Ｎ，Ｎ‐ジメチルホルムアミド水溶液の逆浸透濃縮

Abstract

Reverse osmotic concentration of aqueous N, N-dimethylformamide solutions was carried out, using cellulose acetate asymmetric membrane and composite membranes (PEC-1000, NS-100 and FT-30). Separation of N, N-dimethylformamide and flux through the membrane were measured within the following ranges : concentrations ; 1-10 wt %, operating pressure ; 3.29-6.86 MPa.PEC-1000 membrane shows the best performance among the membranes tested. Its separation for every condition was above 98.5% and was 99.2% at 5wt%, 5MPa. At the same experimental condition, separation of FT-30 BW was 88%, FT-30 SW 73%, NS-100 p1700 94%, NS-100 p3500 96%, cellulose acetate heat treated at 90°C 73%, 87°C 65% and 85°C 60%.An analysis of data with Spiegler-Kedem's transport model was carried out to obtain membrane constants such as reflection coefficient σ, solute and hydraulic permeabilities ω and Lp, and solute induced compaction coefficients for ω and Lp, βs and βv. Values of σ for composite membrane are 1.0. FT-30 shows the largest value of βv and solute v and cellulose acetate membranes are the smallest.Energy and membrane area required using best membrane PEC-1000 were calculated to concentrate N, N-dimethylformamide from 0.5w% to 10.5wt% by reverse osmosis. The energy per one kilogram of concentrated N, N-dimethylformamide is proportional to operating pressure and slightly depends on final concentration and concentration polarization and is found 0.3 to 0.7 kWh/kg-DMF. The membrane area is inversely proportional to the operating pressure and found 0.65 [m3/kg-DMF/day] for 5MPa, at no concentration polarization.