Viabilidade de incorporação de resíduo de cromo proveniente de curtume em materiais cerâmicos, utilizando argilas distintas

Abstract

The ceramic industry supplies mainly to the construction sector due to its growth in Brazil. Even though there are large clay reserves scattered around the country, it is still difficult to reach those mineral resources because of the restrictive laws and conservation units. Moreover, ceramics have been studied as a way of encapsulate residues aiming cost benefit and sustainability. As an example, there is the residue coming from the leather tanning which contains in its composition chromium (Cr) III. Due to this residue has pollutants characteristics and of high dangerousness. This research aims to study the feasibility of incorporating chromium residue coming from the tannery industry in ceramic materials using different clays. In order to achieve the goals of this research, two types of clay were collected in different places and molded into ceramic bodies, where it was incorporated 0, 1 and 2% of the chromium residue into the clay mass and then extruded. Afterwards they were dried and burned at temperatures of 900 ºC and 1050 ºC. Finally, it was evaluated the manufactured ceramics characteristics. The characterization of the raw materials, through limits of Atterberg shows that the red clay is more plastic than the black one. The chemical composition of both of them are similar, except by the quantities of silicon (Si), which the black one contains 44.14% and red 38.79%. For the other compounds, the results are following, for the iron (Fe) with 6.31% in black clay and 5.39% in red, potassium (K) with a content of 1.76% in black clay and 0.51% in red. The residue coming from tannery presented 8.03% of Cr, moreover the red clay has more carbon than the black one, with 0.86% and 2.92% respectively. Regarding the ceramics physicochemical properties, it was observed the tendency of reducing the porosity and the water absorption capacity when it is increased the burning temperature from 900 ºC to 1050 ºC. Besides, the bulk density and the linear retraction are greater in the red clay. Also for the red clay the tendency of mass loss and rupture tension are lower than in the black one. About the addition of chromium associated with a temperature of 1050 °C, it can be said that the ceramic characteristics from the red clay were improved, mainly the rupture tension. Even though the black clay has shown a reduction in the tension resistance, it still can be used to manufacture of different types of brick. Therefore, it can be concluded that it is feasible the incorporation of chromium salts in ceramics, due to its presence does not interfere on the plasticity parameters and the physical-chemical properties of the tested ceramics.