Consolidated 3D Co3Mn-layered double hydroxide aerogel for photo-assisted peroxymonosulfate activation in metronidazole degradation

Novel 3D Co3Mn-layered double hydroxide aerogel (Co3Mn-LDH/rGA) was synthesized for photo-assisted peroxymonosulfate (PMS) activation to degrade aqueous metronidazole (MTZ). The observed rate constant of MTZ removal in the Co3Mn-LDH/rGA/PMS/Vis system exhibited 4.3, 4.1 and 3.6 times higher than that of Co3Mn-LDH/PMS, Co3Mn-LDH/rGO/PMS and Co3Mn-LDH/rGA/PMS processes, respectively. Therein, the efficiency of PMS activation can be simultaneously promoted by the 3D graphene aerogel as extensive electron transfer channels and visible light that stimulates the separation of electron-hole pairs in Co3Mn-LDH/rGA. The photo-generated electrons and transformation of Co2+/Mn3+ to Co3+/Mn4+ on the surface of Co3Mn-LDH/rGA co-contributed to PMS activation in producing •SO4−, •OH and 1O2 for MTZ degradation. Moreover, the 3D Co3Mn-LDH/rGA was consolidated in cyclic equipment to achieve an outstanding reusability, in which MTZ could be efficiently and continuously removed for up to 10 cycles with acceptable metal leaching. This work not only takes deep insights into the reaction mechanism of visible light assisted PMS activation by 3D Co3Mn-LDH/rGA, but also provides promising method for the continuous degradation of pollutants.