1985 Volume 10 Issue 6 Pages 371-379
Reverse osmotic separation of aqueous urea solutions was carried out using cellulose acetate membranes and composite membranes : PEC-1000, NS-100 and FT-30. Separation of urea and flux through the membranes were measured within the following ranges : concentration; 1 to 10 wt%, operating pressures ; 3.92 to 6.86 MPa.
PEC-1000 membrane shows the best performance among the membranes tested. Its separation at 1 wt% and 5.5MPa was 91%. At the same experimental condition, separation of FT-30 BW was 59%, FT-30 SW 65%, NS-100 75% and cellulose acetate heat treated at 90°C 66%, at 87°C 50%, and at 85°C 43%.
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, concentration induced compaction coefficients for ω and Lp, βs and βv. Values of σ for composite membranes PEC-1000 and NS-100 are 1.0 but for FT-30 and cellulose acetate less than 1.0. PEC-1000 shows the largest value of βs, then FT-30, NS-100 and cellulose acetate shows the smallest. FT-30 shows the largest value of βv, then PEC-1000, cellulose acetate and NS-100.
Concentrations of main components in RO permeate were calculated, assuming that PEC-1000 membrane were used to treat one crew man's waste water in space station. Two stages of reverse osmosis units is still needed to recover drinkable water.
