The impact of thermodynamic potentials on the design of electrodialysis desalination plants. (1st February 2020) - Qasem, Naef A.A.
Highlights: The accuracy of 'lumped' model is further improved by considering all possible potentials. The model considers the boundary films, water transport through membranes, and the Donnan potential. The resistance due to boundary films is important for brackish water purification. Water transport is critical for improving ED design model for high salinities. Results are discussed in terms of important design and performance parameters. Abstract: Electrodialysis desalination (ED) is an efficient method to desalinate brackish water and to mitigate the salinity of high saline resources (>50 parts per thousand (ppt)). Many models were proposed to investigate ED systems; however, these models require detailed simulations. One of the simplest methods is a lumped model, which shows a reasonable and limited accuracy that can only be used for low salinities, i.e., brackish water (<8 ppt). In this paper, an improved lumped model is presented to tackle the salt separation by ED for a wide range of salinities (~200 ppt). Electrochemical equilibrium is implemented in a membrane interface to determine Donnan's potential and concentrations on the membrane surface based on membrane characteristics and bulk solution. The boundary film effect is then calculated based on the pre-calculated concentrations at the membrane and bulk solution. The spacer effect is also included which is important for the separation process in terms of area shading factor and channel porosity more than its contribution in cell pair resistance. Water transport through charged membranes is also considered. The modified model results show a substantial improvement in ED performance values. It could help researchers, engineers, and designers for the design and analysis of desalination plants.