Steam Activation of Acid-Chars for Enhanced Textural Properties and Pharmaceuticals Removal

The present work aims to explore steam activation of sisal or glucose-derived acid-chars as an alternative to KOH activation to prepare superactivated carbons, and to assess the adsorption performance of acid-chars and derived activated carbons for pharmaceuticals removal. Acid-chars were prepared from two biomass precursors (sisal and glucose) using various H₂SO₄ concentrations (13.5 M, 12 M, and 9 M) and further steam-activated at increasing burn-off degrees. Selected materials were tested for the removal of ibuprofen and iopamidol from aqueous solution (kinetic and equilibrium assays) in single-solute conditions. Activated carbons prepared from acid-char carbonized with 13.5 M and 12 M H₂SO₄ are mainly microporous solids composed of compact rough particles, yielding a maximum surface area and a total pore volume of 1987 m² g^-1 and 0.96 cm³ g^-1, respectively. Solid state NMR reveals that steam activation increased the aromaticity degree and amount of C=O functionalities. Steam activation improved the acid-chars adsorption capacity for ibuprofen from 20-65 mg g^-1 to higher than 280 mg g^-1, leading to fast adsorption kinetics (15-20 min). The maximum adsorption capacities of selected activated samples for ibuprofen and iopamidol were 323 and 1111 mg g^-1, respectively.