Surface interactions of oxytetracycline on municipal solid waste-derived biochar–montmorillonite composite

A composite material prepared from municipal solid waste-derived biochar and montmorillonite (MSW-BC-MMT) was studied as a remediation medium for the removal of oxytetracycline (OTC) from aqueous systems. The morphological characterization using SEM images revealed that the composite had a heterogeneous flaky, plate-like surface appearance. Based on N₂ adsorption experiments and compared to the pristine biochar, the composite showed an increased specific surface area by 1.5 folds. The three-parameter Redlich Peterson isotherm model and two-parameter Temkin isotherm model were best fitted with R² = 0.998 and 0.997, respectively, both for the pristine biochar and the MSW-BC-MMT composite. Additionally, the kinetics was best described using the pseudo-second-order model, suggesting that OTC adsorption onto the composite takes place via chemisorption. A capacity of 233 mg g⁻¹ was observed for the MSW-BC-MMT, which is suggested to be predominantly governed by π-π electron donor–acceptor interactions, electrostatic attraction and surface complexation. As evidenced by FTIR results, OTC was presumed to be adsorbed via hydrogen bonding as well. The value addition of MSW by producing MSW-derived biochar is considered a favorable solution for solid waste management. Therefore, the production of the MSW-BC-MMT composite becomes useful due to its significance in acting as a simultaneous MSW management technique and a low-cost material for antibiotic OTC remediation.