Application of Fenton and photo-Fenton process for decolorization of Direct Red 80 dye from synthetic wastewater

Abstract

The present study was performed to evaluate the efficiency of Fenton (FP) and photo-Fenton (PFP) processes for direct red 80 (DR80) dye removal from synthetic wastewater. The effects of primary variables viz solution pH, contact time, Fe2+ concentration, H2O2 dose, and DR80 concentration on DR80 removal by FP and PFP were examined. The results showed that DR80 removal in acidic pH is higher than that of alkaline pH. Moreover, in both processes, with increasing the contact time, Fe' concentration, and H2O2 dose, the DR80 removal efficiency improved. However, with increasing initial DR80 concentration, the removal efficiency decreases. Under optimum conditions for FP (solution pH: 2, H2O2 dose: 80 mg/L, contact time: 35 min, Fe2+ concentration: 35 mg/L, and initial DR80 concentration: 20 mg/L), the highest DR80 removal efficiency was obtained (95). Also, at initial DR80 concentration of 20 mg/L and optimal conditions for PFP (solution pH: 2, contact time: 20 min, H2O2 dose: 15 mg/L, and Fe2+ concentration: 2 mg/L), the DR80 removal efficiency reached to 99.5. The results demonstrating that the PFP has higher ability for DR80 removal in a short time than FP using significantly lower amount of H2O2 and Fe2+. The empirical model yielded a R-2 of 0.81 and 0.72 for FP and PFP, respectively, and indicating relatively good describe of DR80 removal efficiency under different conditions. The sensitivity analysis showed that the solution pH implying the strongest effect on DR80 removal efficiency for both FP and PFP. The significant difference between costs of FP and PFP was achieved and is due to the electrical energy of mixing for high contact time in FP process.