Study On Preparation Of Bismuth Subcarbonate Materials And Their Photocatalytic Performance And Mechanism

The rapid development of various industries has caused an increase in organic matter pollution,which has become a global issue of concern.Synthetic dyes are widely used in modern industry and have a great impact on the organic pollution of the environment,so their degradation and removal has become a research hotspot in environmental engineering.Semiconductor photocatalytic oxidation technology has become a promising alternative for wastewater purification because it is a green and sustainable technology.Recently,Bi-based photocatalysts,such as bismutite?Bi₂O₂CO₃?,have been widely studied owing to their multiple advantages,such as excellent photocatalytic activity and unique crystal and electronic structures.However,the degradation pathways and catalytic mechanism of different-type organic dyes over Bi₂O₂CO₃ are seldom studied which limited their wide application in organic degradation.Moreover,the Bi₂O₂CO₃ catalysts can be only excited under UV irradiation due to its wide band gap and its photocatalytic activities are weakened by the rapid recombination of photoelectron–hole pairs,which significantly limits their photocatalytic efficiencies and development in the field of photocatalysis.Consequently,designing a highly efficient visible-light-driven photocatalyst,fast photogenerated electron-hole pair separation and stable photocatalyst is the key to the development of photocatalytic technology.This article mainly compares and discusses the degradation pathways and catalytic mechanisms of different-type organic dyes on Bi₂O₂CO₃.Through the doping of the external element reduced graphene oxide?GO?and the modification of functional materials polydopamine?PDA?,a new and efficient Bi₂O₂CO₃-based composite material is designed for the purification of organic wastewater.The main research contents and obtained results are shown as follows:?1?By selecting three typical dyes with different charge properties as model pollutants,the inherent roles of adsorption,degradation pathways and mechanism of using Bi₂O₂CO₃ photocatalyst to remove organic pollutants from aqueous solution were systematically studied.Bismutite can effectively degrade dyestuffs[e.g.,anionic dye methyl orange?MO?,amphoteric dye rhodamine B?RhB?,cationic dye methylene blue?MB?,and their mixed solutions].Degradation kinetics is different when treating different types of dyes and possibly because of their significantly different adsorption behaviors on bismutite.The inherent molecular structure,charge properties of dyes,and attraction between dye and bismutite may particularly dominate degradation efficiency.Moreover,h⁺and?O₂^-were main active species for MO and RhB degradation,whereas rich adsorption of MB on bismutite significantly inhibited the separation of electron-hole pairs and thus?OH was dominant for MB degradation.According to the intermediates generated during the reaction,the degradation pathways of three dyes were proposed.This study revealed the adsorption and photocatalytic behaviors of different-type dyes on the tetragonal bismutite catalyst,which facilitates in understanding the degradation processes and mechanism of different-type organic pollutants and promotes the practical application of bismutite in complex wastewater purification.?2?To overcome the drawbacks of large band gap and high electron–hole recombination rate of Bi₂O₂CO₃ for organic pollutants degradation,novel Bi₂O₂CO₃?BOC?/reduced graphene oxide?rGO?/polydopamine?PDA??BGP?ternary hybrids were first designed through a green chemical method.By incorporating rGO and PDA in BOC,the kinetic constant of BGP to catalytically degrade methyl orange?MO?was significantly increased;over fourfold elevated rather than that of Bi₂O₂CO₃ due to the high electron transfer capability of rGO and superior adhesive force of PDA.UV–Vis diffuse reflectance spectrum and photoelectrochemical results confirmed the improvement of the light absorption range and charge transfer capability because of the synergistic effect of rGO and PDA.Electron spin resonance results unraveled the catalytic mechanism that both holes?h⁺?and superoxide radicals?·O₂^-?were the main oxidative species for MO degradation.This study developed a highly efficient BGP material and provided deep understanding of the structure–performance relationships of materials for organic pollutant degradation.