Preparation And Photocatalytic Properties Of Shape-controllable Ultrafine ZnO Powders

Zinc oxide ore is the secondary deposit of ZnO and attracts much attention due to the gradual depletion of zinc sulfide ore and the sustainable development of the industry.Based on the comprehensive utilization of resources,this paper aims at the green metallurgy and value-added metallurgy of zinc oxide ore.The ZnSO4 solution obtained from the zinc oxide ore roasted by(NH4)2SO4 was investigated for value-added use.The shape-controllable ultrafine ZnO powders and SiO2/ZnO were prepared by hydrothermal method and coating method,respectively.And the photocatalytic performance of those were investigated.The main contents in the thesis are as follows:(1)Employing zinc sulfate solution as raw material and sodium hydroxide as precipitant,the ZnO powder with sheet,rod-like and flower structure morphologies were successfully synthesized through hydrothermal method.The influcences of the dispersant type,dispersant consumption,molar ratio,reaction time,reaction temperature and initial reactant concentration on the phase structure and micro morphologies of ZnO powders were studied.The suitable reation conditions for preparing flower structure ZnO powder are as follows:When PEG20000 was used as dispersant,and the concentrations of NaOH and ZnSO4 were 1mol·L-1 and 5mol·L-1,respectively,the appropriate conditions were as below:the mass percentage 10%PEG20000 solution consumption of 5ml,molar ratio of OH-/Zn2+=5:1,reaction temperature of 150?,reaction time of 8h.When SDBS was used dispersant,and the concentration of NaOH and ZnSO4 were 1mol·L-1 and 5mol·L-1,respectively,the appropriate conditions were as below:the mass percentage 10%SDBS solution consumption of 2ml,molar ratio of OH-/Zn2+=5:1,reaction temperature of 150?,reaction time of 8h.(2)The photocatalysis degradation of rhodaminB by zinc oxide suspension system was studied,and the influences of the different morphologies ZnO powder,solution state,dosage of ZnO,initial concentration of rhodamin B on the degradation efficiency were dicussed.The results showed that the appropriate dosage of ZnO was 300mg,initial concentration of rhodamin B was 15 mg·L-1 under magnetic stirring,the degradation ratio could reach 99%after lighted for 4h.(3)Employing TEOS and Na2SiO3 as raw materials,SiO2/ZnO composites were synthesized by hydrolysis of alkoxide and precipitation,respectively.The photolytic degradation of rhodamin B by SiO2/ZnO were studied.The results showed that the photocatalytic performance of SiO2/ZnO powder prepared by hydrolysis of alkoxide was better than that btained by precipitation,and it was close to the photolatalytic performance of flower structure ZnO powder,which offered an alternative for photocatalytic material.