A PRELIMINARY EVALUATION OF BRAZIL NUTS WASTE USED TO PREPARE THERMALLY ACTIVATED CHARCOAL TO HEAVY METALS ABSORPTION

Abstract

This paper aims to use Brazil nut barck (Bertholletia excelsa L.) to produce thermally modified activated charcoal and evaluate its ability to absorb heavy metals, as: hexavalent chromium (VI) and bivalent copper (II). The concentrations of heavy metals in industrial effluents can be lower applying different methods, such as: adsorption, ion exchange, membrane separation, and electrochemistry. A promising technique for capturing heavy metals is adsorption by porous solids. In this process, it is essential that the adsorbent has high selectivity for with the metals as well great adsorption capacity. The activated charcoal from Brazil nut bark was characterized according to specific area, pore size, porosity, pH, surface functional groups by Boehm method and Fourier transformed infrared spectroscopy (FTIR). Experiments to determine the chrome and copper efficiency removing were performed for the initial concentration of solutions: 5, 10, 20, 30, 50, 100, 150 e 200 mg L^-1. The hexavalent chromium (VI) adsorption, without changing the natural pH of the synthetic solution, was not satisfactory since the removal was around 10%.  On the other hand, the results presented for the removal of bivalent copper, in the same adsorption conditions, reaching above 90% for most of the initial concentrations. The results showed greater affinity for copper than chrome by activated charcoal. Furthermore, this study motivates future research, especially in evaluating the adsorption capacity for different pH solutions.