The Synthesis Of CdS-TiO₂ Composite Catalyst And The Photocatalytic Degradation Mechanism Of OTC Under Visible Light

In this paper,the CdS-TiO2 photocatalyst was prepared by the precipitation-hydrothermal method.The prepared CdS-Ti02 photocatalyst was characterized by SEM,TEM,UV-ViDRS,XRD,ICP-MS,TG-DXT,FT-IR,and its synthesis mechanism was investigated.The degradation efficiency of OTC under visible light was studied and its influence factors were discussed.Furthermore,the photocatalytic degradation mechanism of OTC was examed by HPLC-MS.The main results were as follows:(1)The prepared CdS-TiO2 by the precipitation-hydrothermal method showed a good respond to visible light.The TiO2 and CdS existed in the form of anatase and tetragonal phase,respectively.The optimal mole rational of CdS to TiO2 was 1:2.CdS and TiO2 connected with the sulfenyl and carboxyl of 2-Mercaptopropionic acid,respectively.(2)The opitimal experiment conditions were as follows:the concentration of OTC was 30 mg/L,the initial pH was 7,the dosage of catalyst was 1.0 g/L.After 4 h visible light irradiation,the degradation efficiency of OTC was 94.2%,the TOC removal efficiency reached 65%.Under different solar light intensity,the degradation efficiency of OTC was more than 96.31%in 4 h reaction time.And on recycle of the CdS-TiO2 5 times,the degradation efficiency of OTC could still reach 86.78%.(3)The influence of many kinds of ions in the solution on the OTC degradation efficiency was discussed.The obatined results indicated that Cl-,Ca2+ Mg2+ had little influence on the degradation efficiency,while NO3-,SO42",HCO3-,Fe3+ and HA had synergisiuic effect on the OTC degradation.(4)·O2-played the most important role in the photocatalytic degradation of OTC.Thirteen primary intermediates were identified by HPLC-MS analysis.These compounds were formed via removal group of aromatic ring,aromatic ring opening,intramolecular cyclization,hydrogenation and oxidation.The main intermediates of OTC degradation were(?).