Study On Preparation Of Magnesium Aluminum Hydrotalcite By Ultrasonic Assisted Coprecipitation And Its Adsorption Behavior Of Tetracycline

In recent years,the persistence of overuse of antibiotics in aquaculture,animal husbandry and medical treatment,and the improper handling of some expired antibiotics have posed a significant threat to environmental safety,ecosystems and human health.The current common removal process cannot effectively remove such antibiotics.Therefore,the development of new materials to deal with such antibiotics contaminated water is particularly important.In order to obtain highly effective antibiotic adsorbent,Tetracycline?TC?was selected as the research object and Mg/Al layered double metal oxide?Mg/Al-LDO?was chosen as the adsorbent material which with large specific surface area,easy to obtain raw material and simple synthesis in this paper.The adsorption conditions,adsorption properties,regeneration of adsorbent,thermodynamics and kinetics of the adsorption of tetracycline,and the mechanism of the removal of tetracycline by Mg/Al-LDO was discussed,The results are as follows:1.Mg/Al-LDHs was prepared by the constant pH coprecipitation method,hydrothermal method and ultrasonic assisted coprecipitation method.According to the adsorption rate and physical properties of the product,the best preparation condition was ultrasonic assisted coprecipitation method.The optimum adsorption conditions of Mg/Al/CO₃-LDH for tetracycline adsorption was obtained by single factor and orthogonal experiments: the synthesis temperature was 45 ?,Mg/Al ratio was 4:1,the synthesis time was 45 min,[Mg]+[Al] = 1.2.2.The thermal decomposition process of Mg/Al/CO₃-LDH showed that the decomposition process is divided into five phases.The study of the adsorption rate of Mg/Al/CO₃-LDH calcined products showed that the adsorption rate of the material was highest after calcination at 400 ?.After calcined at 400 ?,SEM showed lamellar structure change to the original uniform the lamellar structure,XRD showed material change to Mg/Al composite oxide.3.The TC of removal efficiency on Mg/Al-LDO by static adsorption experiments was studied in this paper,and the results showed that the optimum adsorption conditions were as follows: 25 ?,p H = 5.0 ± 1,NaCl concentration is 0.10 mol/L,adsorption time is 60 min,Removal rate of TC?100 mg/L?on Mg/Al-LDO?0.15 g/50 m L?was above 90 %,and the equilibrium adsorption capacity achieved 183.15 mg/g.The adsorption capacity of Mg/Al-LDO is still reach up to 150 mg/g after four timesused.The interference of common anions is relatively large,and interference of CO₃2-is the maximum.4.The results of thermodynamic adsorption experiment showed that the adsorption of TC on Mg/Al-LDO followed the Langmuir isotherm model which belongs to the single molecular layer adsorption at 25 ?,35 ?,45 ?,55 ?.The thermodynamic parameters: ?H = 20.31 kJ/mol,?S = 86.90 J/mol·K,?G < 0 kJ/mol.Therefore,it is concluded that the adsorption is a spontaneous endothermic reaction.5.The results of adsorption kinetics experiment about TC on Mg/Al-LDO showed that the adsorption can be described by the pseudo two order kinetics equation,and the linear correlation coefficient is 1.000.It shows that the adsorption including external film diffusion and particle diffusion,surface adsorption.It inferred that the adsorption process is mainly particle surface chemical adsorption rate of diffusion in the dominant control.