The Effect of Solute Concentration in Feed and Operating Pressure on Reverse Osmosis Concentration of Aqueous Methanol and 1-Butanol Solutions

Reverse osmosis concentration of aqueous methanol and 1-butanol solutions was carried out using cellulose acetate asymmetrical membrane and composite membranes (PEC-1000, FT-30 and NS-100). PEC-1000 showed the best solute separation. Membrane constants were evaluated, assuming that the membrane transport is expressed by the Spiegler-Kedem transport model. Reflection coefficients decreased with increasing solute concentration in the feed. Dependences of the solute and hydraulic permeabilities calculated on operating pressure and solute concentration in the feed can be explained well by the existence of two types of compaction phenomenon. That is to say, the increase in solute permeability with increasing operating pressure can be explained by the decrease in active layer thickness induced by operating pressure, and the decrease in permeabilities with increasing the solute concentration in the feed can be explained by shrinking of polymer matrix of the active layer caused by decrease in swelling pressure of the membrane.