Removal of Naproxen from Aqueous Solutions using Eco-Friendly Bio-Adsorbent Prepared from Orange Peels

The purpose of this work is to investigate the efficiency of orange peel (OP) in the removal of a pharmaceutical product (Naproxen) from aqueous solutions. Adsorption isotherms were determined experimentally. The results showed that orange peel has an appreciable affinity for Naproxen, with an elimination capacity of 45 mg/g and that the temperature has a very significant effect on the adsorption process. The obtained data were then tested by three models (Langmuir, Freundlich and Temkin) and the Langmuir model provided a good fit with the experimental values. A thermodynamic study proved that the adsorption process is physical, spontaneous and endothermic. In the adsorption kinetics study, the influence of certain parameters, such as pH and the initial concentration of the naproxen solution, was investigated by three models (pseudo-first-order, pseudo-second-order and Elovich kinetics). The results show that the kinetics decrease with the initial naproxen concentration, and that the first-order model describes the adsorption kinetics well.