Análise da remoção do corante azul de metileno através de adsorção pela casca da castanha do brasil (Bertholletia excelsa).

Abstract

The effluent from the textile industry is classified as the most polluting among the sectors of the chemical industry. These effluents have high values of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD), high concentration of organic matter, high tem perature, variable pH, colored organic compounds and large amounts of suspended solids. Among the textile dyes present in these effluents, methylene blue stands out. One of the most used treatment methods in this type of industrial effluent is adsorption, which is a separation process in which substances contained in a fluid phase are transferred to the surface of a solid that has adsorbent characteristics. With a view to reducing costs, special attention is given to agro-industrial residues as an alternative to commercial adsorbents that make the removal pro cess more expensive. Among these alternative residues is the Brazil nut (Bertholletia excelsa) which has an annual production of about 33 thousand tons in Brazil and that each processed ton generates around 1,4 ton of residues. Given the above, the objective of this work was to analyze the removal of methylene blue dye through the adsorption process by the Brazil nut shell. For the adsorption tests, the variables concentration of methylene blue and dry mass of Brazil nut shell (Tyler 100) were studied, varying the concentrations from 10 to 20 mg/L of methylene blue and adsorbent load of 0,01 to 0,02 g. The tests consisted of stirring this solution in a shaker for 30 min, 150 rpm and 25 oC. according to the central composite factorial design 22, with rotation 21/2. To obtain the adsorption isotherm, an adsorbent charge of 0,015 g was fixed, 25 oC and stirred for 30 min; varying only the concentrations of methylene blue. In the adsorption experiments, the high adsorption capacity of the Brazil nut shell was verified, so that the highest removal was 98,99%. The response surface provided the optimal condition: methylene blue at 12,0058 mg/L and 0,01843 g of Brazil nuts, with an estimated removal percentage of 99,06%. The adsorption isotherm best fitted the Lang-muir model which estimated a maximum adsor ption capacity of 79,3651 mg/g. Therefore, the analysis of the removal of the methylene blue dye made it possible to highlight the bark of the Brazil nut (Bertholletia excelsa) as an alterna tive low-cost adsorbent.