Water-Soluble Polymer Depressants in Froth Flotation

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Metal extraction from ores requires that the metal-bearing minerals in the ores be separated and upgraded into individual mineral concentrates. Most of the mineral separation today is done by froth flotation, which separates minerals based on their surface hydrophobicity. Hydrophobic minerals are floated (like oil drops) to a concentrate while hydrophilic minerals stay in water. However, when the particle sizes of the hydrophilic minerals are very small (<~10 micron), they can be carried to the concentrate by entrainment, lowering separation efficiency. Also, many toxic inorganic reagents such as sodium cyanide, potassium dichromate, etc., are used to separate base metal minerals into individual concentrates. A potentially effective solution to counter both problems is to use polymer depressants, which have low or no toxicity and can also increase particle size, thus restore separation efficiency.One of the key requirements for the polymer reagents is that they selectively act on some minerals but not on all minerals in the ore. This can be achieved by incorporating different functional groups in the polymers. The other requirement for the polymer reagents is that they are good flocculants. We recently observed that the latter seems to depend on how the polymer solution is prepared. Literature contains contradictory information on polymer solution preparation and its flocculation performance. The proposed project is aimed at addressing these two issues. It contains two sub-projects: (1) grafting chitosan with phosphate or xanthate groups, (2) effect of ageing of polymer solutions on the flocculation activity of the polymers. The research results will benefit Canada as metal extraction from mineral resources is one of the major contributors to Canadian economy.