Polysaccharide Depressants for the Reverse Flotation of Iron Ore

Review of reverse flotation of iron ore is presented with a focus on the polysaccharide depressants used and the corresponding adsorption phenomena. Iron oxide minerals have a special affinity for starch and other polysaccharides, and this special property facilitates their depression during the reverse cationic flotation of silica with ether amines in Brazil (Peres and Correa, in Miner Eng 9:12 [1]). Adsorption of polysaccharides at the hematite surface is explained by the acid/base interaction model in which hydroxyl groups at the hematite surface interact with polysaccharide molecules. Of course adsorption of modified or unmodified starch makes the surface of iron oxide minerals, such as hematite, hydrophilic. In Brazil more than 250 M tons of iron ore concentrate production per annum is achieved using polysaccharides in the reverse flotation process to remove silica gangue. For example, in 1996 40,000 metric tons of corn starch were consumed in Brazil, out of which 80 % was used for iron ore concentration. Reverse flotation technology has not been commercialized for the concentration of iron ores from India and Australia which contain aluminum gangue minerals such as kaolinite. In this regard, improved flotation chemistries need to be developed for such ores.