Estudo eletrocinético e de flotabilidade do pirocloro com coletores aniônicos e catiônico na presença de íons de cálcio e magnésio

• Ano de defesa: 2023
• Autor(a) principal: André Luiz Alvarenga Santos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ENG - DEPARTAMENTO DE ENGENHARIA MINAS; Programa de Pós-Graduação em Engenharia Metalúrgica, Materiais e de Minas; UFMG
• Palavras-chave em Português: Nióbio; PHREEQC; Coletor aniônico; Purificação/desativação de superfície; Potencial zeta; Adsorção; Engenharia de minas; Tecnologia mineral; Niobio; Água - Reutilização; Lixiviação; Eletrólitos; Termodinâmica; Superfície
• Link de acesso: http://hdl.handle.net/1843/58550; https://orcid.org/0000-0001-6764-2014

The water reuse is mandatory in mineral industry. However, water recirculation modifies the physicochemical characteristics of process water. The focus of this doctoral thesis is to investigate the variation of the pyrochlore zeta potential in the presence of electrolytes as well as to evaluate its flotability using anionics and cationic collectors in the water reuse scenario. A Nb ore concentrate with 91.9% of pyrochlore grade was used in this thesis. This sample contains small amount of fine particles (-38m < 2.5%) and is composed by 61.8%(Nb2O5), 16.5%(CaO), 7.19%(TiO2), 6.30%(Na2O). Methods of solvent desorption in wide range of polarity, acid leaching and heat treatment were used for purification/de-activation of the hydrophobized surface of the sample. The association of acid leaching (HCl 0.1mol/L, 70°C, 120min, 20g/L and 300rpm) and heat treatment (300°C, 120min and 5g/crucible) reduced the sample's flotability by 94% that was considered suitable for the fundamental studies. The zeta potential was evaluated in the presence of Ca and Mg ions from Cl and SO4 sources in a wide range of concentration, asssociated to thermodynamic simulations in PHREEQC for aqueous ions speciation. Ca and Mg ions modified the zeta potential curve of the pyrochlore without causing any changes in the pHPIE, which occurs between 2.9 to 3.1. Mg(OH)2 precipitate formation was associated to metal hydroxycomplexes that contributed to the zeta potential reversal of the sample. Below the Ca and Mg saltssolubilities, the zeta potential is independent of the source of metal cations. Microflotation studies were performed with the -212+53m sample in a 370mL modified Hallimond tube for Acetadiamin T50 (amine – 3.125-50mg/L), Aero 6493 (hydroxamate 12.5-200mg/L), Aero 845 (3.125-50mg/L) and NaOL (fatty acid, 12.5-200mg/L) in the presence and absence of electrolytes (200mg/L Ca and 100mg/L Mg). The pH 2; 3.1; 6 and 10 were selected by representing distinct regions of zeta potential curve. Conditioning times of 3 min (electrolyte/distilled water) and 3 min (collector) were used and the microflotation tests were carried out for 1 min in N2 flow of 20mL/min. At pH 2 the electrolyte presence increased the flotability from 60 to 80% in amine collector (25mg/L). On the other hand, for lower collector concentrations (<6.25mg/L), the flotability of pyroclore was reduced in the presence of electrolyte. The TOC and TN reduction and the presence of 1365cm-1 (CH3), 1280cm-1 and 1216cm-1 (aliphatic C-N) bands in FTIR evidenced the Acetadimin T50 adsorption. The presence of electrolyte was deleterious to the flotability of pyrochlore with the Aero 6493 and higher concentrations were required to reach the same level of flotability. The advent of 970cm-1 and the displacement of the band from 1378 to 1365cm-1 suggested the adsorption of collector forming chemical bonds relating to C-O, N-O and OH bonds of N-OH. The sulfosuccinate-based collector exhibited a better performance in the presence of electrolytes at pH 2 and 3.1, raising the pyrochore flotability from 60-70% to 90%. However, the flotability was not observed at pH 6 and 10, neither any alteration at sulfone and sulfoxide zones in FTIR. The pH 6 is considered optimal for the flotability of pyrochlore with NaOL. In the presence of eletrolyte, the CaOL precipitation at pH 10 reduced the flotability from 85 to 52% (100mg/L), however, in its absence, the electrostatic repulsion between the oleate and the pyrochlore surface, justify a drop down in the flotability from 67 to 26% at 100mg/L. FTIR bands at 1572 and 1536cm-1 as a split of the 1559cm-1 band associated to asymmetric stretch of –COO-, structure suggested a chemical adsorption mechanism of NaOL in pyrochlore.