Calix[4]arene-crown-5 as a selective extraction reagents for K+/H+, Rb+/H+ and Rb+/Cs+ separations

From extraction experiments, the exchange extraction constants corresponding to the general equilibriums M+ (aq) + NaL+ (org) ⇔ ML+ (org) + Na+ (aq) or M+ (aq) + CsL+ (org) ⇔ ML+ (org) + Cs+ (aq), which take place in the two-phase water–nitrobenzene extraction system (M+ = Li+, H3O+, Ag+, K+, NH4 +, Tl+, Rb+; L = calix[4]arene-bis crown5(1,3-alternate), 26,28-dipropoxycalix[4]arene-crown-5(1,3-alternate), 11,23-dibromo-25,28-dipropoxycalix[4]arene-crown-5 (1,3-alternate) and 1,3-alternate-25,27-dihydroxycalix[4]arene-crown-5; aq = aqueous phase, org = organic phase), were evaluated. The stability constants of the NaL+ and CsL+ complexes were calculated from the extraction of the respective picrates in the system of water–nitrobenzene solution of L. Further, the stability constants of the ML+ complexes in nitrobenzene saturated with water were determined. High selectivities were found in some systems under study.

Experimental study of the extraction of chromium (III) from nitrate medium by lauric acid

The solvent extraction of chromium (III) with lauric acid (HL) at 25°C is studied as a function of various parameters: pH of the aqueous phase, the concentration of lauric acid and the nature of the solvent. The solvent effects on the extraction of chromium (III) using polar and nonpolar solvents has been observed. It was shown that extracted species of the [Cr(OH)L2·2HL] formula are formed in cyclohexane, dichloromethane, chloroform, and toluene. However, in 1- -octanol or methyl isobutyl ketone, it was found a complex of the type [Cr(OH)L2]. The extraction constants and extraction yield (%E) are also calculated for different solvents. It was found that cyclohexane is the preferred solvent for this extraction system, The maximum extraction yield is accomplished using the cyclohexane as a solvent on 1:1 L/L ratio, and pH value of 4.73.

Pb(II) Extraction with Benzo-18-Crown-6 Ether into Benzene under the Co-Presence of Cd(II) Nitrate in Water

Extraction of Pb(II) with picrate ion [Pic−] and 0, 0.58, 15, 48, or 97 mmol dm−3 Cd(NO3)2 by benzo-18-crown-6 ether (B18C6; L as its symbol) into benzene (Bz) was studied. Three kinds of extraction constants, Kex, Kex±, and KPb/PbL (or Kex2±), were determined at 298 K: these constants were defined as [PbLPic2]Bz/P, [PbLPic+]Bz[Pic−]Bz/P, and [PbL2+]Bz/[Pb2+][L]Bz (or [PbL2+]Bz([Pic−]Bz)2/P), respectively. The symbol P shows [Pb2+][L]Bz[Pic−]2 and the subscript “Bz” denotes the Bz phase, Bz saturated with water. Simultaneously, conditional distribution constants, KD,Pic (=[Pic−]Bz/[Pic−]), of Pic− with distribution equilibrium-potential differences (dep) were determined. Then, based on the above four constants and others, the component equilibrium constants of K1,Bz (=[PbLPic+]Bz/[PbL2+]Bz[Pic−]Bz), K2,Bz (=[PbLPic2]Bz/[PbLPic+]Bz[Pic−]Bz), and KD,PbL (=[PbL2+]Bz/[PbL2+]) were obtained. Using these constants, the Pb(II) extraction with B18C6 under the co-presence of Cd(II) in the water phase was characterized. In such a characterization, I and IBz dependences on the constants were mainly discussed, where their symbols denote the ionic strength of the water phase and that of the Bz one, respectively.

