Efficient Removal of Carbamazepine from Synthetic Wastewater Using Potato Peel-Derived Hydrochars: A Comparative Study of Hydrothermal and Pyrolytic Conversion

The increasing occurrence of pharmaceutical contaminants in aquatic environments has intensified the demand for sustainable and cost-effective water treatment technologies. This study investigated the conversion of potato peel waste into carbonaceous adsorbents through hydrothermal carbonization (HTC) and conventional pyrolysis (PRYR) for the removal of carbamazepine (CBZ) from synthetic wastewater. Hydrochars and biochars were synthesized under varying processing conditions and characterized using scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), elemental analysis, and Brunauer–Emmett–Teller (BET) surface area analysis. Adsorption experiments were conducted using a 50 mg/L CBZ solution at pH 6, room temperature, and an adsorbent dosage of 1 g/L. The adsorption performance was evaluated after short contact times to assess rapid-removal capability. HTC-derived hydrochars exhibited significantly superior performance compared with pyrolysis-derived biochars, achieving up to 97% CBZ removal and adsorption capacities approaching 50 mg g−1 within 1 min of contact. In contrast, pyrolysis-derived biochars achieved removal efficiencies between approximately 7 and 55% under similar conditions. Correlation analysis between adsorption behaviour and physicochemical properties revealed that adsorption performance was more strongly influenced by surface chemistry, aromaticity, and mesoporosity than by BET surface area alone. FTIR analysis suggested that hydrogen bonding, π–π electron donor–acceptor interactions, and pore filling contributed to CBZ adsorption. HTC hydrochars retained abundant oxygen-containing functional groups that promoted rapid and stable adsorption, whereas pyrolysis-derived biochars exhibited weaker adsorption interactions despite possessing higher surface areas. The findings demonstrate that hydrothermal carbonization provides an effective low-temperature route for valorising potato peel waste into efficient adsorbents for rapid pharmaceutical removal from water and highlight the critical role of adsorbent surface chemistry in determining adsorption performance.