Preparation And Its Photocatalytic Performance Of BiOI-based Photocatalyst

Dye wastewater is dark in color,highly toxic and difficult to be degraded,which is very harmful to environment.It is difficult to remove it from water with existing environmental technologies.Therefore,the treatment of dye wastewater has been highly valued worldwide.Photocatalytic technology can realize degradation and mineralization of organic compounds,with the advantages of rapid reaction,low process cost,mild operating conditions and no secondary pollution.So it is a new process suitable for dye wastewater treatment.With the smallest band gap in bismuth halide oxide,BiOI has the widest absorption range of light and good photocatalytic performance of visible light.However,BiOI photocatalyst still has the disadvantages of low visible light utilization rate,low organic mineralization rate and poor stability,which restrict its application in practical environmental pollution treatment.Therefore,based on the shortcomings of BiOI,this paper mainly carried out the following research work:1?BiOI photocatalyst was prepared by low temperature liquid precipitation method,using salicylic acid as the structure control agent.The morphology and structure of the BiOI photocatalyst was characterized by XRD,FESEM,EDX,BET et al.The effects of reaction conditions and photocatalytic conditions on photocatalytic dye degradation by BiOI photocatalyst was investigated.The results showed that BiOI photocatalyst had a porous lamellar structure with stacks between them.BiOI photocatalyst had a high degree of crystallinity,an energy gap of 1.83 eV and a corresponding absorption edge of 678 nm.BiOI photocatalyst had maximum photocatalytic dye degradation in the conditions of Bi³⁺/salicylic acid mole ratio of1:1,Bi³⁺/I^-mole ratio of 1:1,reaction temperature of 25?,pH of 4 and the reaction time of 3 h.After 60 min LED light illumination,photocatalytic methyl orange dye?100 mL 10 mg/L?degradation reached 95.8%for 0.1g BiOI photocatalyst.Photocatalytic dye degradation was 80.2%after five times recycling for BiOI photocatalyst.Photocatalytic degradation of methyl orange dye for BiOI photocatalysts agreed with the quasi-first-order kinetic equation.holes?h⁺?and super oxide free radical?×O₂^-?ions were the main active species in the process of photocatalytic dye degradation for BiOI photocatalyst.2?BiOI/GO photocatalyst was prepared by in-situ low temperature liquid precipitation method.The morphology and structure of the BiOI/GO photocatalyst was characterized by XRD,FESEM,XPS,EDX,BET et al.The effects of reaction conditions and photocatalytic conditions on photocatalytic dye degradation by BiOI/GO photocatalyst was investigated.The results showed that BiOI/GO photocatalyst had lamellar structure with stacks between the lamellar layers.GO flakes were in close contact with BiOI.BiOI/GO photocatalyst had a high degree of crystallinity,an energy gap of 1.81 eV and an absorption edge of 685 nm.XPS spectra showed that BiOI/GO photocatalyst had Bi-O bond and I-O bond for BiOI as well as C-C,C=C,C-H,C-O and O-C=O bonds for graphene oxide.BiOI/GO photocatalyst had maximum photocatalytic dye degradation in the condition of GO content of 2%,Bi³⁺/I^-mole ratio of 1:1,reaction temperature of 25?,pH of 3 and reaction time of 2h.After 60 min LED light illumination,photocatalytic methyl orange dye?100 mL 10mg/L?degradation reached 90.1%for 0.05g BiOI/GO photocatalysts.Photocatalytic dye degradation was 78.2%after five times recycling for BiOI/GO photocatalyst.Photocatalytic degradation of methyl orange dye for BiOI/GO photocatalyst agreed with the quasi-first-order kinetic equation.The addition of GO could reduce the luminous intensity of BiOI/GO photocatalyst,and the hole?h⁺?and superoxide free radical?·O₂^-?were the main active species in the photocatalytic dye degradatio for BiOI/GO photocatalyst.