Performance evaluation of sucrose concentration using forward osmosis

Concentrating sugar solutions is a common process used in the production of many food products for either dewatering a high value product or concentrating waste streams prior to disposal. Thermal and pressure-driven dewatering methods are widely used, but they are prohibitively energy intensive and hence, expensive. Osmotically driven membrane processes, like forward osmosis, may be a viable and sustainable alternative to these current technologies. Using NaCl as a surrogate draw solution, this investigation shows that forward osmosis processes can lead to sucrose concentration factors that far exceed current pressure-driven membrane technologies, such as reverse osmosis. For instance, a concentration factor of 5.7 was achieved by forward osmosis with a starting sucrose concentration of 0.29 M, compared to reported concentration factors of up to 2.5 with reverse osmosis. Water fluxes were found to be lower than those commonly obtained in reverse osmosis, which is a consequence of the significantly higher concentration factors in conjunction with internal concentration polarization. The latter is a common problem in forward osmosis processes that utilize current generation anisotropic polymeric membranes. Further advances in forward osmosis membrane technology would yield higher water fluxes and concentration factors.