Membrane transport systems. V. Coupled countertransport of alkaline earth cations and protons

1984 ◽  
Vol 62 (3) ◽  
pp. 498-506 ◽  
Author(s):  
Lynn M. Dulyea ◽  
Thomas M. Fyles ◽  
Dennis M. Whitfield
Keyword(s):  
Metal Ion ◽  
Alkaline Earth ◽  
Ion Concentration ◽  
Transport Systems ◽  
Kinetic Regime ◽  
Artificial Membrane ◽  
First Order ◽  
Membrane Transport Systems ◽  
Rate Limiting ◽  
Alkaline Earth Cations

The extraction and transport of alkaline earth cations from a basic to an acidic solution across an artificial membrane by crown ether carboxylic acids are reported. Monocarboxylate carriers achieve the transport via 2:1 complexes or by ternary complexes in the presence of readily extractible anions, while dicarboxylate carriers transport cations as 1: 1 complexes. Both types of carrier exhibit two regimes of kinetic behaviour depending on the relative concentrations of the carrier and the metal ion: a zero order regime in which the rate depends only on the carrier concentration, and a reversible consecutive first order regime in which the rate depends only on the metal ion concentration. In the former, the rate of adsorption of the carrier on the interface is presumed to be rate limiting while in the latter, the diffusion of metal ion to the interface is rate limiting. Carrier structure exerts a general influence over both the rate and selectivity of transport but this influence varies with the kinetic regime considered.

Membrane transport systems. II. Transport of alkali metal ions against their concentration gradients

1981 ◽  
Vol 59 (12) ◽  
pp. 1734-1744 ◽  
Author(s):  
Thomas M. Fyles ◽  
Virginia A. Malik-Diemer ◽  
Dennis M. Whitfield
Keyword(s):  
Alkali Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Complex Function ◽  
Membrane System ◽  
Ion Concentration ◽  
Transport Systems ◽  
Alkali Metal Ions ◽  
Concentration Gradients ◽  
Membrane Transport Systems

An artificial membrane system based on a series of macrocyclic polyether carriers (crown ethers) is described. Under the influence of a proton gradient the carriers move alkali metal ions from basic to acidic solution through a chloroform membrane phase. Transport occurs against the concentration gradient of the transported ion as a result of a coupled counterflow of protons. Different transport behaviors are observed depending upon the metal ion concentration. At high metal ion concentration the amount transported is a linear function of time; at lower metal ion concentration the amount transported is a complex function of time which may be described as the result of a pair of consecutive first order processes. Effects of metal ion, carrier, and proton concentration on transport rate are considered. The rate increases with increasing metal ion or carrier concentration but is essentially independent of the pH of either aqueous phase. Increased lipophilicity of the carrier also results in a rate increase. Carriers derived from 18-crown-6 transport potassium selectively and all ions more rapidly than 15-crown-5 derivatives which are, however, selective for sodium. The overall efficiency of the system is discussed in terms of competing "leak" reactions, either of cations from the basic phase or of anions from the acidic phase.

Micelle formation as a factor influencing the mode(s) of metal ion partitioning into N-alkylpyridinium-based ionic liquids (ILs): implications for the design of IL-based extraction systems

2017 ◽  
Vol 19 (23) ◽  
pp. 5674-5682 ◽  
Author(s):  
James L. Wankowski ◽  
Michael J. Kaul ◽  
Mark L. Dietz
Keyword(s):  
Ionic Liquids ◽  
Crown Ether ◽  
Metal Ion ◽  
Alkaline Earth ◽  
Micelle Formation ◽  
Ion Pair ◽  
Neutral Complex ◽  
Ion Partitioning ◽  
Alkaline Earth Cations ◽  
Complex Ion

In the extraction of alkali and alkaline earth cations by a crown ether into certain N-alkylpyridinium-based ILs, the balance between neutral complex/ion-pair partitioning and ion exchange is significantly altered by the formation of micelles in the aqueous phase involving the IL cation.

