Contrastive removal of oxytetracycline and chlortetracycline from aqueous solution on Al-MOF/GO granules

The presence of tetracycline antibiotics (TCS) in the water and wastewater has raised growing concern due to its potential environmental impacts; thus, their removal is of high importance. In this study, a novel aluminum-based MOF/graphite oxide (Al-MOF/GO) granule was prepared as an adsorbent for the removal of TCS including oxytetracycline (OTC) and chlortetracycline (CTC). The adsorbent was characterized via XRD, FTIR, BET, SEM, and XPS methods. The granules exhibited similar crystal structure and some new mesopores appearing compared to the parent Al-MOF/GO powder. In addition, the adsorption behavior of OTC and CTC on samples was explored as a function of initial concentration, contact time, pH, and ionic strength by means of batch experiments. The adsorption capacity reached to 224.60 and 240.13 mg·L^-1 for OTC and CTC, at C₀ = 60 mg·L^-1 as well as ambient temperature respectively. Moreover, the adsorption process of OTC and CTC on Al-MOF/GO samples can be better delineated by pseudo-second-order kinetics and Freundlich isotherm models. Besides, the adsorption mechanism over Al-MOF/GO granules was proposed, which could be ascribed to π-π interaction, cation-π bonding, and hydrogen bond. Finally, the great water stability, separation performance, and regeneration efficiency of these novel granules indicated their potential application in the OTC and CTC removals from aqueous solution.