Adsorptive removal of oxytetracycline in wastewater by Cu/Al doped carbon microspheres prepared from low-molecular-weight chitosan

A series of Cu/Al doped nitrogen-containing carbon microspheres prepared from low-molecular-weight chitosan (Cu/Al@NC-x, x = 1, 2, 3) were synthesized by a facile one-pot hydrothermal strategy and used for the adsorptive removal of oxytetracycline (OTC) contaminants to polish up the quality of water. Batch adsorptive experiments were performed to appraise the potential of Cu/Al@NC-x as an effective adsorbent for OTC. The effects of initial OTC concentration, solution pH, coexisting ions, adsorption time, and temperature on adsorptive performance were systematically studied. Cu/Al@NC-2 possessed the highest adsorption performance for OTC with maximum equilibrium adsorption capacity of 1727.65 mg g−1 (25 °C), 2583.10 mg g−1 (35 °C), and 2900.84 mg g−1 (45 °C), respectively. The kinetics and isotherm simulation data complied well with the pseudo-second-order kinetic and Langmuir isotherm models, respectively. The thermodynamic analysis (ΔH° > 0, ΔG° < 0) illustrated the spontaneous endothermic process of Cu/Al@NC-2 adsorbing OTC. Especially, Cu/Al@NC-2 still retained an excellent removal efficiency of 92.25 % for OTC after five adsorption cycles, verifying the feasibility of Cu/Al@NC-2 in antibiotic wastewater treatment.