Propriedades físico-químicas de caulinita com diferentes tamanhos de partículas

Abstract

The lattice of three kaolinites as well as their ability to remove ions orthophosphate was investigated. The soil samples were collected in the following places: i) Estrada do Turismo (Oxisol, and ii) Bacia do Educandos (sediment) and Campus of the Universidade Federal do Amazonas (sediment). The kaolinites were obtained from soil samples using the physical fractionation (sieving/siphoning) and chemical treatment (HCl, H2SO4, H2O2, and KCl). The kaolinite lattice were determined by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analyses (TG / DTA / DTG) and Mössbauer spectroscopy. The adsorption capacity of orthophosphate ions was calculated by equations of Freundlich and Langergren. Despite transitions of typical pure kaolinites, findings indicate the presence of a clay mineral isomorphically substituted by Fe3+. The Fe3+ substitution changed kaolinites lattice such as optical propriety mainly pleochroism, reducing mean particle size, rinsing number of defects, magnetic proprieties. Mössbauer spectroscopy showed that the isomorphic substitution by Fe3+ occurs in octahedral sites. In whole kaolinite lattices there are different octaedral sites of Al bounded by cis-Fe3+ and trans-Fe3+ octaedral sites. The Kao1, which has higher number of cis-Fe3+ octaedral sites, adsorbed higher contents of orthophosphate ions than Kao2 and Kao3.