Effective removal of antibiotics from aqueous solutions by a robust activated carbon: experimental and theoretical...

The continuous discharge of antibiotics into water bodies is a potential threat to the ecosystem. We prepared a coal-based activated carbon and characterized it via BET, SEM, FTIR spectroscopy, XRD, TEM, TGA and Raman spectroscopy. Its surface area was 3470 m² g^-1, and its pore size and volume were 1.808 nm and 1.568 cm³ g^-1, respectively. It was evaluated for the removal of moxifloxacin (MOX) and linezolid (LINZ) from water using the Freundlich, Langmuir Temkin and D-R isotherm models and the pseudo-second-order kinetic model. This material removed ∼99.5% of antibiotics, with adsorption capacities of 839 and 832 mg g^-1 for MOX and LINZ, respectively. Thermodynamic parameters i.e. change in Gibb's free energy (ΔG = -11.248 to -24.376 kJ mol^-1), enthalpy (ΔH = 185.52 kJ mol^-1) and entropy (ΔS = 263 J mol^-1 K^-1) and ΔG (-9.52 to -13.818 kJ mol^-1), ΔH (62.36 kJ mol^-1) and ΔS (108 J mol^-1 K^-1) reveals spontaneous and endothermic nature of adsorption for MOX and LINZ respectively. The material is very effective in real water samples and is recyclable, demonstrating its stability and reusability. The DFT results, including band gaps, the E _HOMO-LUMO energy gap, density of states, atoms-in-molecules analysis and charge transfer phenomena, revealed the presence of hydrogen bonding and electrostatic interactions. The study highlights that this material is a potential scavenger of emerging contaminants in water.