Study On Bi₂Fe₄O₉ Photocatalyst And Its Composite Materials For Photocatalytic Degradation Of Xanthate

Xanthate is widely used as a collector for sulfide ore flotation because of its low cost,strong collection ability,and high solubility.However,xanthate is toxic,and it may damage the human nervous system and pollute the environment if discharged without treatment.Traditional treatment methods such as acid-base neutralization,natural degradation,adsorption,and the Fenton method are limited by their low degradation efficiencies,secondary pollution,or high costs.Thus,it is necessary to develop an eco-friendly and cost-effective method for xanthate emission control.Photocatalysis has received much attention in the degradation of organics due to its nontoxicity and high cost-effectiveness.Bi₂Fe₄O₉,a type of bismuth ferrite,is widely used for the degradation of organic pollutants due to its narrow band structure and visible light response ability.However,the rapid recombination of photogenerated carriers limits the photocatalytic activity of Bi₂Fe₄O₉.Firstly,this study synthesized successfully Bi₂Fe₄O₉ photocatalysts by hydrothermal method.The prepared samples were characterized by XRD and SEM,and the effects of hydrothermal temperature,mineralizer type,and mineralizer concentration on the phase and morphology of the products were investigated.Based on the xanthate degradation efficiency for Bi₂Fe₄O₉,the optimal process parameters for synthesizing Bi₂Fe₄O₉ were determined,the hydrothermal temperature of 200℃,mineralizer using KOH,and KOH concentration of 4.5 mol/L.To further improve the photocatalytic activity of Bi₂Fe₄O₉,Bi₂Fe₄O₉ and Zn In₂S₄are coupled to form a heterojunction.Bi₂Fe₄O₉/Zn In₂S₄ composites,denoted as x BFO/ZIS with x as BFO to ZIS mass ratio in percentage,are synthesized using a facile impregnation method and tested for photocatalytic degradation of xanthate for the first time.Then,the effects of catalyst dosage,initial concentration of xanthate,the p H value of xanthate solution,and Ca²⁺/Mg²⁺ions on xanthate photodegradation are investigated systemically.Furthermore,the possible photocatalytic mechanisms of 30BFO/ZIS are proposed based on the results of scavenging tests,Mott-Schottky measurements,and density functional theory（DFT）simulations.Results show that the degradation efficiency of 30BFO/ZIS is 98.25%during 90 min of irradiation under visible light;this efficiency is 2.63 and 2.89 times higher than those of pure ZIS and BFO,respectively.The great photocatalytic activity of 30BFO/ZIS is mainly attributed to the formation of TypeⅡheterojunction between the BFO and ZIS,which improves the separation of photogenerated carriers.This explanation is verified by a smaller PL intensity and greater transient photocurrent responses.In addition,EIS results show that the formation of heterojunction enhances the migration of h⁺and e^-pairs.The O₂·^-plays a key role in the xanthate degradation process,according to the scavenging test results.Finally,xanthate degradation efficiency over 90 min of 30BFO/ZIS decreases slightly from 98.25%to 92.86%after four cycles,indicating its excellent durability and stability.There are 27 figures,5 tables,and 174 references in this thesis.