Interaction of Alkaline Earth Metal Ions with Acetic and Lactic Acid in Aqueous Solutions Studied by 13C NMR Spectroscopy

1997 ◽  
Vol 52 (4) ◽  
pp. 351-357 ◽  
Author(s):  
A. Kondoh ◽  
T. Oi
Keyword(s):  
Lactic Acid ◽  
Nmr Spectroscopy ◽  
Metal Ion ◽  
Alkaline Earth ◽  
Isotope Effects ◽  
Earth Metal ◽  
Ion Concentration ◽  
Alkaline Earth Metal ◽  
Hydroxyl Groups ◽  
Alkaline Earth Metal Ions

Abstract Interaction of alkaline earth metal (magnesium, calcium, strontium and barium) ions with acetic and lactic acid in aqueous media was investigated by 13C NMR spectroscopy. In the acetate systems, signals whose chemical shifts were the averages of those of the free and bound acetate ions were observed. Downfield shifts of the carboxylate carbon signals with increasing metal ion concentration indicated that the acetate ion acted as a monodentate ligand coordinating to the metal ion using the carboxylate group. The metal ion concentration dependence of the peak positions of the methine and carboxylate carbon signals of the lactate ion in the lactate systems suggested that the lactate ion coordinated to a metal ion using the carboxylate and hydroxyl groups. Unique upfield shifts upon complexation in the magnesium lactate systems suggested that the lactate ion coordinated to the magnesium ion from outside the primary hydration sphere.The present results were consistent with the isotope effects of the alkaline earth metals observed in cation exchange chromatography.

Voltage-Switchable HCl Transporters: The Effect of Lipid Headgroup Binding

2019 ◽  
Author(s):  
Xin Wu ◽  
Jennifer Small ◽  
Alessio Cataldo ◽  
Anne Withecombe ◽  
Peter Turner ◽  
...  
Keyword(s):  
Anion Binding ◽  
Transport Systems ◽  
Transport Mechanisms ◽  
Artificial Membrane ◽  
Ph Gradients ◽  
New Approach ◽  
Anion Transporters ◽  
Anti Cancer ◽  
Voltage Dependent ◽  
Membrane Transport Systems

Synthetic anion transporters that facilitate transmembrane H<sup>+</sup>/Cl<sup>-</sup>symport (cotransport)have anti-cancer potential due to their ability to neutralize pH gradients and inhibit autophagy in cells. However, compared to the natural product prodigiosin, synthetic anion transporters have low-to-modest H<sup>+</sup>/Cl<sup>-</sup>symportactivity and their mechanism of action remains less well understood. We here report a chloride-selective tetraurea macrocycle that has a record-high H<sup>+</sup>/Cl<sup>-</sup>symportactivity similar to prodigiosin and most importantly demonstrates unprecedented voltage-switchable transport properties that is linked to the lack of uniport activity. By studying anion binding affinity and transport mechanisms of four other anion transporters, we show that the lack of uniport and the voltage-dependent H<sup>+</sup>/Cl<sup>-</sup>symport originate from strong binding to lipid phosphate headgroup that hampers the diffusion of the free transporters through the membranes, leading to an unusual H<sup>+</sup>/Cl<sup>-</sup>symport mechanism that involves only charged species. Our work provides important mechanistic insights into different classes of anion transporters and a new approach to achieve voltage-switchability in artificial membrane transport systems.

scholarly journals Synthesis of citric acid-modified resins and their adsorption properties towards metal ions

2018 ◽  
Vol 5 (8) ◽  
pp. 171667 ◽  
Author(s):  
Xiong Liu ◽  
Longqi Xu ◽  
Yaqing Liu ◽  
Wenqi Zhou
Keyword(s):  
Citric Acid ◽  
Metal Ion ◽  
Adsorption Properties ◽  
Langmuir Model ◽  
Ion Concentration ◽  
First Order ◽  
Adsorption Capacities ◽  
Equilibrium Data ◽  
Pseudo First Order ◽  
Order Rate Equation

Types of resins anchored on citric acid were synthesized and identified. The citric acid-modified resins PS-CA, PS-O-CA and PS-N-CA were synthesized by anchoring citric acid on PS-Cl, PS-OH and PS-NH 2 , respectively. The PS-CA, PS-O-CA and PS-N-CA were used to adsorb Fe 3+ , Al 3+ , Cu 2+ , Pb 2+ , Cd 2+ and Hg 2+ . The influences of pH, adsorption time and metal ion concentration on the adsorption capacities of the resins were investigated. After optimization, PS-CA was a good adsorbent to Fe 3+ , Cu 2+ , Pb 2+ and Cd 2+ with q m values of 143.9 mg g −1 , 77.4 mg g −1 , 18.9 mg g −1 and 119.9 mg g −1 , respectively. PS-N-CA was a good adsorbent to Al 3+ and Hg 2+ with q m values of 176.6 mg g −1 and 114.9 mg g −1 , respectively. The adsorption kinetics and adsorption isotherm experiments indicated that the pseudo-first-order rate equation was more appropriate for characterizing the kinetic data and the Langmuir model was more suitable for fitting the equilibrium data. The reusability of the citric acid-modified resins was also evaluated and these resins exhibited considerable reusability.

