Transport and Selectivities of Amino Acids on Periderm and Cuticular Membranes

Abstract

The transport of amino acids through isolated potato periderm and pear fruit cuticular membranes were investigated. The transport rate depended on the molecular size of amino acids and decreased with an increase in molecular size through extension of the hydrophobic —CH₂— group. The selectivity coefficients of amino acids for the ammonium ion form of periderm and cuticular membranes were also determined, using the mass action law. They were found to be correlated with various physicochemical parameters such as the partial molar volume and the molecular weight.     

Diffusion of Amines through Polysulfonated Ion-Exchange Membranes

Abstract

The permeabilities and diffusion behaviors of aniline, p-chloroaniline, and p-nitroaniline were investigated in polysulfonated ICE-450 ion-exchange membranes as a function of pH at 25°C. The permeabilities for these compounds increased with decreasing of receiver side pH. The modes of membrane/solution distribution and diffusion of amines, as a controlling factor to the membrane permselectivity in terms of basicity value, molecular size, and electrophilic groups of amines, were correlated consistently with the flux data as well as with the estimated membrane permselectivity parameters. The transport system depends on the basicity values of amines, and the pH gradients were the main driving force. It is shown that the diffusion parameters measured on single component experiments provide a good prediction of behavior.     

乳状液膜中1,3-桥连杯[4]芳烃/冠醚对碱金属离子的选择性萃取(英文)

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by inclu sion-facilitated emulsion liquid membrane process. The novelty of this study is application of nano-baskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this aim, four derivatives of diacid calix[4]-1,3-crowns-4,5 were synthesized, and their inclusion-extraction parameters were optimized including the calixcrown scaffold （4.4%, by mass） as the carrier/demulsifier, the commercial kero sene as diluent in membrane, sulphonic acid （0.2 mol.L-1） and ammonium carbonate （0.4 mol.L-1） as the strip and the feed phases, the phase and the treat ratios of 0.8 and 0.3, mixing speed （300 r.min-1）, and initial solute concentration （100 mg.L-1）. The selectivity of membrane over more than ten interfering cations was examined and the re sults reveled that under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98%-99%.     

Saturation Kinetics of Acetic Acid Transport through Perfluorosulfonated Ion-Exchange Membranes

Abstract

Permeation of acetic acid through perfluorosulfonated polymeric membranes exhibit Michaelis-Menten-type saturation kinetics characterized by a maximum flux for permeating species. It is postulated that the saturation kinetics is probably a result of the solubility of acetic acid reaching a maximum limit in the membrane.     

Diffusion and Selective Transport of Alkali Cations on Cation-Exchange Membrane

Abstract

The diffusion coefficients and selective transport for alkali metal cations through a charged polysulfonated ICE-450 ion-exchange membrane were measured as a function of pH at 25°C. The permeability and diffusion coefficients were found to increase in the sequence Cs⁺ ≥ K⁺ > Na⁺ > Li⁺. The relationship between the permeability and the diffusion coefficients, and the hydrated radii of cations in the membrane were shown. This sequence was also explained by considering the hydration of ions in the membrane. The selectivity transport of K—Na and K—Li binary systems at various pH gradients through the membrane were also investigated under various conditions. In the selective transport of metal ions, the selectivity depended on both the hydrated ionic size and the interaction between the fixed groups in the membrane and the metal ions.     

Cation Transport Through Liquid Membranes Mediated by Photoreactive Crown Ethers. Effects of Alkali Metal Cations on Their Photoreactivities and Transporting Properties

Photoreactivities and cation transporting properties of monomeric, dimeric, and polymeric crown ethers which contain cinnamoyl residues were investigated. Photochemical cycloaddition reaction of the cinnamoyl moieties was accelerated by NaCl or KCl for the dimeric and polymeric derivatives but not for the monomeric one. The dimeric and polymeric crown ethers after irradiation in the presence of KCl showed a significant enhancement in the transport rates for Rb⁺ cation.     

