Caracterização de argilomineral proveniente da região sudeste do estado de São Paulo por difração de raios x: cristais orientados

Abstract

The clay minerals are structural elements of the soil that having several applications according to their properties. The characterization of this material is made increasingly necessary by technological, environmental, ecological and strategic factors. This work presents the following main objectives: (i) characterization of a clay from the southeast region of the state of São Paulo through the technique of X-ray diffraction from oriented crystals and (ii) implementation of the methodologies to obtain oriented crystals by procedure called "Millipore filtration". The clay in nature, only by visual inspection, presents some relevant physical characteristics: fine texture, softness, tactile absorption, plasticity, white color to gray tones and easy sprayability in the surface. In this work, three distinct samples were obtained from the in nature clay. The obtained fractions were denominated: sample A1 of white clay, sample A2 of gray clay, and sample A3 of in nature clay and sample A4 of dark gray clay. The samples were characterized by the following techniques: X ray diffraction (XRD), composition (FRX), simultaneous thermal analysis (TGA/DSC) and morphological characterization (SEM). The dark in natura clay sample was characterized by composition analyzes (FRX), TGA/DSC and SEM. The so-called dark gray fraction was characterized only by TGA/DSC and SEM. From the of X ray results, it was possible to infer the presence of clay minerals of the 2:1 group (smectites and illite) and probably, a kind of chlorite is present, as well. The presence of non-clay minerals (quartz) was also identified and the large cells (superstructures) of the interstratified clay minerals were not observed. However, further study is needed to confirm these inferences. The thermogravimetric analysis (TGA) indicated that, in general, the shape of the TGA curves is more consistent with the clay minerals of the group 2: 1 for both white clay and gray clay because were observed several stages of mass losses. In relation to dark gray clay, it was observed that the losses occurred only in two stages and this seems to indicate a specific type of clay minerals present in this fraction. The SEM results show that these fractions have a homogeneous and distinct distribution for the three fractions investigated, with the presence of predominant platy-like morphologies of the clay minerals and the presence of ribbons and spherical structures for white clay and gray clays. Dark gray clay presents a distinct morphology like “snowflake” with highly disordered structures.