Reaproveitamento do rejeito de enriquecimento do minério de ferro – lodo de Mariana – MG, para a produção de cerâmica ambientalmente correta

Abstract

This work sought to develop new composites, inserting the waste from iron ore mining, called Iron ore tailings – IOT, into the matrix of the primary raw material for coating ceramics production. The tailings come from the FUNDÃO dam, located in the city of Mariana, Minas Gerais (MG), where the vast environmental disaster occurred in 2015. Such tailings are highly toxic for both environment and humans, given their high alkalinity (PH above 10). The objective was to transform IOT, associated with other wastes such as foundry sand and glass cutting sludge from the automotive industry, using kaolin as a binder, into raw material for manufacturing new construction materials. Others researchers have demonstrated the compatibility of IOT with others components of raw material in ceramics, concrete and Portland cement clinker. Dissolution and leaching studies show that traces of heavy metals remain within limits established in specific technical standards when sintered at temperatures above 1000 ºC. Thirty compositions were prepared, each with 6 (six) different percentages of raw material, where in each group, the IOT content was maintained, varying foundry sand, glass, and kaolin contents. Five specimens of each composition were randomly selected, resulting in a total of 30 (thirty), which were burned in a muffle furnace of the maximum temperature of 1200 ºC, at 950, 1000, 1050, 1100, 1150 and 1200 ºC. The results showed that the composition 30, with 25, 30, 30, and 10% of IOT, foundry sand, glass, and kaolin, respectively, reached flexural strength of 10,17 MPa, water absorption of 5.48%, volume of 6.53 cm3, and apparent density of 1.54 g/cm3 at a temperature of 1150 ºC. Compositions 13, 19, 20, 21, 25 and 26 at 1200 ºC showed absorption rates of 3% < ev ⋜ 6%, higher than 6 and ≤ 10% and absorption > 10% whit flexural strencth modulus (MRF) ≥ 12 MPa, according to the absorption groups of brazilian technical standards ISO 13006 (ABNT) for testing and classification specifications and methods, respectively, they can be classified as BIIa, BIIb e BIII %. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) tests were performed to determine the chemical elements formed. The crystallographic formations, responsible for increasing the mechanical strength, were obtained by Xray diffraction (XRD).