Adsorption of the non-steroidal anti-inflammatory drug (ibuprofen) onto biochar and magnetic biochar prepared from chrysanthemum waste of the beverage industry

Abstract

Biochar and magnetic biochar prepared from chrysanthemum waste of the beverage industry are effective adsorbents for the removal of the non-steroidal anti-inflammatory drug, ibuprofen (IBP), from aqueous systems. The development of magnetic biochar using iron chloride, overcame poor separation characteristics from the liquid phase of the powdered biochar after adsorption. Characterisation of biochars was achieved through Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), N₂ adsorption/desorption porosimetry, scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), moisture and ash content, bulk density, pH and zero-point charge (pH_pzc). The specific surface area of non-magnetic and magnetic biochars was 220 and 194 m² g⁻¹, respectively. Adsorption of ibuprofen was optimised with respect to contact time (5–180 min), solution pH (2–12) and initial drug concentration (5–100 mg L⁻¹), with equilibrium being reached in 1 hour, and the maximum ibuprofen removal occurred at pH 2 and 4 for biochar and magnetic biochars, respectively. Investigation of the adsorption kinetics was achieved through application of the pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion models. Adsorption equilibrium was evaluated using Langmuir, Freundlich and Langmuir–Freundlich isotherm models. The adsorption kinetics and isotherms for both biochars are well described by pseudo-second order kinetic and Langmuir–Freundlich isotherm models, respectively, with the maximum adsorption capacity of biochar and magnetic biochar being 167 and 140 mg g⁻¹, respectively. Chrysanthemum derived non-magnetic and magnetic biochars exhibited significant potential as sustainable adsorbents toward the removal of emerging pharmaceutical pollutants such as ibuprofen from aqueous solution.