New Dissolved Nitrogen Predispersed Solvent Extraction Method, 2: Selectivity

Abstract

Dissolved Nitrogen Predispersed Solvent Extraction (DNPDSE) is a new method in which the two-phase mixture operation is based on bubble dispersion of the organic phase, instead of its drop dispersion into the aqueous phase. This substitution is intended to increase the two-phase contact area (to improve recovery of metal ions from the dilute solutions) and also to enhance the buoyancy force of organic phase (to improve separation of two phases). However, the performance mode of this method can increase the recovery of interfering elements, because of increased surface contact, entrainment, and precipitate flotation, and thus have an unfavorable effect on the selectivity of this method. Therefore, selectivity of this innovative method was compared with the conventional solvent extraction (SX) method. The results of experiments conducted on the dilute and dense copper, zinc, and iron synthetic solutions within the copper extraction pH values (1.2–2.1) showed a lack of zinc recovery (i.e., no effect on total selectivity) in both methods and increased iron recovery (i.e., effect on partial selectivity) only in the DNPDSE method. The results also showed that increased iron recovery was not just dependent on increased contact area of the two phases, and gel-like precipitates observed on the surface of organic phase indicated precipitation of Fe ions and their transfer onto the surface by bubble entrainment and precipitate flotation.