Production of fructose sugar from aqueous solutions: nanofiltration performance and hydrodynamic analysis

Nanofiltration (NF) is a rapidly advancing membrane technique for concentration of sugar and multivalent salt solutions. The performance of indigenously synthesized functionalized polyamide (FPA) nanofiltration membranes of 150 and 250 molecular weight cut off (MWCO) was studied with respect to their ability to concentrate 2% (w/v) aqueous fructose with minimum losses of the sugar in permeate. Water flux and fructose retention properties of the NF membranes were compared to that of commercial reverse osmosis (RO) membranes. At an applied feed pressure of 10 bar, fructose rejection was found to be 94.14, 60.2 and 98.7% for FPA-150, FPA-250 and RO membranes, respectively. Hydrodynamic analysis was performed to study detailed fluid flow profile inside the membrane module to aid design of membrane systems. Economic estimation revealed that nanofiltration by FPA-150 membrane costs just 15.27% of that required by conventional evaporation for treating 1 m3/h fructose, owing to high flux combined with minimum sugar loss.