Adsorption of the textile dye Dianix® royal blue CC onto carbons obtained from yellow mombin fruit stones and activated with KOH and H3PO4: kinetics, adsorption equilibrium and thermodynamic studies

The purpose of this study was to use yellow mombin fruit stones, a residue from the food industry, as a precursor material for the synthesis of activated carbon and dye removal, using the textile dye Dianix (R) royal blue CC as a model molecule. Activated carbons were obtained by chemical activation using phosphoric acid or potassium hydroxide as activating agents. The effect of the nature of the activating agent on the physicochemical properties of the adsorbents was analyzed. The influence of pH of the solution, the time required for reaching the equilibrium, the adsorption isotherms at different temperatures, and the thermodynamic parameters of the dye adsorption onto the synthesized carbons were also evaluated. The activation with phosphoric acid had a more effective effect on the precursor structure, providing an adsorbent with greater surface area and higher pore size, which is favorable for dye adsorption. Adsorption data were adjusted to different kinetic models (pseudo first order, pseudo-second order, and Elovich) and isotherms (Freundlich and Langmuir), showing a maximum monolayer adsorption capacity of 147.47 mg.g(-1). and 82.28 mg.g(-1) for the acidic and basic treatments of activated carbons, respectively. The thermodynamic parameters indicated that the dye adsorption by the activated carbons is a spontaneous and exothermic process. Published by Elsevier B.V.