Efficient removal of hydroxychloroquine sulfate using cocoa shell activated carbon: a green approach investigating equilibrium, kinetics, and thermodynamics

Abstract

In recent years, the world has suffered from the pandemic of the century, known as COVID-19. A significant effort has been exerted to develop new and more efficient treatments in order to find an effective cure. As a result, various pharmaceutical products have been tested and utilized. However, the presence of emerging contaminants such as these pharmaceuticals in aquatic environments poses a serious threat, as their actual effects on both the environment and human health remain largely unknown. Therefore, the present study aims to investigate the potential use of activated carbon derived from cocoa shells for the effective removal of hydroxychloroquine (HCQ) from aqueous solutions. Batch experiments were conducted to evaluate the capability of this type of activated carbon to eliminate this persistent pharmaceutical from aqueous systems. The cocoa shell activated carbon demonstrated a high adsorption capacity (98%) under mild operating conditions, including an adsorption time of 180 min, a pH of 7, an activated carbon dosage of 1.5 g L−1, an initial HCQ concentration of 10 mg L−1, and a stirring speed of 400 rpm at 297 K. The adsorption kinetics were best described by the pseudo-second-order model, while intraparticle diffusion was found to be a suitable description for higher concentrations. Further insight was gained by applying isotherm and thermodynamic studies. The results indicated that the adsorption isotherm followed Langmuir, Freundlich, and Temkin models. Moreover, the thermodynamic analysis revealed that the adsorption of HCQ onto the cocoa shell-activated carbon is exothermic and spontaneous.