Improved sparge compositions for reverse froth flotation separation and uses thereof, and methods of reverse froth flotation are described. The sparge compositions comprise sulfonated polymeric modifiers which can act as dispersants and depressants, and the compositions are suitably used in the reverse froth flotation of particulate material containing ultrafine particles. For example, the compositions and methods can be used in the separation of iron oxide beneficiary from iron ores comprising silica, silicates, and the like.
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