Aplicaciones de los minerales arcillosos de Cayo Guan, Cuba, como adsorbentes de metales pesados y materia prima cerámica

It has been studied by Analysis Heating Microscope – Optical the behaviour of some kaolinitic clays from a reservoir of Cayo Guan rich in iron oxides and low silica content proving to be a refractory materials whose softening appears after 1500 °C. It has obtained the workability diagram of the different clay minerals calculating the plasticity by the method of Casagrande spoon; only one of the samples is in the area suitable for extrusion. Vitrification diagrams report that the capacity of water absorption is < 0.6 % when the temperature of 1400 oC is achieved. We have designed a program to calculate compositions of porcelain stoneware prepared from these modified clays adding low-cost raw materials that facilitate the formation of glassy phase ((potassium feldspar and glass cullet) and/or increase the silica (sand and diatomaceous earth used as filters in the brewing industry). With one of these compositions, prepared in the laboratory (60 % of clay, 30 % feldspar and 10 % of diatomaceous earth), calcined at 1250 oC with a heating rate of 15 °C/min, the results were: water absorption 0.8 %, and linear shrinkage 21 % without any deformation observed. These clays have been treated with acid to eliminate its high iron content and study its application as an sorbent of heavy metals as Cd2+, Cr3+. The results of the immobilization of these elements have been compared with those obtained with thermally activated vermiculite at 800 °C, showing that the treated samples show sorption of both cadmium and chromium below the vermiculite, but the non-treated ones are suitable to remove chromium; this is because these clays do not contain in its composition exchangeable ions (Ca2+, Mg2+, Na+, K+), and even if they are chemically activated only the presence of Fe ions is which produces form bindings (Crx.Fe1-x) (OH)3 which favor Cr sorption. En Cayo Guan, municipio de Moa, hay junto a las importantes explotaciones industriales de lateritas, minerales arcillosos cuya caractarización química, mineralógica y evolución de fases con la temperatura han sido objeto de estudio por estos autores en un anterior trabajo; entre las características físicas, químicas y mineralógicas del yacimiento destacan los altos contenidos de óxidos de hierro y aluminio, bajas concentraciones de SiO2 y óxidos alcalinos, y la caolinita como mineral más abundante, además de hematita, gibsita y goethita en forma de geles. Se pretende en esta investigación estudiar sus propiedades tecnológicas para dilucidar la posible aplicabilidad a estos recursos minerales en la fabricación de ladrillos, baldos