Unusual Catalytic Effect of Fe3+ on 2,4-dichlorophenoxyacetic Acid Degradation by Radio Frequency Discharge in Aqueous Solution

2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide for controlling broad-leaved weeds. The development of an efficient process treating the refractory 2,4-D wastewater necessary. In this study, liquid-phase degradation induced by radio frequency discharge (RFD) was studied. Experimental results showed that more effective in acidic than neutral or alkaline solutions. During degradation, large amount hydrogen peroxide (H2O2, 1.2 mM/min, almost equal to without 2,4-D) simultaneously produced, and catalytic effects both ferric (Fe3+) ferrous (Fe2+) ions on were examined compared. It found degraded rapidly case Fe3+ Fe2+. Such scenario explained successively reduced Fe2+ atomic (•H) •OH-adducts resulting from RFD, which turn catalyzed H2O2 form •OH radicals through Fenton’s reaction, indicating not only accelerates rate but also increases available suppressing back reaction between •H •OH. 2,4-dichlorophenol, 4,6-dichlororesorcinol, 2-hydroxy-4-chloro- 2-chloro-4-hydroxy- phenoxyacetic acids, hydroxylated 2,4-Ds, carboxylic acids (glycolic, formic oxalic) identified as byproducts. Energy yields RFD have been compared with those other nonthermal plasma processes.