Effect of Cerium on the Ion-Exchange Parameters in Alkali Silicate Glasses

Alkali gallosilicate glasses containing 1–8 mol % CeO₂ after ion-exchange treatment in a NaNO₃ melt at different temperatures are studied. The refractive index distributions in glasses with different cerium oxide contents are obtained, and the profiles of the Na₂O concentration distribution in the samples containing 2 mol % CeO₂ after ion-exchange treatment at temperatures T = 500–550°C are determined. It is revealed that, as the cerium oxide content increases, the interdiffusion coefficient decreases, whereas the refractive index increment increases. The results obtained are analyzed within the framework of the model of dopant segregation, according to which cerium undergoes selective incorporation and concentration displacement into polar microregions of the glass.     

Separation of Humic Substances by Porous Ion-Exchange Membranes from Sulfonated Polysulfone

Abstract

Ultrafiltration involving sulfonated polysulfone membranes provides high efficiency for humic matter removal from water. The increase in ion-exchange capacity of the polymer matrix from 0.24 to 0.96 mmol SO₃H groups per 1 g of dry membrane increases the membrane pore diameter and its hydrophilicity, and thus the permeate flux from 0.05 to 3.69 m³/m²·d. In order to decrease the manufacturing cost, membranes from polysulfone and sulfonated polysulfone blends were investigated. It was shown that a one-to-one blend resulted in a membrane having similar antifouling properties to pure sulfonated polysulfone. Both membranes reject humic matter in the 91–98% range and show a flux decline of 5–30% as a result of surface fouling.     

Properties of Interpolymer PESS Ion-Exchange Membranes in Contact with Solvents of Different Polarities

Abstract

PESS membranes with sulfonic ion-exchange groups were prepared by chemical modification of a polyethylene/poly(styrene-co-divinylbenzene) interpenetrating polymer network with varying content of the crosslinking agent (DVB). PESS membranes were loaded with different alkali metal ions as counterions. Swelling and pervaporation properties of these membranes in contact with water and aliphatic alcohols were obtained. The obtained data show that properties of PESS membranes depend strongly on the kind of counterions, the degree of crosslinking, and the solvent polarity.     

Modeling of Mass Electrotransfer in Terms of the Transport and Structural Properties of Ion-Exchange Membranes

Mass electrotransfer in membrane systems is modeled in terms of the transport and structural properties of the membranes. Experimental concentration-dependent conductivity and diffusion flux data are used to calculate and compare the transport and structural parameters of cation- and anion-exchange membranes employed in electrodialyzers.     

Separation of Nickel and Cobalt by Electrodialysis Using Ion-Exchange Membranes in the Presence of EDTA

Abstract

Electrodialytic separation of Ni²⁺ and Co²⁺ cations has been realized by using ion-exchange membranes in the presence of EDTA by preferentially complexing Ni²⁺(Ni²⁺ concentration = EDTA concentration). The degree of complexation is calculated as a function of the pH and of the concentration by using data taken from the literature. Due to a systematic study of the influence of the different separation parameters (nature of the membranes, flow rate, electric current intensity, pH), the conditions_of_separation have been optimized on a computer, and then pure solutions of nickel and cobalt ions have been obtained experimentally. The decomplexation of Ni²⁺ is accomplished in acidic medium by cooling.     

A Study of the Separation Possibilities of Cations Using Glass Membranes

Abstract

The separation possibilities of Pyrex glass membranes at high temperatures have been investigated for the separation of sodium and potassium. A separation factor of 11 was obtained for this separation. The limitations of glass membranes for separation purposes are discussed, particularly for the separation of the alkali metal ions.     

Glycine Permeation through Na+, Ag+, and Cs+ Forms of Perfluorosulfonated Ion-Exchange Membranes

Abstract

We have studied the effect of counterions in perfluorosulfonated ion-exchange membranes on glycine permeation and found that counterions controlled permeation behavior. The Na⁺ form of the membrane exhibited saturation kinetics of the Michaelis-Menten type; that is, the flux rapidly increased with concentration and reached a limiting flux at a concentration of about 2 mol/L. The Cs⁺ form exhibited markedly lower fluxes which were nearly Fickian. For the Ag⁺ form, however, the fluxes increased rapidly and nonlinearly at low concentrations, but attained Fickian linearity at high concentrations. Ionizability of the sulfonate groups and hydration numbers of the counterions appeared to cause departure from Fickian behavior.     

