Photo-Fenton and photo-Fenton-like processes for the degradation of methyl orange in aqueous medium: Influence of oxidation states of iron

摘要

Degradation of methyl orange (MO) was carried out by the photo-Fenton process (Fe~(2+)/H_2O_2/UV) and photo-Fenton-like processes (Fe~(////23222_UUV,SH VaSnd,)+ F OFea~ (teO ~_t_h(_)e acidic pH of 3 using hydrogen peroxide and ammonium persulfate (APS) as oxidants. Oxidation state of iron had a significant influence on the efficiency of photo-Fenton/photo-Fenton-like processes. It was found that a process with a source of Fe~(3i+) ons as the catalyst showed higher efficiency compared to a process with the Fe2+ ion as the catalyst. H_s22erved aOs a beter o_xidant for both oxidation states of iron compared to APS. The lower efficiency of APS is attributed to the generation of excess protons which scavenges the hydroxyl radicals necessary for degradation. Further, the sulfate ions produced from S_2O_ if/223onrms t haF ecr~oembyp +lrexd uwec8itnhg F tehe concentration of free iron ions in the solution. This process can also reduce the concentration of hydroxyl radicals in the solution. Efficiency of the various MO degradation processes follows the order: Fe~(///2232UAUVPS, VH/FUeOV~,+(, 2FF+e)~/eA(~P_