Preparation Of Cu/g-C₃N₄ Photocatalyst And Its Degradation Performance Of Tetracycline Under Visible Light

In recent years,the problem of residues of pharmaceutical antibiotics in the water environment has caused great concern.Among all types of antibiotics used,tetracycline（TC）has become one of the most used antibiotics.It is discharged into the environmental matrix,and it is a threat to the ecosystem and human health through the enrichment and concentration of the food chain.Therefore,effective control of tetracycline in the water environment is urgent.Photocatalytic technology mainly oxidizes a series of organic compounds effectively by generating highly oxidized hydroxyl radicals,which has great advantages in removing non-biodegradable tetracycline.Among them,the efficient visible light catalysis technology needs further study.In view of the above problems,this paper synthesized copper element-doped graphite carbon nitride composite materials by a simple hydrothermal method,and systematically studied the adsorption of TC and the visible light photocatalytic removal performance of the synthesized composite materials;Based on relevant characterization and experimental analysis,the mechanism of synergy of composite materials was discussed.The specific research work of this paper is as follows:A composite material with both adsorption and photocatalysis was synthesized by hydrothermal method.The composite material was synthesized with Cu particles modified photocatalyst g-C₃N₄.The optimal compounding ratio of the material was determined,and the reaction conditions of the compound photocatalyst were optimized,including pH value and catalyst dosage;the composite material was characterized by object image,crystal type,specific surface area and morphology.The results show that Cu and g-C₃N₄ are compounded in a 1:1 ratio（Cu/CN-1）to have the best tetracycline pre-removal effect.The best reaction conditions for the composite photocatalyst to remove tetracycline under visible light are: p H 5-7,the dosage of the catalyst is 10mg/50 m L;there is no other impurity peak in XRD analysis,and there is no new element valence information in XPS.The above shows that the composite material has no other impurities and the carbon nitride bond information is retained after compounding integrity.The BET characterization shows that Cu/CN-1 has the optimal specific surface area and pore volume.This is because when the doping amount of Cu is too much or too little,it will cause the limitation of the modification effect of Cu between the carbon nitride layers or the space blockage.Only when the doping ratio is appropriate,the optimal interlayer structure is formed between the composite materials,which is consistent with the SEM and TEM characterization.The TC removal performance of the prepared composite material was investigated.The effect of the composite photocatalyst adsorption performance under dark processing conditions and the absorption/photocatalysis synergy performance under visible light conditions was compared,and then,through recycling performance The experiment considers the economics of composite materials.The results are as follows: the modification of Cu in the composite material does give carbon nitride excellent adsorption capacity;the adsorption kinetics and isotherms of Cu/CN-1 conform to the pseudo-second-order kinetic model and langmuir model,respectively,Cu/CN-1 The adsorption of TC is mainly chemical adsorption,and it is a single layer adsorption;the photocatalytic/adsorption synergistic removal ability of TC is enhanced than the adsorption effect,of which Cu/CN-1 achieves the most outstanding tetracycline removal effect,within 30 min The removal rate of TC（50 mg L-1）is almost as high as 99%.The composite photocatalyst retained 94% of the TC effect after four cycles of experiments,confirming the material’s reusability.FTIR,PL,EIS,Uv-vis,transient photocurrent response and free radical trapping experiments were used to explore the adsorption mechanism and photocatalytic mechanism of TC on composite materials,and to explain the mechanism of adsorption/photocatalysis.The results are as follows: the adsorption mechanism of the composite photocatalyst for TC is mainly attributed to the electrostatic interaction and surface complexation between the introduced copper ions and amino groups.The mechanism of the enhanced photocatalysis of the composite material comes from two aspects.The UV-Vis characterization shows that the composite photocatalyst material has enhanced absorption of visible light.The PL,EIS and transient photocurrent response characteristics show that the recombination rate of photogenerated electronholes of the composite material is reduced.Synergistic mechanism of adsorption/ photocatalysis The modification of Cu particles firstly significantly increases the adsorption sites of Cu/CN-1 for TC,giving the composite with excellent adsorption capacity,and secondly,the excellent conductivity of Cu metal effectively suppresses charge recombination and expanded visible light absorption.Based on this,the composite photocatalyst prepared achieves efficient removal of TC.