Nickel Ore Dispersion Evaluation and Consequences in Flotation Process
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IN the flotation process, selectivity is based on the hydrophobicity differences of the mineral species surfaces present in the pulp.[1] The mineral surface becomes hydrophobic after the addition of suitable surfactants called collectors.[2–4] As such, flotation optimization by examining the influences of each mineral system has been and continues to be the objective of research, and the simple use of a collector cannot warrant the success of the process. Several factors can influence the performance of a flotation, including particle size, specific reagents schemes, desliming and dispersion steps, among others. The dispersants act to increase the scattering between the particles in aqueous medium, nullifying the effect of aggregation between mineral particles.[5] Bogdanov et al.[6] studied the flotation of fine particles showing the importance of the dispersion to have a flotation with high recovery and their work also points a low selectivity rate as the main problem of this process. However, there are rare investigations about the effect of the dispersion state in the flotation of sulfide minerals. Usually, the creation of a dispersed system is done by adding inorganic electrolytes called dispersants. Dispersant ions adsorb in the solid/liquid interface, changing the electrical charge of the mineral surface and increasing the electrostatic repulsion between the minerals. This stability can be explained based on the DLVO theory FA´BIO DE SA˜O JOSE´ and FRANCIELLE CAˆMARA NOGUEIRA, Metallurgist Engineers, Masters in Mineral Engineering, and PhD Students, and CARLOS ALBERTO PEREIRA, Mining Engineer, Master in Mineral Engineering, Doctor in Mineral Engineering, and Professor, are with the Federal University of Ouro Preto, Ouro Preto, Brazil. Contact e-mail: [email protected] ALAINE MOREIRA IMBELLONI, Mining Engineer, Master in Mineral Engineering, and Professor, is with the CEFET, Araxa´, Brazil. Manuscript submitted February 10, 2015. Article published online January 6, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
that considers energy of interaction intended for aggregation or dispersion of the particles.[7] The Van der Waals forces are always attractive for particles of the same nature, and the interaction between the electrical double layers of particles with the same charge is always repulsive. When the repulsive force predominates on the attraction force, the system is considered dispersed.[8] The pH value of the pulp in the flotation is also of fundamental importance for the proper performance of the reagents employed, including the dispersant selected. It also influences the state of mineral particle dispersion in aqueous media, and the surface charge of oxidized minerals and silicates. There is a critical pH value, as well as a collector concentration, above which the mineral cannot float.[3] For example, the critical pH value for pentlandite varies around 10 because there is a competition for the adsorption sites between the mineral ions and xanthate hydroxyl ions.[9] Pentlandite, the object of this st
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