Experimental data and model prediction of tetracycline adsorption and desorption in agricultural soils

In this work, tetracycline (TC) adsorption and desorption were studied, and the soil properties that most influenced the process were identified. Batch experiments were carried out on 63 crop soil samples, which showed a wide range of values in their physicochemical characteristics. Adsorption curves fit well to the Freundlich equation, with K_F values varying between 901 and 9202 Lⁿ μmol^1-n kg^-1. K_d values ranged between 53 and 6899 L kg^-1 for an initial concentration (C_o) of 400 μM, whereas the adsorption capacity (q_a) ranged from 8541 to 14,852 μmol kg^-1. TC retention on soils was high, with adsorption values always higher than 58%, and desorption values lower than 9%. Bivariate correlations and multiple linear regressions were performed to identify those soil variables having a greater influence on TC adsorption and desorption. The results indicate that organic carbon, clay, exchangeable aluminum, available phosphorus, effective cation exchange capacity content, and pH are the main characteristics affecting TC adsorption and desorption. The models, developed by means of multiple linear regression, gave satisfactory and robust predictions for TC adsorption and desorption, using easily determinable soil characteristics as input.