Recovery of magnesium sulfate from a zinc ore flotation tailing using hydrometallurgical route.

• Ano de defesa: 2020
• Autor(a) principal: Costa, Raquel Hungaro
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Cementação; Cementation; Leaching; Lixiviação; Magnesium sulfate; Metais tóxicos; Rejeito de zinco; Sulfato de magnésio; Toxic metals; Zinc tailing
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/3/3137/tde-20052021-113607/

The reuse of minerals from tailings is essential to generate less impact on the environment. The investigation of methods that aim to recover elements that can generate by-products from mining tailing has been studied, such as, for example, the zinc beneficiation tailing. The tailing acquired in the flotation step of the zinc beneficiation was initially characterized to investigate alternatives routes to obtain by-products from the gangues found in this tailing. The gangue of zinc tailing may contain dolomite, hematite, and impurities that are considered toxic elements, e.g. lead and cadmium. This work aimed to obtain MgSO4 and CaSO4 from real flotation tailing generated in zinc beneficiation. Thus, using physical processing, thermodynamic simulation (FactSage software), and hydrometallurgical route from dolomite. The following composition was identified in the characterization of zinc tailing by inductively coupled plasma optical emission spectrometry (ICP-OES): 7.96% Fe, 10.3% Mg, 17.4% Ca, 1.47% Si, 1.74% Zn, 0.2% Pb, 0.33% Al, 0.02% Cd, and 0.07% Mn. X-ray diffractometry (XRD) identified the phases of dolomite, hematite, and quartz. In the SEM-EDS analyses, it was possible to observe the disintegrated hematite, dolomite, and quartz particles, which allow the physical processing of these phases. Therefore, a dolomite concentration was investigated in the magnetic and gravity separation to eliminate mainly iron from the material understudy. The magnetic separation with the rougher cleaner route showed a better concentration of dolomite (90.3%) found in the non-magnetic fraction. The non-magnetic fraction was characterized by ICP-OES and presented a composition of 0.34% Al; 21.6% Ca; 0.04% Cd; 2.7% Fe; 11.9% Mg; 0.08% Mn; 0.2% Pb; 1.37% Si; and 1.73% Zn. Subsequently, a simulation was performed with the FactSage software to evaluate the leaching conditions varying the S:L ratio, the sulfuric acid concentration, and temperature were studied. Initially, pure dolomite was used in the simulation as a reference. Afterward, the composition was provided in the non-magnetic fraction of 90.3% and the other phases found in the zinc tailing were considered. The conditions for the pure dolomite were selected in 1.2mol.L-1 in a S:L ratio equal to 1:10, at room temperature showed 100% Mg extraction. Then, the simulation with 90.3% dolomite had 100% Mg extraction in 1.0mol.L-1 H2SO4 in a S:L ratio equal to 1:10 at room temperature. The leaching tests were performed using these conditions, varying the temperature in 25 - 50 - 75 and 90°C and the time from 5 to 180min, which a Mg and Ca extraction yield of 72% ± 5% and 2%, respectively, were obtained at 50°C in 35min. Using the cementation step, the purification method resulted in a 92.3% cadmium removal in the liquor from leaching with zinc powder in a 100:1 ratio in 5min at 25°C. The by-products obtained were MgSO4 and CaSO4, to be used in agriculture, magnesium sulfate (40% of MgSO4·7H2O for each 1kg) as a fertilizer (secondary macronutrient), and calcium sulfate as a soil conditioner (7.5% for each 1kg).