| With the development of industrialization,the excess use of fossil fuels such as coal,oil,as a result environmental pollution has greatly affects the sustainable environment.Therefore,scientists are progressively concerned about energy shortage and environmental pollution.Photocatalysis technology is a sustainable,clean and green method,such as photocatalytic splitting of water to produce H2,and the use of solar energy to degrade various harmful pollutants.Recently,the most valuable and inexpensive reported photocatalysts,such as CdS,TiO2,Bi2S3 and Bi2WO6 etc.have potential applications in environment and energy.However,their practical applications are greatly limited due to their low quantum yield,fast recombination of photogenerated charge carriers and low utilization of solar energy.Therefore,the design of advanced photocatalysts with effective visible light absorption,high quantum yield and easy recovery is a hot topic.In recent years,the loading of noble metals(Ag,Au and Pd)and non-noble metal Bi nanoparticles can desirably solve the problems of fast photogenerated electron&hole recombination and poor visible light absorption in CdS,Bi2WO6 and Bi2S3 semiconductors.However,these traditional composite photocatalysts still have the following problems:(?)if there is no stirring,the powder catalyst is easy to aggregate and cannot effectively utilize light energy(?)if stirring is used in practical applications,it will cause additional expenditure and energy consumption.In this research work,expanded perlite(EP)is used as a carrier to solve the above problems by constructing a series of multi-component floating photocatalysts.The photocatalytic efficiency of CdS semiconductor decreases with the prolongation of illumination time due to the photochemical corrosion of CdS semiconductor photocatalyst owing to its unstable structure.Therefore,dispersion and immobilization of CdS nanoparticles on EP support can avoid aggregation,inhibit photochemical corrosion and improve its recycling efficiency.In this research works,CdS/EP and Ag-CdS/EP composite photocatalysts with different contents were fabricated.CdS/EP and Ag-CdS/EP floating photocatalysts have been successfully prepared under ambient conditions.The apparent rate constants(k)of Rhodamine B for CdS,20-CdS@EP,1.5%Ag-CdS and 1.5%Ag-CdS@EP were 0.00653 min-1,0.0099 min-1,0.0307 min-1 and 0.0456 min-1,respectively.The efficient photocatalytic degradation of RhB is attributed to the homogenous dispersion of CdS and Ag-CdS on EP support and direct visible-light illumination and aerated oxygenation.TiO2 semiconductor is a suitable photocatalyst because of its photochemical stability,strong oxidation ability,low price,non-toxicity and high photocatalytic activity.However,because of its wide band gap(Eg=3.2eV)and only absorption of UV light takes place in less than 380nm,which seriously limits its applications in solar energy.In this paper,ternary(3C)CdS QDs-CQDs@TiO2 heterojunction was prepared by developed hydrothermal method and accompanied with simple liquid phase deposition process.TEM and HR-TEM results show that CdS QDs are deposited on CQDs@TiO2 with a size range of 3-8nm.The enhanced photocatalytic performances of the optimal designed 1%CdS QDs-CQDs@TiO2 nanocomposite were tested by degradation of dyes pollutants(Methylene Blue;MB&Rhodamine B;RhB)in 30 min,and phenol aqueous solutions were degraded in 50 min with enhanced rate constants(k)of 0.051 min-1,0.045 min-1 and 0.03 min-1,respectively,utilized solar-like irradiation.Flower-like floating Bi-Bi2WO6@EP photocatalyst doped with reduced graphene oxide QDs(rGO QDs)was synthesized by simple hydrothermal method and liquid phase deposition method.Citric acid,Bi(NO3)3 and Na2WO4.2H2O were used as reductant,precursors of Bi and W sources respectively,while rGO QDs was used as electron acceptors from Bi nanoparticles.The reaction mechanism of the designed floating photocatalyst was studied by comprehensive physicochemical techniques.TEM and HR-TEM results showed that rGO QDs and Bi nanoparticles were deposited on Bi2WO6@EP in a size range of 5-1 Onm and 2-7nm,respectively.The enhanced photocatalytic performances of the as-fabricated nanocomposites were tested by degradation of RhB and colorless phenol with enhanced rate constants(k)of 0.230 min-1 and 0.047 min-1,respectively,under sun-like irradiation.The enhanced photocatalysis were assigned to the optimal contents deposition of rGO QDs,Bi nanoparticle and Bi2WO6,aerated oxygenation and direct illumination owing to the floating behavior of the nanocomposites.Hierarchical cabbage-like Bi-Bi2S3-B12WO6@EP floating photocatalyst was prepared by an improved one-pot hydrothermal method.Ethanolamine,Bi(NO3)3,Na2WO4.2H2O and L-cysteine were used as reducing agents,Bi,W and S source precursors,respectively,while polyvinylpyrrolidone(PVP K-30)was used for size and morphology control.EP is used as a low-cost and sustainable floating carrier.TEM and HR-TEM results showed that Bi and Bi2S3 nanoparticles were deposited on Bi2WO6@EP in the size range of 3-8nm and 5-1 Onm,respectively The enhanced photocatalytic performances of the designed nanocomposites were tested by degradation of dyes pollutants(Methyl Orange;MO&Rhodamine B;RhB)in 25 min,and colorless 4-Chlorophenol(4-CP)aqueous solutions(prolonged time 50 min),optimal 1%Bi-Bi2S3-Bi2WO6@EP with enhanced rate constants(k)of 0.075 min-1,0.073 min-1 and 0.051 min-1,respectively,utilized sun-like illumination.The efficient photocatalysis of as-prepared heterojunctions were attributed to the optimal contents deposition of Bi&Bi2S3 nanoparticles,and Bi2WO6,maximum mobility and minimized recombination of photoinduced charges,aerated oxygenation and direct illumination due to the floating behavior of the heterojunctions. |
PDF Full Text Request