ULTRAFILTRATION FLUX AND REJECTION CHARACTERISTICS OF BLACK LIQUOR AND POLYETHYLENE GLYCOL

Comparative experimental studies were carried oul on ultrafiltration with black liquor, and polyethylene glycol as a standard molecule, using an asymmetric membrane in a stirred batch cell. Effects of pressure, concentration, and stirrer speed were studied on flux and salute rejection characteristics for both the solutes.

The experimental results were analysed using the osmotic pressure limitation model to account for concentration polarization. It was found that, apart from the rise in osmotic pressure with pressure and concentration, there was a uniform rise in the polarization layer resistance (R_p) with membrane surface concentration (c_m). The results were correlated by the equation:

where ∝ and βt are constants. The membrane was characterized by determining the solution permeability (P_m) and reflection coefficient (a). The value of a was found to be close to unity—a representative value for high rejection membranes.