Sorption thermodynamics and kinetics properties of tylosin and sulfamethazine on goethite

In order to understand the sorption processes of tylosin (TYL) and sulfamethazine (SMT) on soils, the sorption thermodynamics and kinetics properties of two chemicals on goethite were investigated through sorption equilibrium and sorption rate experiments. The results showed that the sorption of TYL and SMT were nonlinear and the sorption capacities were influenced by the pH conditions of solution. The sorption rates for TYL and SMT decreased as the initial concentration increased. The sorption process might be constituted with the initial boundary layer diffusion or external surface, then the intraparticle diffusion or pore diffusion stage and finally equilibrium stage related with the sorption on the interior surface of sorbent. Thermodynamic calculations of sorption of TYL and SMT on goethite revealed that the sorption of TYL on goethite was exothermal and spontaneous and SMT was endothermic and spontaneous. The results indicated that the transportation abilities of TYL and SMT might be weak for the soils rich in iron oxide. The significant differences in the sorption behavior of two chemicals might be related with their physicochemical properties and suggested that the sorption mechanisms of TYL and SMT on goethite would be complicated and the domain sorption mechanism for each chemical at different pH conditions would be variable. It should be noted to assess the environmental risks of TYL and SMT.