Dewatering of Metal Concentrates

Later, the metal-bearing bubbles, now known as concentrates, have the water removed from them before shipment. This is typically done by pressure filters. This dewatering step is carried out to reduce the weight of the concentrate if the shipping distance is great and to prevent freezing (in rail cars, for example) during winter shipment.

By employing various flotation reagents, different kinds of metal sulphides can be floated or separated one at a time. Thus, if an ore contains copper, zinc and iron sulphides, it is possible to make separate concentrates for each metal.

Flotation is occasionally applied to gold ores, to make a gold flotation concentrate that is then treated with cyanide, with or without roasting. This method is especially applicable when the metal is very fine and intimately associated with minerals containing sulphur or arsenic. In this matter, it is possible to make, say 10 tonnes (11 tons) of gold concentrate from 300 tonnes (330 tons) of mill feed. This concentrate can be economically treated much more intensely (finer grinding and longer agitation) than the original ore.