Catalytic hydrodechlorination and advanced oxidation processes of 2,4-dichlorophenoxyacetic acid over CMK-3 supported catalyst: the bi-functional effect of metal Pd

Abstract The eliminate of 2,4-dichlorophenoxyacetic acid (2,4-D) was achieved via individual and combination of catalytic hydrodechlorination (HDC) and AOPs involved peroxymonosulfate activation. The CMK-3 supported monometallic Pd catalysts with varied Pd loadings were prepared and applied in the reactions. The results showed that Pd/CMK-3 were highly active and competitive in both the HDC and AOPs of 2,4-D, and the removal efficiencies were 91.6 and 95.2% over Pd3/CMK-3 respectively after reaction for 90 min. The dechlorination of 2,4-D was completed via both the stepwise and concerted pathways while the reactant experienced free radical oxidation processes in the AOPs. For the combined HDC-AOPs reaction, Pd/CMK-3 reflected a good advanced oxidation ability after the effective HDC of 2,4-D. Additionally, the catalysts exhibited higher Pdn+/Pd0 ratios after reactions and metal Pd was more stable after the reductive dechlorination than that of advanced oxidation.