Technical Notes -Extraction of Silica from Wisconsin Gogebic Taconite by the Soda Ash Sinter Process

Extraction of silica from the taconites of the Wisconsin Gogebic range by high temperature digestion in caustic solutions has been described.1,2 The ores consist essentially of hematite, goethite, and microcrystalline quartz, detailed descriptions of which appear in the literature.1,3 It is the purpose of this communication to describe some results obtained from a laboratory investigation of an alternative method, that of sintering the ore with sodium carbonate followed by water extraction of the sodium silicate produced. This is analogous to the Deville-Péchiney4,5 soda ash sinter process for the production of alumina from bauxites in which soluble sodium aluminates are formed. Raw mixes of the desired composition were prepared from 10.0 g minus 200 mesh samples of taconite and sintered in nickel crucibles in a muffle furnace controlled to within ±10°F of the operating temperatures. The resulting sinters were pulverized and then leached in distilled water with continuous agitation for 30 minutes at 95°C. The suspensions were vacuum filtered and the residues dried, ignited and weighed. Iron assays on the ignited samples were made by the standard dichromate procedure after dissolution in hydrochloric acid. The percentage of extraction was calculated from the iron assays by the relation: