Isabel Grape Bagasse as a Potential Biosorbent of Zinc in the Effluents Treatment

Effluent treatment has become important because of its possible environmental impact as well as its possible adverse effects on human health. Additionally, improvements in environmental laws are another element of pressure for paradigm changes. Due to these factors, investigations concerning efficient effluent treatments have greatly increased. Alternatively, inexpensive natural materials have also been proposed for this task, which can reduce overall costs, thus making both investigation and use of these materials to be of utmost importance. Different unconventional substrates generated as byproducts of the agricultural and food industries are being tested to evaluate their efficiency in the removal of metal ions. Because of their low-cost, these materials can be profitably used as alternatives or complements to the more commonly used methods for effluent treatment. However, the application of such materials to the real conditions of industrial effluent treatment requires knowledge of their reactivity and the content of their adsorption sites to optimize the retention processes. In view of these facts, the aim of this work was to describe the equilibrium and kinetics of the adsorption process of Zn in aqueous medium, in order to demonstrate its potential for use in effluents treatment. In general, the Freundlich isotherm provided the better fit of the equilibrium experimental data, and the adsorption of Zn by grape bagasse showed a value of KF and n equal to 6.43 mg g and 1.45, respectively. The kinetics of the adsorption process, on the order hand, was better described by the pseudo-second order model and, furthermore, the removal percentage (~ 50%) was similar for all tested concentrations. Finally, the low cost, the availability of the agroindustrial waste, and the rapid adsorption promoted by the adsorbent, suggest that grape bagasse has great potential to be used in removal of zinc present in effluents.