Aplicação do farelo da casca de pinhão na remoção de metais traço e corantes de amostras de água

Abstract

Contamination of water bodies by industrial wastewaters is a growing environmental problem that needs attention, not only for the water crisis faced by the country but also for the preservation of this asset for future generations. Two major pollutants present in these effluents are heavy metals and textile dyes. These pollutants are toxic to many living organisms and not biodegradable, tend to accumulate in organisms causing various diseases and disorders. Thus, the removal of these pollutants from industrial effluents is a major concern. In this work, the pinhão coat bran, Araucaria angustifolia seed, was used in the no treatment form and also treatments were found in the literature to potentiate the adsorptive capacity of the material with HNO3, EDTA, NaOH and citric acid. All the samples were physico-chemically characterized by IR, X-ray, thermogravimetry, FEG and EDS, where the results were similar to those found in the cellulose literature. A Cu2+ adsorption test was performed with the samples, where the bran no treatment, treated with NaOH and citric acid obtained satisfactory results. In order to optimize the adsorption process, a factorial design was performed for the three best samples of the coat bran involving Cu2+, Pb2+ and methylene blue, to study the variables agitation time and contaminant concentration. The statistical results show that the concentration exerts a greater influence on the adsorption process, especially at low concentrations, since the agitation time doesn’ t have much interference in the removal of the contaminants. In order to determine which adsorption isotherm would best represent the adsorption process, the model was compared to the Langmuir and Freundlich isotherms, where both the Cu2+ and the methylene blue contaminants, no treatment and treated with NaOH samples, are more adapted the Langmuir isotherm. The maximum adsorption capacity for the Cu2+ ion, the treated with NaOH pinhão coat bran is much larger than the no treatment sample, 51.81 and 8.77 (mg.g-1), respectively, for the dye methylene blue, 263.16 and 108.69 (mg.g-1). One hypothesis for the pinhão coat bran treated with NaOH to have a higher adsorptive capacity than no treatment bran is that in the treatment the hydroxyl groups (OH) deprotonated acidic clusters present in the composition of the pinhão coat bran biomass, thus, the bran treated with NaOH is more electronegative compared to the no treatment bran, thus favoring the removal of positively charged contaminants, such as metals and the methylene blue dye. In general, the pinhão coat bran samples showed promise for the removal of metallic ions such as Cu2+ and Pb2+ and also the methylene blue dye, however, further studies are still needed to better elucidate this adsorption process.