A polymer inclusion membrane for extracting thiocyanate from weakly alkaline solutions

A new polymer inclusion membrane (PIM) has been developed for the extraction of thiocyanate from weakly alkaline aqueous solutions. The composition of this membrane in mass percent (m/m) is 20% (m/m) Aliquat 336 as carrier, 10% (m/m) 1-tetradecanol as modifier and 70% (m/m) PVC as the base-polymer. This composition has been arrived at after extensive screening of a large number of CTA and PVC-based membranes using various plasticizers and modifiers. This membrane is homogeneous, flexible and transparent and extracts thiocyanate from weakly alkaline solutions with considerable speed for a PIM with an initial flux value of 7.86 × 10−6 mol m−2 s−1. Quantitative back extraction is achieved using 1 M NaNO3.The membrane has been cycled 10 times through extraction and back extraction without loss of performance. Its use in the extraction of thiocyanate from wastewater from the cyanide leaching of low grade gold ores has been successfully tested.

Research highlights▶ A PVC based polymer inclusion membrane containing Aliquat 336 and 1-tetradecanol has been developed for the extraction of thiocyanate from weakly alkaline solutions. ▶ The rate of extraction of thiocyanate is comparable to rate values typical of supported liquid membranes. ▶ The membrane has been cycled 10 times through extraction and back extraction without loss of performance. ▶ The membrane has been successfully applied to the extraction of thiocyanate from tailings water arsing from the cyanide processing of low grade gold ores.