1. Investigation Of Ion Facilitation Using Corrugated Membrane In Electrodialysis
Priyabrata Mandal, Priya Goel, Anusha Chandra, Dr. Sujay Chattopadhyay
Polymer and Process Engineering, IIT Roorkee Saharanpur Campus, Saharanpur, UP, India
Introduction: Electrodialysis (ED) process is a robust and efficient method for the selective removal of ionic species using charged membranes in the presence of electrical potential. The efficiency of ED process depends on nature of polar membranes, flow hydrodynamics of electrolytes, concentration polarization. Fluid flow through non-conducting spacers are caused pressure drop besides creating shadow effect of the electric field exposed to the ions in bulk. To avoid this shadow effect corrugation membranes are promoted. Fluid flows over corrugated polar membrane surface create turbulence.
The shape, dimension, size (square, rectangular semicircle, ellipse) and spacing between corrugations were systematically investigated and compared with netted spacer which is commonly used to find best corrugation for charged ions removal. All different size geometry was simulated using COMSOL to find their influence on ion separation. In present investigation, mathematical model based on Nernst-Planck equations, continuity, mass balance equations were framed and solved using COMSOL Multiphysics ( version 5.1) to understand the flow and concentration profile within ED cell.
Results:
Figure 2. Adaptive mesh sizes and its configurations at different location
in the obstructed flow channel obtained using the three predefined
configurations ( Coarse, Normal, Fine) available in COMSOL.
Figure 3. Fluid flow profile inside ED channel with (a) netted spacer
geometry, (b) square corrugation, (c) rectangular corrugation,
(d) semicircle corrugation, (e) elliptical corrugation.
Conclusions: In ED ion removal efficiency is purely depends on the fluid flow profile. Corrugated membrane having different geometry shape would facilitate better mixing of fluid layers and reduces diffusion boundary layer thickness. Selected corrugated membranes performed better at low velocities and became ineffective at higher velocities.
References:
Jogi Ganesh Dattatreya Tadimeti, Varghese Kurian, Anusha Chandra, Sujay Chattopadhyay, Corrugated membrane surfaces for effective ion transport in electrodialysis, JMS, 499, (2016).
G.A. Fimbres-Weihs, D.E. Wiley, Review of 3D CFD modeling of flow and mass transfer in narrow spacer-filled channels in membrane modules, Chem. Eng. Process. Process Intensif. 49, (2010).
Figure 1. Different types of membrane flow channels selected for analysis.
Property
Variable
Value
Density
rho
1 kg/m3
Dynamic viscosity mu
0.001 pa·s
Table 1. Basic input properties with value