Caracterização dos minerais do grupo da apatita e carbonatos no minério sílico-carbonatado de Catalão, GO, e sua relevância no processo de flotação

Abstract

Sample of the silico-carbonate ore (SIC) of Catalão, Goiás, was analyzed and submitted to the mineral processing routes designed for the Catalão (Catalão I) and Araxá (Barreiro) deposits ores. Although both are located in the same geological province and the ores have the same weathering profile, the flotation routes used for apatite concentration are different due to particular characteristics. The objective of this work was to evaluate the impact of the substitutions and the crystalline parameters of the apatites and carbonates of the flotation feed, tailings and concentrates samples from the SIC tests with and without addition of CO2. The use of Xray diffractometry (XRD) with the Rietveld method, QEMSCAN, scanning electron microscopy (SEM) with EDS (microanalysis by X-ray), electron microprobe, and LAICPMS (laser ablation coupled to mass spectrometer) enabled a thorough qualitative and quantitative characterization. Cathodoluminescence imaging associated with microanalyses by WDS (microprobe) and LA-ICPMS allowed the distinction of three types of apatites; a) blue color, richer in rare earths; b) green color, richer in Sr and F; c) yellow color, richer in Na and F. Blue and green apatites occur commonly associated in mixed grains with blue apatite nucleus and greenish-colored borders. The electrokinetic studies on the pure apatite, calcite and dolomite in the absence and presence of sodium sulfosuccinate showed that this collector adsorbs in the three minerals and causes an increase in the absolute value of the negative charge of the zeta potential in the pH range of 2 to 10. The use of CO2 in the conditioning stage results in the reduction of the pulp pH to values near 4.8 and a reduction in the values of the negative charge for the carbonates. This is probably due to the increased dissolution of these minerals. In the infrared spectroscopy analyzes, bands of the sulfosuccinate hydrocarbon chains (2950 to 2800cm-1) were observed for the mineral samples after conditioning in the presence of air and of CO2. A diagnostic adsorption band (1725cm-1) was detected only for the apatite sample, under both conditions. Three different benchtop flotation conditions were tested. The best result in terms of P2O5 overall content and recovery were 38% of P2O5 in the final concentrate, with an overall P2O5 recovery near 47%. In this test, the apatite collector was sulfosuccinate, with air in the rougher stage, followed by cleaner and recleaner steps with addition of CO2 in the bubble generation system. In the other two trials, the content or recovery were lower. Surface analysis by the XPS technique (X-ray photoelectron spectroscopy) showed that the ratio of sulfur/carbon concentrations on the surface of the sample treated in the presence of CO2 was the same of that found in the standard sulfosuccinate, much higher than with the use of air. This indicates that the adsorption in the presence of CO2 is more concentrated than in an air atmosphere