This paper presents results or the analysis of process variables for separating light REE and heavy REE, in chloride media, by solvent extraction. DEHPAIsoparaffin was used as the extraction system and the liquor was produced in the laboratory by dissolving REE oxides in HCl to simulate leaching liquor originating from monazitic ores after cerium removal. The following parameters were determined: pH of work, extractant concentration, reaction time, and number of extraction stages. A continuous extraction circuit was operated and its behavior was similar to that shown by batch extraction tests.

As algas e microalgas vêm sendo estudadas quanto à sua habilidade em biossorver elementos de terras-raras através da troca iônica com grupos ligantes presentes na superfície dos revestimentos celulares. Assim, o presente trabalho buscou avaliar a capacidade da biomassa liofilizada da microalga Chlorella vulgaris (Chlorophyta) na biossorção do lantânio-La, visando seu uso na separação de terras-raras. Os ensaios de biossorção de La foram conduzidos em batelada, onde suas concentrações residuais foram determinadas com o uso de ICP-OES. Constatou-se que a biossorção de espécies iônicas de La foi dependente do pH inicial de cada ensaio. A capacidade de biossorção foi maior em valores de pH mais baixos. Uma vez que o ponto de carga zero foi determinado em valor de pH 5,59, pode-se concluir que espécies aniônicas de La estejam presentes em solução. Os valores de qmáx revelam a capacidade de biossorção de espécies iônicas de La pela biomassa de C. vulgaris, a qual apresentou um valor de 1,11 mg/g (0,8 mmol/g). As isotermas demonstraram que, nas condições experimentais avaliadas, a biossorção de La ocorre de acordo com o modelo proposto por Freundlich, em um processo de adsorção reversível em sistema heterogêneo.

Unlike the available mineral resources, the steelmaking processes have demanded raw material with lower phosphorus content to decrease the costs, energy use, and the residue generated within the steel plant. One alternative is to develop pretreatment of the iron ore concentrates producing raw materials with lower phosphorus. Depending on the mineral structure, a heat treatment combined with leaching could be an efficient way to achieve concentrates with low phosphorus (less than 0.01%), suitable for steelmaking processes. A fast and efficient way of applying energy to iron ore particles is the use of microwave to heat the particles. Thus, we propose a treatment using microwave heating while mixing with a dilute aqueous solution of sulfuric acid, followed by quenching during leaching with water, as a feasible route for the phosphorus removal from iron ore particles. We performed a design of experiment (DOE) to investigate the optimal conditions of heating and leaching, which maximize the rate of phosphorus removal. The structure of the iron ore particles after their treatment with microwave energy was observed by scanning electron microscopy (SEM). Thus, we analyze the optimal conditions for heating and leaching, the structure of the iron ore particles and which mechanism and rate equations are controlling the phosphorus removal. The results indicated that the average heating time is 10 min, the size of the crack of the order of 20µm and a leaching time of 8 min are adequate to achieve less than 0.01% of phosphorus. We demonstrated that under the most favorable combination of conditions for heating followed by leaching proposed in this study, the removal of the phosphorus content in the iron ore samples could reach 100%.

The study aimed to employ a comprehensive methodology for the acid processing of a rare earth element (REE) concentrate obtained from the ore from Araxá (MG-Brazil). The most important process variables have been identified and their levels determined to maximize REE extraction (%RE) and minimize Fe extraction (%Fe). The thermodynamic analysis showed that the roasting temperature (TF) is crucial for the control of Fe solubilization in the aqueous leaching step of the acid processing. A statistic design of laboratory experiments and a process optimization method were applied to address the interaction among the process variables. Experimental results showed that a TF of about 700 °C can significantly reduce the Fe concentration in the aqueous leaching liquor. Mathematical models were proposed to predict the effect of process variable on REE and Fe extraction of the concentrate. A multi-objective technique was employed for optimization of chemical processing and the best conditions were reached for roasting temperature (TF) = 700 °C, acid to sample mass ratio (ACs) = 0.8 and leaching time (tL) = 20 min, which led to %RE = 96.91% and %Fe = 21.69%.

The extraction of gold from refractory gold mineral deposits is becoming increasingly necessary. The presence of gold encapsulated within the crystalline matrix of iron sulfide minerals, such as pyrite, pyrrhotite, and arsenopyrite significantly reduces the efficiency of cyanidation. Therefore, the use of oxidative pretreatments, such as calcination, pressure oxidation, or bacterial leaching, enables a high gold recovery from refractory deposits. Calcination has been widely employed. However, it has a high energy cost and environmental issues due to the release of toxic gases containing arsenic. In the treatment of refractory gold ores containing arsenic, pressure oxidation (POX) represents an attractive approach for arsenic immobilization, since the conditions are suitable for both sulfide oxidation and the formation of stable arsenates. In the present study, tests of alkaline and acidic pressure oxidation followed by sodium cyanide leaching were conducted on a composite sample of the Faina Project, owned by Jaguar Mining Inc., located in de northwest portion of the Iron Quadrangle, Minas Gerais, Brazil. The mineralization is hosted by metabasalts and komatiitics metabasalts of an archean metavulcano sedimentary sequence, in the Greenstonebelt Pitangui. The tests demonstrated that it is possible to achieve a 98.40% gold recovery using a concentrate initially containing 12% sulfur, which underwent acidic oxidation with a 0.28 M H₂SO₄ solution at a temperature of 220°C, oxygen pressure of 500 kPa, and a residence time of three hours. This result was 19.19% higher than that obtained in an alkaline medium using a 3.0 M NaOH solution.