Determination of Distribution Equilibrium-Potential Differences Based on Extraction with Several Crown Ethers by Nitrobenzene, 1,2-Dichloroethane and Dichloromethane

Extraction constants (Kex± & Kex) were determined at 298 K for the extraction of sodium picrate (NaPic) by nitrobenzene (NB), 1,2-dichloroethane (DCE) and dichloromethane using 3m-crown-m ethers and their benzo-derivatives (m = 5, 6; abbreviated as L) together with the determination of conditional distribution constants (KD,Pic) of picrate ion, Pic-, into these diluents. The K1,org (= [NaLPic]org/[NaL+]org[Pic-]org) values at the organic (org) phases, such as NB & DCE, were calculated from the relation Kex/Kex± = K1,org. Distribution equilibrium-potential differences (Dfeq) at extraction equilibria were evaluated from the equation Dfeq = -0.05916´(log KD,Pic - constant) at 298 K. Correlations of the above equilibrium constants, particularly Kex±, with Dfeq were examined. Furthermore, the standard formal potentials for Na+ transfers across the interfaces were briefly evaluated from calculated Dfeq, [Na+] and [Pic-]org. The above extraction systems were characterized by K1,org and the complex formation constants of Na+ with L in the org phases.

Extraction of Sodium Picrate by 3m-Crown-mEthers and Their Monobenzo Derivatives (m= 5, 6) into Benzene: Estimation of Their Equilibrium-Potential Differences at the Less-Polar Diluent/Water Interface by an Extraction Method

Individual distribution constants (KD,A) of picrate ion (Pic−) and extraction constants (Kex±) of NaPic by some crown ethers (L) into benzene (Bz) at 25°C were calculated from data reported previously. These constants were defined asKD,Pic=Pic-o/[Pic-]andKex±=NaL+oPic-o/(Na+Lo[Pic-]), respectively. Here, the subscript “o” denotes an organic (o) phase and practically o = Bz. 15-Crown-5 ether (15C5), 18-crown-6 one (18C6), and their monobenzo (B) derivatives (B15C5 and B18C6) were selected as L. Interfacial equilibrium-potential differences (Δϕeq) at extraction were estimated at 298 K. A plot oflog⁡Kex±versus-Δϕeqfor the four L extraction systems gave a straight line with slope = 84 V−1. This slope was compared with those, reported before, of the dichloromethane (DCM), 1,2-dichloroethane (DCE), and nitrobenzene (NB) extraction systems. The slopes of the regression lines were in the order NB < DCM ≤ DCE < Bz. Also, the individual distribution constants of the complex ionNaL+and an ion-pair complex (NaL+Pic-) into Bz phase were calculated from the above extraction data. At least, a comparison between these values suggests that Bz molecules mainly interact withNaL+moiety ofNaL+Pic-.

Liquid-Liquid Extraction of Transition Metal Cations by Glyoximes and Their Macrocyclic Glyoxime Ether Derivatives

Liquid-liquid extraction of various alkalis (Li+, Na+, K+, and Cs+), transition metals (Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+), and Pb2+cations with phenylglyoxime (L1), p-tolylglyoxime (L2),N′-(4′-Benzo[15-crown-5])phenylaminoglyoxime (L3), andN′-(4′-Benzo[15-crown-5])-p-tolylaminoglyoxime (L4) from the aqueous phase into the organic phase was carried out. For comparison, the corresponding two glyoximes and their macrocyclic glyoxime ether derivatives were also examined. Crown ether groups having ligands (L3,L4) carry especially Na+cation from aqueous phase to organic phase. The extraction equilibrium constants (Kex) for complexes of ligands with Cu2+and Hg2+metal picrates between dichloromethane and water have been determined at 25°C. The values of the extraction constants (logKex) were determined to be 12.27, 13.37, 12.94, and 12.39 for Cu2+and 10.29, 10.62, 11.53, and 11.97 for Hg2+with L1–L4, respectively.

Complexation of some univalent organic cations with benzo-18-crown-6 in nitrobenzene saturated with water

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium C+(aq) + 1·Na+(nb) 1·C+ (nb) + Na+(aq) taking place in the two-phase water-nitrobenzene system (C+ = methylammonium, ethylammonium, propylammonium, ethanolammonium, diethanolammonium, triethanolammonium, cation TRIS+, hydrazinium, hydroxylammonium; 1 = benzo-18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the 1·C+ cationic complex species in nitrobenzene saturated with water were calculated; they were found to increase in the following cation order: triethanolammonium +