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Abstract
Extraction with microcapsules is a novel separation technique. It has some advantages over the conventional solvent extraction and liquid membrane extraction. In this paper, the extraction of metal ions with polyurea microcapsules is presented. Experimental results showed that when N235 was used as an extractant encapsulated within the microcapsules, the extraction rate for chromium(VI) was much faster than that for cobalt(II) and copper(II). Among the extractants tested, trioctylamine (TOA) gave the best results. When tributyl phosphate (TBP) was used as an extractant, the mean diameter of the microcapsules was smaller due to the lower interfacial tension of the oil/water interface. The extraction rate increased with a decrease in the pH of the feed solution, but increased with an increase in TOA concentration in the microcapsules. The membrane formulation had a significant impact on the mass transfer across the membrane. The stripping of the chromium ions from the microcapsules can be promoted by raising the pH of the stripping solution.