Caracterização, estudos fundamentais e flotação de minério de ferro goethítico

Abstract

Dealing with low grade iron ores with complex mineralogy has become a day-to-day reality for the mineral industry. A good example is found in the case of hydrated iron ores, which are composed by the minerals haematite, goethite, quartz, gibbsite and kaolinite. The martitic haematite and goethite usually have contaminants such as P, Al, Si and Mn, which may be located in the crystalline structure or in the pores of the minerals, in addition to the LOI content, which lowers the iron content in the final concentrate. Aiming to understand better that type of ore, the characterization of a low grade hydrated iron ore was undertaken through XRD, XRF, chemical analysis, RLM, SEM/EDS, specific area analysis (BET) and pore size analysis (BJH) through N2 adsorption/desorption, helium pycnometry, TG and DSC. On the next step, fundamental studies were conducted with pure minerals through electrophoretic mobility measurements (zeta potential) and microflotation in Hallimond tube. The IEPs obtained in NaCL 10-3 M for haematite, goethite, gibbsite and kaolinite were 6.8, 8.2, 9.2 and 4.9, respectively. The IEPs of haematite, goethite and gibbsite were reduced, respectively, to 4.2, 5.4 and 6.3 in the presence of sodium oleate and to 4.9, 6.6 and 7.2 in the presence of AERO 6493 hydroxamate. In the microflotation experiments, the floatability of haematite, goethite and gibbsite were high for both collectors. It was observed selectivity between haematite and goethite in the pH range 5,0 to 6,0 with sodium oleate. Quartz and kaolinite presented floatability lower than 15% with both collectors. The conditioning time and temperature raised the floatability of haematite and goethite. The floatabilities of gibbsite, quartz and kaolinite with AERO 6493 hydroxamate were reduced for higher temperatures. Starch, sodium fluorsilicate and Floatan M3 showed poor responses as depressants. The bench scale flotation experiments were undertaken with a coarse ore sample (-0,150+0,045mm) and a fine ore sample (-0,045+0,010mm). In the sodium oleate system, it was obtained a concentrate with 44.69% Fe, 32.92% SiO2, 2.97% LOI, 89.34% Fe recovery and SI = 2.52, for the coarse sample, and 61.10% Fe, 7.91% SiO2, 4.18 LOI, 5.09% Fe recovery and SI = 1.83 for the fine sample. In the AERO 6493 hydroxamate system, it was achieved a concentrate with 46.77% Fe, 27.41% SiO2, 5.50% LOI, 66.98% Fe recovery and SI = 1.41, for the coarse sample, and 60.21% Fe, 9.31% SiO2, 4.05% LOI, 32.23% Fe recovery and SI = 1.92 for the fine sample. In the reverse cationic flotation, it was achieved 63.75% Fe, 2.93% SiO2, 5.88% LOI, 74.98% Fe recovery and SI = 9.86, for the coarse sample, and 64.39% Fe, 2.15% SiO2, 5.14% LOI, 81.05% Fe recovery and SI = 8.15 for the fine sample.