The use of sonication to increase extraction rate in polymer inclusion membranes. An application to the extraction of gold(III)

The extraction of Au(III) from hydrochloric acid solutions using poly(vinyl chloride) (PVC) based polymer inclusion membranes containing the commercial extractant Aliquat 336 as a carrier and 2-nitrophenyl octyl ether, 1-hexanol, 1-octanol, 1-decanol, 1-dodecanol, or 1-tetradecanol as a modifier is described and the rate of extraction and membrane stability are shown to be significantly dependent on the membrane composition. The membrane providing the highest extraction rate and good stability has the composition of 20% (m/m) Aliquat 336, 10% (m/m) 1-dodecanol and 70% (m/m) PVC. The effect of sonication on the extraction is examined and it is shown to increase significantly the extraction rate of Au(III). This is suggested to be due to the physical effects generated during acoustic cavitation, which eliminate the aqueous stagnant diffusion layer at the membrane/solution interface. These effects also eliminate the dependence of the initial extraction rate on the initial Au(III) concentration in the aqueous phase.

Research highlights▶ A polymer inclusion membrane (PIM) containing 20% (m/m) Aliquat 336 and 10% (m/m) 1-dodecanol is capable of extracting efficiently Au(III) from its 2.5 M hydrochloric acid solutions. ▶ Sonication has been found to increase the extraction rate between 200 and 300%. ▶ Acoustic cavitation near the membrane/solution interface eliminates the stagnant diffusion layer which results in the initial flux value becoming independent of the initial Au(III) concentration in the solution.