A novel mesoporous Hydroxyapatite@Montmorillonite hybrid composite for high-performance removal of emerging Ciprofloxacin antibiotic from water: Integrated experimental and Monte Carlo computational assessment

Abstract The extensive use of persistent antibiotics to prevent human and animal infectious diseases has emerged as a global environmental concern. In this study, we report the effective removal of Ciprofloxacin (Cipro) antibiotic from aqueous solutions using a novel Hydroxyapatite@Montmorillonite (HAP@Mt) hybrid composite, which was synthesized via a facile co-precipitation route. The as-prepared HAP@Mt composite was thoroughly characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), N2 adsorption-desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric and differential thermal analysis (TGA-DTA). The adsorption performance of HAP@Mt for Cipro antibiotic was investigated as a function of various physicochemical parameters. The Cipro adsorption process on the HAP@Mt composite was well described by pseudo-second-order kinetics and the Langmuir isotherm. The maximum uptake capacity reached 91.18 mg g−1. The Cipro binding mechanism was predominantly controlled by the electrostatic interactions, hydrophobic interactions, hydrogen bonding and n-π electron donor/acceptor interactions. HAP@Mt exhibited easy regeneration and excellent reusability for Cipro removal. Monte Carlo/SA simulations were performed to more clearly illuminate the atomic-level interactions between Cipro molecule and HAP@Mt surface under different pH conditions. The simulation data correlate well with actual results. The obtained experimental and computational findings provide new relevant insights on the application of HAP@Mt composite as a potential binder material to remove Cipro antibiotic from wastewater.