Photodeposition synthesis of CdS QDs-decorated TiO_2 for efficient photocatalytic degradation of metronidazole under visible light

摘要

Photocatalysis technology has received much attention on the treatment of antibiotics residues. In this paper, CdS quantum dots (QDs)-decorated TiO_2 (CDS-T for short) have been prepared successfully through a photodeposition method and utilized as photocatalysts for degradation of metronidazole (MTZ). Under visible light irradiation for 60 min, the degradation ratio of MTZ over CDS-T-3 that was prepared by 3 h of photodeposition reached up to 90.9%, which was 1.5 times than that reached over commercial CdS. The decoration of CdS QDs onto TiO_2 can enlarge light absorption range to visible region. Furthermore, greatly improved separation efficiency of photogenerated carriers is realized through forming heterojunction. Activity control experiments demonstrate that O_2.~- serve as the main active species, while OH and holes (h~+) play secondary roles on the MTZ degradation. Moreover, electron spin resonance (ESR) technique, terephthalic acid photoluminescence (TA-PL) technique and N,N-diethyl-p-phenylenediamine (DPD) method confirm that larger amounts of active species are generated from CDS-T-3 than that from commercial CdS under visible light. This study can not only offer an easy method to prepare CdS quantum dots-decorated TiO_2 but also enlarge its application in solving the problem of metronidazole contamination.