Modeling of gadolinium recovery from nitrate medium with 8-hydroxyquinoline by emulsion liquid membrane.
The extraction equilibrium of Gd(III) from nitrate medium by 8-hydroxyquinoline (HOX) in toluene was studied. Liquid-liquid investigations were first carried out. Based on the equilibrium results, the extraction of Gd(III) from aqueous nitrate medium into an emulsion liquid membrane system (ELM) containing 8-hydroxyquinoline in toluene as extractant, HNO(3) as stripping solution, Span-80 as surfactant was studied. The stability of the prepared ELM was studied in terms of the degree of membrane breakage. The different parameters affecting the permeation of gadolinium (III) were also studied. A general permeation model for the recovery of Gd(III) by the selected membrane is presented. The internal mass transfer in the water in oil (W/O) emulsion drop, the external mass transfer around the drop, the rates of formation and decomposition of the complex at the external aqueous-organic interface were considered.
Rare earth metal extraction by liquid surfactant membranes containing a calixarene carboxylate derivative: permeation acceleration effect of sodium ions
ABSTRACT Calixarene carboxylate derivatives were used as a mobile carrier for rare earth permeation in a liquid surfactant membrane (LSM) system. The effect of alkali metal ions on the extraction behavior of rare earth metals in both liquid-liquid extraction and LSM systems has been studied. The addition of sodium ions considerably enhanced the extraction ability of rare earth metals in the extraction equilibrium. Furthermore, the presence of alkali metal ions in the material solution affected the rate of rare earth permeation in LSMs. The most accelerative transport of rare earth metals by LSMs was achieved by the addition of sodium ions. This acceleration effect of sodium ions was predominant in a tetracarboxylate calixarene whose cavity size just fits the ionic diameter of sodium ions. The sodium-loaded calix[4]arene derivative showed good performance as an effective mobile carrier for rare earth metals in the presence of sodium ions.
Solvent Extraction of Transition Metal Cations by Calixarene-Based Cyclic Ligands
Calix[n]arenes (n = 4 and 6) bearing carboxyl groups (1n), hydroxamate groups (2n), and dimethylamino groups (3n) on the lower rim and their monomeric analogs (11, 21, and 31) were synthesized to estimate selective extraction of transition metal cations from the aqueous phase to the organic (chloroform) phase. 14 and 16 showed the selectivity toward Fe3+, Cu2+, Zn2+, and Pd2+. In particular, 16 showed the unusually high extractability toward Fe3+. 24 and 26 showed the selectivity toward Fe3+, Cu2+, and Pd2+, but only Fe3+ was extracted to a significant extent at pH 2.2, the order of the extractability being 26 > 24 > 21. 34 and 36 showed the selectivity toward Pd2+ and Pt4+. The detailed examination of the extraction mechanism established that the ion-pair extraction mechanism is operative in Pt4+ (i.e., extracted as [PtCl6]2−) whereas both the ion-pair extraction mechanism and the chelatecomplex extraction mechanism are operative in Pd2+ (i.e., extracted as [PdCl4]2− in the ion-pair extraction mechanism)...