P.R. Brown

Thermodynamic quantities for the interaction of SO 4 2? with H+ and Na+ in aqueous solution from 150 to 320C

AbstractThe aqueous reactions,n

The influence of halocarbon solvent on macrocycle-mediated cation transport through liquid membranes

begin{gathered} H^ + + SO_4^{2 - } = HSO_4^ - ,Na^ + + SO_4^{2 - } = NaSO_1^ - , hfill and H^ + + HSO_4^ - = H_2 SO_4 (aq) hfill end{gathered}

Cation transport at 25°c from binary Na+Mn+, Cs+Mn+ and Sr2+Mn+ nitrate mixtures in a H2OCHCl3H2O liquid membrane system containing a series of macrocyclic carriers

nnwere studied as a function of ionic strength(I) at 150, 175, 200, 250, 300 and 320°C using a flow calorimetric procedure. Log K, ΔH, ΔS and ΔCp values at I=0 were derived from the data at each temperature. Using these experimental values, equations describing log K, ΔH, ΔS and ΔCp at I=0 and temperatures from 150 to 320°C were derived for each system. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was evaluated as a technique for the extrapolation of log K values valid below 100°C to temperatures above 150°C. This evaluation indicated that the principle gives good estimates up to 320°C.

Facilitated transport from ternary cation mixtures through water-chloroform-water membrane systems containing macrocyclic ligands

The aqueous reactions, {ie865-1}were studied as a function of ionic strength at 275, 300, and 320°C using a flow calorimetric technique. Log K, ΔH and ΔS values were determined from the fits of the calculated and experimental heats while ΔCp values were calculated from the variation of ΔH values with temperature. The log K and ΔH values for the first two reactions agree well with literature values at these temperatures. No previous results have been reported for the third reaction. The use of equations containing identical numbers of positive and identical numbers of negative charges on both sides of the equal sign (isocoulombic reaction principle) was applied to the log K values determined in this study. The resulting plots of log K for the isocoulombic reactions vs. I/T were approximately linear, which demonstrates that the ΔCp values for these reactions are approximately zero.

Liquid Membrane Separations of Metal Cations Using Macrocyclic Carriers

Abstract Models which describe the macrocycle-mediated flux of cations through bulk liquid membranes indicate that membrane solvent exerts an important influence on membrane performance. Specifically, four of the parameters which determine flux are solvent dependent: the equilibrium constant for cation—macrocycle interaction in the membrane, the thickness of the unstirred boundary layers in the membrane, the partition coefficients, and the diffusivities of the species present. The series of halocarbons dichloromethane, trichloromethane, tetrachloromethane, 1,2-dichloroethane, 1,1,2-trichloroethane and 1,1,2,2-tetrachloroethane were used as membrane solvents in otherwise identical experiments. The macrocycle used was dicyclohexano-18-crown-6. The relative fluxes of Na + , K + , Rb + , Cs + , Ca 2+ , Sr 2+ , and Ba 2+ were determined and found to have distinctive patterns with changing solvent, with monovalent and divalent cations each demonstrating similar behavior. These trends are discussed in terms of various physical properties of the solvents involved.

Transport of Eu2+ in a H2OCHCl3H2O liquid membrane system containing the macrocyclic polyether 18-crown-6

An isothermal flow calorimeter suitable for measuring heats of reaction in aqueous solutions from 373 to 773 K and from 0.1 to 40.5 MPa is described. Chemical and corrosion resistance was obtained by using only tantalum metal in the calorimeter proper. An automatically controlled pulsed heater and a highly stable heat-leak path are used to maintain the reaction zone at a constant temperature. Energy effects from 0.15 to 120 J min−1 can be measured to an accuracy of ±1.0% at constant temperature and pressure. The calorimeter was tested by measuring the heat of mixing of water-ethanol at 373 K and 1 MPa and of hexane-toluene at 413 K and 10.50 MPa and was found to produce data in good agreement with previously measured values.

Thermodynamic quantities for the interaction of SO42− with H+ and Na+ in aqueous solution from 150 to 320°C

Abstract Cation fluxes from binary mixtures of either Na + , Cs + or Sr 2+ with other alkali metal cations, alkaline earth metal cations, and Pb 2+ through a H 2 Oue5f8CHCl 3 ue5f8H 2 O bulk liquid membrane system containing one of several macrocyclic carriers have been determined Nitrate salts were used in all cases. The most selective transport of Na + over all other cations studied was found with the carrier cryptand [2.2.1]. Selective transport of Na + relative to Li + , Cs + and the alkaline earth cations was found with cryptand [2.2.2B] and cryptand [2.2.2D]. The ligands 21-crown-7 and dibenzo-24-crown-8 showed selective transport of Cs + over the second cation in all cases. Several macrocycles showed selectivity for Sr 2+ over the second cation with the macrocycle 1,10-diaza-18-crown-6 showing the highest selectivity for this cation of all ligands studied. Relative fluxes from binary cation mixtures are rationalized in terms of macrocycle cavity size, donor atom type and ring substituents.

Selective M+-H+ coupled transport of cations through a liquid membrane by macrocyclic calixarene ligands

Abstract Cation fluxes were determined for various three-component, equimolar mixtures of alkali metal, alkaline earth, and Pb2+ cations in a H2Oue5f8CHCl3ue5f8H2O liquid membrane system incorporating macrocyclic polyethers as carriers. Carrier ligands studied were 18-crown-6, dicyclohexano-18-crown-6, 1,10-diaza-18-crown-6, 21-crown-7, dibenzo-24-crown-8, and cryptand [2.2.2]. Correlations were found between transport and relative cation:polyether cavity radii, the type of substituents present on the polyether ring, and the type and number of donor atoms present. All the ligands studied transported Pb2+ at higher rates than the other Mn+ in the mixtures. Transport behavior in these multi-cation systems can be predicted from Mn+—polyether complex stability constant data in most cases.