Cu@Ce-MOF doped coconut shells-derived mesoporous activated carbon as efficient composite for remediation of oily wastewater.

The development of efficient, sustainable sorbents for oily wastewater treatment is of growing interest within circular economy and surface engineering frameworks. In this study, Cu-Ce MOF doped mesoporous activated carbon (AC), obtained from coconut shell waste, have been prepared and evaluated as an eco-friendly efficient adsorptive composite adsorbent for oil removal from aqueous solutions. Surface and structural characterization for both MOF and AC (using nitrogen adsorption-desorption BET, SEM, EDX and FTIR analyses) revealed highly porous structures enriched with oxygen-containing functional groups, providing abundant active sites for interfacial adsorption. Batch adsorption experiments have demonstrated that optimal oil removal occurred at 5 g L-1 adsorbent dose and ambient temperature, achieving a maximum capacity of 9.1 mg g-1. Kinetic data fit the pseudo-second-order model, indicating that surface-controlled chemisorption governs the uptake process. Equilibrium adsorption behavior has been best described by the Langmuir and Sips isotherms, confirming formation of a monolayer on a primarily homogeneous surface with minor heterogeneity. Thermodynamic analysis has revealed that the process was endothermic (ΔH° = +5.9 kJ mol-1), spontaneous (ΔG° < 0), and entropy-driven (ΔS° > 0), consistent with physical interactions such as van der Waals forces, π-π stacking, and capillary condensation. The proposed mechanism involves initial surface coalescence of oil droplets, followed by capillary-driven infiltration into mesopores. This study demonstrates the potential of the coconut shell-derived activated carbon and MOF mixture as a circular surface-functional material for environmental remediation and a contributor in advancing sustainable interfaces in the technologies of wastewater treatment.