Electrochemical Properties of Ultrafiltration and Nanofiltration Membranes in Solutions of Sodium and Calcium Chloride

Abstract

Ultrafiltration and nanofiltration membranes that are traditionally used in baromembrane processes have become increasingly frequently applied in electromembrane and baroelectromembrane processes. In the latter case, two driving forces, an electric field and a pressure gradient, are simultaneously used. This study presents data on the specific electrical conductivity, diffusion permeability, and transport numbers of ions as well as current-voltage characteristics and chronopotentiograms of AMN-P and OPMN-P weakly ionized nanofiltration membranes and a number of track membranes in solutions of NaCl and CaCl 2. The relationship of obtained characteristics with the structure and exchange capacity of membranes is discussed. It is shown that both nanofiltration and track membranes can exhibit a quite high selectivity towards the electrical transport of ions with a certain charge sign. Such selectivity is especially high in respect of the transport of Ca 2+ ions. In the case of an AMN-P membrane, the transport number of Ca 2+ reaches 0.98, while it is noticeably lower for Na + ions. This result correlates well with a known fact about a higher rejection coefficient of doubly charged ions in comparison with singly charged ions in baromembrane processes. Track membrane #115 is also distinguished by high selectivity in respect of cations, the transport number of sodium ions in it is close to 0.96.

Structural Characterization and Physicochemical Properties of Functionally Porous Proton-Exchange Membrane Based on PVDF-SPA Graft Copolymers

“…Figure 10 presents the counterion transport numbers in these membranes. We measured the characteristics of the CJMC-4 in this study; the data for other commercial membranes are taken from the literature: Nafion® 117 [ 79 ], MF-4SK [ 63 ], TEM#811 track-etched membrane [ 62 ], and CJMC-3 [ 38 ].…”

“… Concentration dependences of the electrical conductivity κ* ( a ) and integral diffusion permeability coefficient P ( b ) of the membranes: PEM-RCF, Nafion® 117 [ 79 ], MF-4SK [ 63 ], TEM#811 [ 62 ], CJMC-3 [ 38 ], and CJMC-4 in NaCl solutions; if the data were taken from a reference, it is indicated. The solid lines are guides for the eye.…”

Pore Filled Ion-Conducting Materials Based on Track-Etched Membranes and Sulfonated Polystyrene

“…Despite the above, the original track membrane has a conductivity of about 0.1 mS/cm, apparently due to the transfer of protons formed as a result of the dissociation of carboxyl groups along the water sorbed on the surface of the tracks. The described features distinguish the studied track-etched membrane from a similar material based on polyethylene terephthalate, which has a high ionic conductivity in salt solutions [24]. Apparently, this difference is associated with the chemical properties of polymers; unlike polyvinylidene fluoride, polyethylene terephthalate, when etched, gives a high content of carboxyl groups on the track surface.…”

Application of Hybrid Electrobaromembrane Process for Selective Recovery of Lithium from Cobalt- and Nickel-Containing Leaching Solutions

“… * The results are presented in Ref. [ 30 ] for sample #811. ** Estimated by scanning electron microscopy (SEM); *** estimated by hydraulic permeability.…”