Abstract Demand for iron ore worldwide has been steadily increasing, thus implying an increase in the volume of mining resulting in the extraction of ores with higher levels of silicon, phosphorus and sulfur impurities. An extensively used alternative is to perform a pre-treatment of the particles in order to reach the acceptable phosphorus limit in iron ore before its use in steel production. This study aims at the evaluation of the heating process and decrease of the phosphorus content of the particles using microwave energy in iron ore samples percolated by sulfuric acid followed by the leaching technique as a feasible route for the remotion of the phosphorus content in iron ore particles. Using the scanning electron microscopy (SEM) and statistical analysis techniques, it was possible to observe the characteristics of the iron ore particles after treatment with microwave energy. The results indicated that the developed process is feasible. The results of the kinetic simulation contribute to a better understanding of the phenomena of heating using microwave energy and also to the development of new cleaner technologies aiming to improve the efficiency of the acid baking - leaching technique for the reduction of the phosphorus content in iron ore particles.

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%.

Abstract 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.

The extraction of divalent metals (Mn2+, Ni2+, Co2+ and Cu2+) in the system MSO4 - H2SO4 - H2O - D2EHPA in isoparaffin (17/21) was studied by a thermodynamic model based on chemical equilibria with mass and charge balance equations. The activity coefficients of all solutes in the aqueous phase were calculated by Davies equation. By applying this model, the equilibrium concentrations of solutes were calculated from de concentration of divalent metals and pH. The predicted distribution coefficients for the divalents metals were in good agreement with experimental results.

A extração do níquel, em um sistema NiSO4 - H2SO4 - H2O - D2EHPA - Isoparafina, foi estudada por um modelo termodinâmico com base em equações de balanço de massa e carga. Os coeficientes de atividade de todos os solutos, na fase aquosa, foram calculados pela equação de Davies modificada. Ao aplicar esse modelo, a concentração das espécies no equilíbrio foram calculadas a partir dos valores de concentração total de níquel em solução e pH. O metal extraído das espécies foi determinada a ser NiA2 (onde HA é D2EHPA) e a constante de equilíbrio da extração foi encontrado para ter um valor de 2,83 E-2 a partir do cálculo de regressão não-linear realizado com os dados experimentais. Os valores dos coeficientes de distribuição previstos pelo modelo, para a extração de níquel, tiveram uma boa concordância, quando comparados com resultados experimentais.

The nickel extraction, from the system NiSO4 - H2SO4 - H2O - D2EHPA - Isoparaffin, was studied by a thermodynamic model based on balanced equations for mass and charge. The activity coefficients of all solutes in the aqueous phase were calculated by the modified Davies’s equation. By applying this model, the concentration of solutes in the equilibrium was calculated from the values of the total concentration of nickel in solution and pH. The metal extracted species was determined to be NiA2 (where HA is D2EHPA), and the equilibrium constant of the extraction was found to have a value of 2,83 E-2 from the calculation of non-linear regression realized with the experimental data. The values of distribution coefficients predicted by the model for nickel extraction were in good agreement when compared with experimental results.