Synergetic effect of photocatalysis and peroxymonosulfate activated by Co/Mn-MOF-74@g-C3N4 Z-scheme photocatalyst for removal of tetracycline hydrochloride

A new Z-type heterojunction photocatalytic material Co/Mn-MOF-74@g-C3N4 was prepared by a simple solvothermal method. Co/Mn-MOF-74@g-C3N4 was found to have a much higher photocatalytic activity than simple Co/Mn-MOF-74 due to the formation of Z-scheme heterojunction, which inhibited the recombination of photogenerated electrons and holes. Photocatalytic activity was further enhanced by activating peroxymonosulfate with Co/Mn-MOF-74@g-C3N4. The removal rate of doxycycline hydrochlorid was 94 % within 60 min after adding 0.5 mmol peroxymonosulfate in the system. Furthermore, XPS, EPR and radical quenching experiments were used to demonstrate the electron transfer of Co/Mn (II) and Co/Mn (III) in Co/Mn-MOF-74 and peroxymonosulfate activation mechanism for enhanced photocatalytic performance. The possible vulnerable sites and degradation pathways of doxycycline hydrochlorid by Co/Mn-MOF-74@g-C3N4 were studied by density functional theory and UPLC-MS. Toxicity Estimation Software predicted that the degradation processes of doxycycline hydrochloride could gradually reduce toxicity. This study could provide an efficient and green method for the subsequent treatment of antibiotic wastewater.