Novel Adsorbent Material from Plinia cauliflora for Removal of Cationic Dye from Aqueous Solution

The food industry is responsible for the generation of large amounts of organic residues, which can lead to negative environmental and economic impacts when incorrectly disposed of. The jaboticaba peel is an example of organic waste, widely used in industry due to its organoleptic characteristcs. In this study, residues collected during the extraction of bioactive compounds from jaboticaba bark (JB) were chemically activated with H₃PO₄ and NaOH and used to develop a low-cost adsorbent material for the removal of the cationic dye methylene blue (MB). For all adsorbents, the batch tests were carried out with the adsorbent dosage of 0.5 g L^-1 and neutral pH, previously determined by 2² factorial design. In the kinetics tests, JB and JB-NaOH presented a fast adsorption rate, reaching equilibrium in 30 min. For JB-H₃PO₄, the equilibrium was reached in 60 min. JB equilibrium data were best represented by the Langmuir model and JB-NaOH and JB-H₃PO₄ data by the Freundlich model. The maximum adsorption capacities from JB, JB-NaOH, and JB-H₃PO₄ were 305.81 mg g^-1, 241.10 mg g^-1, and 122.72 mg g^-1, respectively. The results indicate that chemical activations promoted an increase in the volume of large pores but interacted with functional groups responsible for MB adsorption. Therefore, JB has the highest adsorption capacity, thus presenting as a low-cost and sustainable alternative to add value to the product, and it also contributes to water decontamination studies, resulting in a zero-waste approach.