Desempenho de argilas bentoníticas na remoção de cátions de cádmio e cobre em colunas de leito fixo.

Abstract

The adsorption became a separation process more attractive in the last times, mainly after the discovery of new adsorbents. In order to be possible to project and to optimize the adsorption equipments, it is indispensable the characterization of the adsorbent and the knowledge of the adsorption of the components dynamics in a experimental system. In this work it was analyzed the adsorption of Cu2+ and Cd2+ cations, individually, from the synthetic effluent in fixed bed column and having the bentonite clays (be called Bofe and Verde Lodo ones), originating from the Boa Vista-PB town. The characterization methods that were used in the work are the following ones: X-ray Fluorescence (XRF), Differential Thermal Analysis (DTA), Thermogravimetry (TG), Scanning Electron Microscopy (SEM) and Nitrogen Physissorption to determine the B. E. T. surface area of the samples. The fixed bed column that was built in acrylic had height of 13.3 cm and internal diameter of 1.4 cm. From the experimental projection technique with three central points it was possible to realize a more including study of the operational factors. Were utilized to adjust the balance data the following models: Langmuir, Freundlich, BET and GAB. In agreement with the characterization, the studied bentonite clays presented chemical composition in agreement with the most clays of their group. The presence of water in the interlamellar spaces of the clays, it was confirmed by DTA and TG. The Bofe and Verde-Lodo TG curves indicated a weight loss of 12.15 wt.% and 14.3 wt.% respectively. The Bofe clay, calcined at 500°C, presented surface area of 83.18m2/g, while the Verde-Lodo clay, which was calcined at 500°C, showed a surface area of 51.9m2/g. From the rupture curves obtained in all the adsorption systems, the incognita that most influences is the initial feeding concentration. The experimental projections last results showed that: the Cu2+ adsorption on the Bofe clay presented good performance under particle diameter of 0.46mm and Cu2+ initial concentration of 50ppm; the Cd2+ adsorption on the Bofe clay presented good performance under particle diameter of 0.65mm and Cd2+ initial concentration of 100ppm; the Cd2+ adsorption on the Verde-Lodo clay presented good performance under particle diameter of 0.46mm, Cu2+ initial concentration of 250ppm and flow of 4mL/min. The Verde-Lodo clay did not remove the Cu2+ cation. The adsorption balance data of the Cd2+ and Cu2+ cations on the Bofe clay were better adjusted through the Langmuir model. The adsorption balance data of the Cd2+ cation on the Verde-Lodo clay were better adjusted through the GAB model. Key Words: adsorption, bentonitic clay, fixed bed, metals removal.