Abstract: Tetracycline hydrochloride is not completely absorbed in the organism and is discharged from the body, which is toxic to the soil and threatening the ecological environment. Tetracycline hydrochloride residue in the soil environment is not easy to be biodegraded because of its structure containing naphthol ring. Adsorption method has excellent characteristics like simple, economical, efficient and cheap, which is an effective way to treat tetracycline hydrochloride wastewater. Magnesium-aluminum hydrotalcite was prepared by uniform co-precipitation method. The products were characterized by X-ray diffraction (XRD), fourier transform infrared spectra (FT-IR) and scanning electron microscope (SEM). The effects of the different time on the microstructure of Mg-Al hydrotalcite were studied. The effects of reaction conditions on the adsorption properties of Mg-Al hydrotalcite were investigated by using tetracycline hydrochloride as adsorbent. It has important practical significance for soil pollution control and remediation. The results show that when the reaction time is 12 h, the maximum adsorption rate of tetracycline hydrochloride on Mg-Al hydrotalcite is 70.82%. The adsorption behavior of Mg-Al hydrotalcite for tetracycline hydrochloride is in accordance with Langmuir isothermal equation and quasi first-order kinetic model. The results show that the thermodynamic parameter of ΔH^O is 7.40 kJ/mol, and ΔG^O is less than 0, ΔS^O is 40.82 J/(mol·K), respectively, indicate that the adsorption process is endothermic, spontaneous and entropy increasing process in this study temperature range.

Key words: Mg-Al hydrotalcite, reaction time, adsorption property, tetracycline hydrochloride, sorption kinetics, adsorption thermodynamics