Evaluation of Electrodialysis Desalination Performance of Novel and Conventional Ion Exchange Membranes
It was revealed from relevant recent literature that the electrodialysis (ED) desalination performance of commercial and laboratory-made ion exchange membranes (IEMs) had been studied previously but not in a systematic way so that the planners, designers, and engineers can evaluate a trade-off in selecting the suitable IEMs and optimum ED experimental conditions for their desired outcomes such as high ion selectivity, high salinity removal, high water recovery, low energy consumption, or low water transport. Furthermore, the existing conventional and laboratory-made IEMs reported previously showed various technical and economical limitations with respect to permeability, permselectivity, ion selectivity, electrical resistance, stability (mechanical, chemical, and thermal), and production costs. Thus, this research was mainly focused on the systematic comparison of ED desalination performances of five well-known commercial IEMs and two newly developed IEMs (i.e., bio-inspired and polyethersulfone polymeric) under a set of well-controlled experimental conditions. The desalination performance of IEMs was evaluated by determining the key ED operational parameters such as the limiting current density (LCD), current efficiency (CE), salinity reduction (SR), normalized specific energy consumption (nSEC), osmotic water flux (oWF), individual ion concentration reduction rate, and relative ion transport ratio (divalent versus monovalent) as a function of feed solution concentration and composition, applied stack voltage, and velocity of feed solution. A laboratory-scale single stage ED stack was used with five cell-pairs of cationic and anionic membranes with an active cross-sectional area of 7.84 (2.8 x 2.8) cm2. A programmable power supply, pH/conductivity meter, mass balance, pressure gauges, and magnetic stirrers were used for the ED experimental setup. A supervisory control and data acquisition (SCADA) system was developed by VIEW 2017 for automatic recording of experimental data at five seconds intervals for diluate reservoir mass change, applied voltage and current, pH, temperature, and conductivity. Periodic samples were also collected from process streams (diluate and concentrate reservoirs) for post analysis using Ion Chromatography. The entire research work was divided into three projects. In first project, ED desalination performance difference between five commercial IEMs and a novel bioinspired cation exchange membrane (CEM) developed recently at Sandia National Laboratory was compared for synthetic sodium chloride (NaCl) feed solutions concentration of 1, 3, 10, 35, and 100 g/L, voltage application to ED stack of 0.4, 0.8, and 1.2 volts per cell pair, and superficial feed velocity of feed solution of 2, 4, and 8 cm/s. Sandia’s bioinspired CEM performed relatively well compared to the commercial membranes. The second project investigated the effects of key ED operational parameters on the desalination performance of five pairs of commercial IEMs used in the first project for brackish groundwater feed solutions (2.79 and 5.26 g/L TDS), 0.4 and 0.8 volts per cell pair stack voltage application, and 4 cm/s superficial feed velocity of feed solution. The membranes were ranked according to performance with respect to several figures of merit. The results of this work will be helpful for ED process optimization and performance analysis for the specific application and expected outcomes. In the third project, a set of novel nanocomposites polymeric CEMs was developed from a highly durable and relatively inexpensive material polyethersulfone (PES) and the influence of CEM’s microstructure, fabrication method, physiochemical properties of polymeric substances, nanofillers, and crosslinkers on ED desalination performance were evaluated. The results showed the potential of using sulfonated PES with graphene oxide (GO) nanofillers and polyvinylpyrrolidone (PVP) crosslinkers for fabricating CEMs using phase inversion methods.
Environmental engineering|Hydrologic sciences|Water Resources Management
Golam Hyder, A. H.M, "Evaluation of Electrodialysis Desalination Performance of Novel and Conventional Ion Exchange Membranes" (2021). ETD Collection for University of Texas, El Paso. AAI28715164.