Catalytic wet peroxide oxidation of phenolic wastewater on novel Cu/Mn-UiO-66@Al2O3 ceramic tube membrane catalysts

Novel Cu and Mn supported UiO-66@Al2O3 ceramic tube (UiO-66CT) membrane catalysts were synthesized by solvothermal method combined with secondary incipient wetness impregnation method and used for efficient catalytic wet peroxide oxidation (CWPO) of phenolic wastewater. Synthesis conditions of UiO-66CT were optimized by investigating the secondary soaking times and UiO-66 content. The experimental set-up based on a novel membrane reactor was designed for the catalytic activity evaluation of the ceramic tube catalysts. Results indicated that solvothermal time of 24 h and secondary soaking time of 1 h in the UiO-66 (12.8 g/L) can effectively shorten the synthesis time with a UiO-66 loading ratio about 2.0 wt% obtained. The SEM and EDS mapping results certificated the loading of UiO-66 in the macro-pores of the ceramic tube and the successfully supporting of Cu species on the UiO-66CT. The Cu-UiO-66CT catalysts exhibited good catalytic activity (X-phenol > 99% without toxic by-products detected in the final treated wastewater). By contrast, the Mn-UiO-66CT catalysts exhibited lower catalytic activity because of the fast decomposition of H2O2 on the MnO2 catalysts. The Cu-UiO-66CT catalyst showed excellent stability with phenol conversion (initial concentration of 500 ppm) kept above 90% after reused for 5 times. The immobilization of UiO-66 into the macro-pores of Al2O3 ceramic tube and the supporting of Cu species in the UiO-66CT can not only keep the high activity of MOFs catalysts but also enhance the stability of Cu-UiO-66 in the CWPO process. This research provides a promising strategy to solve the unstability of MOFs catalysts when used for the CWPO process of wastewaters.