Effect of shear rate on the performance of nanofiltration membrane for water desalination

Abstract

Asymmetric nanofiltration membranes were fabricated from a ternary dope composition consisting of cellulose acetate (CA), formamide and acetone using a simple drylwet phase inversion process. In order to fabricate a high performance nanofiltration membrane, the effects of rheological factor of dope solutions, that is shear rate on the performance of nanof~tration membranes for water desalination has been studied. The membranes performances that are based on percentage of rejection of sodium chloride (NaCl) and fluxes with different concentrations of sodium chloride are reported. Generally, the percentage of rejection and fluxes were found to increase with increasing of shear rate until a critical level of shear rate is achieved. The experimental results showed that the fluxes were increased and percentage of rejection is decreased With sodium chloride concentrations. An optimum percentage of rejection and fluxes obtained were about 56.76 % and 7.44 x lo4 ds, respectively. The optimum shear rate was found to be at 304 s'l. It was also found that membranes with shear rate below 152s" are not suitable to be used as a nanofiltration membrane due to their low mechanical strength.