Sustainable remediation of macrolide antibiotic from water using a novel Fe oxide/biochar nanocomposite: Adsorption behaviour and mechanistic analysis

The presence of macrolide antibiotics in water represents a serious environmental risk that may contribute to the global threat of developing antimicrobial resistance in waterborne organisms. As conventional wastewater treatment plants (WWTPs) are ineffective in removal of macrolides such as clarithromycin (CLR), new approaches that target such priority substances must be evaluated. Here, a novel Fe oxide/biochar nanocomposite (FeBN) generated from brewery spent grain was evaluated as an adsorbent for CLR removal from water. Maximum CLR removal was observed at pH 6 with qmax of 7.91 mg/g at 30 ○C. Morphology, texture and surface chemistry of FeBN were explored using SEM, EDX, XRD, BET, FTIR, Raman and XPS techniques. The Elovich kinetic model and the Langmuir isotherm model correlated satisfactorily to the experimental data. Thermodynamic studies revealed the adsorption processes to be endothermic (ΔH≤8.75 kJ/mol) and that physisorption governed macrolide removal. Instrumental characterisation after CLR adsorption further confirmed that low energy interactions (physisorption) dominated the adsorption such as hydrogen (H)-bonding (i.e., Dipol-dipol and Yoshida) and π-π/n-π EDA interactions. Desorption studies showed methanol could effectively regenerate the used biochar (but further optimisation is needed). The results showed the FeBN potential for sustainable CLR or other macrolide removal from water.