Fluoride based control of Ca and Mg concentrations in high ionic strength base metal sulphate solutions in hydrometallurgical circuits

Georgalli, G.A.; Eksteen, Jacques; Pelser, Max; Lorenzen, L.; Aldrich, Chris

doi:10.1016/j.mineng.2007.09.010

Cited by 10 publications

(5 citation statements)

References 10 publications

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“…This model proved to be more practical regarding experimental approaches and was able to precisely predict the total dissolution process of a dissolving NaCl solution microdroplet with changing water activity. Thus, being able to predict parameters such as diffusion coefficients, solubilities, and supersaturations governing the dissolution process is important for processes such as nucleation/precipitation, ,, nano/micro particle/microdroplet formulations, ,− pharmaceutical formulations, ,− and ore processing. − Furthermore, crystal morphology and water activity are important in food sciences, especially when talking about conservation and longevity of food products, where salted food can take up water from the surrounding environment to reduce longevity.…”

Section: Saturation and Supersaturation In Single Microdropletsmentioning

confidence: 99%

Manipulating Single Microdroplets of NaCl Solutions: Solvent Dissolution, Microcrystallization, and Crystal Morphology

Utoft

Kinoshita

Bitterfield³

2018

Langmuir

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A new "three-micropipette manipulation technique" for forming, dehydrating, crystallizing, and resolvating nanograms of salt material has been developed to study supersaturated single microdroplets and microcrystals. This is the first report of studies that have measured in situ both supersaturation (as homogeneous nucleation) and saturation (as microcrystal redissolution) for single microdroplets of NaCl solution using the micropipette technique. This work reports a measure of the critical supersaturation concentration for homogeneous nucleation of NaCl (10.3 ± 0.3 M) at a supersaturation fraction of S = 1.9, the saturation concentration of NaCl in aqueous solution as measured with nanograms of material (5.5 ± 0.1 M), the diffusion coefficient for water in octanol, D = (1.96 ± 0.10) × 10 cm/s, and the effect of the solvent's activity on dissolution kinetics. It is further shown that the same Epstein-Plesset (EP) model, which was originally developed for diffusion-controlled dissolution and uptake of gas, and successfully applied to liquid-in-liquid dissolution, can now also be applied to describe the diffusion-controlled uptake of water from a water-saturated environment using the extended activity-based model of Bitterfield et al. This aspect of the EP model has not previously been tested using single microdroplets. Finally, it is also reported how the water dissolution rate, rate of NaCl concentration change, resulting crystal structure, and the time frame of initial crystal growth are affected by changing the bathing medium from octanol to decane. A much slower loss of water-solvent and concomitant slower up-concentration of the NaCl solute resulted in a lower tendency to nucleate and slower crystal growth because much less excess material was available at the onset of nucleation in the decane system as compared to the octanol system. Thus, the crystal structure is reported to be dendritic for NaCl solution microdroplets dissolving rapidly and nucleating violently in octanol, while they are formed as single cubic crystals in a gentler way for solution-dissolution in decane. These new techniques and analyses can now also be used for any other system where all relevant parameters are known. An example of this is control of drug/hydrogel/emulsion particle size change due to solvent uptake.

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Section: Saturation and Supersaturation In Single Microdropletsmentioning

confidence: 99%

Manipulating Single Microdroplets of NaCl Solutions: Solvent Dissolution, Microcrystallization, and Crystal Morphology

Utoft

Kinoshita

Bitterfield³

2018

Langmuir

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“…Mn concentration in the electrolyte is maintained at between 7 and 8 g/dm 3 in order to produce the MnO 2 layer required for the corrosion protection of the Pb-Ag anodes [27][28][29]. However, the high concentration of Mg (11-12 g/dm 3 ), besides causing the blockage of pipe systems [30][31][32] and difficulties in the mass-transfer process of zinc deposition [33], could also create extra electrolyte overpotential. From Aalto-I and Equation ( 18), approximately 15% of the electrolyte ohmic drop can be reduced by lowering the Mg concentration from 11.2 g/dm 3 to 2 g/dm 3 .…”

Section: Model Utilizationmentioning

confidence: 99%

Modelling the Effect of Solution Composition and Temperature on the Conductivity of Zinc Electrowinning Electrolytes

Wang

Aji

Wilson

et al. 2021

Metals

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Zinc electrowinning is an energy-intensive step of hydrometallurgical zinc production in which ohmic drop contributes the second highest overpotential in the process. As the ohmic drop is a result of electrolyte conductivity, three conductivity models (Aalto-I, Aalto-II and Aalto-III) were formulated in this study based on the synthetic industrial electrolyte conditions of Zn (50–70 g/dm3), H2SO4 (150–200 g/dm3), Mn (0–8 g/dm3), Mg (0–4 g/dm3), and temperature, T (30–40 °C). These studies indicate that electrolyte conductivity increases with temperature and H2SO4 concentration, whereas metal ions have negative effects on conductivity. In addition, the interaction effects of temperature and the concentrations of metal ions on solution conductivity were tested by comparing the performance of the linear model (Aalto-I) and interrelated models (Aalto-II and Aalto-III) to determine their significance in the electrowinning process. Statistical analysis shows that Aalto-I has the highest accuracy of all the models developed and investigated in this study. From the industrial validation, Aalto-I also demonstrates a high level of correlation in comparison to the other models presented in this study. Further comparison of model Aalto-I with the existing published models from previous studies shows that model Aalto-I substantially improves the accuracy of the zinc conductivity empirical model.

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“…Problems have been noted in the prevention of magnesium and calcium accumulation which would affect nickel solvent extraction using versatic acid and copper electrowinning. Several researchers (Lorenzen et al, 2009;Eksteen et al, 2008;Georgalli et al, 2008) have looked at partial calcium and magnesium removal using ammonium fluoride to precipitated fluorite (CaF 2 ) and sellaite (MgF 2 ) with alumina based adsorption to remove excess fluoride ions. The ActivOx Ò process for copper was demonstrated at the Tati Hydrometallurgical Demonstration Plant (THDP) in 2004 (Palmer and Johnson, 2005).…”

Section: Outokumpumentioning

confidence: 99%

Direct leach approaches to Platinum Group Metal (PGM) ores and concentrates: A review

Mpinga

Eksteen

Aldrich

et al. 2015

Minerals Engineering

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Fluoride based control of Ca and Mg concentrations in high ionic strength base metal sulphate solutions in hydrometallurgical circuits

Cited by 10 publications

References 10 publications

Manipulating Single Microdroplets of NaCl Solutions: Solvent Dissolution, Microcrystallization, and Crystal Morphology

Manipulating Single Microdroplets of NaCl Solutions: Solvent Dissolution, Microcrystallization, and Crystal Morphology

Modelling the Effect of Solution Composition and Temperature on the Conductivity of Zinc Electrowinning Electrolytes

Direct leach approaches to Platinum Group Metal (PGM) ores and concentrates: A review

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