Characterisation and kinetic studies of Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) polymer inclusion membrane for the Malachite Green (MG) extraction

Polymer inclusion membranes (PIMs) was introduced in order to overcome the imperfection of supported liquid membrane (SLM) such as leaching of solvent, instability and short lifetime. In this study, PIMs was applied as an intermediate membrane to facilitate the extraction of aqueous cationic dye (Malachite Green; MG) from the feeding phase to the receiving phase. The fabricated PIMs consist of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) as base polymer, bis-(2-ethylhexyl) phosphate (B2EHP) as carrier, dioctyl phthalate (DOP) as plasticizer and tetrahydrofuran (THF) as diluent. It was then characterised physically by Scanning Electron Microscopy (SEM), Atomic Force Microscope (AFM), contact angle and water uptake, whereas the chemical properties of PIMs are determined by Fourier Transform Infrared Spectroscopy (FTIR) and ions exchange capacity (IEC). The formulations of PIM were varied by altering the composition of carrier B2EHP to determine the optimum PIM for the MG extraction. As a result, the PIM with 18% w/w PVDF-co-HFP, 21% w/w B2EHP, 1% w/w DOP and 40% w/w THF shows the optimum membrane for the extraction. The average extraction efficiency obtained from the membranes is >97%. In kinetic studies, the experimental data were fitted to the kinetic models and it showed that pseudo-second-order model gives the best correlation coefficient, R2. This indicates that the MG extractions were performed under chemical sorption mechanisms.