Remoção de Cromo VI em Efluentes Sintéticos Utilizando Borra de Café como Adsorvente

Abstract

This work shows the results of Cr VI adsorption using the coffee grounds as adsorbent. The adsorbent was initially treated by three methods, determining which more feasible for the process. Then, finite baths were carried out for 6h and 24h with the The objective of this study was to determine the ideal parameters: pH, granulometry and the amount (g) of adsorbent, as well as the solute concentration (ppm) for the adsorption process. Two parameters, 150 rpm and 27 ° C, were set due to bibliographic references and cost benefits. Of all three methods performed for the treatment of sludge, the third method presented the most reliable, inert to the results. No coloration was observed in the samples, shortly after 6h, as well as no significant variation in pH of samples. However, the other two methods presented unsatisfactory results. O method, showed a brown coloration in the samples after the period of 6h, in addition to of a significant pH variation. The second method, although it did not coloration and no exorbitant pH variation in the samples, its use is not yet viable, because it demands a great volume of water to treat a little sludge. For pH variation, after 6h and 24h, the best result was with pH 3.0, being consistent with the references literature, in addition to having presented an excellent removal rate for the adsorption of the hexavalent chromium metal. In the adsorbent granulometry variation, the highest (0.355mm), showed to be more efficient in the process, since it obtained a greater removal rate, compared to the results of the lower particle size (0.250mm). At solute variation, 100 ppm is the most suitable to work with. Because, the removal rates for smaller concentrations did not have a significant difference. With the adsorbent, 1g of sludge / 100 ppm was the best result obtained for the adsorption process, obtained a higher removal rate. According to the parameters obtained by the Freundlich, Langmuir and Redlich-Peterson, the coffee grounds proved to be a good adsorbent for or chromium (VI) metal. By means of the non-linear adjustments to determine the isotherms of Langmuir, Redlich-Peterson and Freundlich, the results were satisfactory and consistent. However, the Langmuir and Redlich-Peterson isotherms obtained the best adjustments, R2 = 1, comparing with Freundlich, R2 = 0.9949. After all the determined ideal parameters, adsorption kinetics were performed. The adsorption time fell from 6h, used to find the ideal parameters, for less than 3h.