Fabrication of a Polymer Inclusion Membrane Containing Dicyclohexano-18-Crown-6 for Extraction of Cr(VI) from Aqueous Solutions

A variety of polymer inclusion membranes (PIMs) based on the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), cellulose triacetate (CTA) and poly(vinyl chloride) (PVC) polymers with different proportion of dicyclohexano-18-crown-6 (DC18C6) as extractant, 2-nitrophenyl octyl ether (NPOE) as plasticizer were fabricated. PIM containing 45% PVC, 20% DC18C6 and 35% NPOE was selected as the optimum PIM composition because of their satisfactory physical, mechanical and extraction properties. The effect of parameters affecting the extraction process such as pH, extraction time, type and concentration of electrolyte and initial concentration of Cr(VI) were investigated and its shown that the PIM were able to extract 57% of chromium ions from 50 mL solution containing 2×10-4 mol/L of chromium(VI) and 1.2 mol/L HCl in 22 h. The maximum capacity of the selected PIM for extraction of chromium ions was 7 mg of of Cr per 1 g of membrane. The selectivity of the PIM towards Cr(VI) was tested in the presence of Zn(II), Cu(II), Fe(II), Cd(II), Ni(II) and nitrate ions and indicated that the PIM can extract selectively V(V) from the mixtures containing these heavy metal ions. The PIMs were used successfully for extraction of Cr(VI) from various water samples. The isotherms and kinetics of the processes were well described by Dubinin Radushkevich and pseudo second order models, respectively. These analyses revealed the process might be chemical processes.