Activated carbons prepared from stump wood of various tree species by chemical activation and their application for water purification

Abstract

Activated carbons (ACs) were produced from stump wood of different tree species, such as pine, bearded birch, and American black cherry using chemical activation with KOH and NaOH. The activated carbons were characterized and evaluated as adsorbents for eliminating bisphenol A (BPA) from aqueous solutions. The kinetics of adsorption and equilibrium adsorption, as well as the impact of solution pH and ionic strength, were examined. The kinetics were analyzed using the pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Boyd kinetic models. The findings suggest that the adsorption kinetics followed the pseudo-second-order model. Additionally, the film diffusion was found to be the rate-determining step for the adsorption of BPA on all of the activated carbons. The data for adsorption equilibrium were tested using the Langmuir, Freundlich, and Sips equations, with results indicating that the Langmuir model was the most applicable. The capacity of activated carbons to adsorb BPA was dependent on their surface area. Higher BET surface areas resulted in increased adsorption. The birch-derived AC activated by NaOH had a monolayer adsorption capacity of 1.980 mmol/g, while the AC from black cherry activated with KOH had 2.195 mmol/g. The adsorption of BPA was pH-dependent, and no effect of ionic strength was observed. The activated carbons had very high adsorption capacities, indicating that stump wood is an excellent precursor for the production of highly effective adsorbents.