Study On Preparation Of Ag₆Si₂O₇-based Composite Photocatalysts And Their Performance In Dye Decolorization

Dye wastewater contains various stubborn dye molecules and dyeing auxiliaries.Unreasonable wastewater discharge will pose a potential danger to human health and aquatic environment.Therefore,the development of effective and reliable dye wastewater treatment method has become a key task to create sustainable ecological conditions.Photocatalytic oxidation technology has attracted much attention due to its high efficiency and low cost.However,most semiconductor photocatalysts are still limited by insufficient visible light utilization and high light carrier recombination rate,leading to low catalytic efficiency and restricting the practical application of photocatalysts.Therefore,the development of visible light-induced photocatalysts with high stability and wide spectral response is an ideal solution to above problems.In this study,the narrow band gap Ag₆Si₂O₇ with strong visible light response was used as the core matrix material,four different silver-based semiconductors were used as the doping components to composite it,finally loaded on Fe₃O₄ to endow magnetic properties,the photodegradation of rhodamine B（Rh B）properties was used as the evaluation index to screen the optimal photocatalytic composites.In addition,the effects of reaction conditions on the photocatalytic performance of composite materials were systematically investigated,and the degradation mechanism of Rh B by heterojunction composite photocatalysts was revealed from the aspects of characterization of the physicochemical properties of photocatalysts,determination of the types of active substances in the reaction system,and analysis of Rh B degradation intermediates.The research conclusions obtained were as follows:（1）Compared with Ag₆Si₂O₇ single material,the photocatalytic degradation performance of Ag₆Si₂O₇/Ag₃PO₄and Ag₆Si₂O₇/Ag Br composite materials was significantly improved,while the photocatalytic activity of Ag₆Si₂O₇/Ag₂WO₄ and Ag₆Si₂O₇/Ag₂Mo O₄ composite materials was inhibited.After loading Fe₃O₄,the efficiency of Rh B degradation of Ag₆Si₂O₇/Ag₃PO₄/Fe₃O₄composite pholocatalyst was suppressed by 54.8%.Finally,Ag₆Si₂O₇/Ag₃PO₄ and Ag₆Si₂O₇/Ag Br/Fe₃O₄ composite photocatalytic materials were selected for subsequent experiments.（2）Ag₆Si₂O₇/Ag₃PO₄ and Ag₆Si₂O₇/Ag₃PO₄/Fe₃O₄ composite photocatalysts had excellent light absorption properties in both ultraviolet and visible light regions,and Ag₆Si₂O₇/Ag₃PO₄/Fe₃O₄ could achieved rapid separation under an external magnetic field.The surface of the two photocatalysts was negatively charged when the p H was greater than 3.5,and the change of the initial p H of the system had little effect on the degradation efficiency of Rh B.In addition,cycling experiments showed that both composite catalysts had a certain degree of stability and reusability,and the active species h⁺and·O₂^-played major roles in the catalytic process of the two composite photocatalysts.（3）For Ag₆Si₂O₇/Ag₃PO₄ composite materials,the formation of p-n heterojunction effectively reduced the charge transfer resistance and promoted the transfer of photogenerated carriers.For Ag₆Si₂O₇/Ag₃PO₄/Fe₃O₄ composite materials,the formation of Z-type heterojunction increased electron mobility while maintaining high redox capability.In addition,the degradation path of Rh B was divided into four processes:deethylation,benzene ring cracking,ring opening and mineralization.This study confirmed that the two Ag₆Si₂O₇-based heterojunctions prepared exhibited enhanced photocatalytic activity.The construction of multi-electron transmission paths improved the separation of photogenerated carriers,which was beneficial to promote the development and application of Ag₆Si₂O₇-based photocatalysts.