Royal Blue Dianix CC Dye Adsorption Onto Biochars: Kinetics, Diffusion Modeling, Equilibrium and Thermodynamic Adsorption Data

This work presents a detailed analysis of the adsorption process of royal dianix CC blue dye on biochars, synthesized from the bark of cupuaçu, a lignocellulosic residue generated by the food industry. The biochars were activated with KOH or H3PO4 and carbonized at a temperature of 450°C. The kinetic parameters, the diffusion coefficients, the equilibrium data, and the thermodynamic parameters of the dye adsorption were also determined. The chemical and physical properties of the porous materials were affected by the activating agent used. The adjustment of the kinetic models to the experimental data suggested that the dye adsorption onto both biochars occurred predominantly by chemisorption, which was controlled by the external mass transfer. The acid and basic carbons presented a maximum adsorption capacity of 98.45 and 66.95 mg g–1, respectively. The negative values of Gibbs free energy and enthalpy indicate that the adsorption is spontaneous and exothermic.