Removal of dyes brilliant blue and methyl violet from aqueous solution using cassava peel (Manihot esculenta) modified with phosphoric acid

In this paper, the ability of cassava peel modified with phosphoric acid to remove Methyl Violet and Brilliant Blue FCF from aqueous solutions was evaluated. The best temperature conditions (127 degrees C) and biomass/acid ratio (1: 1) were determined for the modification of cassava peel, using the Methylene Blue Index method. Then, the adsorption capacity of the cassava peel selected in the removal of the Brilliant Blue and Methyl Violet dyes was evaluated, finding values of percentage of removal and maximum adsorption capacity of 16.1% and 0.00207 mmol / g for Brilliant Blue, and 97.95% and 0.0249 mmol / g for Methyl Violet, achieving equilibrium in 285 and 330 minutes, respectively. The data of the adsorption kinetics of each of the dyes were adjusted to the pseudo- first order and pseudo- second order models: the adsorption of Violet of Methyl was better represented by the pseudo- second order model, whereas the adsorption data of Bright Blue was better fitted to the pseudofirst order model. To study the adsorption equilibrium, the data were adjusted to the Langmuir, Freundlich, and Tekim models, showing that the Freundlich model has the best fitting to the experimental values. nf values indicate the favorability in the adsorption processes for each dye. Finally, in the thermodynamic analysis it was determined that the adsorption of both dyes occurs spontaneously and is also favored with the increase in temperature, proving to be an endothermic process.