Preparation,Adsorption And Photocatalytic Properties Of Zinc-based Nanomaterials

Energy shortage and environmental pollution have become one of the major constraints to China's development.Promoting energy transformation can effectively reduce the dependence on primary energy and decrease air pollution.New energy sources(such as H2,CH3OH,etc.)have become a hot topic in recent years.Photocatalytic technology can effectively utilize sunlight and convert low-density solar energy into high-density chemical energy for storage.In addition,with the development of Chinese industry,the output of waste water also increases.Adsorption and photocatalysis are widely concerned because of their high efficiency,convenience and low energy consumption.In this paper,the adsorption and photocatalytic properties of zinc-series nanomaterials were improved by morphological regulation and element doping.Its main contents are as follows:(1)Zn(OH)2/Co(OH)2 nanocomposites were synthesized by microwave assisted heating method.Their morphology and chemical composition were analyzed by XRD,SEM,XPS,EDX,BET and other characterization methods.The analysis results show that Zn and Co exist in the form of+2 valence in the sample,and Zn,Co and O atoms are evenly distributed,and the ratio is close to the theoretical value of 1:2:6.The specific surface area was 84.2 m2·g-1,and the pore volume was 0.13 cm3·g-1.(2)The adsorption behavior of the above materials on cationic dyes(MB,CV and MG)was investigated.The experimental results showed that the maximum adsorption capacity of Zn(OH)2/Co(OH)2 on MB,CV and MG was 470,1100 and 2200 mg·g-1,respectively.Moreover,the adsorption capacity increased with the rising of temperature and pH.The adsorption isotherm,kinetics and thermodynamic experimental data showed that the adsorption of cationic dyes by Zn(OH)2/Co(OH)2 belongs to the Langmuir model,ie single-molecular surface adsorption.According to the average free energy calculated by the two-parameter model,the adsorption of Z1C2 on the three dyes is physical adsorption.It conforms to the quasi-secondary kinetic model,indicating that the adsorption rate of the cationic dye is proportional to the square of the contact time.The adsorption process is an endothermic process and can be performed spontaneously.In addition,we explored its adsorption mechanism.According to FT-IR,Zeta potential datas and the difference in the amount of adsorption of anionic and cationic dyes.The adsorption of cationic dyes was attributed to the electrostatic adsorption between cationic groups of dyes and OH-on layers or surfaces of Zn(OH)2/Co(OH)2.Finally,after the calcining of the adsorbed MB samples,we found that the calcined samples still had certain adsorption and photocatalytic degradation performance.(3)The monodisperse SiO2 nanoparticles with uniform particle size were synthesized by improved Stober method,and the effects of TEOS dosage and temperature on particle size were discussed.Ce doped porous Zn(OH)2/Co(OH)2 layered materials were prepared in situ using SiO2 as template,and their light absorption and photocatalytic degradation properties were evaluated.The experimental results showed that the porous structure can effectively enhance the absorption of light,and Ce doping can increase the utilization of visible light.Under the synergistic effect of SiO2 and Ce,The degradation ability of Zn(OH)2/Co(OH)2 on RhB was increased by 130%.(4)Series of Ce doped ZnS nanoparticles were prepared by a low temperature chemical precipitation method.The XRD,SEM,XPS,EDR and other characterizations show that the samples were made by the accumulation of 20-30 nm particles,and Ce existed in the two valence states of Ce3+and Ce4+.Moreover,the doping amount of Ce led to the red shift of light absorption of the samples.The effects of reaction time,reaction temperature and amount of Ce on the photocatalytic hydrogen production performance were investigated.The optimal preparation conditions were as follows:Ce doping amount of 5%,the reaction temperature of 75?,the reaction time of 5 h.In addition,the effect of the concentration of the sacrificial agent on the UV performance of 5wt%Ce-ZnS was also investigated.When the methanol volume fraction was 15%,the hydrogen production was 37.971 mmol·g-1·h-1.When the sacrificial agent was not added,the H2 production was 1.454 mmol·g-1·h-1.Finally,RhB was used instead of methanol to combine photocatalytic degradation with hydrogen production.Two hours after illumination,RhB solution was completely degraded and H2 was generated.