Antimicrobial magnetic Glycyrrhiza glabra nanocomposite for decolouration of water through adsorption and photodegradation

Abstract

A sustainable hybrid magnetic nanocomposite based on Glycyrrhiza glabra (GG), GG/γ-Fe₂O₃, was synthesized via one-pot co-precipitation method, and efficiently utilized for adsorption and photocatalytic degradation of two toxic model dyes, Congo red (CR) and Nile blue (NB) dyes from water. The characterization of the GG/γ-Fe₂O₃ was performed by using FT-IR, P-XRD, BET-BJH, FE-SEM-EDX, TEM, SAED, XPS, TGA, UV-visible, and PL techniques. The GG/γ-Fe₂O₃ showed significant inhibition of bacterial and fungal growth. The inhibition statistics towards gram-(+) and gram-(−) bacteria, and fungal strains were found superior as compared to the naive plant material. The influence of adsorption parameters, on dye removal efficiency, was appraised via batch methodology. The fitting of isothermal and kinetic datasets into their respective models indicated that the adsorptive removal process was governed by the Freundlich isotherm and pseudo-second order kinetics. The Langmuir saturation capacity for CR and NB was found to be 47.50 and 15.36 mg g⁻¹, respectively. The spontaneous and physical sorption of CR and NB was delineated to be exothermic and endothermic, respectively, from 30 to 50 °C. The band gap of the GG/γ-Fe₂O₃ were found 1.69 eV (indirect), and 2.30 eV (direct) which established its semiconducting design, with CR solar-degradation efficiency of 92.7%, following pseudo-first-order kinetics. The degradation intermediates and mechanism have been investigated from radical quenching experiments and high-resolution LC-MS. The GG/γ-Fe₂O₃ exhibited structural integrity and excellent regeneration, supported by post-treatment FT-IR analysis. The reproducibility of the optimum experimental dataset under realistic conditions, including real wastewater, co-existing ions, and dye mixtures, revealed potent application of multifunctional and cost-effective GG/γ-Fe₂O₃ for the efficient removal of both cationic and anionic water contaminants, as well as for reducing microbial loads.