Coconut Shell Biochar for the Removal of Acetaminophen and Ciprofloxacin in Low Concentrations: Single and Competitive Adsorption Studies

Pharmaceutical compounds at lower concentrations have been found in surface water bodies and sewage. This study investigated the removal of acetaminophen (ACP) and ciprofloxacin (CIP) using coconut shell biochar (CBC) as an adsorbent. Characterization by X-ray microtomography and scanning electron microscopy (SEM) revealed micro- and macropores in CBC, with a surface area of 368.071 m2/g determined by Brunauer–Emmett–Teller (BET) isotherm analysis. The formation of oxygen-rich functional groups and aromatic groups on the CBC was indicated by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra. Optimal removal of 1 mg/L ACP and CIP was observed at a CBC dosage of 100 mg/L and at an optimum pH of 7.0 for ACP and 3.0 for CIP. Adsorption kinetics fitted the pseudo-second-order model and Freundlich isotherm fitted the data well, suggesting strong chemical adsorption. Competitive adsorption reduced the efficiency, particularly for ACP. Reusability tests showed high CIP adsorption rates across multiple cycles, indicating CBC’s potential for water purification. The disposal measures of reused CBC with reference to the spent adsorbents to avoid environmental pollution have also been discussed in this study.