Study of the effect of iron on the recovery of scandium from mining waste.

• Grant number: 22/16507-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2023
• End date: October 11, 2024
• Field of knowledge: Engineering - Chemical Engineering - Chemical Technology
• Principal Investigator: Jorge Alberto Soares Tenório
• Grantee: Vítor Moor Pinheiro Braz
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/11866-5 - Development of innovative processes for the recovery of critical metals, AP.TEM
• Associated scholarship(s): 23/15491-1 - Production of scandium from mining waste to obtain high-pure product, BE.EP.IC

Abstract

The solvent extraction process is composed of the extraction steps themselves, in which the metal of interest is transferred from the aqueous phase to the organic phase, followed by the washing step, in which the organic solution from the first step comes into contact with a solution for removing impurities that may have been co-extracted. The third step is re-extraction, to remove the metals of interest present in the organic phase, and the last step is the regeneration of the organic phase, so that it can then return to the beginning of the process (MOLDOVEANU; DAVID, 2015; TODD, 2014 ). The advantage of this separation technique is the selectivity, which can provide high purity products, especially important for rare earth elements of low concentration (XIE et al., 2014). Wang et al. (2013) compared three different extractants, DEHPA, Cyanex 272 and Ionquest 801 to separate scandium after Red Mud leaching. In this case, it was possible to separate 99% of the scandium at pH 0.2 - 0.6 with almost no iron from the solution using DEHPA (WANG; PRANOLO; CHENG, 2013). Other extractants such as Cyanex 923 and Cyanex 925 diluted in kerosene were explored by Ahmed et.al. (2013) for gallium extraction in hydrochloric medium, and they obtained 92% of the metal using Cyanex 923 (AHMED; EL-NADI; EL-HEFNY, 2013). However, in the recovery of scandium from mining waste, mainly for the waste from the Bayer Mud Red Process, iron is the main contaminant, and studies on its effect on solvent extraction are scarce or have not yet been explored for a better understanding. In the present work, a synthetic solution of the liquor generated in the acid leaching of the Red Mud residue will be prepared, in order to simulate the real solution. Iron, titanium, sodium, aluminum and scandium sulfate salts will be used. The extractants to be used will be Cyanex 272 and Cyanex 923 in kerosene. For solvent extraction tests, the following steps will be performed for both extractants: * Effect of the aqueous/organic phase ratio, extractant concentration, pH and temperature, in batch, for a single elemental scandium solution, at the same concentration in which it is present in the liquor; * Effect of iron concentration on scandium batch recovery; * Scandium recovery analysis using the synthetic liquor from the acidic leaching of Lama Vermelha; * Scandium re-extraction study using 2mol/L sulfuric acid; * Process analysis in a continuous system, to simulate the industrial solvent extraction process The aqueous/organic phase ratios will be 1/1 - 1/10, extractant concentration 15 - 30% (in kerosene), pH between 0.5 - 2.0 and the temperatures studied will be 25-90°C. The samples will be analyzed in atomic emission spectrometry (ICP-OES) to determine the chemical composition.