Effects of temperature on the adsorption and desorption of tetracycline in soils

Batch experiments of OECD Guide were conducted to the adsorption and desorption of tetracycline in soils. The adsorption and desorption isotherms of tetracycline in cinnamon soil and red soil were expressed well by the Freundlich equation at 20, 25 and 35 degrees C. According to lg K-f and 1/n values of fitting parameters, tetracycline was strongly adsorbed by two soils with adsorption capacity (lg K-f) values from 3.06 to 3.59. Temperature from 20 to 30 degrees C had little effects on the tetracycline adsorption in two soils. Thermodynamic parameters depict the exothermic nature of adsorption, and the process was favorable and spontaneous. Hysteresis effect was observed. The maximum adsorption capacity and hysteresis index of tetracycline were found at 20 degrees C for cinnamon soil and 30 degrees C for red soil, so there was little risk of tetracycline remobilization with temperature lower than 25 degrees C in cinnamon soil or higher than 25 degrees C in red soil.