Evaluation of the Global S-Entropy Production in Membrane Transport of Aqueous Solutions of Hydrochloric Acid and Ammonia

Abstract

The results of experimental studies of volume osmotic fluxes (Jvkr) and fluxes of dissolved substances (Jkr) in a system containing a synthetic Nephrophan® membrane (Orwo VEB Filmfabrik, Wolfen, Germany) set in a horizontal plane are presented. The membrane separated water and aqueous HCl or ammonia solutions or aqueous ammonia and HCl solutions. It was found that for the homogeneity conditions of the solutions Jvk and Jk depend only on the concentration and composition of the solutions. For concentration polarization conditions (where concentration boundary layers are created on both sides), Jvkr and Jkr depend on both the concentration and composition of the solutions and the configuration of the membrane system. The obtained results of the Jvk and Jk flux studies were used to assess the global production of entropy for the conditions of homogeneity of solutions (ΦSk), while Jvkr and Jkr—to assess the global production of entropy for concentration polarization conditions (ΦSkr). In addition, the diffusion-convective effects and the convection effect in the global source of entropy were calculated. The concentration polarization coefficient ζir was related to modified concentration Rayleigh number, e.g., the parameter controlling the transition from non-convective (diffusive) to convective state. This number acts as a switch between two states of the concentration field: convective (with a higher entropy source value) and non-convective (with a lower entropy source value). The operation of this switch indicates the regulatory role of earthly gravity in relation to membrane transport.

Management of Energy Conversion Processes in Membrane Systems

“…For the conditions of the polarization of concentration solutions, the creation of CBLs l r l and l r h reduces J v to J r v and J sk to J r sk [36]. In polarization concentration conditions, the volume flux (J r v ) and solute fluxes (J r sk ) depend on the configuration of the membrane system and the concentration characteristics of J r v and J r k are nonlinear [36,40]. These volume and solute fluxes can be described by the Kedem-Katchalsky equations for ternary solutions of non-electrolytes and the conditions of concentration polarization:…”

“…Dividing both sides of this equation by A, we obtain the equation for the conditions of concentration polarization[25] U = A −1 dU r /dt-internal energy flux (U-energy), Φ r F = A −1 dF r /dt-free energy flux (F-energy), Φ r S = TA −1 d i S r /dt is the dissipated energy flux (function of energy dissipation per unit area) (S-energy) and Φ r S = T(ϕ r S ) K r . If the solutions contain a solvent and two dissolved substances, then the global source of entropy for the concentration polarization conditions denoted by (ϕ r S ) K r is described by the equation[40] (ϕ r S ) K r = (ϕ r S ) J r v + (ϕ r S ) J r s1 + (ϕ r S ) J r s2 = 1 T J r v (∆P − ∆π 1 − ∆π 2 ) +…”

Modelling of the Electrical Membrane Potential for Concentration Polarization Conditions

“…Both biological and synthetic membranes are sensitive to changes in the physicochemical properties of the environment [ 1 , 2 , 3 , 4 ]. Therefore, membrane transport of its solution components can be governed by local fields (such as concentration, temperature, electric potential, or pressure fields) and global fields (such as gravitational or electromagnetic fields) [ 1 , 5 ].…”

“…The term concentration polarization is also used to describe the phenomena accompanying the formation of concentration boundary layers (CBLs) in both electrolyte and non-electrolyte solutions [ 3 , 4 , 7 , 8 , 9 , 15 , 16 , 17 ]. The effect of concentration polarization is to reduce membrane transport [ 7 , 8 , 9 , 16 , 17 ].…”

“…The effect of this field is natural convection, which modifies the concentration fields in the membrane regions [ 7 , 15 ]. Its consequence is a partial restoration of concentration gradients across the membrane and increased membrane transport [ 3 , 16 , 17 ]. One of the effects of changing the concentration field are gravitational effects in passive osmotic and diffusive transport [ 1 , 18 , 19 ] and the gravielectric effect [ 16 ].…”