Abstract

This study investigates the physicochemical transformation of soybean husk into activated carbon using phosphoric acid (H₃PO₄) and potassium carbonate (K₂CO₃) as activating agents. Results revealed significant reductions in moisture content from 10 % in the raw husk to 5 % and 3 % in acid and base-activated samples, respectively, indicating dehydration and increased hydrophobicity. Ash content increased in both treatments more markedly in the base-activated carbon due to retention of potassium salts and other inorganic residues. Bulk density rose from 0.38 g cm⁻³ in the raw husk to 0.54 g cm⁻³ (acid) and 0.62 g cm⁻³ (base), suggesting improved structural consolidation. Surface pH shifted from 6 to 7.4 and 8.0 for acid- and base-activated carbons, respectively, reflecting modified surface acid–base behavior and adsorption selectivity. FTIR analysis confirmed the removal of O–H, C=O, and C–O groups, enhancement of aromatic C=C bonds, and emergence of P–O and K–O vibrations associated with the activating agents. Overall, both activation routes successfully produced porous, functional carbon materials. H₃PO₄ activation favored microporous, phosphate-enriched carbon suitable for neutral or organic pollutant adsorption, while K₂CO₃ activation generated hydrophobic, alkaline carbon advantageous for acidic species removal and catalytic applications.

Keywords

soya bean husk, fourier transform infrared spectroscopy, acid treatment, base treatment, bulk density, potential of Hydrogen