Synthesis And Intelligent Prediction Of YMnO₃-based Photocatalyst

Pollutants from pharmaceutical and industrial wastes have a serious impact on human health and water environment.Textile wastewater has a large number of non-fixed dyes,and some dyes and their degradation products such as aromatic amines are highly carcinogenic.Tetracycline antibiotics are one of the most widely used antibiotics in aquaculture and veterinary medicine.These drugs will release harmful residual components in surface water and develop multidrug-resistant strains,thus posing a potential threat to human health and ecosystems.There is therefore a great need to develop cost-effective alternative technologies to degrade these drugs and dyes that will be released into the environment.Photocatalysis technology is a green technology that converts sustainable solar energy into required energy to degrade various pollutants into environmentally friendly small molecule organics,which has the advantages of low cost and environmental protection.In this thesis,YMnO₃ was used as the research object,and the binary and ternary heterojunctions formed by different substances and different proportions of YMnO₃ for the photocatalytic degradation of drugs and dyes were systematically studied.Based on the experimental results and intelligent optimization algorithm models,the physicochemical properties of YMnO₃-based photocatalysts were trained and predicted.The main research results are as follows:（1）The pure YMnO₃ and YMnO₃/MgAl₂O₄ heterojunction photocatalysts with the different mass percentages of MgAl₂O₄ were synthesized by the polyacrylamide gel method combined with the low temperature sintering technology.The effects of manganese salts including Mn SO₄·H₂O,Mn CO₃ and C₄H₆MnO₄·4H₂O on the phase structure,functional group,morphology,charge state and optical performance of YMnO₃ were investigated in detail.The pure YMnO₃ with uniform particles can be obtained by using C₄H₆MnO₄·4H₂O as manganese source.The results confirmed that the YMnO₃/MgAl₂O₄ heterojunction photocatalysts showed high optical absorption coefficient and the highest adsorption capacity of 122.86 mg/g for the adsorption of Congo red.The degradation percentages of YMnO₃/MgAl₂O₄ heterojunction photocatalysts for the degradation of Congo red,tetracycline hydrochloride and tetrabromobisphenol A under simulated sunlight irradiation were 98.98%,86.16%and 72.51%,respectively.It was also proved that the hydroxyl and superoxide radicals played a major role in the photocatalytic reaction of YMnO₃/MgAl₂O₄.（2）The YMnO₃/Ce O₂/MgAl₂O₄ heterojunction photocatalysts were prepared by a low temperature sintering technology,which showed good Congo red adsorption capacity and photocatalytic activity for the degradation of tetracycline hydrochloride under visible light irradiation.Systematic studies indicated that the YMnO₃/Ce O₂/MgAl₂O₄ composite photocatalysts have high light absorption coefficient,carrier transfer and separation efficiency,adsorbed oxygen concentration and photocatalytic activity.The adsorption capacity of YMnO₃/Ce O₂ composite photocatalysts was predicted by BP neural network,and BP neural network optimized by whale algorithm and genetic algorithm.The results show that the prediction ability of BP neural network optimized by genetic algorithm is the best.The adsorption mechanism analysis proved that the high adsorption capacity of YMnO₃/Ce O₂ composite photocatalysts was mainly attributed to the synergistic effect of electrostatic interaction,ion exchange and hydrogen bonding.The capture experiments show that the hole,hydroxyl and superoxide radicals are the main active substances in the photocatalytic process of YMnO₃/Ce O₂/MgAl₂O₄ composite photocatalysts.Combined with the experimental result and energy band theory,the photocatalytic mechanism of YMnO₃/Ce O₂/MgAl₂O₄ composite photocatalysts was proposed.（3）The MgAl₂O₄/C₃N₄/YMnO₃ heterojunction photocatalysts were synthesized by a low temperature sintering technology.The phase purity,microstructure,functional group information,elemental composition and photocatalytic activity of the synthesized samples were deeply explored by various characterization methods.The photocatalytic experiment confirmed that the MgAl₂O₄/C₃N₄/YMnO₃ heterojunction photocatalysts had high selectivity for the degradation of antibiotics.The photocatalytic activity of YMnO₃-based heterojunction photocatalysts was predicted by BP neural network model and BP neural network model optimized by various intelligent algorithms,and the training results optimized by whale algorithm were highly consistent with the experimental results.Simultaneously,the photocatalytic activity of YMnO₃-based heterojunction photocatalysts was predicted by this model.Combined with the energy band theory and high performance liquid chromatography-mass spectrometry characterization results,the possible degradation pathway of oxytetracycline hydrochloride was analyzed.The toxicity analysis showed that the final product was a non-toxic and harmless small molecule substance.