Study On Degradation Of Pollutants By G-C₃N₄-based Composite Photocatalyst

Pharmaceutical antibiotics are worldwide employed for preventing and treating bacterial infections.Antibiotic tetracycline（TC）as one of the broad-spectrum bacteriostasis agents has been used for decades.However,due to the misuse of antibiotics and the metabolism-resistant property,it has been monitored and excessively accumulated in the aquatic environment,which will pose a huge threat to human health.For purpose of alleviating this threat,a great deal of approaches have been adopted,including photocatalytic technology,chemical reaction,physical absorption,biological degradation etc.Among these methods,photocatalytic degradation is an effective and promising technique to remove the environmental contaminants because of its high capability.The main contents of this thesis are as follows:（1）Z-scheme heterojunction research has become a hotspot in the field of photocatalysis owing to the strong oxidative and reductive capacity for driving photocatalytic reactions.In this work,for the first time,a Z-scheme ternary bismuth phosphate/reduced graphene oxide/protonated g-C₃N₄（BiPO₄/rGO/pg-C₃N₄）photocatalyst was fabricated for photocatalytic degradation of tetracycline（TC）.The optimal mass ratios of rGO and pg-C₃N₄ were confirmed as 1.2 wt%and 40 wt%,respectively.This Z-scheme heterojunction exhibited an enhanced TC degrading ability with an 80.0%of TC decomposition after 50 min simulated solar light irradiation,which was 3.3 and 6.3times that of pg-C3N4 and BiPO4,respectively.Importantly,the internal electric field（IEF）forced Z-scheme charge transfer of BiPO₄/rGO/pg-C₃N₄ composites,possessing higher charge separation efficiency.The formation of the Z-scheme heterojunction was substantiated by radical scavenging experiments and Mott-Schottky measurements,and it was beneficial for the photocatalytic reaction by accelerating the charge separation and improving the redox ability.Moreover,rGO as cocatalyst could not only provide TC adsorption and catalytic sites but also further promote the charge transfer.（2）The g-C₃N₄/Ag₃PO₄/rGO ternary photocatalyst was prepared to study its catalytic degradation of phenol by precipitation method.The results showed that the removal rate of phenol under visible light was the highest when the amount of catalyst was 1.0 g/L.The visible light irradiation for 120 min,the removal rate by g-C₃N₄/Ag₃PO₄/rGO photocatalyst was over 92%.After 3 cycles of photocatalytic degradation of phenol,the photocatalytic efficiency remained 85.0%,showing great stability.The active radical trapping experiment proved that the degradation process is mainly completed by the oxidation of·O₂^-and h⁺.The preparation of g-C3N4/Ag3PO4/rGO by precipitation method was simple,the conditions were controllable,and it had a good application prospect.