Investigation On Catalytic Performance Of Metal Oxide Quantum Dots/carbon Nitride Hybrid For Pollutants Degradation

With rapidly growing urbanization and industrialization,water shortage and water pollution are becoming increasingly serious.Water pollution caused by organic pollutants poses a severe threat to the environment and human health.Because of its chemical stability,excellent water solubility and low bioavailability,Tetracycline（TC）became one of the organic compounds that were difficult to degrade in wastewater.In recent years,advanced oxidation process（AOPs）has been demonstrated excellent efficiency for water treatment,and due to its environmental friendliness,it has attracted widespread attention in the field of degradation.Among them,Fenton/Fenton-like oxidation is considered as an effective way to remove refractory pollutants.Transition metal oxide,as an effective and low-cost Fenton/Fenton-like catalyst,is capable to catalyze Fenton/Fenton like reactions to produce active species such as hydroxyl radicals（·OH）,superoxygen radicals(O₂^·–)for water treatment.Unluckily,traditional transition metal oxide catalysts are limited by their disadvantages of poor dispersion,easy agglomeration,less active sites exposed onto the surface and so on.Carbon nitride,a promising visible light responsive semiconductor material,has been widely used in the field of photocatalysis because of its facile preparation and stable property.However,the insufficient absorption of visible light,low efficiency of photo-generated charge separation and transfer limited the catalytic activity of carbon nitride.Based on the above considerations,herein,a novel metal oxide quantum dots/carbon nitride composite is fabricated through coupling carbon nitride nanosheets and transition metal oxide quantum dots for photo-Fenton or photo-Fenton-like oxidation to achieve high degradation efficiency of TC.The specific research contents are as follows.A Cu O QDs/ultrathin CNNSs with abundant nitrogen vacancies(N_vac)composite was successfully constructed via Na BH₄treatment followed by one-step chemical reaction and annealing.Compared with pristine CNNSs and Cu O QDs/CNNSs hybrid without N_vac,Cu O QDs/CNNSs-N_vac-300 exhibited excellent performance for photo-assisted PMS activation towards the removal of TC,wherein 96.4%TC（50 mg/L）can be degraded in 30 min under visible light irradiation and the presence of PMS.Cu O QDs/CNNSs was able to expose more active sites,which could improve the photo-generated charge separation and created more radical species.The quenching tests displayed that ¹O₂and h⁺were the dominant active species in vis/PMS/Cu O QDs/CNNSs-N_vacsystem.The excellent catalytic performance was attributed to the synergistic effect of photocatalysis and PMS activation.The development of catalysts with multi-active sites is of great importance for enhancing catalytic performance.A novel copper-iron bimetallic oxide quantum dots/carbon nitride nanosheets（Cu Fe O QDs/CNNSs）catalyst was successfully synthesized through a simple synthesis strategy.The optimal catalyst,namely,Cu Fe O（7:3）QDs/CNNSs,exhibited excellent performance,and about 98.6%TC（50 mg/L）can be degraded under vis/H₂O₂system in 30 min in a wide p H value range of 3-9.The strong interfacial coupling between CNNSs and Cu Fe O QDs,and the synergistic effect between Cu-Fe oxide quantum dots were able to expedite the separation and transfer of electron/hole pairs and improve Fe（III）/Fe（II）conversion.Based on the quenching tests,the active species in the reaction were determined,and the mechanism of the photo-Fenton degradation process towards TC was estimated.