Design And Synthesis Of G-C₃N₄-based Composites And Study On Their Photocatalytic Degradation Of Xanthate

The xanthate collector is one of the most effective and most used flotation reagents for treating sulfide ore,which is widely used in sulfide ore dressing plants,resulting in the presence of a certain amount of xanthate in the flotation wastewater.However,even low-concentration xanthophyte wastewater will emit a foul odor;if xanthophyte wastewater enters the river,it will seriously affect the normal physiological activities of aquatic plants,and endanger the surrounding ecological environment and human health.Traditional xanthate wastewater treatment methods have the disadvantages of high cost,long time required for purification,and easy generation of secondary pollution.Photocatalytic technology has the advantages of low cost,pollution-free,and effectively removal of organic pollutants.Therefore,the application of photocatalytic technology has a great theoretical and practical meaning for the treatment of flotation wastewater.In this paper,photocatalytic technology is used to treat xanthate wastewater.Firstly,two-dimensional g-C₃N₄ nanosheets were prepared by air oxidation etching.The defects of the g-C₃N₄ nanosheets with high reactive sites were used to construct Ni Fe-LDH@Fe₃O₄@g-C₃N₄?recorded as LFCN?and Fe₂O₃@TiO₂@g-C₃N₄?recorded as FTCN?composite photocatalysts.The g-C₃N₄ is coupled with the metal semiconductor to form a heterojunction which is easy to separate and transport photoexcitons.Through the energy level matching,the stepwise transfer of photogenerated carriers is realized,and the composite probability of photogenerated excitons is reduced.The effects of morphology and energy band structure on photocatalytic activity were studied.The photocatalytic activity and stability of photocatalysts were studied systematically.The degradation mechanism of photocatalytic materials for xanthate was analyzed in detail.The specific research contents and results are as follows:?1?In order to increase the reactive sites,and improve the quantum efficiency,the three-membered Fe₃O₄,Ni Fe-LDH and g-C₃N₄ are used to form a flower-like heterostructure LFCN composite photocatalyst.The band structures of LFCN photocatalysts were controlled by changing the total molar amount of iron and nickel in precursor.The photo-generated electrons were obtained by the energy level matching of Fe₃O₄,Ni Fe-LDH and g-C₃N₄,reducing the composite probability of photo-excitons;Photocatalytic performance of LFCN was evaluated by degrading ethyl sodium xanthate solution.When the total nickel-iron molar amount is 3 mmol,the synthesized photocatalyst?expressed as 3LFCN?has the best performance in degradation of ethyl sodium xanthate.The best experience conditions were obtained by exploring the initial concentration and pH of ethyl sodium xanthate solution.Under the condition of the initial concentration of sodium sulphate solution is 50 mg/L,pH = 6,the weight of photocatalyst is 20 mg and visible light irradiation for 5 h,the degradation rate of alkaline sodium xanthate is 94.7%.?2?Starting from broaden the spectral response range and the improvement of photo-carrier separation and migration efficiency,a hetero-junction photocatalyst FTCN was prepared by coupling Fe₂O₃,TiO₂ and g-C₃N₄.The band structures of FTCN photocatalysts were controlled by changing the mass ratio of TiO₂ to g-C₃N₄,broadening the spectral response range of FTCN.Good photogenerated electron transport path is achieved by energy level matching among Fe₂O₃ TiO₂ and g-C₃N₄,which realizes electron-staged transmission and reduces photo-induced excitation recombination.The photocatalytic activity and stability of FTCN were evaluated by degrading ethyl sodium xanthate solution.The photocatalyst prepared at the mass ratio g-C₃N₄/TiO₂ = 5%/95%?denoted as 5FTCN?has the best photocatalytic performance for degradation of ethyl sodium xanthate.The best experience conditions were obtained by exploring pH and the initial concentration of sodium sulphate.Under the condition of the initial concentration of sodium xanthate was 50 mg/L,pH = 7,the amount of photocatalyst was 20 mg and visible light degradation for 100 min,the degradation rate of selenium sodium xanthate was 98.33%.