Adsorption of styrene sulfonate from aqueous solutions onto carbon fibers and mesoporous carbon

• Activities of the species are used in the kinetic and thermodynamic models.
• Better agreement between unities obtained from kinetic and thermodynamic studies.
• Slow kinetic due to electrostatic repulsion between styrene sulfonate and carbons.
• Validation of the thermodynamic models by calorimetry.

The removal of styrene sulfonate from aqueous solution by using different activated carbons, microporous or mesoporous, is studied from kinetics and thermodynamics points of view. The results are interpreted in term of pore size distribution, pore organization and surface charge. Several classical models are tested both for kinetics and thermodynamics aspects. Very different behaviors are observed between the carbons but for all adsorbents, the kinetics were faster in presence of a saline solution and the amount adsorbed at saturation higher, showing the importance of surface charge that introduces an energy barrier against adsorption when molecules and surface have the same charge. Adsorption isotherms were modeled with Langmuir and double Langmuir equations and the thermodynamic parameters were calculated and correlated with the adsorption behaviors. By using adsorption calorimetry to map the adsorption site distribution, it is possible to validate or not the models.

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