Extraction and stripping of Cu(ii) ions from aqueous solution by continuous waste cooking oil-based liquid membrane / Alif Azwan Abdul Wahab

This study aimed to extract and strip Cu(II) ions from aqueous solution by a waste cooking oil-based liquid membrane (WCLM). At first, the physicochemical properties of different types of waste cooking oil (WCO) were examined. The most favourable type of WCO was then selected for extraction behaviour study of Cu(II) ions from aqueous solution to determine the effects of pH, di-2-ethylhexylphosphate (D2EHPA) concentration and operating temperature using liquid – liquid extraction (LLE). Eventually, the optimum conditions from LLE experiments were used to operate WCLM system. Only the remaining parameters which associated to WCLM were selected and optimized in the response surface methodology (RSM). It was found that the densities among different types of WCO samples studied were relatively similar to each other, while the viscosity, free fatty acid (FFA) content and acid value increased with the darkness of the oil samples. The most favourable types of WCO was selected as it showed the percentage of extraction (%E) of Cu(II) ions was 96% when added with D2EHPA (carrier) and tributylphosphate (TBP) (phase modifier). In the extraction behaviour of Cu(II) ions, it was found that the pH equilibrium was 4.5, the optimum D2EHPA concentration was 20 mM and the operating temperatures shown insignificant effect on the Cu(II) extraction while the stoichiometric ratio of Cu(II) to D2EHPA was calculated as 1:2 in Cu(II)–organic complexes. In the effect of stripping reaction, H2SO4 at 1 M was found as effective condition with 94% percentage of stripping (%S) of Cu(II) ions. Eventually the maximum conditions for the optimization study in WCLM system for responses %E and %S were 90.21% and 52.62% respectively which were given by feed phase flowrate at 2.52 L/h, membrane phase flowrate at 2.69 L/h, extraction time in 5.15 h and stripping time in 23.36 h. Confirmation test was conducted to validate the optimum results and found the small deviation on the %E (3.66%) and %S (0.11%). Therefore, this study shows that the WCO has high potential as organic solvent for the continuous system of WCLM and is suitable for expanding to the industrial scale.