Biossorção de corante reativo utilizando biomassa residual de origem lignocelulósica e fúngica

Abstract

The textile industry uses a diversity of processes that become eventually generating large volumes of effluents with a high polluting load. During the dyeing process, an amount of 15-50% of the original concentration of the dyes which are not fixed on textile materials is release as wastewater. Adsorption is one of the techniques, which may used in order to get an effective color removal. However, the process efficiency depends on the choice of a proper adsorbent. Due to the high cost of some conventional adsorbents, researches have been directed to the use of alternative adsorbents, such as yeast biomass and rice hulls. In this context, the aim of this work was to study the biosorption of reactive blue 198 dye, in two adsorbents: yeast biomass of Saccharomyces cerevisiae discarded from the brewing process and rice hulls, because these are biomasses with some advantages such as: the renewable character, abundance and low cost. The selected biosorbents were chemically modified by acid and alkaline treatment to evaluate the effect on the biosorption process. Moreover, in order to achieve the best conditions for the removal of the dye, the following parameters were investigated: pH of the aqueous solution, agitation, addition of salts and granulometry of the adsorbents. The models of pseudo-first order and pseudo-second order were used to evaluate data obtained in the kinetic study. The Isotherm models of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich were used to provide a better understanding of the biosorption mechanism. According to the experimental data, the presence of zinc sulfate in the solution affected less the efficiency of dye removal than the other salts. The model that better described the kinetic data was pseudosecond order and the model, which showed a better isotherm data fitting was Dubinin-Radushkevich. This model suggests the occurrence of a chemical mechanism in the biosorption process. The analyses of Mid-infrared attenuated total reflectance (MIR-ATR), was carried out to characterize the interaction of the biomasses with the dye, and showed the functional groups that were probably involved in the biosorption process: C-O, C-H, C=O and C=C. Data from EDS (energy dispersive x-ray detector) of the biosorbents indicated that differences in chemical elements composition between yeast biomass and rice hulls are mainly characterized by nitrogen, silicon, calcium, phosphorus and sodium. Evaluating all the results from the biosorption studies, it is possible to affirm that chemically modified yeast biomass and rice hulls are potential biosorbents of the reactive blue dye in aqueous environments.