scholarly journals Evaluation of Cd(II) Ion Removal from Aqueous Solution by a Low-Cost Adsorbent Prepared from White Yam (Dioscorea rotundata) Waste Using Batch Sorption

2018 ◽  
Vol 2 (3) ◽  
pp. 35 ◽  
Author(s):  
Edidiong Asuquo ◽  
Alastair Martin ◽  
Petrus Nzerem
Keyword(s):  
Aqueous Solution ◽  
Langmuir Isotherm ◽  
Metal Ion ◽  
Aqueous System ◽  
Ion Concentration ◽  
Dioscorea Rotundata ◽  
First Order ◽  
White Yam ◽  
Pseudo First Order ◽  
Adsorbent Dose

An agricultural residue, white yam (Dioscorea rotundata) tuber peel (YTBS), was used for the removal of Cd(II) ion from an aqueous solution using a batch method. The adsorbent was characterized using FTIR, TGA, SEM, EDX, N2 BET, XRD, and XRF. The optimization of sorption variables such as pH, contact time, adsorbent dose, and initial metal ion concentration at 25 °C were also carried out. The results indicated the dependence of sorption on the adsorbate pH and adsorbent dose, while the adsorption system reached equilibrium in 180 min. The sorption kinetics was fitted to three models (pseudo first order, pseudo second order, and Elovich) to validate the kinetics, and the pseudo first order was the best model for the description of Cd(II) uptake. Equilibrium isotherm modelling was also carried out using the Langmuir, Freundlich, and Temkin models, with the Langmuir isotherm giving the best fitting to the experimental results. The maximum loading capacity (qmax) of the adsorbent for Cd(II) obtained from the Langmuir isotherm model was 22.4 mg∙g−1 with an isotherm constant (KL) of 3.46 × 10−3 L·mg−1 and r2 value of 0.99. This result indicates that the YTBS residue was a good adsorbent for the removal of Cd(II) ion from aqueous system.

scholarly journals Removal Of Copper From Aqueous Solutions By Using Natural And Fe-Modified Clinoptilolite

2015 ◽  
Vol 23 (36) ◽  
pp. 33-40
Author(s):  
Marek Lipovský ◽  
Maroš Sirotiak ◽  
Maroš Soldán
Keyword(s):  
Metal Ion ◽  
Ion Concentration ◽  
Order Kinetic ◽  
Langmuir Adsorption ◽  
First Order ◽  
Adsorption Processes ◽  
Pseudo Second Order ◽  
Pseudo First Order ◽  
Static Conditions ◽  
Modified Clinoptilolite

Abstract Removal of copper from aqueous solution on the natural and modified clinoptilolite was studied under static conditions. Batch adsorptions of copper were performed to investigate the effects of contact time and initial metal ion concentration. The Freundlich and Langmuir adsorption isotherms were used to analyse the experimental data. The kinetic analyses of the adsorption processes were performed using the pseudo-first-order and pseudo-second-order kinetic models.

Adsorption of Cr(III) from aqueous solutions by polyacrylamide-grafted rubberwood fibre: Kinetics, equilibrium, and thermodynamic studies

BioResources ◽  
2010 ◽  
Vol 6 (1) ◽  
pp. 22-33
Author(s):  
Mahnaz Mahdavi ◽  
Mansor B. Ahmad ◽  
Md Jelas Haron ◽  
Mohamad Zaki Ab. Rahman
Keyword(s):  
Adsorption Capacity ◽  
Metal Ion ◽  
Entropy Change ◽  
Ion Concentration ◽  
Ceric Ammonium Nitrate ◽  
Maximum Adsorption Capacity ◽  
First Order ◽  
Pseudo Second Order ◽  
Aqueous Conditions ◽  
Langmuir And Freundlich Models

