María D. Marqués

Lignin-based activated carbons for adsorption of sodium dodecylbenzene sulfonate: Equilibrium and kinetic studies

The adsorption of sodium dodecylbenzene sulfonate (SDBS) from its aqueous solution at different temperatures has been studied using three activated carbons prepared in our laboratory. Lignin was used as raw material for the preparation of activated carbons (ACs). The results of the adsorption equilibrium were analyzed and fitted to the Langmuir model. Thermodynamic magnitudes were estimated as well, and their values indicated that the adsorption processes were spontaneous and exothermic. The kinetic study showed that the processes are of second apparent order related to the concentration of the vacant active centers on the surface of the activated carbons. The values of the effective internal diffusion coefficients have been calculated applying the equations developed by Crank and Vermeulen.

Activated Carbons from Lignin: Their Application in Liquid Phase Adsorption

Abstract The extent of the methylene blue (MB) adsorption from an aqueous solution is a convenient indicator in the evaluation of activated carbons. The adsorption of MB (cationic dye) from aqueous solution has been studied using twenty activated carbons. The activated carbons were prepared from acid‐precipitated eucalyptus kraft lignin following a two‐step process consisting of CO2 partial gasification after carbonization in N2 atmosphere. The adsorbed amount was studied as a function of the contact time, temperature, pH, concentration of adsorbate, and burn‐off of the activated carbons. The equilibria results obtained in a batch contactor were fitted by the Langmuir equation. The calculated values of ΔG demonstrate that the adsorption of the dye onto these activated carbons occurs by physical adsorption. Both the apparent values of ΔH and ΔS are positive, indicating that the adsorption process is endothermic and can produce spontaneously in our experimental conditions. The kinetic study was developed using a second‐order exponential decay equation and the results were correlated using the Lagergren first‐order equation relative to the concentration on the solid phase. The intraparticle diffusion coefficients have been estimated on the basis of an internal diffusion controlling mechanism for the net adsorption rate.