A new generation of highly stable and permeable polymer inclusion membranes (PIMs) with their carrier immobilized in a crosslinked semi-interpenetrating polymer network. Application to the transport of thiocyanate

A novel type of polymer inclusion membrane (PIM) composed of a poly(vinylidene fluoride-co-hexafluoropropylene) and poly(ethylene glycol) dimethacrylate (PVDF-HFP/PEG-DMA) semi-interpenetrating crosslinked polymer network and Aliquat 336 as the carrier was successfully fabricated. Crosslinking was achieved by UV irradiation (15 min) with 2,2-dimethoxy-2-phenylacetophenone as photoinitiator (0.6 wt%). The optimum PIM composition contained PVDF-HFP and PEG-DMA in a mass ratio of 5:5 and 40 wt% Aliquat 336. Thiocyanate extraction and transport studies using this PIM demonstrated its potential for the clean-up of this anion from process and tailings waters in the gold mining industry which is of significant technological and environmental importance. The newly developed PIM exhibited excellent stability in five consecutive thiocyanate transport experiments with very little change in its permeability. In addition, this PIM produced an initial flux value of 2.18×10−5 mol m−2 s−1 which is more than an order of magnitude higher than those of the best performing PIMs using traditional base polymers such as poly(vinyl chloride) and cellulose triacetate and close to an order of magnitude higher than a recently developed PVDF-HFP based PIM. The results obtained in this study indicate that incorporating a semi-interpenetrating crosslinked polymer network of PEG-DMA into a PVDF-HFP-based PIM leads to a significant increase in both membrane stability and permeability.