Leaching of tin slags and subsequent chlorination of the tantalum and niobium concentrate

This paper reports on the physicochemical characterization of three samples of amorphous tin slags by microprobe, SEM, chemical analysis, etc. and the data factor analysis which led to the definition of their pseudo-structure. This was used to design an experimental protocol in order to concentrate the valuable metals. With alternative basic and acid leaching, the Al, Ca, Si, Fe, Mn, etc. compounds are dissolved giving a residue containing about 62% of (Ta + Nb)2O5 with a recovery rate of about 75%. This represents an enrichment of about three times that of the initial content of the raw slag. The selective chlorination and/or carbochlorination of this concentrate permit the separation of tantalum and niobium from the leaching residue. The condensates are composed of almost pure mixture of Ta and Nb compounds. The chlorination residue contains essentially Ca and Si compounds