Adsorption of pharmaceutical compounds from solutions using activated biochar pellets from barley straw

Pharmaceutical compounds are increasingly detected in aquatic environments and represent contaminants of emerging concern due to their persistence and biological activity. This study evaluates the performance of steam-activated biochar pellets derived from barley straw and bran as a sustainable sorbent for the removal of pharmaceutical pollutants from aqueous solutions. Biochar pellets were produced via pyrolysis followed by steam activation, resulting in a substantial improvement in textural properties, with the BET specific surface area increasing from 119 to 423 m 2 g −1 and the development of pronounced microporosity. Adsorption performance was assessed using five frequently detected pharmaceuticals (acetaminophen, metformin, caffeine, diclofenac and naproxen). Rapid adsorption was observed at the initial stage, followed by a gradual approach to equilibrium. Among the investigated compounds, metformin exhibited the highest adsorption capacity, followed by caffeine and acetaminophen, while diclofenac and naproxen showed lower removal efficiency. Kinetic analysis indicated that the adsorption process is well described by the pseudo-first-order model, suggesting diffusion-controlled sorption. Adsorption isotherms for acetaminophen and metformin corresponded to Type I behaviour and were adequately described by the Langmuir and Freundlich models. The maximum Langmuir adsorption capacities were 1.196 mg g −1 for acetaminophen and 0.480 mg g −1 for metformin. The results demonstrate that steam-activated biochar pellets derived from agricultural residues provide an effective and scalable alternative to conventional carbon sorbents for the removal of pharmaceutical contaminants from water.