Affinity of Cation-Exchange Membranes Towards Metallic Cations: Application in Continuous Electropermutation

The objective of this work was to correlate the separation process of the metallic cations (M(II)) by electropermutation (EP) of multications solution with the affinity of ion-exchange materials (IEMs). The obtained results show that the affinity order is similar for all tested IEMs and is as follows: Pb(II)>Cd(II)>Zn(II)>Mg(II). Furthermore, the order of the transfer flux (J) of metallic cations obtained with different tested cation-exchange membranes (CEMs) is identical to that encountered for the affinity order. Further analysis of the results demonstrated that the affinity of IEMs and the transfer flux change in reverse order of hydration ionic radius (r) of metallic cations: r_Mg(II)>r_Zn(II)≥r_Cd(II)>r_Pb(II). During the EP, the order of metallic cations transfer is as established previously when using different electro-regeneration cations (H⁺, Na⁺, NH₄⁺) and different co-ions (NO₃^?, Cl^?_, SO₄^2?). However, the extent of the transfer flux as a function of the nature of electro-regeneration cation follows the order: J_M(II)(H⁺)>J_M(II)(NH₄⁺)>J_M(II)(Na⁺). The removal rates of metallic cations vary in the range 89?99%. This work shows that the orders of the IEMs affinity and the transfer are mainly determined by the properties of metallic cations such as the hydration ionic radius. Nevertheless, the importance of the fixation and the transfer of metallic cations depend on the IEMs’ nature.     

Extraction of Alkali Metal Cations by Lipophilic Dibenzo-14-crown-4-carboxylic Acids

Abstract

The extraction of alkali metal cations by the lipophilic crown ether, bis-t-octylbenzo-14-crown-4 (BOB14C4), three derivatives of BOB14C4 having pendant carboxylic acid sidearms, and a lipophilic carboxylic acid, 2-methyl-2-heptylnonanoic acid (HMHN) was studied by two-phase potentiometric titration and ion-chromatography. The lipophilic, ionizable crown ethers, BOB14C4-acetic acid (BOB14C4AA), BOB14C4-propanoic acid (BOB14C4PA), and BOB14C4-oxyacetic acid (BOB14C4OAA) extract cations efficiently from aqueous mixed alkali metal chloride solutions into 1-octanol by an ion-exchange mechanism in the range p[H] > 7, as does HMHN. The mode of attachment of the ionizable sidearm, via an ether linkage (BOB14C4OAA) versus a carbon linkage (BOB14C4AA and BOB14C4PA), has a significant effect on the cation selectivity and extraction efficiency of these extractants. BOB14C4 exhibits no p[H] dependent extraction behavior and has no significant effect on the extraction of alkali metal cations by HMHN in a mixture of these two compounds. Although BOB14C4AA and BOB14C4PA extract cations at lower p[H] than HMHN, all three compounds exhibit similar selectivity for Li⁺ over Na⁺, K⁺, Rb⁺ and Cs⁺. A significant reversal in selectivity is observed with BOB14C4OAA, which extracts Na⁺ and K⁺ selectively over Li⁺, Rb⁺, and Cs⁺ and at significanty lower p[H] than BOB14C4AA, BOB14C4PA, or HMHN. The unique behavior of BOB14C4OAA may be attributed to the presence of the ether linkage between the crown ether and the pendant carboxylic acid.     

Proton-Ionizable Crown Compounds: Transport of Alkali and Alkaline Earth Cations Using Proton-Ionizable Triazolo Macrocycles

Abstract

The macrocycle-mediated flaxes of the alkali and alkaline earth metal cations have been determined in a H₂O-CH₂Cl₂-H₂O bulk liquid membrane system. Water-insoluble proton-ionizable macrocycles of the triazolo type were used. The proton-ionizable feature allows the coupling of cation transport to reverse H⁺ transport. This feature offers promise for the effective separation and/or concentration of alkali metal ions with the metal transport being driven by a pH gradient. A counter anion in the source phase is not co-transported. Transport of the alkali cations only occurred when the source phase pH was greater than the aqueous pK_a value for the carriers. Transport increased regularly with increasing source phase pH. Transport of alkaline earth cations from neutral pH source phases was minimal. The alkali cation selectivity order was K⁺ > Rb⁺ > Cs⁺ > Na⁺ > Li⁺ for the l8-crown-6 sized macrocycles, while little selectivity was observed with the 15-crown-5 sized macro-cycle.     

