Formation and Characterization of Cellulose Membranes from N-Methylmorpholine-N-oxide Solution

Regenerated cellulose membranes have been traditionally manufactured using the viscose or the copper-ammonia process. Today, membranes made by this process are still used in many fields such as dialysis. However, there are some serious environmental problems inherent in the existing processing routes. The new N-methylmorpholine-N-oxide (NMMO) process can overcome these disadvantages and provides membranes with improved mechanical properties. In the present work, cellulose membranes were successfully prepared from NMMO solution under various conditions. It was found that the cellulose concentration is a decisive factor in controlling the membrane permeation properties. For a given coagulation system, higher cellulose concentration leads to membranes with greater rejection of bovine serum albumin (BSA) and lower pure water flux. It was also found that both the degree of polymerization (DP) and the type of cellulose pulp have great effect on the morphology and permeation properties of the membrane support layer. With increasing NMMO concentration and temperature of the coagulation bath, the pure water flux increases while the rejection of BSA decreases; a result of the larger mean pore size formed during coagulation.