH4.0,86mmol/L H₂O₂ and 2.87mmol/L Fe²⁺.Under the optimal condition,2-CP was removed completely,COD removal rate reached 80.02%and BOD₅/COD increased to 0.41.The pretreated 2-chlorophenol wastewater was fed to SBR,the result show that complete mineralization is achieved.