Study On Adsorption Of Chlortetracycline Hydrochloride By Iron-Yttrium Bimetallic Metal-Organic Gel

As a representative of tetracycline antibiotics（TCs）,chlortetracycline hydrochloride（CTC）is widely used in human treatment and animal husbandry.However,antibiotics cannot be fully absorbed or metabolized by organisms,and a large number of antibiotics remain in the feces,which are then released into the environment.The long-term presence of antibiotics in the environment may threaten human health through toxic effects.At the same time,the accumulation of waste antibiotics from different sources in groundwater,surface water,and wastewater can induce the evolution of antibiotic resistance genes,increasing potential risks to ecosystems.Therefore,the effective treatment of chlortetracycline hydrochloride（CTC）is of great significance for environmental protection and human health.Adsorption method is considered to be an effective method for treating antibiotic pollutants due to its wide application range,low cost,and simple operation.Therefore,searching for materials with high adsorption performance is the key to adsorbing and treating antibiotic pollutants.Metal-organic gel（MOG）is a promising candidate material for CTC adsorbent because of its layered porous structure,excellent chemical/physical stability and convenient preparation.In addition,adding bimetallic nodes to MOG may improve adsorption potential and optimize the performance of MOG materials.Inspired by the above problems,different iron-yttrium bimetallic organic gels were prepared by solvothermal method with iron and yttrium as the metal center and TATB as the organic ligand.Bimetallic MOGs with different iron-yttrium ratios were constructed to remove chlortetracycline hydrochloride（CTC）from water.and an iron yttrium bimetallic organic gel JLUE-MOG-Fe/Y with a better preparation ratio was selected,and its structural characteristics were characterized and analyzed.According to the adsorption and removal effect of different proportions of iron-yttrium bimetallic metal-organic gels on CTC,it showed that the iron-yttrium bimetallic metal-organic gel had better adsorption performance when the molar ratio of Fe³⁺to Y³⁺was 1:1.and the TGA characterization results showed that it had better thermal stability.Therefore,the iron-yttrium bimetallic metal-organic gel JLUE-MOG-Fe/Y with the molar ratio of Fe³⁺to Y³⁺of 1:1 was selected as the best adsorbent for CTC adsorption.Detailed characterization of JLUE-MOG-Fe/Y was carried out,and adsorption experiments were conducted using JLUE-MOG-Fe/Y as an adsorbent to explore the mechanism of its adsorption of CTC.The research results showed that JLUE-MOG-Fe/Y exhibited an irregular spherical shape with wrinkles on the surface,a particle size of about 50 nm,and an amorphous character with a hierarchical pore structure.JLUE-MOG-Fe/Y had strong thermal stability,and the material remained stable at 411℃.The adsorption process of CTC by JLUE-MOG-Fe/Y was systematically studied using kinetic,thermodynamic,and isotherm analysis methods.The adsorption process of CTC by JLUE-MOG-Fe/Y was a spontaneous endothermic process that conformed to the pseudo-second-order kinetic model and the Freundlich isothermal model.At 25°C,its adsorption capacity for CTC could reach584.83 mg·g^-1,indicating that it had good adsorption performance.According to the experimental results of the influencing factors,the adsorption efficiency slightly improved with the increase of the dosage.Considering the time cost and economic cost,1.00 g·L^-1was the appropriate dosage of adsorbent for subsequent experiments.Within the experimental p H range,the adsorption and removal rate of CTC by JLUE-MOG-Fe/Y fluctuated slightly,indicating that it was suitable for a wide p H range.The effect of different types of inorganic salt ions and different concentrations of humic acid on adsorption and removal efficiency was very weak,indicating that JLUE-MOG-Fe/Y had good anti-interference ability in practical applications.According to the adsorption experiments and characterization results,pore filling,coordination bonds,electrostatic interactions,π-πinteractions,hydrogen bonds,and hydrophilic/hydrophobic interactions participated in the adsorption process.After seven cyclic experiments,the removal efficiency of regenerated JLUE-MOG-Fe/Y for CTC remained above 90%,and its structure remained stable,indicating that it had good recycling performance.The research results provide reference and experience for the preparation of a new adsorbent for the removal chlortetracycline hydrochloride from wastewater by adsorption method,and provide theoretical support for the practical application of metal-organic gel materials in the treatment of antibiotic wastewater.