SEMIBATCH RECOVERY OF POLYVINYL-ALCOHOL FROM AQUEOUS-SOLUTION BY ULTRAFILTRATION

Recovery of polyvinyl alcohol (PVA) by ultrafiltration (UF) from aqueo us solution is investigated. Semi-batch experiments were conducted to examine the performance characteristics of the UF membranes of the hyd rophilic and hydrophobic types and of different pore sizes. The perfor mances of those membrane were compared using several characteristic pa rameters of the ultrafiltration process. The experimental results have indicated that the ultrafiltration performances of different membrane s can not be easily judged by a single characteristic parameter alone. Instead, characteristic parameters of different context must be consi dered simultaneously. In terms of overall performances, the hydrophili c membranes are found to be superior to the hydrophobic types for the present application. The UF membrane of a lower molecular weight cut-o ff (MWCO) is definitely a better choice than that of higher MWCO. The effects of operating pressure, temperature and mixer speed on the ultr afiltration performances were also explored. Reduction of the pollutio n strength of the permeate in terms of chemical oxygen demand (COD) wa s also considered.