Efficient removal of tetracycline and norfloxacin contaminants in wastewater onto N-dopped Cu/Al@Biochar as low-cost sorbent: kinetic and adsorption mechanism investigation.

In the present study, an adsorbent material (N-dopped Cu/Al@Biochar) was synthesized by integrating N, Cu, and Al atoms into the structure of a biochar. This material was characterized by several physicochemical methods, then applied to the elimination of tetracycline (TC) and norfloxacin (NC). The results obtained showed that the modification method used, although significantly altering the mesoporous structure of the original biochar, generates several functional groups on the surface of the material, giving it excellent adsorption properties. These properties were evaluated by studying the influence of various experimental parameters such as the pH of the solution, the mass of doped biochar, and the contact time on the amount of antibiotic adsorbed. Adsorption studies revealed maximum amounts of TC and NC adsorbed of 65 and 96 mg/g at pH = 8 and 6 respectively with 50 mg of adsorbent for an equilibrium time of 90 min for TC and 60 min for NC at a concentration of 15 mg/L for both antibiotics. This adsorption capacity led to the removal percentages of up to 90 and 82% for TC and NC, respectively. After five cycles of use, a decrease in adsorption efficiency of 9% for TC and 11% for NC was observed, demonstrating the impressive stability of the synthesized material. Kinetic studies revealed that the Elovich and pseudo nth order models are the most appropriate to describe the adsorption kinetics of TC and NC respectively. In addition, the two- and three-parameter isotherm models used in this study revealed multilayer adsorption processes, based on both $\pi -\pi$ , $n-\pi$ , van der Waals bond formation and hydrogen bonds.