Adsorption of diclofenac and ibuprofen on organobentonites: Kinetic, thermodynamic, and simultaneous adsorption

In this study, bentonite clay was modified with a primary amine – dodecylamine and a quaternary ammonium salt – di(hydrogenated tallow)dimethylammonium chloride (Arquad® 2HT-75) to enhance its affinity for nonsteroidal anti-inflammatory drugs, specifically diclofenac sodium (DCF) and ibuprofen (IBU). The structural and surface properties of prepared organobentonites were characterized using XRPD, SEM, FTIR, zeta potential, and simultaneous thermal analysis techniques. Adsorption experiments revealed that organobentonites exhibited significantly higher capacities for DCF and IBU compared to natural bentonite, with adsorption kinetics following a pseudo-second-order model and isotherms fit the Langmuir model. Thermodynamic analysis indicated spontaneous and exothermic adsorption at all temperatures. Additionally, simultaneous adsorption experiments provided insight into the competitive interactions between DCF and IBU, showing that despite a decrease in adsorption performance, both drugs could be effectively removed by the modified bentonites. Post-adsorption characterization confirmed drug adsorption within the organobentonites structure, highlighting the potential of these materials for wastewater treatment.