Preparation Of GO/MnO₂/BiOI Photocatalyst And Its Catalytic Effect Of Potassium Persulfate On RhB Degradation

Dye wastewater is a kind of common industrial wastewater,which has the characteristics of refractory,highly toxic and toxic organisms.Therefore,it is of great significance to develop economical and efficient dye wastewater treatment technology.Photocatalytic persulfate oxidation technology is considered to be a potential water treatment technology,the core of this technology is the preparation of high-efficiency photocatalysts.Photocatalysts should meet two requirments:one is to have good absorption of visible light,and the other is to catalyze persulfate to generate active species.BiOI has attracted much attention due to its special layered structure and good absorption of visible light.MnO₂ acts as a good catalyst for persulfate,and its composite with BiOI can improve the activity of the composite photocatalyst.This paper intends to prepare GO/MnO₂/BiOI ternary composite catalyst by doping graphene（GO）,optimize the preparation conditions,characterize the structure of the catalyst,and the photocatalytic persulfate degradation efficiency and mechanism of the composite catalyst for Rh B are studied with Rhodamine B（Rh B）as the target pollutant.The flower-like and rod-like MnO₂ with graphene composites were prepared by hydrothermal method and water bath co-precipitation method,respectively,and further loaded with BiOI,and the photocatalytic activity of rod-shaped MnO₂/GO/BiOI with a ratio of 3∶1∶2 is the best.The SEM measurement results showed that the diameter of rod-shaped MnO₂ is about 400 nm,and it is supported by staggered between graphene oxide sheets,and BiOI microspheres are successfully supported on the surface and gap of rod-shaped MnO₂ and lamellar graphene.Using it as a photocatalyst to degrade Rh B,the effects of catalyst dosage,initial Rh B concentration,initial p H,anion concentration and cycle times are investigated.The results show that:when the p H is 3,the dosage of GO/MnO₂/BiOI is 0.5 g/L,and under the conditions of visible light irradiation for 60min,the degradation rate of Rh B（20 mg/L）is about 97%,and the removal rate after four cycles reaches 94.77%.Radical trapping experiments show that the main active species are holes（h⁺）,followed by·O2^-.GO/MnO₂/BiOI is applied to the photocatalytic persulfate system for the degradation of Rh B.The results show that at p H=7,the catalyst dosage is 0.5 g/L,and the K2S2O8 dosage is 5 m M,the catalyst could degrade 20 mg of catalyst within 20 min.The removal of Rh B is more than 96%,and the excellent degradation effect of 60 mg/L Rh B is also more than 66%.The addition of Cl^-（10 m M）promotes the degradation of Rh B by the system,while the addition of NO3^-and CO3^2-inhibite it.The catalyst has good cycle stability,and the removal rate is more than 95%after five cycles.The free radical trapping experiments show that h⁺and SO4·^-are the main active species of the photocatalytic system.Since the GO/MnO₂/BiOI photocatalytic persulfate system further widens the applicable range of p H,it provides a new idea for the practical application of this photocatalyst,and has reference significance for the photocatalytic purification of dye wastewater.