scholarly journals Thermo-osmosis in Membrane Systems: A Review

2017 ◽  
Vol 42 (3) ◽  
Author(s):  
V. María Barragán ◽  
Signe Kjelstrup
Keyword(s):  
Waste Heat ◽  
Osmotic Coefficients ◽  
Membrane System ◽  
Electrolyte Solutions ◽  
Volume Transport ◽  
Experimental Program ◽  
Pure Liquid ◽  
Hydraulic Permeability ◽  
Hydrophilic Membranes ◽  
Entropy Of Adsorption

AbstractWe give a first review of experimental results for a phenomenon little explored in the literature, namely thermal osmosis or thermo-osmosis. Such systems are now getting increased attention because of their ability to use waste heat for separation purposes. We show that this volume transport of a solution or a pure liquid caused by a temperature difference across a membrane can be understood as a property of the membrane system, i. e. the membrane with its adjacent solutions. We present experimental values found in the literature of thermo-osmotic coefficients of neutral and hydrophobic as well as charged and hydrophilic membranes, with water and other permeant fluids as well as electrolyte solutions. We propose that the coefficient can be qualitatively explained by a formula that contains the entropy of adsorption of permeant into the membrane, the hydraulic permeability, and a factor that depends on the interface resistance to heat transfer. A variation in the entropy of adsorption with hydrophobic/hydrophilic membranes and structure breaking/structure making cations could then explain the sign of the permeant flux. Systematic experiments in the field are lacking and we propose an experimental program to mend this situation.

scholarly journals Simulation of S-Entropy Production during the Transport of Non-Electrolyte Solutions in the Double-Membrane System

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 463
Author(s):  
Andrzej Ślęzak ◽  
Wioletta M. Bajdur ◽  
Kornelia M. Batko ◽  
Radomir Šcurek
Keyword(s):  
Entropy Production ◽  
Transport Theory ◽  
Membrane System ◽  
Electrolyte Solutions ◽  
Solute Flux ◽  
Initial Moment ◽  
Hydraulic Permeability ◽  
Transport Parameters ◽  
Double Membrane ◽  
Solute Permeability

Using the classical Kedem–Katchalsky’ membrane transport theory, a mathematical model was developed and the original concentration volume flux (Jv), solute flux (Js) characteristics, and S-entropy production by Jv, ( ( ψ S ) J v ) and by Js ( ( ψ S ) J s ) in a double-membrane system were simulated. In this system, M1 and Mr membranes separated the l, m, and r compartments containing homogeneous solutions of one non-electrolytic substance. The compartment m consists of the infinitesimal layer of solution and its volume fulfills the condition Vm → 0. The volume of compartments l and r fulfills the condition Vl = Vr → ∞. At the initial moment, the concentrations of the solution in the cell satisfy the condition Cl < Cm < Cr. Based on this model, for fixed values of transport parameters of membranes (i.e., the reflection (σl, σr), hydraulic permeability (Lpl, Lpr), and solute permeability (ωl, ωr) coefficients), the original dependencies Cm = f(Cl − Cr), Jv = f(Cl − Cr), Js = f(Cl − Cr), ( Ψ S ) J v = f(Cl − Cr), ( Ψ S ) J s = f(Cl − Cr), Rv = f(Cl − Cr), and Rs = f(Cl − Cr) were calculated. Each of the obtained features was specially arranged as a pair of parabola, hyperbola, or other complex curves.

scholarly journals Electro-Osmotic Behavior of Polymeric Cation-Exchange Membranes in Ethanol-Water Solutions

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 692
Author(s):  
V. María Barragán ◽  
Juan P. G. Villaluenga ◽  
Víctor Morales-Villarejo ◽  
M. Amparo Izquierdo-Gil
Keyword(s):  
Cation Exchange ◽  
Streaming Potential ◽  
Membrane System ◽  
Electrolyte Solutions ◽  
Joule Effect ◽  
Potential Coefficient ◽  
Water Solutions ◽  
Onsager Reciprocity ◽  
Ethanol Content ◽  
Reciprocity Relations

