Extraction of palladium(II) with through-hole type microcapsules containing trioctylamine

Large-diameter and through-hole type microcapsule with entrapped trioctylamine (TOA) as an extractant were prepared by (W/O/W) emulsification and in-situ polymerization method. The morphologies of the microcapsules, their encapsulation efficiencies for TOA, and their forward and back extraction properties for palladium(II) were investigated. The microcapsules ranged in size from 210-420 ěm. The encapsulation efficiency of TOA was approximately 100% for all the microcapsules, which indicates minimal loss of TOA during preparation of the microcapsules. Through-hole type microcapsules were obtained when inner aqueous phase contained a high concentration of sodium chloride, and at a moderate agitation speed in the first emulsification. With the through-hole type microcapsules the extraction equilibrium approached one, and the extraction rate was very high compared to other preparation conditions and (O/W) type microcapsules.