Evaluation of electrodialysis for scaling prevention of nanofiltration membranes at high water recoveries

Electrodialytic removal of NaCl from water: Impacts of using pulsed electric potential on ion transport and water dissociation phenomena

“…The values for Stokes radius, ion equivalent conductivity, bulk diffusion coefficient and ion mobility that are found in the literature are often able to explain transport of the ions within aqueous mixtures but in many cases they fail to fully support the transport behaviours seen through dense membranes (i.e. nanofiltration and ion-exchange membranes) [31,151,154,160,232,233].…”

“…As a result, such ions have smaller hydration shells and thus larger Gibbs free energy, that holds the hydration shells to the ion, compared to the ions with bigger ionic radius [235]. In order to pass through the ion-exchange membrane, it has been hypothesised that an ion is required to be dehydrated, either partially or fully, from its hydration shells [151,160,161,233]. Therefore, in order for the separation to take place the energy of transport is required to be larger than the Gibbs free energy of hydration.…”

Diagnostics of the Structural and Transport Properties of an Anion-Exchange Membrane MA-40 after Use in Electrodialysis of Mineralized Natural Waters

“…The ratio of the scale-forming ions is an additional factor affecting scaling due to their competition during the migration from the compartment with a diluate to the compartment with a concentrate and due to the crossinfluence of different scalant ions on the formation and growth of crystals [7,8,10,11]. Comparing the scale formation on homogeneous and heterogeneous membranes and its prevention has been shown in [12][13][14]. It was found in [14] that a gypsum (CaSO 4 • 2H 2 O) scale mainly grows in the bulk of an MA-40 heterogeneous membrane, while in the case of an AMV homogeneous membrane, it mainly grows on the membrane surface facing the concentrate compartment.…”

Transport of arsenate through anion-exchange membranes in Donnan dialysis

“…Indeed, it has been recently found that sulphate anions have a remarkably high permeation rate through the FTAM membrane compared to that of nitrate and chloride [21]. However, if an arsenate contaminated drinking water source contains also sulphate (that is often the case in practice), the use of more hydrophilic membranes would probably not favor significantly the transport of any of them, since the Gibbs energies of hydration (at 25 1C) are very similar and equal to À744.6 kJ mol À 1 in the case of SO 4 2 À and to À 748.5 kJ mol À 1 and À 707.1 kJ mol À 1 for H 2 AsO 4 À and HAsO 4 2 À , respectively [22].…”