Enhanced chloroquine adsorption using cobalt-modified mesoporous silicas for water treatment

The widespread use of chloroquine (CQ) during the COVID-19 pandemic has led to its accumulation in water bodies due to the inefficiency of wastewater treatment plants (WWTPs). This study synthesized, characterized, and evaluated mesoporous silicas MCM-41 and MCM-48 modified with cobalt oxide nanoparticles for CQ removal. Characterization was conducted to assess the adsorbent properties and their correlation with the adsorption process. The materials exhibited high surface areas (S_BET > 369.49 m² g⁻¹) and uniform mesoporous structures, confirming their suitability for adsorption and desirable properties for recalcitrant contaminant removal. Adsorption kinetics followed the Elovich model, with equilibrium capacities of 25.3 mg g⁻¹ (MCM-41-CoO) and 24.04 mg g⁻¹ (MCM-48-CoO), and intraparticle diffusion governed by a multi-step process. Isotherms were best described by the Sips model, with maximum adsorption capacities of 24.78 mg g⁻¹ (MCM-41-CoO) and 24.00 mg g⁻¹ (MCM-48-CoO) at temperatures ranging from 15 to 45 °C. Thermodynamic parameters indicated a spontaneous, endothermic process with low randomness, suggesting chemical interaction in a monolayer followed by electrostatic interactions. These findings highlight the efficiency of modified mesoporous silicas as adsorbents for CQ, a critical pharmaceutical contaminant, and contribute to developing sustainable water treatment technologies essential for environmental protection and public health.