Photo assisted electro-peroxone to degrade 2,4-D herbicide: The effects of supporting electrolytes and determining mechanism

Abstract

Abstract In this work, photoelectro-peroxone (PEP) was utilized for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The influential operating parameters were studied and their results showed that complete degradation took place at pH = 7.0, applied current of 350 mA, 42.3 mg/L O3 and 25 min reaction time. The first-order kinetic model was fitted for 2,4-D degradation with the rate constant of 0.169 min−1. PEP showed a synergistic performance compared to individual and binary systems. The results of effect of supporting electrolytes showed that chloride, dihydrogen phosphate, nitrate and bicarbonate had an inhibitory effect on 2,4-D degradation. The presence of transition metal especially ferrous ion enhanced the degradation rate constant significantly. Activated carbon fiber cathode exhibited high function in 2,4-D degradation and H2O2 electrogeneration compared to graphite felt and stainless steel. PEP performance in divided cell showed that the main reaction occurred at the cathode compartment. Scavenging experiments showed that hydroxyl radical and singlet oxygen participated in degradation reaction. The presence of UV and ferrous ion increased the role of hydroxyl radical in the degradation of 2,4-D. Mineralization study indicated that 58.9% of total organic carbon (TOC) was removed during 30 min electrolysis. This result proved that PEP process was an effective and promising process for the degradation of refractory organic pollutant.