Forward Osmosis Membrane Concentration of Raw Sugarcane Juice

Abstract

Conventional thermal evaporation and pressure driven process that is reverse osmosis are widely used to concentrate liquid foods, but they are highly energy intensive and expensive. Forward osmosis which is promising membrane process is extensively studied as an alternative process to concentrate liquid foods. This paper focuses on comparison of thermally concentrated and forward osmosis membrane processes to concentrate sugarcane juice. Forward osmosis (FO) stands next in cutting edge membrane technology to concentrate the sugarcane juice to syrup. The difference in osmotic pressure across the membrane is the driving force for FO, wherein the water from sugarcane juice is transferred to the other side that is to draw solution through the membrane at atmospheric pressure and ambient temperature. The effect of various operating conditions on transmembrane flux for different concentrations of draw solution and the effect of flow rate were studied. At optimum operating conditions, maximum transmembrane flux was determined as 0.79 L/m2 h. The sodium chloride (draw solution) transferred to feed solution was found to be 179.3 ppm which was determined using flame photometer. In the large scale experiment, the sugarcane juice was concentrated from 17.6 to 31.7 °Brix (twofold). Forward osmosis membrane offers energy efficient methods for concentrating raw sugarcane juice when compared to energy intensive evaporative methods. Further, improved FO membrane technologies and new draw solutions will improve the performance of the membrane process.