Aproveitamento de resíduos do beneficiamento do caulim e da tantalita para produtos cerâmicos

Abstract

The mineral industry occupies a prominent place in the Brazilian economy and the national production of this sector is one of the largest in the world, being an important segment for the country. However, large volumes of waste are generated by mining activities that are disposed near mineral processing areas. Thus, the objective of this work was the utilization of residues generated in kaolin and tantalite beneficiation process for ceramic products. It referred to the production of products composed exclusively from these waste materials, without the use of any other raw material as a starting material. The residue from the second stage of kaolin processing (coarse kaolin waste) and the tantalite processing waste were sieved in sieves with different openings and the residue from the first stage of kaolin processing (fine kaolin waste) was hydrocycloned. These applied treatments generated fractions with different chemical and particle size characteristics in relation to the residues without any processing, showing the influence of the employed processes and allowing the selection of portions of greater interest for ceramic formulations. To evaluate physical and mechanical properties – water absorption (WA), apparent porosity (AP), linear firing shrinkage (LFS), mass loss to fire (LOI) and flexural rupture stress (FRS) – specimens were made by uniaxial pressing from the formulations and sintering processes were performed in industrial furnaces of red ceramic, porcelain tile and sanitary ware producing. The ceramic formulations were designed using mixture experiments methodology that allowed obtaining mathematical models correlating the behavior of physical and mechanical properties to the proportions of the components in the formulations, under the different firing conditions used. Properties obtained presented average values ranging from 3.29 to 8.88 % for LOI, from 3.74 to 18.64 % for WA, between 7.10 and 32.41 % for AP, from 1.30 to 13.87 MPa for FRS and between -1.33 and 2.36 % for LFS, among the various experimental formulations and burns performed. Mixtures with higher percentages of the tantalite beneficiation waste portion showed lower LOI, WA and AP, higher dimensional stability, but lower FRS. Formulations with larger amounts of the fine kaolin beneficiation waste portion achieved the highest FRS values, but high LOI, WA, AP and LFS values, based on the obtained results. The presence of larger amounts of the coarse kaolin beneficiation waste portion in the formulations resulted in high LOI, WA and AP values, low FRS values and intermediate dimensional stability in relation to the behavior of the other two wastes. The results showed that it is possible to obtain ceramic pieces from the mixture of these wastes portions, being able to promote economic and environmental benefits for mining and ceramic industries. The formulations achieved WA results compatible with those required for bricks, tiles and ceramic tiles, depending on composition and firing employed. The obtained pieces show potential for use as decorative wall tiles for interior walls, considering the achieved properties and the interesting aesthetics presented by the products.