Polyvinyl alcohol recovery by ultrafiltration: effects of membrane type and operating conditions

Recovery of polyvinyl alcohol (PVA) by ultrafiltration (UF) from simulated desizing wastewater is investigated. Batch experiments were conducted to examine the performance characteristics of the OF membranes of the hydrophilic and hydrophobic types and of different pore sizes. The performances of those membranes were compared using several characteristic parameters of the ultrafiltration process. The experimental results have indicated that the ultrafiltration performances of different membranes are not be easily judged by a single characteristic parameter alone. Instead, several characteristic parameters must be considered simultaneously. In the context of overall performances, the hydrophilic membranes are found to be superior to the hydrophobic types. The OF membrane of a lower molecular weight cut-off (MWCO) is definitely a better choice than that of a higher MWCO. The effects of operating pressure, temperature and mixer speed on the ultrafiltration performances were also explored. Reduction of the pollution strength of the permeate in terins of chemical oxygen demand (COD) was also considered.