Orthogonal array design for the optimization of supercritical carbon dioxide extraction of platinum(IV) and rhenium(VII) from a solid matrix using cyanex 301

Recently, metal complex solubilities and metal extractions in the presence of chelating agents have been investigated using supercritical fluid extraction (SFE) system. In this study, Re(VII) and Pt(IV) were removed from a solid matrix using supercritical CO2 which contained bis-(2,4,4-trimethyl pentyl)-dithiophosphinic acid (cyanex 301) as a chelating agent. Using the Taguchi method an orthogonal array design (OAD), OA25 (55), was employed to optimize the SFE of these ions from spiked filter paper matrices. Effect of five experimental factors: pressure, temperature, volume of 20% (w/v) cyanex 301 solution in methanol, static and dynamic extraction times and each factor at five-levels on the SFE of these ions were studied and optimized. Quantitative analysis of the extracts was performed by inductively coupled plasma optical emission spectrometry (ICP-OES). The effects of these parameters were investigated using the analysis of variance (ANOVA). The results showed that Pt(IV) and Re(VII) could be quantitatively extracted from the solid matrix at 308 K, 202.6 bar, ligand to metal ratio of 60, flow rate of 0.5 ml min−1, 15 and 10 min of static and dynamic extraction times, respectively. Finally, an experiment was performed under conditions predicted by the Taguchi method; results showed that obtained recoveries are similar to those predicted by the Taguchi method.