Removal of hardness by electrodialysis using homogeneous and heterogeneous ion exchange membranes

Abstract

A B S T R A C TThe effect of membrane characteristics on removal of hardness ions from its dilute solutions using electrodialysis (ED) system by applying batch recirculation mode has been investigated. Two types of membrane pairs were used. Type I: Ionac MC3470 and MA3475 (Sybron Chem. Co.); Type II: Neosepta CMX and Neosepta AMX (Astom Corp.). These membranes have different ionic permselectivity, electrical resistance and thickness. In the first part of the study, the effects of the feed concentration, dilute flow rate and dilute pH on the hardness removal were investigated using Type I membranes. The optimum values for feed concentration, flow rate and pH were determined as 0.01 M, 2.6 mL/ s and 6.8, respectively. In the second part, the experiments were conducted at different voltage values using Type II membranes under the optimum conditions of these variables obtained. The 95% removal of Mg 2+ with the energy consumption of 2.07 kWh/mol and 93% removal of Ca 2+ with the energy consumption of 2.12 kWh/mol were obtained in 200 min, applying 20 V potential using Type I membranes. On the other hand, the 100% removal of Mg 2+ was achieved by the energy consumption of 1.69 kWh/mol in only 60 min. and the removal of Ca 2+ was 98.3% with the energy consumption of 3.39 kWh/mol in 170 min. applying 20 V and using Type II membranes. The results obtained from this study showed that the membrane characteristics affect the efficiency of the ED significantly.

Ionic Mobility in Ion-Exchange Membranes

“…In this case, the issue of separation of mono- and divalent ions is becoming more and more important [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. For example, membrane separation of lithium and magnesium or cobalt ions [ 43 , 44 , 45 , 46 , 47 ] and the removal of magnesium/calcium [ 48 , 49 , 50 , 51 ] have attracted increasing attention. On the contrary, membranes in fuel cells are usually in single ionic form (H + or OH − -form) and contact only with humidified gases or methanol.…”

Bench-Scale and Pilot-Scale Treatment Technologies for the Removal of Total Dissolved Solids from Coal Mine Water: A Review

“…mobility of the transported ions divided by the sum of mobilities of all ions in solution), exchange capacities, and thickness of the cation-and anion-exchange membranes, along with applied voltage, feed flowrate, current density, operational mode, temperature, and time (El Midaoui et al 2002;Sirivedhin et al 2004). Karabacakoglu et al (2015) found 95-100 % Mg 2? removal and 93-98 % Ca 2?…”

Studies on Removal of ions and preparation of NaOCl from the industrial RO reject water by electrodialysis

“…[19][20][21][22][23][24][25][26][27][28][29][30] The main advantage of electrodialysis is that it can be operated out at room temperature and atmospheric pressure. [31][32][33][34][35][36][37] Electrodialysis coupled with RO system can be most effective for high level of water purification.…”