Extraction Equilibrium of Precious Metals from Aqueous Acidic Solutions Using Divinylbenzene Homopolymeric Microcapsules Encapsulating Ternary Amine as a Core Material

Abstract

Divinylbenzene homopolymer microcapsules having porous membranes encapsulating tri‐n‐octylamine as a core material were prepared by in‐situ polymerization accompanied by the evaporation of toluene. The extraction equilibria of hydrochloric acid and precious metals in an acidic solution using the prepared microcapsules were measured at 303 K. The addition of toluene into the dispersed phase resulted in the microcapsule membrane having a porous structure due to the toluene evaporation during in‐situ polymerization, which was verified based on the results obtained both from SEM observation of the microcapsules' morphology and in the extraction equilibrium of hydrochloric acid. Using microcapsules prepared with toluene, hydrochloric acid was sufficiently extracted form an aqueous solution. In contrast, microcapsules prepared without toluene scarcely extracted hydrochloric acid. The microcapsules successfully extracted palladium(II) from the acidic media, and this was explained by the reaction between one palladium ion and two molecules of tri‐n‐octylamine in a similar manner of that taking place in the solvent extraction. The back‐extraction of palladium(II) from the microcapsules was expressed by the back‐reaction of the extraction. Gold(III) and platinum(IV) were also successfully extracted using the prepared microcapsules.

Keywords:

• Microcapsules
• Extraction
• Precious metals
• Tri‐n‐octylamine