Zn/Ce-layered double hydroxide for adsorptive removal of doxycycline from water

Abstract

Since antibiotic overuse created various environmental issues, antibiotic management and separation are critical in ecological research. In this regard, the main objective of this work was to design a simple and reliable solvothermal-synthesis-based sorbent for removing antibiotics such as doxycycline (DOX). The used sorbent was Zn/Ce-layered double hydroxide (Zn/Ce-LDH), and its layered structure was confirmed by the X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) analysis. In addition, the Brunauer-Emmett-Teller (BET) test showed the specific surface area of the Zn/Ce-LDH achieved 45.17 m2 g−1. The sorbent was shown to have a high capability to remove DOX (the maximum experimental adsorption capacity of 1297 mg g−1) at the low equilibrium contact time of 15 min. Also, the obtained negative value of Gibbs free energy (ΔG°), the enthalpy (ΔH°), and the entropy (ΔS°) at the investigated temperatures reveal the fact that the involved adsorption process had spontaneous and exothermic features. Besides, the pseudo-second-order kinetic model favourably described DOX adsorption on the Zn/Ce LDH surface. Furthermore, a combination of classical molecular dynamics and Monte Carlo simulations were utilized to investigate the adsorption properties of DOX on the (001) and (010) Zn/Ce-LDH surfaces. The theoretical findings supported the possibility of DOX coordination with Zn/Ce atoms.