Impact of pulsed electric field on electrodialysis process performance and membrane fouling during consecutive demineralization of a model salt solution containing a high magnesium/calcium ratio

How physico-chemical and surface properties of cation-exchange membrane affect membrane scaling and electroconvective vortices: Influence on performance of electrodialysis with pulsed electric field

“…This current density is higher than limiting current density [8] and was chosen in order to explore a possible scaling mitigation when water splitting and current-induced convection occurred and to compare our results with those reported by CifuentesAraya et al [5,23]. The model salt solution was composed of Na 2 CO 3 (1000 mg/L), KCl (800 mg/L), CaCl 2 (800 mg/L) and MgCl 2 (452 mg/L) in order to maintain a Mg/Ca ratio of 2/5 [10]: this ratio is twice as much compared to that in milk [24] to ensure membrane scaling formation [5,10,23]. The model salt solution was prepared immediately before the beginning of ED process.…”

“…The pH of concentrate solution was maintained constant (pH = 12) during all ED process by manual addition of NaOH (1 M). The ED treatments were stopped after the maximum voltage capacity of the power supply was reached (62.5 V) [5]. To evaluate the influence of the CEM physico-chemical characteristics, two different lots of CMX-SB membranes were tested (CMX-SB-1 and -2).…”

“…Concerning ED performances, better demineralization rates were obtained when Ca 2+ compounds were almost suppressed and scaling was composed mostly of Mg 2+ compounds [8]. Additionally to PEF modes and Mg/Ca ratio, water splitting and OH − leakage were reported as main phenomena affecting membrane scaling formation during ED [5]. Despite of thorough investigations of scaling formation mechanisms, there are two factors, which have been not considered yet in studies: 1) the influence of intrinsic properties of ion-exchange membranes (IEMs) and 2) the influence of electroconvection.…”

“…The application of nonstationary electric current regimes such as pulsed electric field (PEF) was successful in diminishing CP phenomena [4]. Moreover, recent studies revealed reasonableness of using PEF to prevent the formation of scaling [5], organic [6] and protein fouling [7] on membrane surface. More recently, Mikhaylin et al [8] demonstrated that the application of short pulse/pause lapses limits the amount of scaling formed on the cation-exchange membrane (CEM) and completely suppresses scaling on the anion-exchange membrane (AEM).…”

“…In systems containing mineral salts, the main agents contaminating the membrane surface are usually salts of Ca 2+ and Mg 2+ [8,9]. The precipitation of certain type of Ca 2+ and Mg 2+ based compounds depends on the Mg/Ca ratio [10][11][12] and the pulse/pause lapse ratio of applied PEF [5]. Concerning ED performances, better demineralization rates were obtained when Ca 2+ compounds were almost suppressed and scaling was composed mostly of Mg 2+ compounds [8].…”