The aim of this study was to develop an adsorbent from coffee husk, residue from the coffee industry by different activation methods and to evaluate its application in the treatment of effluent containing synthetic Ponceau 4R dye. The activations were with phosphoric acid and zinc chloride, then the samples were characterized in terms of physical and chemical composition, structure and morphology, thermal behavior and kinetic and thermodynamic study. Regarding the characterization of the material, the activation with phosphoric acid showed porous morphology and a high surface area (429.7 m² g -1 ) and with the kinetic study it was possible to obtain an equilibrium time of 60 min and dispersion according to Elovich kinetics (R 2 = 0.96 and RMSE < 0.24). According to the experimental design, the adsorptive capacity can be evaluated with the significant result (qe = 19.87 mg g -1 ) under the conditions of 90 min of the adsorption process and at the concentration of 2 g L -1 of adsorbent. In relation to the equilibrium study the Langmuir model fit the data with coefficient of determination of R 2 = 0.84. Finally, the Ponceau 4R dye adsorption process using coffee husks as an activated carbon was thermodynamically favorable through the negative Gibbs free energy and positive entropy (+0.022 kJ mol -1 K -1 ). Therefore, the use of coffee husk as activated carbon proved to be a favorable material for Ponceau 4R dye adsorption. HIGHLIGHTS• The adsorbent activated with H2PO4 removed around 100% of Ponceau 4R dye.• The increase in temperature influenced the increase in maximum adsorptive capacity.• Langmuir's isotherm was better suited to the experimental data of the Ponceau 4R dye.

Brewers' spent grains are the main residue generated from the brewery industry; they are produced on a large scale and at a low cost. During the brewing process, approximately 85% of all barley used is transformed into solid residue, which is currently destined for animal feed or just discarded. A possibility to increase the value of this byproduct is the production of carbonaceous materials, such as activated carbon, for the treatment of tartrazine yellow dye solutions. The structures and morphologies of the samples were characterized. Furthermore, the adsorptive capacity and kinetic behavior were studied. Regarding the characterization of the material, the activated carbon presented a porous morphology and high surface area (768.4 m² g-1). Additionally, the kinetic study showed that the equilibrium time of the adsorption process from the tartrazine yellow dye discoloration was 60 min., and the data presented dispersion according to Elovich’s kinetics. It was possible, from the experimental design, to evaluate the adsorptive capacity of the material in which it performed best at pH < 5. Finally, in the equilibrium study carried out by the adsorption isotherms, it was found that the increase in temperature influenced the process, raising the maximum adsorptive capacity in which the data fit into the Langmuir isothermal model

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