Preparation And Photocatalytic Properties Of Metal Sulfide Composites

The depletion of fossil fuel resources leads to the rapid development of nuclear energy,but this development is also accompanied by a series of environmental problems.Uranium in radioactive nuclear waste water is the most prominent because of its chemical toxicity and radioactivity.CdS has widely used as an efficient photocatalyst due to a suitable band gap and light absorption range.However,the defects of pure CdS(e.g.,easy photocorrosion and small specific surface area)affect the photocatalytic efficiency of.In this study,MoS2/CdS and MoS2/CdS/TiO2 photocatalyst were firstly synthesized and then used as the photocatalytic reduction of U(Ⅵ)under differen conditions(e.g.,pH,U(Ⅵ)concentration and catalyst content).The optimized experimental conditions were obtained through batch technology.In addition,the chemical stability and photocatalytic mechanism of the materials after recycling was explored.The main conclusions of this study are as follows:(1)Porous MoS2/CdS materials were prepared by simple hydrothermal method and then used to photocatalytic U(Ⅵ)reduction under the optimized conditions(e.g.,pH=7.0,C0U(Ⅵ)=20 ppm and photocatalyst=1.0 g/L).The high removal rate of U(Ⅵ)pollutants(97.53%within 15 min,reaction rate constant of 0.07125 min-1)was twice higher that of CdS.After five cycles,the high removal rate of U(Ⅵ)under 50 minirradiation indicated good chemical stability of 2.5 wt%MoS2/CdS.According to quenching experiment and ESR experiment,it is inferred that ·O2-radical was an important active species in photoreduction of U(Ⅵ).The results showed that CdS-based catalysts had great potential in the actual environmental remediation.(2)In order to further improve the photoreduction efficiency,MoS2/CdS/TiO2 was prepared by solvothermal method.MoS2/CdS/TiO2 photocatalyst showed the best efficiency of photoreduction of U(Ⅵ)such as complete removal within 20 min.After five cycles of experiments,the photocatalysts exhibited the high photocatalytic reduction efficiency(96.18%)and excellent stability and recyclability.Electrochemical tests show that the high light current density(38.33 μA/cm2)of MoS2/CdS/TiO2-200 was 19 times higher that of CdS/TiO2(2.12 μA/cm2)due to enhanced light response and more carriers.In addition,the possible way of photocatalytic electron transfer(·O2-radical)is the main active radical.The highlight of this study is simple synthesis of MoS2/CdS/TiO2 ternary heterojunction,which has potential application in the remediation of radioactive wastewater.