Hydrophobic chelates flotation

Chelating agents that can form insoluble, hydrophobic chelates on the surface of minerals are potential collectors for the selective flotation of minerals.3 4 As early as 1927, Vivian5 reported the use of cupferron, a well-known analytical reagent, as a collector for the flotation of cassiterite (Sn02). Since then, there have been a number of reports on the use of chelating agents in flotation. 

These collectors are effective only under oxidizing conditions, and it is generally accepted that the species that confers hydrophobicity on the mineral surface is either a chemisorbed metal thio compound or the oxidized form of the collector, dithiolate. The amounts of each species formed will depend on the relative stabilities of the metal—sulfur and sulfur—sulfur bonds. The formation of four-membered chelate rings is also possible with soft metal ions such as copper(I) because the largely covalent character of the bond in this instance is able to overcome the strain within the ring by extensive electron delocalization. This could account for the >artial selectivity of some of these reagents for the copper minerals, which has been put to good use in the sequential flotation of copjrer, lead and zinc from complex sulfide ores. ... 

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