Abstract The mineral processing of low-grade iron ores commonly generates large volumes of slime, which are disposed as tailings. Modern mining requires strives to eliminate the use of tailings dams in a maximum effort to increase metallurgical recovery, the security and reduction of the operational cost. This research aims for the recovery of iron contained in the slime, which consists of a material with 38% Fe and <40 µm, originating from the desliming cyclones. Pilot tests were performed on the Wet High-Intensity Magnetic Separator (WHIMS) and on the Vertical Ring Pulsating High Gradient Magnetic Separator (VPHGMS) considering different configurations in terms of operating parameters and routes. The best results were obtained for VPHGMS with an iron content in the concentrate of 67.06% and mass and metallurgical recovery of 32.42% and 56.86%, respectively. In the best condition tested, around 540 thousand tons of concentrate can be incorporated into production and has great environmental relevance.

Abstract The presence of slimes is harmful to the flotation process: the performance and consumption of reagents are negatively affected. Traditionally, the desliming stage has been responsible for removing slimes. However, depending on the porosity of the mineral particles, desliming may not be sufficient to maximize the concentration results. An attrition process before the desliming operation can improve the removal of slime, especially when slimes cover the surface and/or are confined to the cavities/pores of the mineral particles. Attrition is present in the flowcharts of the beneficiation process of phosphate and industrial sand (silica sand). Research has been undertaken for its application to produce pre-concentrates of zircon and iron ore. However, there is still little knowledge of the influence of the attrition variables on the beneficiation process of iron ore. This study presents a factorial design and analysis of the effects of these variables on the reverse flotation of iron ore. The standard of the experimental procedures for all tests included the attrition of pulp, under the conditions of dispersion, desliming and flotation. The parameter analysed (variable response) was the metallurgical recovery in reverse flotation tests. The planning and analysis of the full factorial experiment indicated that with 95% reliability, the rotation speed of the attrition cell impeller was the main variable in the attrition process of the iron ore. The percentage of solid variables in the pulp and the time of the attrition, as well as their interactions, were not indicated to be significant.

Abstract This paper presents a potential condition to separate kaolinite through flotation when it is present in bauxite ore. This research anticipates a Brazilian industry requirement, considering the tendency towards the need for aluminosilicates removal from bauxite ores, as has already occurred in China. Kaolinite is the most abundant aluminosilicate, and gibbsite is the main aluminum bearing mineral in Brazilian bauxite ores. The first step was a fundamental study involving microflotation experiments with pure samples of kaolinite and gibbsite. Ammonium quaternary salts and amines were used as the collector and corn starch as the depressant. In a fundamental study, the best conditions determined in the first step were evaluated for the flotation of kaolinite from bauxite ore using laboratory scale experiments. Tests with AQ142/starch (pH 10) and CTAB (pH 7) led to satisfactory results. In general, the highest values of alumina/silica mass ratio were obtained with AQ142/starch and the highest values of mass recovery and metallurgical recovery were achieved with CTAB.

Abstract The dispersion degree of the mineral particles in the pulp is especially relevant regarding the performance of the cationic reverse flotation of iron ores. The gangue minerals should remain dispersed while hematite particles should be selectively flocculated. The present study addressed determinations of dispersion degree and zeta potential of hematite in the presence of different dispersants, classified as organic polymeric (natural and synthetic), organic monomeric, and inorganic. Special attention was paid to results achieved at pH 10, used in plant practice. For natural organic polymers, correlation was observed between the dispersion degree and the increase in the negative value of zeta potential. Some synthetic organic polymers enhance the dispersion of hematite particles despite not affecting significantly the zeta potential. Sodium silicates, irrespectively of the SiO2/Na2O ratio, at pH 10, did not impact significantly either the dispersion degree or the zeta potential.

O número de estudos a respeito de flotação de caulinita tem crescido nos últimos anos, principalmente, devido às contribuições dos pesquisadores chineses. As bauxitas chinesas apresentam alta quantidade de aluminossilicatos, entre eles caulinita, o que prejudica sua utilização no processo Bayer. Esse trabalho apresenta resultados de testes de microflotação de caulinita com três aminas: dodecilamina (amina primária), Flotigam EDA (eteramina) e Duomeen T (amina graxa). Dodecilamina e Flotigam EDA apresentaram eficiente ação coletora na concentração de 1x10-4 mol/L. DuomeenT se mostrou eficiente em concentração mais alta, 1x10-3 mol/L. O ponto isoelétrico da caulinita, determinado a partir de medidas de potencial zeta, ocorreu em pH = 4,6. O estudo do potencial zeta da caulinita, na presença e na ausência de dodecilamina e Flotigam EDA, mostrou que a presença de amina no sistema altera seu ponto isoelétrico. Tal variação sugere que ocorreu adsorção dos coletores na superfície da caulinita.

The number of studies addressing kaolinite flotation is steadily increasing, mainly, due to Chinese research contributions. The Chinese bauxites present high amounts of aluminosilicates, for example kaolinite, hindering the application of the Bayer process to the ore. Herein are presented the results of kaolinite microflotation tests with three amines: dodecylamine (primary amine), Flotigam EDA (etheramine), and Duomeen T (fatty amine). Dodecylamine and Flotigam EDA presented enhanced collecting action at the concentration of 1x10-4 mol/L. Duomeen T was effective at a higher concentration, 1x10-3 mol/L. The kaolinite isoeletric point, determined by zeta potential measurements, occurred at pH = 4.6. The kaolinite zeta potential determinations, in the presence and absence of dodecylamine and Flotigam EDA, showed that the amine presence in the system changes the isoelectric point. This change suggests that collector adsorption occurred on the kaolinite surface.