The aim of this work is to apply linear non-equilibrium thermodynamics to study the electrokinetic properties of three cation-exchange membranes of different structures in ethanol-water electrolyte solutions. To this end, liquid uptake and electro-osmotic permeability were estimated with potassium chloride ethanol-water solutions with different ethanol proportions as solvent. Current–voltage curves were also measured for each membrane system to estimate the energy dissipation due to the Joule effect. Considering the Onsager reciprocity relations, the streaming potential coefficient was discussed in terms of ethanol content of the solutions and the membrane structure. The results showed that more porous heterogeneous membrane presented lower values of liquid uptake and streaming potential coefficient with increasing ethanol content. Denser homogeneous membrane showed higher values for both, solvent uptake and streaming coefficient for intermediate content of ethanol.

scholarly journals The Role of Gravity in the Evolution of the Concentration Field in the Electrochemical Membrane Cell

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 680 ◽  
Author(s):  
Kornelia M. Batko ◽  
Andrzej Ślęzak ◽  
Wioletta M. Bajdur
Keyword(s):  
Boundary Layers ◽  
Concentration Polarization ◽  
Concentration Field ◽  
Membrane System ◽  
Volume Transport ◽  
Cellulose Acetate Membrane ◽  
Concentration Boundary ◽  
Concentration Boundary Layers ◽  
Mechanical Stirring

The subject of the study was the osmotic volume transport of aqueous CuSO4 and/or ethanol solutions through a selective cellulose acetate membrane (Nephrophan). The effect of concentration of solution components, concentration polarization of solutions and configuration of the membrane system on the value of the volume osmotic flux ( J v i r ) in a single-membrane system in which the polymer membrane located in the horizontal plane was examined. The investigations were carried out under mechanical stirring conditions of the solutions and after it was turned off. Based on the obtained measurement results J v i r , the effects of concentration polarization, convection polarization, asymmetry and amplification of the volume osmotic flux and the thickness of the concentration boundary layers were calculated. Osmotic entropy production was also calculated for solution homogeneity and concentration polarization conditions. Using the thickness of the concentration boundary layers, critical values of the Rayleigh concentration number ( R C r ), i.e., the switch, were estimated between two states: convective (with higher J v i r ) and non-convective (with lower J v i r ). The operation of this switch indicates the regulatory role of earthly gravity in relation to membrane transport.

Thermodynamics of electrolyte solutions: activity coefficients of NaCl in the NaCl–NiCl2–H2O system at 25, 35, and 45 °C

1990 ◽  
Vol 68 (2) ◽  
pp. 294-297 ◽  
Author(s):  
Ch. Venkateswarlu ◽  
J. Ananthaswamy
Keyword(s):  
Activity Coefficients ◽  
Silver Chloride ◽  
Osmotic Coefficients ◽  
Reference Electrode ◽  
Nickel Chloride ◽  
Electrolyte Solutions ◽  
Pitzer Formalism ◽  
Harned Coefficients ◽  
Silver Silver ◽  
Silver Silver Chloride

The activity coefficients of NaCl in the NaCl–NiCl2–H2O system were estimated at 25, 35, and 45 °C and total ionic strengths of 0.5, 1.0, 2.0, and 3.0 m by an EMF method using a Na-ion selective electrode and a silver–silver chloride reference electrode. The Harned coefficients were calculated at all the temperatures studied. At 25 °C the data were analysed using the Pitzer formalism. The osmotic coefficients and the excess free energies of mixing were also calculated at 25 °C. Keywords: activity coefficients, sodium chloride, nickel chloride, Pitzer equations, thermodynamics.

Application of a Chemical Thermodynamic Model to the Gibbs Free Energy of Aqueous Electrolyte Solutions. New Equations for the Activity and Osmotic Coefficients

1991 ◽  
Vol 44 (9) ◽  
pp. 1195
Author(s):  
JV Leyendekkers
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Short Range ◽  
Van Der Waals ◽  
Osmotic Coefficients ◽  
Electrolyte Solutions ◽  
Solute Concentration ◽  
Volume Effect ◽  
Chemical Thermodynamic ◽  
Short Range Repulsion

The chemical thermodynamic (CT) model, based on the extended Tait equation, has been applied to the Gibbs free energy of aqueous solutions of sodium chloride and potassium chloride at 25°C. Equations for the activity and osmotic coefficients were derived. These are made up of the Debye-Huckel limiting slope term, a van der Waals co-volume effect term covering short-range repulsion, a term covering the water compression by the solute and a short-range attractive term. The distance of closest approach derived from the model is the same as that expected for the van der Waals effect. The individual components of the partial molal free energy, that is, the effects of solute concentration on the water and solute respectively, have been calculated.

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