Non-traditional methods of treating high-silicon ores containing rare elements

Abstract

Several methods of reducing or eliminating the problem of silica in solutions following leaching are available including modification of the leaching conditions, addition of flocculants or coagulants to improve filtration of the silicic acid, and modification of subsequent solvent extraction process to operate under organic phase continuous conditions. These have limited success and often reduce the metal content of the leachate by adsorption on the silica precipitate. A novel technique is described which involves a combination of extractive leaching with nitric acidltri-n-butylphosphate (TBP) coupled with intense mechanical activation in a specially designed reactor. Using the mineral eudialyte (>50% Si02) as a model for high silicate minerals it has been shown that high recovery of the rare metal content is possible and the silica released remains as an easily filtered residue. This technique should be widely applicable to other minerals where the desired metals can be extracted by TBP.