Optimization of the evaporation step in cellulose acetate membranes preparation by dry-wet phase inversion technique for water desalination applications

In this study, cellulose acetate (CA) membranes were prepared by the dry-wet phase inversion technique for desalination application. The effect of evaporation time on the properties of the prepared cellulose acetate membrane has been investigated. Different evaporation time was selected such as (30, 60, 90 and 120 s). The membrane characterization was carried out by using Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), contact angle measurements. Brackish water was used as a feed solution in a cross flow unit to evaluate the membrane performance. The effect of the evaporation time on the membrane's water flux and salt rejection was tested. The results showed that the different evaporation time has affected the structure as deduced by the FTIR analysis. The SEM analysis showed the asymmetric CA membranes structure, where a thin dense selective barrier layer was deposited (in a finger-like structure) on the surface of the prepared membranes. As the evaporation time increased, the thickness of this layer has increased and the value of the contact angle has decreased. The highest rejection, obtained from the membrane that was prepared with the evaporation time 60 s, reached 96.5% salt rejection with a relatively low flux of 1.0234 L/m(2) h.