Tetracyclines adsorption onto alumina: A comparative experimental and molecular dynamics simulation study

Using alumina (Al2O3) as the adsorbent, a static adsorption experiment was carried out in this study. It comprehensively evaluated the factors including Al2O3 dosage, adsorption temperature, and pH that influence the adsorption capability of three tetracyclines (TCs), namely, tetracycline hydrochloride (TC), chlortetracycline hydrochloride (CTC) and oxytetracycline hydrochloride (OTC). The results demonstrate that the adsorption efficiency increases with Al2O3 dosage. In addition, low-acid or natural solution is benefit for the adsorption. The adsorption behavior is more reasonably described with the Freundlich isotherm, and fits well with the pseudo-second-order kinetic model (R2 > 0.999). The results of molecular dynamics (MD) simulation show that the structures of TCs deformed during the combining process. The values of binding energy of TCs follow the order as: CTC (88.45 kcal/mol) > OTC (73.54 kcal/mol) > TC (54.28 kcal/mol). The MD simulation results agree well with the adsorption experimental results, which indicates that the MD simulation is reliable and reasonable. The MD simulation will provide theoretical knowledge in understanding the adsorption mechanism and environmental behavior of TCs.