Modeling of gel layer transport during ultrafiltration of fruit juice with non-Newtonian fluid rheology

Abstract

The rheology of fruit juice mixtures generally follows non-Newtonian behavior of power law form. The clarification of fruit juices by membrane separation illustrates an example of enhancing the shelf life of a real fruit juice by removing degradable components. However, the presence of high molecular weight proteins, pectins, polysaccharides, fibers, etc., tends to form gel over the membrane during filtration causing fouling and affecting its performance. The proposed model developed from the first principle boundary layer analysis, describes the physical mass transport phenomena and quantifies the various extents of fouling using different membrane materials and operating conditions. The model results are useful in understanding the complex solute–membrane interplay in fouling and can predict the effect of gel layer thickness on the process throughput. In this work, the model results were validated experimentally in clarification of blood orange juice in batch mode using two polysulphone (PS) membranes and polyacrylonitrile (PAN) membrane in hollow fiber configuration, with different molecular-weight-cut-off (MWCO). The results clearly indicated that PS membranes are more prone to fouling at higher pressures compared to PAN membrane. An increase in the feed flow rate had a significant effect in reducing the growth of gel layer mainly in PS membranes.