Antimony selective extraction

Another point is related to the high acidity level of the final solution, which leads to certain limitations in the subsequent technological steps. Specifically, the high acidity of the initial solution eliminates any possibility for selective extraction, i.e. sequential separation of tantalum and then of niobium. Due to the high concentration of acids, only collective extraction (of tantalum and niobium together) can be performed, at least at the first step. In addition, extraction from a highly acidic solution might cause additional contamination of the final products with antimony and other related impurities. In order to reduce the level of contaminants in the initial solution, some special additives are applied prior to the liquid-liquid extraction. For instance, some mineral acids and base metals are added to the solution at certain temperatures to cause the precipitation of antimony [455 - 457]. 

Selective extractive separation of antimony (usually Sbm), as well as selective complexation of Sbm (Mohammad et al., 1990), followed by hydride generation have been used for the determination of antimony in water. Four species of antimony in natural water have been identified Sbv, Sbm, methylantimony and dimethylantimony (Apte et al., 1986). The analyses were carried out using hydride generation cold trapping procedures. Sbm was separated from Sbv in natural and waste waters by extraction with N-p-methoxyphenyl-2-furylacrylohydroxamic acid into chloroform (Abbasi, 1989). The extracted antimony was determined by means of graphite-furnace AAS. The detection limit was 10 2mgdm 3. 

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