At present, there is a large and unreasonable use of veterinary drugs in the medical and health industry, causing varying degrees of pollution to soil, sediment, and groundwater. It is worrying that this situation is expanding and spreading.

The main reason for the expansion of the spreading trend is the increasing support from the government for the animal husbandry industry. Some practitioners without breeding technology or with low breeding technology have flocked to the animal husbandry industry. These new practitioners are completely ignorant of animal husbandry drugs, especially in the low-priced animal tetracycline.

At present, Huazhong Agricultural University is trying to use organic montmorillonite with characteristics such as expansibility, large specific surface area, and high cation exchange capacity to solve this problem, and has achieved good results.

The use of organic montmorillonite to adsorb tetracycline in soil is mainly based on the following characteristics:

1.The initial adsorption rate of organic montmorillonite for tetracycline is not very high, but the adsorption amount can reach over 80% after two hours, and the adsorption equilibrium is basically reached within 24 hours. The time for high addition of organic montmorillonite to reach adsorption equilibrium is relatively short, and the quasi second order kinetic equation can well fit the adsorption kinetics of organic montmorillonite for tetracycline;

2.The isothermal adsorption curves of sodium based montmorillonite and organic montmorillonite for tetracycline both conform to the Langmuir model and Freundlich model. The adsorption capacity of organic montmorillonite for tetracycline (1000-2000mmol/kg) is higher than that of sodium montmorillonite (769mmol/kg), and the performance of organic montmorillonite for tetracycline is mainly affected by the type of modifier. The adsorption capacity (Qmax) increases with the increase of quaternary ammonium salt chain length;

3.The fitting results of the Freundlich equation indicate that the adsorption parameters (n and KF) of organic montmorillonite for tetracycline are higher than those of sodium based montmorillonite, and with the increase of the amount of organic modifier added, the parameter n value increases, the heterogeneity of mineral surface is enhanced, and the adsorption performance for tetracycline is improved;

4.When the pH of the system is low (3-4), the effect of pH on the adsorption of tetracycline by organic montmorillonite is significant, and it increases with the increase of the amount of quaternary ammonium salt added; As the pH of the system increases (4-5.5), the adsorption and distribution of tetracycline by organic montmorillonite gradually decreases; When the pH of the system is between 5.5-7, the adsorption distribution coefficient tends to be constant, and the effect of system pH on the adsorption of tetracycline by organic montmorillonite is relatively small; (Reference: Paper from Huazhong Agricultural University)