Fractional factorial design for the optimization of supercritical carbon dioxide extraction of La, Ce and Sm ions from a solid matrix using bis(2,4,4-trimethylpentyl)dithiophosphinic acid + tributylphosphate

In this study, La³⁺, Ce³⁺ and Sm³⁺ were removed from a solid matrix using supercritical CO₂ which contained bis(2,4,4-trimethylpentyl)dithiophosphinic acid (Cyanex 301) as a chelating agent and tributylphosphate (TBP) as a co-extractant. The fractional factorial design, 2⁵⁻¹, was employed to optimize the SFE of these ions from spiked filter paper matrices. Effect of five experimental factors: amount of Cyanex 301, flow rate, temperature, pressure and amount of TBP and each factor at two levels on the SFE of these ions were studied and optimized. The results showed that these ions could be quantitatively extracted from the solid matrix at amount of Cyanex 301 of 0.14 g, flow rate of 4 ml min⁻¹, 313 K, 250 bar and amount of TBP of 30 μl. Finally, by employing a regression analysis a model was proposed. Results showed that obtained recoveries are similar to those predicted by the model.