Preparation Of RGO-AgI/Bi₂MoO₆ Composite Catalyst And Its Photocatalytic Degradation Of Rhodamine B

Dyes have always been industrial materials that are consumed by various industries.Because dye wastewater has the characteristics of high chroma,high toxicity and low biodegradability,dye wastewater poses serious threat to the surrounding environment.Pollution,which in turn affects water sources and aquatic organisms,indirectly poses a hazard to humans.The research on photocatalytic degradation of dye wastewater has been widely concerned,but common photocatalytic methods such as TiO₂ can only utilize the light energy in the ultraviolet band,and the utilization rate in the solar energy range is too low.The RGO-AgI/Bi₂MoO₆ composite catalyst was prepared and its related characterization,experimental results and influencing factors were investigated.The possible photocatalytic mechanism was proposed.In this paper,the RGO-AgI/Bi₂MoO₆ composites were prepared by the hydrothermal-liquid phase precipitation method.The mass fraction of RGO in the composites was controlled by adjusting the dosage of graphene oxide.The concentration of AgI and Bi₂MoO₆ is used to control the mass ratio of AgI and Bi₂MoO₆,and the two parameters are comprehensively controlled to obtain the RGO-AgI/Bi₂MoO₆ composite with the best photocatalytic property.SEM result showed that Bi₂MoO₆ material with special plate-like structure and AgI particles were combined with RGO.The lattice fringes corresponding to the（002）crystal plane of AgI and the（060）crystal plane of Bi₂MoO₆ were observed by TEM and HRTEM.And the EDX analysis indicated that the composited of C,O,Bi,Mo,Ag,I.XRD patterns of the composite indicated that typical（020）,（131）,（002）,（060）,（151）,（280）and（240）of Bi₂MoO₆ and（100）,（002）,（110）,and（112）of AgI could be detected.This demonstrated that the composite has a good Bi₂MoO₆ orthorhombic structure and aβ-AgI hexagonal crystal structure.At the same time,UV-DRS analysis showed that the RGO-AgI/Bi₂MoO₆ composite material showed red shift and the light absorption intensity was improved compared with that of Bi₂MoO₆ material.In this study,rhodamineB（RhB）was selected as the target contaminant to evaluate the photocatalytic performance of the ternary RGO-AgI/Bi₂MoO_6,the xenon lamp was used as the light source to simulate visible light.The photocatalytic reaction of the material showed excellent photocatalytic performance.The experimental kinetics fitted well with the pseudo first-order kinetics model.The reaction rate was 1.7 times,2.1 times and 14.6 times that of AgI/Bi₂MoO₆,AgI,Bi₂MoO₆,respectively.In the investigation of the effect of degradation AgI:Bi₂MoO₆ ratio,it was found that the rhodamine B degradation increase first and then decreased with the increase of the ratio,and the mass ratio is 6:4.moreover,it was found that with the increase of RGO mass fraction,the rhodamine B degradation increased first and then decreased,and the optimal content was 1%.At the same time,experiments were also explored to study the influencing factors related to photocatalysis,including the photocatalyst dosage,rhodamine solution concentration,light intensity,initial pH of rhodamine B solution,different coexisting anions,etc.The cycle experiment indicated the good repeatability of the composite.The XRD analysis of the RGO-AgI/Bi₂MoO₆ composite catalyst before and after the reaction showed that the sharpness and peak height of the diffraction peak of the material crystal showed almost no change,and there was no obvious peak shift,this suggested that the compositean catalyst has stable structure and good photocatalytic ability.The results of quenching experiments showed that·O₂^-,and h⁺played crucial role in the degeradation process,and the effect of·OH could be ignored.Based on the quenching experiment and the structural composition of the material,the possible reaction mechanism of RGO-AgI/Bi₂MoO₆composite toward RhB degradation was proposed.The photo-generated carriers were generated by photoexcitation,the photo-generated carriers migrated to the surface of the material,and the photo generated electrons moved to the reduced graphene oxide.The electron on the reduced grapheme oxide was consumed by the dissolved oxygen to produce·O₂^-.on the other hand,the holes（h⁺）remaining on the valance band of AgI could oxideze RhB directly.