Competitive Retention of Sulfamethoxazole (SMX) and Sulfamethazine (SMZ) from Synthetic Solutions in a Strong Anionic Ion Exchange Resin

Numerous antibiotics such as sulfonamides have been found in effluents from drug manufacturers. Removal of pharmaceuticals by adsorption and ion exchange comprise some of the most promising techniques for the retention of these compounds from wastewaters due to their low cost, easy regeneration, and selective removal of pollutants. This article studies the removal of sulfamethoxazole (SMX) and sulfamethazine (SMZ), the most common sulfonamide antibiotics detected in municipal sewage. Lewatit MP500 (Lanxess Chemical) ion exchange resin was used to remove SMX, SMZ present in solutions. Batch experiments were carried out in cylindrical stirred tanks. Binary system solutions of equal mass concentration were prepared containing 30-250 mg/L of each compound, SMX and SMZ, and tested with an L/S ratio (mL solution/g resin) = 1000 obtained in previous experiments. Also, the adsorption of SMX mixed with trimethoprim (TMP) in batch experiments was analyzed due to the fact that both compounds are usually administered together. Equilibrium and kinetics were studied in order to characterize the operation. The adsorption equilibrium constants for SMX and SMZ were determined using a modified extended Langmuir model for multicomponent equilibrium sorption. Kinetics was analyzed using the pore diffusion model. Finally, several loading and elution cycles were carried out in fixed bed to obtain the breakthrough curves, comparing the experimental data to predicted values from a fixed bed model.