Activation of persulfate by molecularly imprinted Fe-MOF-74@SiO2 for the targeted degradation of dimethyl phthalate: Effects of operating parameters and chlorine

Abstract

In this work, persulfate (PS) activation by a novel functioned metal-organic framework catalyst was investigated for the targeted degradation of DMP, a toxic phthalate pollutant. The catalyst, a molecularly imprinted water-stable Fe-MOF-74 (Fe-MOF-74@SiO2@MIP), showed excellent capability of PS activation, high selectivity and efficient targeted degradation performance of DMP. The results of total organic carbon indicated that DMP was mineralized during the catalysis. EPR measurement and quenching experiments suggested the coexistence of SO4•− and •OH, and SO4•− was predominant in this system. It was found that increasing catalyst loading (0.01 - 0.05 g L-1) inhibited the DMP elimination, due to the aggravated radical consumption. A higher pseudo-first order rate of DMP degradation was observed with an increasement of PS (5.2 - 52 mM) and temperature (15 - 45 °C). Besides, coexisting chloride ions (Cl−) promoted the DMP degradation at the concentration 1 mM, but decreased the degradation performance at other concentrations. According to EPR and XPS analysis, the effect of Cl− was ascribed to the formation chlorine radicals, which changed the radical distribution and the catalytic site property. Chlorinated intermediates were detected by LC-MS, confirming the involvement of Cl-related radicals. Finally, possible degradation pathways were proposed.