Fabrication Of Carbon Quantum Dots Decorated Semiconductor Composites And Study On The Treatment Of Azo Dye Wastewater Under Visible Light Radiation

Nowadays,azo dye is one of the most popular and widely used production in dyeing and printing industry.However,nearly 15% of the dyestuffs are discharged into the environment during the dyeing process.This throws great threaten on our healthy and life.Thus,industrial wastewater containing azo dyes must be treated before released into the environment.Unfortunately,the effects of traditional treatment on azo dye wastewater are unsatisfactory,and toxic aromatic amines may generate under some extame conditions?for example anaerobic condation?.Therefore,a novel technique,which is efficient,green and sustainable,is must for dealing of industrial wastewater.Thus,semiconductor photocatalytic technology has come into people's view under this background.Nevertheless,the photocatalytic activities of the single semiconductor photocatalysts are insufficient for practical application.Therefore,carbon quantum dots was used to improve the photocatalytic activities of photocatalyst in this work.The main contents of our work are summarized as the follows:1.The CQDs/Zn Fe2O4 composite was prepared by a simple ultrasonic assisted method.The results of multiple analysis technologies show that ZnFe2O4 microspheres are coated with low contrast carbon quantum dots to form a core-shell structure.The photocatalytic activity of CQDs/ZnFe2O4 hybris material were evaluated by the degradation of methylene blue,and 20wt% CQDs/ZnFe2O4 sample shows the best photocatalytic activity,which is 4.9 times higher than that of pure ZnFe2O4.Based on the results of UV-vis absorption spectra,fluorescence and impedance analysis,we propose a possible mechanism for the improvement of photocatalytic activity.2.A novel carbon dots-decorated In₂S₃ microsphere photocatalyst was synthesized by a simple one-step hydrothermal method,and the carbon dots-decorated In₂S₃ microsphere photocatalyst shows excellent photocatalytic degradation activity of azo dye?the photocatalytic degradation rate is nearly 90% after 120 min?.After the analysis of multiple technologies,we find that the carbon dots decorated In₂S₃ microsphere photocatalyst had excellent performance due to the upconversion fluorescence function and the excellent electron transfer ability of carbon quantum dots.Based on trapping experiments,electron spin resonance technology,UV-Vis absorption and theoretical calculations,·O2-and h+ are determined to be the main active species,and a possible photocatalytic degradation mechanisms is also proposed.3.This work is mainly focused on the photocatalytic degradation of azo dyes?methyl orange?under visible light whit CQDs/Bi4O5I2 composite.In order to better highlight the advantages of CQDs/Bi4O5I2 composite,we prepared the most representative Bi4O5I2-based heterojunction?Bi2S3/Bi4O5I2 composite?as a reference.After a comprehensive study of CQDs/Bi4O5I2 composite and Bi2S3/Bi4O5I2 composite,the results show that CQDs/Bi4O5I2 composite possesses better photocatalytic performance?photocatalytic degradation activity and photocatalytic stability?than Bi2S3/Bi4O5I2 composite.In addition,carbon quantum dots has also the advantages of low toxicity,environmental protection,low cost and easy synthesis compared with Bi2S3.Therefore,the carbon quantum dots decorated semiconductor photocatalysts have great potential in the treatment of azo dyes wastewater.