Study On The Structural Regulation And Photocatalytic Performance Of Clay-based Catalysts

Due to non-toxicity,high chemical stability and high photocatalytic performance,nano-TiO₂ presents broad application prospects in degrading organic pollutants.However,TiO₂ still has some shortcomings,such as easy agglomeration,difficulty recovery,and low sunlight utilization in the process of sewage treatment,which greatly limits its photocatalytic activity.Clay minerals have a large specific surface area and strong adsorption capacity,and graphene oxide?GO?has a high charge carrier mobility.Therefore,the preparation of clay/TiO₂/GO composites can effectively improve the photocatalytic performance of TiO₂.In this work,three composites i.e.kaolinite/TiO₂/GO,montmorillonite/TiO₂/GO and palygorskite/TiO₂/GQDs were prepared by the facile sol-gel method.The microstructure of each clay-based photocatalyst was regulated through the design of the addition process and the adjusting of additon mount of graphene,and the photocatalytic performance of three composites for degradation of MO were compared.The role of the structure of the material,the hydroxyl groups on the clay surface and graphene oxide in photodegradation were discussed and the corresponding promotion mechanism was obtained.The detailed results are as follows:?1?Using kaolinite as the carrier,a series of kaolinite/TiO₂/GO composites?KTG?with support structure and different GO contents were synthesized.Compared with the kaolinite-TiO₂?KT?composite,KTG composites exhibited higher photocatalytic performance in degrading methyl orange?MO?under simulated sunlight,and the photocatalytic performance of KTG increases with GO content?1?4%?.KTG4 has the best photocatalytic performance.By the design of reference experiments and computer simulation,it was found that the improvement of KTG's photocatalytic performance can be attributed to:I,enhanced light absorption;II,Schottky junction formed between GO and TiO₂;III,increased TiO₂ content on GO,and convenient exchange in and out of reactive species in the support structure;IV,the improved adsorption of dissolved oxygen and MO^-on the hydroxyl surface of kaolinite.?2?Using montmorillonite as the carrier,a montmorillonite/TiO₂/GO composites?MTG?with pillar structure was synthesized.Compared with the montmorillonite-TiO₂?MT?composite,the addition of GO increases the photocatalytic rate constant by 1.50?2.50 times.Various analysis results indicate that the improvement of photocatalytic performance of MTG can be attributed to:I,the increase in light absorption;II,the Schottky junction formed between GO and TiO₂;III,the convenient exchange of entry and exit of reactive species in the pillar structure;IV.Accelerated separation of photogenerated electrons-holes by surface and interlayer pillar structures.?3?Using palygorskite as the carrier,palygorskite/TiO₂/GQDs composites?PTG?with different contents of graphene quantum dots?GQDs?was synthesized.Compared with palygorskite-TiO₂?PT?composite,the addition of GQDs increased the photocatalytic rate constant by 1.43?2.27 times.The introduction of GQDs did not significantly improve the light absorption capacity of the material,but it could significantly improve the separation efficiency of photogenerated electrons-holes.The enhancement of PTG photocatalytic performance can be mainly attributed to the heterojunction formed between GQDs and TiO₂,and the adsorption of MO^-on the palygorskite surface structure.The capture experiment showed that the main active species in the photocatalytic reaction process was hydroxyl radical.The thesis includes 45 Figures,2 tables and 158 references.