Kinetic, equilibrium, and thermodynamic performance of sulfonamides adsorption onto graphene

With the extensive production and consumption of sulfonamide antibiotics, their existence in aquatic environments has received increasing attention due to their acute and chronic toxic effects. In this study, graphene was characterized and applied for sulfamethazine (SMT) removal from aqueous solution. The effect of the contact time (0-1440 min), initial concentration (2-100 mg L^-1), and temperature (298-318 K), as well as pH (2-9) and ionic strength (0-0.2 M NaNO₃), have been examined. The maximum adsorption capacity was calculated to be 104.9 mg g^-1 using the Langmuir model. The endothermic adsorption process (△H = 10.940 kJ mol^-1) was pH- and temperature-dependent, and the adsorption data fitted well with the Langmuir isothermal and the pseudo second-order kinetic models. Additionally, ionic strength (0.01 to 0.2 M NaNO₃) had no obvious influence on SMT adsorption by graphene. Ultimately, graphene proved to be an effective adsorbent for sulfonamide antibiotics removal from aqueous solutions.