Caracterização da argila vermiculita expandida para possível aplicação como adsorvente

Abstract

The present work had as objective to characterize by physical chemical and mineralogical standards the expanded vermiculite clay, defining its zero charge point (pHzcp), basic and acid sites, cationic exchange capacity (CEC) and performing analysis by the techniques of X-ray diffraction (XRD), Fourier transformation infrared spectrometry (FTIR) and scanning electronic microscopy (SEM). The interpretation of the results was done as to focus in the possible use of the clay as adsorbent of contaminants and the same results were used as theoretical background for suppositions about the best adsorption conditions and for estimating the quality of the processes. The zero charge point of the vermiculite was found near the pH 8,56, and such value was corroborated by the fact that the number of basic sites found was bigger than the number of acid sites, in concordance with the foreseen chemical structure and negative superficial charge of the mineral. The cationic exchange capacity (CEC) value found was of 1,22x10-3 mmol of methylene blue/100g of clay, this value is below values of CEC found in the existing literature given by other methods. The X-ray diffratogram revealed the material’s high cristalinity and purity. The Fourier transformation infrared spectrum indicated the presence of adsorbed water and the clay’s characteristic functional groups, reaffirming that the clay is pure. The scanning electronic microscopy provided clear images of the sheet structure and allowed the measument of the intersheet distance, suggesting high superficial area and capacity to adsorb different sized molecules. By the results’ study and with the existing literature’s background, it was concluded that the expanded vermiculite clay has great potential as contaminant’s adsorbent, as long as the conditions of adsorption are studied and adequated to the adsorbate’s nature previously.