The Effect Mechanism Of Organic Carboxylates On Dye Degradation In UV-Fenton System Using Iron Oxides As Catalyst

As one of advanced oxidation processes,the heterogeneous photo-Fenton process exhibits great potential applications in wastewater treatment.Iron oxides are the commonly used active species of heterogeneous Fenton catalyst.Studying the difference of catalytic characteristics between iron oxides can provide a theoretical base for developing new and efficient heterogeneous catalysts.And it will contribute to the development of heterogeneous Fenton technology.For this purpose,five kinds of iron oxides with different crystal forms are used as catalysts for heterogeneous Fenton and UV-Fenton system in an aim to compare the degradation efficiency of Orange?.Results showed that,Introducing UV light can strongly increase the degradation of Orange?;in the presence of UV light,the mixed crystal which consists of magnetite and maghemite showed the best catalytic activity and stability,and the catalytic activity of these iron oxides follows the order: mixed crystal>magnetite>goethite ? maghemite>hematite;a certain amount of iron ions in solution was detected of five iron oxides,only the iron ions leaching from mixed crystal could go back to the surface of catalyst after reaction.Furthermore,we introduced organic carboxylates into the heterogeneous UV-Fenton system.It was found that,The effects of different organic carboxylates formed in the proceeding of UV-Fenton degradation are various.The UV-Fenton reaction was enhanced by sodium malonate and sodium oxalate but suppressed by EDTA,trisodium citrate and sodium acetate.The effect of sodium oxalate on the degradation of Orange?was significant,and its optimal concentration was 0.5mmol/L.The further study pointed out that,the additional sodium oxalate enhancing the degradation efficiency is mainly achieved by accelerating the leaching of iron ions from the catalyst.