Comparison of two advanced oxidation processes for the treatment of wastewater from acrylonitrile production

Wastewater from acrylonitrile production was treated by chemical Fenton oxidation or dual electrode iron-promoted electrochemical oxidation using Ti/SnO2 and Fe as the combined anodes.The results from the two processes were compared,and the effects of several factors and reaction behaviors were investigated.The COD removal efficiencies from the electrochemical oxidation with H2O2 added were about 30%~35% higher than those from Fenton oxidation,and more than 90% color removal was achieved by the electrochemical process,but increases of color were observed when the initial H2O2 concentration was less than 1700 mg·L-1 in the Fenton process.COD removal efficiency increased with increasing H2O2 dosage owing to the enhancement of Fenton reactions in both processes.At 2200 mg·L-1 H2O2,t=180 min and 4.0 V,a COD removal efficiency of 75% was obtained.During the course of the two oxidations,H2O2 concentration decreased quickly,and at 60 min(electrochemical)and 30 min(chemical)H2O2 was almost completely consumed.For the electrochemical process,COD removal efficiency and current efficiency were affected by the time length of current passing through the iron anode.The treatment effect of the wastewater by electrochemistry in the presence of H2O2 was also better than the united process:(Ⅰ)Fenton oxidation and(Ⅱ)the electrochemical oxidation with no H2O2 added,which indicates that the former is a promising alternative for the treatment of organic wastewater.