Flux Decline by Formation of Gel-layer in Reverse Osmosis

Abstract

Permeabilities of some polymer solutions in a reverse osmosis process have been examined by using cellulose acetate membrane. The separation degree of each polymer solute was more than 99%, and the solution flux (Jv) was apparently lower than the pure water flux (Jw)The order of JvjJ, was obtained and the polymers were classified into the following three types according to the relationship between Jv/Jw and the polymer concentration:
In the case of type (1), Jv/Jw depended on the polymer concentration, and a polymer gellayer was formed upon the membrane. In the case of type (2), Jv/Jw as about 0.8 and did not show any significant dependence on the polymer concentration. In the case of type (3), the gel-layer was formed little and Jv/Jw as nearly equal to 1.0, although the viscosities of the solutions were very high.
The formation of gel-l ayer was assumed to control the flux, and it was found that the hydrophobic polymer formed gel-layer more easily; Jv of MC or PVP solution increased by the addition of sodium dodecylsulfate. Based on these facts, it was assumed that the hydrophobic bond between the polymer solute and cellulose acetate membrane had an influence on the formation of gel-layer.