Development of a polymer inclusion film incorporating a 1-dodecanol–decanoic acid eutectic mixture for the extraction of Dy3+ and Y3+

The extraction of the rare earth element (REE) ions Dy³⁺ and Y³⁺ by a polymer inclusion film (PIF), composed of poly(vinylidene fluoride-co-hexafluoropropylene) as the base polymer, decanoic acid (DA) as the extractant and 1-dodecanol (DD) as a modifier, was investigated. After observing that combining DA and DD formed a liquid at room temperature, the thermal properties of this mixture were studied using temperature modulated differential scanning calorimetry. The phase diagram of this binary system showed a eutectic composition of approximately 70 %(m/m) DD and 30 %(m/m) DA and a peritectic point at approximately 40 %(m/m) DD and 60 %(m/m) DA. It was also established that compositions with mass ratios of DD:DA in the range 40:60 − 80:20 remained liquid at temperatures above 20 °C, thus making them suitable for use as liquid phases in PIFs. Extraction experiments of Dy³⁺ into PIFs containing 60 %(m/m) film liquid phase with mass ratios of DD:DA in the range 20:40 − 40:20 did not show significant differences in the rate of Dy³⁺ extraction despite the significant variation in the extractant (DA) concentration. Selective extraction of Dy³⁺ over Y³⁺ was demonstrated, indicating the potential applicability of the abovementioned PIFs for the separation of these REE ions.