Molecular (osmotic and electro-osmotic) backwash of cellulose acetate hyperfiltration membranes

A technique using osmosis and/or electro-osmosis was developed to clean and possibly decompact contaminated modified (asymmetric)cellulose acetate membranes. p]The rejuvenation technique developed is called “molecular backwash”. When contaminated with ferric hydroxide, the membranes (cured at 92°C) exhibited considerable flux decrease. After molecular backwashing, the hyperfiltration flux increased again. In some cases, molecular backwash also partially restored the salt rejection loss which had occurred during contamination. Flux loss recovered by molecular backwashing varied from 30% to over 100% (i.e. the flux of the compacted membrane was greater than before contamination, but not greater than the flux of a clean uncompacted membrane).