This work describes the concentration of iron ore slimes on a pilot scale by using a 500-mm diameter flotation column and a novel collector, which renders the use of a depressant unnecessary. The pilot column was operated in series with the industrial plant Vargem Grande 2 (Iron Quadrangle, Brazil) receiving, as feed, part of the underflow from the desliming thickener. These pilot tests represented only the rougher stage of a flotation circuit. The novel collector used was an amidoamine (average collector dosage of 160 g/t), and the tests were carried out in the absence of starch, at pH 10.5 and with bubbles/microbubbles generated by cavitation tube. It was possible to achieve a concentrate, by reverse flotation, with an average iron content of 53% and an average metallurgical recovery of 91.5% The recovery of the silica in the froth was 53.1% in average for one stage of flotation. The high variability of the slime characteristics rendered difficult the stabilization of the SiO₂ recovery; however, the applicability of the amidoamine collector was proven. In an industrial scale circuit, the use of online analyzers for Fe and SiO₂ content and the adoption of control logics based on the adjustment of parameters such as reagents dosage and washing water flow rate adjustment should contribute to the optimization of the results obtained in the pilot scale tests. Further studies adding a cleaner concentration stage should be performed.

A major concern in cobalt electrowinning is the generation of H₂ along with cobalt deposition on the cathode, which results in current efficiency drop, specific energy consumption increase, as well as poor deposit quality. In this paper, the influence of initial pH, temperature, current density, and Co²⁺ ions concentration on current efficiency and specific energy consumption for cobalt electrowinning in a batch cell for 24-h electrolysis was investigated through a two-level factorial design. Preliminary analysis from cyclic voltammograms and current-time curves indicated a current efficiency of 86.2%, with 60 g/L of Co²⁺ at pH 4.0. The statistical study indicated that temperature presented the greatest significant contribution for the response variables. The best result was achieved with initial pH 4.0, 70°C 100 A/m² and 60 g/L of Co²⁺, leading to a current efficiency of 78.8% and a specific energy consumption of 2.3 kWh/kg. As the pH drops considerably during the tests, its influence demands further studies.

Nickel (Ni) and cobalt (Co) are relevant technological metals for the future of the lithium-ion battery (LIB) industry. Based on the current and projected demand for these, an increased interest in developing processing routes to exploit lateritic occurrences has been observed, as these are reported as critical raw materials for future mineral–metallurgical industry. However, the content of Ni and Co in such ores is minimal and requires impracticable mineral-processing operations for concentration before metal extraction. It was identified that information regarding the sulfation roasting of this material is scarce on what concerns the iron sulfates interaction as a function of the temperature. Based on that context, the present work has its purposes associated with the proposition of an alternative chemical pretreatment to upgrade the content of metals of technological interest in lateritic ores through a simple roast–leach process. Thus, the chemical interactions between the mineral sample and iron (III) sulfate (Fe₂(SO₄)₃) through thermodynamic simulations and experimental procedures were explored. The latter included specific water leaching practices for the selective concentration of metals. The equilibrium calculations indicate that Fe₂(SO₄)₃ and FeSO₄ tend to decompose at lower temperatures, and considering the higher stability of other metal sulfates, it could be an interesting reagent in this type of process. Regarding the experimental results, the characterization of materials indicates a recovery of Co as high as 73.4 wt.% after sulfation roasting at 500 °C followed by water leaching, with the full content of Iron (Fe) being reported in the insoluble phase. Based on these findings, the present development could be an interesting alternative to consider within operations for the chemical upgrade of cobalt in such types of mineralogical occurrences.