Photocatalysis-PMS oxidation system based on CQDs-doped carbon nitride nanosheets for degradation of residual drugs in water

Abstract

A novel CQDs-doped carbon nitride nanosheets composite (CNS/CQDs) for visible light-induced activation of peroxymonosulfate (PMS) for meloxicam (Mel) and tetracycline (TC) degradation was studied. The photocatalytic degradation of Mel and TC were remarkably promoted by CNS/CQDs under the simultaneous action of PMS and visible light irradiation. Mel photodegradation of 99.60% was achieved over 30 min with 20 mg CNS/CQDs and 20 mg PMS at pH11. And TC photodegradation of 95.97% was achieved over 45 min with 20 mg CNS/CQDs and 20 mg PMS at nature pH. The TOC mineralization rates of Mel and TC were 75.49% and 52.00%, respectively. The enhanced photodegradation of organic pollutants could be ascribed to be the efficient activation of PMS and the separation of photogenerated electrons and holes of CNS/CQDs. Capture experiments and EPR tests showed that in the CNS/CQDs+PMS+vis system, the effective active substances for Mel were mainly •O2 -, •SO4 -and h + , while the main active substances for TC were •O2 -, h + , and •SO4 -. This study provides valid residual drugs degradation under the dual conditions of visible light catalytic oxidation and persulfate oxidation, which will be a novel perspective for advanced oxidation technology to effectively remove organic pollutants from water.