Effect Of Particle Size And Morphology On Adsorption And Photocatalytic Properties Of ZnSe

Based on nano effect,particle size and morphology have a great impact on the adsorption and photocatalytic properties of nano semiconductor materials.As a II-VI semiconductor with good optical properties,nano ZnSe has a good application prospect in the field of photocatalysis.In order to study the effect of particle size and morphology on the adsorption capacity and photocatalytic performance of nano ZnSe and its mechanism,this paper studied it theoretically and experimentally.In terms of experiment,firstly,spherical and linear nano ZnSe materials were prepared by polyol mediated heat implantation method and silver ion catalyzed hydrothermal method respectively,and their particle size and morphology were analyzed by various characterization methods.Secondly,Congo red dye was selected.Firstly,the technical experiments of adsorption and photocatalysis were carried out,and the effects of particle size and morphology on the adsorption kinetics and adsorption thermodynamics of nano ZnSe and its photocatalytic properties were deeply studied.In terms of basic theory,the adsorption process of nanoparticles is defined according to the transition state theory.Firstly,the effects of particle size on the adsorption kinetic parameters(In k,E5,ln A)and adsorption thermodynamic parameters(ln Kθ,ΔadsGmθ,ΔadsSmθ,ΔadsHmθ)are studied.Then,the morphology factor was introduced to obtain the relationship between adsorption kinetics and adsorption thermodynamics of different morphologies,and the interaction mechanism between different morphologies on adsorption kinetic parameters and adsorption thermodynamic parameters was discussed.Finally,the theoretical and experimental results are compared.The following conclusions are drawn:(1)Spherical nano ZnSe with different particle sizes were prepared by triethylene glycol mediated thermal injection method.The nano ZnSe samples prepared with ZnCl2 as zinc source were spherical with small particle size;The nano ZnSe samples prepared with 1:2 Zn/Se ratio have smaller particle size and higher sphericity;The particle size of spherical nano ZnSe samples decreases with the increase of reaction temperature,the increase of surfactant molecular weight,the decrease of reaction time and the increase of reductant dosage.Linear nano ZnSe samples were prepared by silver ion catalyzed hydrothermal method.The particle size increased with the increase of reaction temperature and AgNO3 dosage.(2)The reciprocal of particle size has a good linear relationship with the adsorption kinetic constants of spherical and linear nano ZnSe.With the decrease of particle size,the adsorption rate constant k increases,the adsorption activation energy Ea decreases and the pre exponential factor ln A decreases.By comparing the experimental results with the theory,it is found that they are consistent.When the temperature is constant,the adsorption kinetic parameters of spherical and linear ZnSe are different,which is shown as follows:Under the same particle size,the lnk of spherical nano ZnSe is larger than that of linear nano ZnSe;The Ea and ln A of spherical nano ZnSe are smaller than those of linear ZnSe.(3)The reciprocal of particle size has a good linear relationship with the adsorption thermodynamic constants of spherical and linear nano ZnSe.When the morphology is the same,the particle size decreases,the lnKθ of nano ZnSe increase,ΔadsGmθ、ΔadsSmθ和ΔadsHmθ of nano ZnSe decrease,and the four have a good linear relationship with the reciprocal of particle size.The results are consistent with the theory in the second part.The positive values of ΔadsHmθand ΔadsSmθ indicate that the adsorption of Congo red by nano ZnSe is an endothermic and entropy increasing process.For the same particle size,lnKθ follows the rule:spherical>linear,while for spherical,ΔadsGmθ,ΔadsSmθ and ΔadsHmθ are smaller than linear.The smaller the particle size,the more significant the effect of morphology on it.(4)The influence of particle size on the photocatalytic performance of spherical and linear nano ZnSe is the same,and their photocatalytic degradation rate η and degradation rate constant kapp decrease with the increase of particle size.When the particle size is the same,the photocatalytic performance of spherical is higher than that of linear,that is,ηspherical>ηlinear,kapp spherical>kapp linear.