Estudos de caracterização química e mineralógica para definição de parâmetros para separação magnética, visando a redução de Fe2O3 em rocha rica em feldspatos extraída em Pedra Lavrada - PB.

Abstract

The demand for high purity feldspars, especially for use in the manufacture of porcelain tiles and whiteware, poses a challenge for the processing of the ore. Due to the need for very low levels of iron oxide (Fe2O3), below 0.15%, operations capable of providing a product with high purity are more complex and costly. Therefore, it is necessary to employ chemical and mineralogical characterization to understand the ore and plan the operations of the beneficiation plant. A rock sample rich in feldspars collected from a pregnant woman in the municipality of Pedra Lavrada/PB was studied, aiming to identify the chemical composition, mineral and release spectrum through XRD, XRF and SEM techniques, with the intention of providing benefits for use of dry magnetic separation for feldspar purification. Aliquots were left to preparation, granulometric classification and magnetic separation steps. X-ray diffractograms indicate that the rock has high concentrations of feldspars (albite, orthoclase and microcline), quartz and a significant content of magnetite and hornblende, these being the main iron-bearing minerals to be concentrated for fuel chemistry. The average content of iron oxide in the rock is 1.25%, with the highest concentrations present in the granulometric fractions of -0.6+0.3mm and -0.3+0.15mm, with percentages of 1.621% and 1.924% , in that order. Scanning electron microscopy images show a greater physical release of magnetic mineral phases below 0.3mm, developing fragmentation operations being designed seeking this granulometric standard for efficiency in mineral concentration operations. Magnetic separation tests promote mass and metallurgical recoveries based on the feed granulometry and the operating speed of the rolls. The most expressive results were obtained in the samples observed under dry magnetic separation, whose granulometric range used was -0.3+0.15mm and low operating speed of the rollers, generating a non-magnetic display containing 0.147% of Fe2O3 (reduction of 76.81% of iron in relation to food), following this index within the standards of chemical products required for application in the composition of porcelain tiles. The other operational conditions of the magnetic tests produce non-magnetic fractions with Fe2O3 contents oscillating between 0.285% and 0.3%, slightly higher than the limits of the porcelain tile industry, however, suitable for the production of less noble ceramics or glasses.