Classifying – separating – and assorting solids – Precedent preparation of items or materials to facilitate... – Selective differentiation
Patent
1985-07-29
1987-04-14
Hart, Charles
Classifying, separating, and assorting solids
Precedent preparation of items or materials to facilitate...
Selective differentiation
209 9, 209 47, 209214, B03G 100
Patent
active
046576665
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to mineral upgrading or concentration method involving the use of magnetic particles having hydrophobic surfaces, as extractants for minerals with hydrophobic surfaces or especially surfaces made hydrophobic by the use of the reagents normally used for air flotation concentration.
A considerable art has been developed to separate minerals from associated gangue using air bubbles. Typically a collecting reagent, such as sodium ethylxanthate, is added to an aqueous suspension of a mineral, for example chalcopyrite containing a silica gangue. The ethylxanthate ions are preferentially adsorbed by the chalcopyrite. If small air bubbles are then made to contact both silica and chalcopyrite particles, only the chalcopyrite particles adhere and they can then be floated to the surface of the suspension and separated by skimming the surface. The air bubbles are attached to the mineral by the surface tension developed in the ring where the mineral protrudes into the air bubbles. The air bubbles have buoyancy which counteracts the gravitational force on the particles of mineral thus allowing flotation to occur. In many instances the bubbles must be stabilised with frothing agents to maintain the bubble with particles on the surface for sufficient time to permit skimming of the floated mineral particles.
SUMMARY OF THE INVENTION
This invention seeks to provide a concentration method which resembles the art of flotation but uses hydrophobic magnetic particles instead of air bubbles as the separating medium. The invention also aims to provide a method of mineral concentration which represents an improvement over the use of air bubbles.
According to the present invention there is provided a method for mineral upgrading or concentration wherein a gangue-associated mineral having a hydrophobic surface and being in particulate form, is contacted with particles of a magnetic material also having a hydrophobic surface, whereby the mineral particles become attached to the surface of the magnetic particles, the magnetic particles with the attached mineral particles are separated from the gangue by magnetic means, and the mineral particles are then detached from the magnetic particles.
DETAILED DESCRIPTION OF THE INVENTION
Contact of the mineral to the magnetic particles may be carried out by mixing the particles in a fluid, preferably aqueous liquid, suspension, or the particles may be mixed together in the dry state.
Generally, the mineral particles will require pre-treatment to provide the necessary hydrophobic surface. Any of the known reagents or treatment procedures used in conventional flotation processes may be used for this purpose.
Although some suitable magnetic materials, such as for example, magnetite, are known to have naturally hydrophobic surfaces and it will usually be necessary to treat the magnetic materials to provide a surface having the desired level of hydrophobicity.
All the currently known magnetic materials can be made hydrophobic. In general, the magnetic oxide materials such as magnetite, haematite, ilmenite, and the ferrites, can be activated by either concentrated acid or alkali to give a surface rich in hydroxyl radicals that can be used to attach alkyl silane or alkyl siloxane and other organic reagents by methods known per se to produce hydrophobic surfaces. Magnetic metals, such as iron, nickel, cobalt and their alloys, e.g., alloys of rare earth elements and cobalt, can be made hydrophobic by producing either hydroxyl-rich surfaces in weak alkaline solutions or by generating a thin glass layer on their surface and then further treating the surface with alkyl silanes, alkyl siloxanes and like organic reagents.
The concentrated mineral particles may be detached from the magnetic particles by any suitable method. For example, the flotation reagent may be destroyed with oxidising reagents such as hypochlorite, hydrogen peroxide or air, or by pyrolitic degradation. Alternatively, the flotation reagent may be displaced by ions such as cyanide o
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Hughes Terence C.
Snook Harvey
Hart Charles
W.S.R. Pty. Ltd.
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