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

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 waterstable 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 center dot- and center dot OH, and SO4 center dot- 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 degrees 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.

Automated summary

This work investigated the targeted degradation of DMP using a novel functioned metal-organic framework catalyst for PS activation. The Fe-MOF-74@SiO2@MIP catalyst showed excellent capability, high selectivity, and efficient performance in DMP degradation. Findings also included the presence of SO4•- radicals during the catalysis, the inhibitory effect of increased catalyst loading on DMP elimination, and the promotion of DMP degradation by coexisting chloride ions at a specific concentration.