A model-based analysis of electrodialysis fouling during pulsed electric field operation

Abstract

When electrodialysis (ED) is applied to process streams that are known to foul and scale the system, it can be operated with an oscillating electric field. This procedure is known as pulsed electric fields (PEF) and has been proven to reduce the fouling susceptibility of the system. In literature, the suppression of fouling is attributed to a combination of three effects: the reduction of concentration polarisation, the promotion of electroconvection and the suppression of water splitting. However, these effects have yet to be substantiated quantitatively. Here we study how much of the fouling suppression during PEF can be attributed to the reduction of concentration polarisation. A Nernst–Planck and Kedem–Katchalsky modelling approach is adopted to simulate the evolution of concentration profiles of a ternary solution of sodium, chloride and dodecyl sulfate (DS) during PEF. The effect of the pulse parameters on the boundary layer concentration of sodium dodecyl sulfate (SDS) is studied along with an evaluation of the current efficiency and energy consumption. Our results illustrate the counterproductivity of low-frequency pulses and the trade-off between the current efficiency and fouling suppression but fail to explain the improvement when compared to the constant current operation. Fouling layer relaxation is put forth to complement to previously mentioned fouling suppression effects and is relevant for future research.