Valorization of Hordeum vulgare Residues into Activated Carbon for Paracetamol Removal from Water

The presence of pharmaceutical compounds in aquatic systems represents a growing concern due to their persistence and potential adverse effects on ecosystems and human health. In this study, activated carbon obtained from Hordeum vulgare residues was developed and evaluated for the removal of paracetamol from aqueous solutions. The adsorbents were prepared through carbonization followed by physical activation with CO2 at 800 °C. Their textural and chemical properties were characterized using BET, FTIR, SEM-EDX, and Boehm titration. The activation process significantly increased the surface area (up to 520 m2 g−1) and promoted the formation of a micro-mesoporous structure. Adsorption experiments were conducted at pH values of 5–7 and temperatures of 30–40 °C, using an adsorbent dosage of 1 g L−1 and initial concentrations ranging from 100 to 500 mg L−1. The highest experimental adsorption capacity (Qe) (363.84 mg g−1) was obtained at pH 5 and 40 °C, with a removal efficiency of 68.81%. This value exceeded the adsorption capacity reported for activated carbon derived from jatoba fruits and Merck activated carbon by 8.81% and 21.91%, respectively. Nevertheless, neither pH (p = 0.629) nor temperature (p = 0.681) exerted a statistically significant effect on adsorption capacity. The equilibrium data were better fitted by the Freundlich model (R2 > 0.93), indicating a heterogeneous surface and multilayer adsorption. These results demonstrate that activated carbon derived from Hordeum vulgare is an efficient and sustainable adsorbent for the removal of emerging contaminants from water, highlighting its potential for biomass valorization.