Solvent Extraction of Alkali Metal Cations from Aqueous Solutions by Crown Ether Carboxylic Acids

Abstract

Competitive solvent extractions of alkali metal cations from aqueous solutions by the crown ether carboxylic acids sym-dibenzo-13-crown-4-oxyacetic acid, 2; sym-dibenzo-19-crown-6-oxyacetic acid, 3, and sym-dibenzo-14-crown-4-oxyacetic acid, 4, in chloroform have been conducted. Influences of aqueous phase pH and metal ion concentrations upon the concentrations of metals and complexing agent in the organic phase are assessed and compared with those reported for sym-dibenzo-16-crown-5-oxyacetic acid, 1. Extraction selectivity orders of K > Rb > Na ≈ Cs > Li, K > Rb ≥ Na ≈ Cs > Li, and K > Na > Rb > Cs ≈ Li were found for extractions using 2, 3, and 4, respectively. In terms of selectivity and metal extractability, 3 surpasses 1, 2, and 4.     

Solvent-Polymeric Membranes for Separation of Li+ From Other Alkali Metal and Alkaline Earth Ions

Lithium may be recovered from the Dead Sea brines by a process which combines membrane separation with ion-exchange. Solvent-polymeric membranes based on alkyl-arylphosphates cause selective permeation of lithium ions with Br⁻₃ as counter ions. Addition of the derivatives of neutral “crown” ethers did not improve their performance and an adverse effect, due to the decrease in the fluidity of the membrane system, was observed. Incorporation of ionizable “crown” ethers compatible with the system may, however, be advantageous; pH gradients could act as a driving force for transport of lithium in such systems. Membranes prepared with (2-ethylhexyl)-diphenyl phosphate (Santicizer 141) gave the best results from the point of view of selectivity of Li⁺ transport vs. Mg²⁺ and Ca²⁺. Maintenance of ca. 10⁻³ M concentrations of Br₂ in the end-brine solutions gives optimal membrane performance. No significant change in membrane permeability and selectivity occurred during six months of their operation. Lithium ions in the product solution of the membrane separation process may be further separated from the residual Mg²⁺ and Ca²⁺ ions and concentrated up to 1 M by ion exchange processes. Lithium may be precipitated from such solutions, free from alkaline earth ions, as Li₂CO₃.     

Ion-Exchange Separation of Silver and Lead

Abstract

Silver and lead were separated on a column of carboxylic cation-exchange resin using a diethanolamine-diethanolammonium nitrate solution to elute silver. Lead was eluted with hydrochloric acid.     

Usnic Acid-Mediated Exchange of Protons for Divalent Metal Cations across Lipid Membranes: Relevance to Mitochondrial Uncoupling

Usnic acid (UA), a unique lichen metabolite, is a protonophoric uncoupler of oxidative phosphorylation, widely known as a weight-loss dietary supplement. In contrast to conventional proton-shuttling mitochondrial uncouplers, UA was found to carry protons across lipid membranes via the induction of an electrogenic proton exchange for calcium or magnesium cations. Here, we evaluated the ability of various divalent metal cations to stimulate a proton transport through both planar and vesicular bilayer lipid membranes by measuring the transmembrane electrical current and fluorescence-detected pH gradient dissipation in pyranine-loaded liposomes, respectively. Thus, we obtained the following selectivity series of calcium, magnesium, zinc, manganese and copper cations: Zn²⁺ > Mn²⁺ > Mg²⁺ > Ca²⁺ >> Cu²⁺. Remarkably, Cu²⁺ appeared to suppress the UA-mediated proton transport in both lipid membrane systems. The data on the divalent metal cation/proton exchange were supported by circular dichroism spectroscopy of UA in the presence of the corresponding cations.