Study On The Photocatalytic Degradation Of Antibiotics In Water By LDHs And Their Composite Materials

With the rapid development of pharmaceutical,medical and aquaculture industries,antibiotic residues in wastewater are increasingly complex,which increases the difficulty of wastewater treatment virtually,and poses a threat to human health and aquatic ecological environment.Based on this,NiFe-LDHs and phosphotungstic acid intercalated NiFe-LDHs composite catalysts（PTA-LDHs）were constructed and their surface morphology,structure,physicochemical properties were investigated.The electron transport mechanism and path in the photocatalytic process of two catalyst systems were studied systematically.To explore the generation,migration and transformation process of active substances in the photocatalytic process,establish the kinetic process of catalyst system adsorption and photocatalytic degradation of tetracycline hydrochloride and related theoretical problems;The mechanism of enhancing the activity and stability of photocatalyst was studied.To realize the controllable construction,screening and optimization of LDHs system;A new method of green photocatalytic degradation of tetracycline hydrochloride residue in wastewater treatment was established.Specific research contents are as follows:1.A flower-like NiFe-LDHs photocatalyst was synthesized by one step hydrothermal method.BET characterization results showed that the synthesized NiFe-LDHs had a large specific surface area and more surface active sites.The photocatalytic test results showed that the degradation rate of tetracycline hydrochloride by NiFe-LDHs reached 84.11%in the heterogeneous photofenton process simulating visible light.Quenching experiments and ESR tests confirmed that·O₂^-and·OH were the main active substances in the system,and tetracycline hydrochloride was degraded through demethylation,oxidation,decarboxylation,demethylation,deamination,hydroxylation and deamidation.2.In order to further improve the photocatalytic degradation performance,PTA-LDHs photocatalyst was synthesized by hydrothermal method and ion exchange method on the basis of flower-like NiFe-LDHs.Compared with pure NiFe-LDHs,the degradation efficiency of tetracycline hydrochloride by intercalated material is greatly improved,reaching 90.30%,and the reaction consumption of H₂O₂is less than that of single NiFe-LDHs material.The intercalation of phosphotungstic acid effectively inhibits the recombination of photoelectrons and holes,which contributes to the photocatalytic degradation of tetracycline hydrochloride.Quenching experiments and ESR tests confirmed that h⁺and·OH were the main active substances in the system,and tetracycline hydrochloride was mainly degraded through dehydration,deamidation,hydroxylation and oxidation under its action.On this basis,the optimum conditions for photocatalytic degradation of tetracycline hydrochloride by the two materials were investigated,and the influences of different anion,humic acid and water quality were explored.The degradation of different kinds of antibiotics confirmed the broad spectrum of the catalyst,and the comparison of the recycling experiment and the characterization results before and after the experiment proved that the photocatalyst had good stability.The photocatalyst synthesized in this paper showed highly efficient photocatalytic activity against tetracycline hydrochloride,which provided a theoretical basis for the development and utilization of LDHs-based photocatalysts and a good reference for the study of synergistic mechanism and performance regulation between polyacids and LDHs.