Synthesis and characterization of copper oxide-loaded activated carbon nanocomposite: Adsorption of methylene blue, kinetic, isotherm, and thermodynamic study

Adsorption of methylene blue from aqueous solution by activated carbon-loaded copper oxide nanocomposites (CuO@AC) was investigated. The activated carbon was derived from Prosopis juliflora (Mesquite) pods which is a noxious wild invader. Both activated carbon and CuO@AC were prepared at low-temperature in shortest possible duration ensuring environmentally-friendly and green synthesis approach. CuO@AC nanocomposites were characterized by XRD, SEM, EDX, and FTIR and tested for adsorption kinetics, isotherm, thermodynamics, mechanism and effect of experimental variables on removal of MB from aqueous solution. The obtained results revealed that >97% MB removal over CuO@AC was achieved within 15 min by using 0.1 g adsorbent dosage, 10 mg/L MB at neutral pH and 313 K. The monolayer adsorption of MB was found to be favourable with maximum adsorption capacity to be 54.73 mg/g at 313 K. Both the gradual decrease in values of ΔG, −5.865 kJ/mol at 293 K to −7.71 kJ/mol at 313 K) and positive values of ΔS (95.12 J/K/mol) and ΔH (22.035 kJ/mol) are indicative of spontaneity and endothermicity of MB adsorption in the current study under studied experimental conditions. CuO@AC nanocomposite has demonstrated stability and recyclability to four adsorption cycles with nearly same adsorption efficiency. These findings prove that CuO@AC nanocomposite can be utilized as an excellent adsorbent for wastewater treatment at wider scale.