Cr(III) ions were adsorbed onto polyacrylamide-grafted rubberwood fibre, and effects of aqueous conditions were evaluated. The adsorbent was prepared via graft copolymerization of acrylamide (Am) onto rubberwood fibre (RWF), using ceric ammonium nitrate as an initiator. Fourier transform infrared spectroscopy was used to confirm the formation of PAm-g-RWF. Various variables affecting the adsorption capacity such as the pH of the solution, adsorption time, initial metal ion concentration, and temperature were investigated. The Cr(III) was up to 92% removed by PAm-g-RWF from an initial concentration of 10 mg/L at pH 5.0. Kinetic data fitted very well to a pseudo-second-order rate expression and less well to a pseudo-first-order equation. The equilibrium parameters for adsorption isotherms of the metal ions on the grafted fibre were obtained using Langmuir and Freundlich models, and the Langmuir model was found to be in better correlation with the experimental data with a maximum adsorption capacity of 18.24 mg/g. Thermodynamic parameters such as enthalpy change (ΔH°), free energy change (ΔG°), and entropy change (ΔS°) were calculated; the adsorption process was spontaneous and endothermic.

scholarly journals ADSORPTION KINETICS OF Pb(II), Cd(II) AND Cr(III) ON ADSORBENT PRODUCED BY PROTECTED-CROSSLINKING OF HUMIC ACID-CHITOSAN

2010 ◽  
Vol 10 (1) ◽  
pp. 80-87
Author(s):  
Dewi Umaningrum ◽  
Uripto Trisno Santoso ◽  
Radna Nurmasari ◽  
Rahmat Yunus
Keyword(s):  
Humic Acid ◽  
Adsorption Kinetics ◽  
Metal Ion ◽  
Second Order ◽  
Adsorption Rate ◽  
Ion Concentration ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

Study on adsorption kinetics of of Pb(II), Cd(II) and Cr(III) on adsorbent which was produced by protected-crosslinking of humic acid-chitosan has been done. The Langmuir-Hinshelwood, pseudo first- and second-order kinetics models were used to describe the kinetic data, and the rate constants of adsorption were also evaluated. The experimental data fitted well the second-order kinetics model, indicating that the chemical sorption is the rate-limiting step, instead of mass transfer. The initial metal ion concentration significantly affects the adsorption rate. An increase in initial metal ion concentration results in the decrease in adsorption rate of the metals.   Keywords: kinetics, adsorption, crosslinking, humic acid, chitosan

Voltage-Switchable HCl Transporters: The Effect of Lipid Headgroup Binding

2019 ◽  
Author(s):  
Xin Wu ◽  
Jennifer Small ◽  
Alessio Cataldo ◽  
Anne Withecombe ◽  
Peter Turner ◽  
...  
Keyword(s):  
Anion Binding ◽  
Transport Systems ◽  
Transport Mechanisms ◽  
Artificial Membrane ◽  
Ph Gradients ◽  
New Approach ◽  
Anion Transporters ◽  
Anti Cancer ◽  
Voltage Dependent ◽  
Membrane Transport Systems

Synthetic anion transporters that facilitate transmembrane H<sup>+</sup>/Cl<sup>-</sup>symport (cotransport)have anti-cancer potential due to their ability to neutralize pH gradients and inhibit autophagy in cells. However, compared to the natural product prodigiosin, synthetic anion transporters have low-to-modest H<sup>+</sup>/Cl<sup>-</sup>symportactivity and their mechanism of action remains less well understood. We here report a chloride-selective tetraurea macrocycle that has a record-high H<sup>+</sup>/Cl<sup>-</sup>symportactivity similar to prodigiosin and most importantly demonstrates unprecedented voltage-switchable transport properties that is linked to the lack of uniport activity. By studying anion binding affinity and transport mechanisms of four other anion transporters, we show that the lack of uniport and the voltage-dependent H<sup>+</sup>/Cl<sup>-</sup>symport originate from strong binding to lipid phosphate headgroup that hampers the diffusion of the free transporters through the membranes, leading to an unusual H<sup>+</sup>/Cl<sup>-</sup>symport mechanism that involves only charged species. Our work provides important mechanistic insights into different classes of anion transporters and a new approach to achieve voltage-switchability in artificial membrane transport systems.

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