Studying the extraction of scandium(III) by macrocyclic compounds from aqueous solution using optimization technique

This study aims to optimize the extraction efficiency of Sc(III) by dicyclohexano-18-crown-6 (DC18C6) and kryptofix 2.2.2 (K 2.2.2) macrocyclic compounds as novel extractants using response surface methodology (RSM). Additionally, it was intended to design a method for recovering Sc from an aqueous model solution using molecular recognition technology (MRT).The independent operating variables (concentration of K 2.2.2 and DC18C6, concentration of Sc, pH and time) influencing the extraction process were optimized by central composite rotatable design (CCRD) found in RSM of the STATISTZICA software. Moreover, the WinQSB software was employed to predict the optimum conditions. The complexation reaction between Sc and macrocyclic ligands was confirmed by ultraviolet visible spectroscopic (UV-Vis) and inductively coupled plasma optical emission spectroscopic (ICP-OES) techniques. Furthermore, the analysis of variance (ANOVA) component indicated that all the process independent variables investigated had significant impacts on the extraction efficiency of Sc. The obtained optimization results showed that at the following optimum conditions: 0.006 mol/L concentration of K 2.2.2 and DC18C6, 11 min contact time, pH 4 of the aqueous solution and 75 mg/L initial Sc concentration resulted in an optimum extraction efficiency of 99.7% and 15.2%, respectively. Moreover, the complexed metal ions can be efficiently recovered/stripped out by HCl or HNO3.