Hydrothermal/Solvothermal Synthesis And Photocatalytic Performance Of ZnS

ZnS is one of the important?-?semiconductor material with direct wide-band gap.Material scientists have aroused wide concern on ZnS because of its unique advantages in the field of optoelectronics,drug delivery,catalysis and so on.This thesis summarizes the harm and treatment methods of organic pollutant phenol,properties and synthesis methods of ZnS semiconductor materials,photocatalytic mechanism of ZnS for phenol degradation.ZnS with different crystal phases and different morphologies was synthesized by hydrothermal/solvothermal method via controlling the sulfur source and the reaction solvent.ZnS was characterized by XRD,SEM,UV-Vis diffuse reflectance spectrum.Furthermore,as-synthesized ZnS was applied in photocatalytic degradation of phenol to investigate the catalytic performance of ZnS via HPLC analysis and explored its photocatalytic mechanism for phenol degradation.The main research results are as follows:?1?Thiourea as the sulfur source,by adjusting the experimental parameters in the reaction process to optimize reaction condition.The results revealed that as-synthesized ZnS microspheres were zinc blende crystalline structure with fine crystalline,regular morphology,self-assembled via ZnS monodispersed nanoparticles under the reaction condition of concentrations of thiourea and zinc acetate dihydrate both 0.250 mol/L at 160?for 16 h.As-synthesized ZnS were applied in photocatalytic degradation of model pollutant phenol.ZnS microspheres synthesized in?CH₂OH?₂-H₂O system revealed much better photocatalytic activity than that of ZnS synthesized in H₂O or?CH₂OH?₂ solvent system.In this case,200 mg of ZnS was added into 200mL of 50 mg/L phenol solution.Then,the photocatalytic test was runned under 300W xenon lamp light illumination.About 97.1%of phenol degradation rate was reached after 6 h of photo-catalytic reaction and ZnS still kept higher activity in the third cycling degradation.?2?Hexagonal wurtzite structure ZnS with diversified morphologies were synthesized by changing the sulphur source into thioacetamide or sodium sulfide in different solvent systems.This investigation provides a low-temperature solvothermal technique to synthesize hexagonal wurtzite ZnS with fine crystal structure:introducting ethylenediamine into water solution,there was chelation interaction between-NH₂ group of ethylenediamine structure and Zn2+ in the solution.The formed coordination ions reduced the energy barrier of phase transition between cubic ZnS and hexagonal ZnS.ZnS with hexagonal wurtzite structure were successfully synthesized at a low temperature.As-synthesized ZnS had good photocatalytic performance for phenol degradation.?3?ZnS synthesized in?CH₂OH?₂-H₂O system and thiourea as the sulfur source was applied in the degradation of phenon solution.The results showed that the concentration of 1.0 g/L ZnS had the best photocatalytic degradation performance in 50 mg/L phenol solution.The degradation intermediates of phenol were investigated via HPLC and the photocatalytic mechanism of ZnS for phenol degradation was presumed.The investigation revealed that the intermediate products were oxalic acid,maleic acid and very little hydroquinone in photocatalytic degradation of phenol.Phenol hydroxylation is the primary pathway of phenol degradation.