Acid-Activated Carbons from Peanut Shells: Synthesis, Characterization and Uptake of Organic Compounds from Aqueous Solutions

Activated carbon with a high adsorption capacity for the removal of organic compounds from aqueous solutions was made from phosphoric acid-activated peanut shells. Adsorption isotherms for the uptake of phenol, iodine, Methylene Blue and tannic acid were obtained at 22°C. Freundlich, Langmuir and previously developed equation models all explained the experimental data satisfactorily. Further analysis using the Dubinin–Radushkevich equation showed that the maximum micropore volume accessible to the adsorbate decreased as the molecular size increased, suggesting a molecular sieve or gate effect. A comparison was made with the micropore volume as determined by nitrogen adsorption at −196°C. The results presented indicate that peanut shell residues provide a suitable option for the preparation of activated carbon with good surface properties and the ability to remove organic compounds from aqueous solutions.