Extraction and separation of metal ions by a column packed with polystyrene microcapsules containing Aliquat 336

Since the 1990s, the use of microcapsules as a supporting material for a metal extractant has developed quickly. Although there are many microcapsule preparation methods that exist now, most are time- and energy-consuming. Economical and simple methods for the preparation of uniform extractant microcapsules are necessary for the development of microcapsule-extraction processes. In this paper, the preparation of polystyrene microcapsules containing Aliquat 336 using the solvent evaporation method as well as the separation of Cr(VI)/Cd(II) and Cr(VI)/Zn(II) using a column packed with these microcapsules were investigated. The results of the preparation showed that both the morphology and monodispersity of microcapsules are greatly related to the dispersion agent. The mean diameter of the obtained microcapsules was 45 to 90 μm with a narrow size distribution and was controlled by changing the agitation speed. The separation studies also showed that the pH value of the feed solution was important for successful separation of the metals with higher separation efficiency at lower pH levels. Both Cd(II) and Zn(II) were obtained from the aqueous effluent solution with high purity and Cr(VI) inside the microcapsules. Finally, the stability experiment showed that the microcapsules had a sufficient metal ions extraction capacity for reuse processing and extraction-stripping cycles indicated no decline in extractability.