Sizing agent recovery by membrane ultrafiltration in hollow-fiber modules

Ultrafiltration of an aqueous solution of polyvinyl alcohol was carried out in an Amicon model H1P30-20 hollow-fiber cartridge made of polysulfone. Fresh water was forced through the macroporous membrane, as the permeate, while polyvinyl alcohol was concentrated and recovered as the retentate. Correlation equations for calculating the permeate Aux of membrane ultrafiltration of the polyvinyl alcohol were derived based on the resistance-in-series and exponential models. Correlation results were confirmed by the experimental data, especially for the results obtained from the exponential model. It was found that the permeate flux increases as transmembrane pressure or fluid velocity increases, but decreases when feed concentration increases. Because membrane ultrafiltration is a pressure-driven process, high cross-flow velocity enhances the mass transfer coefficient of the solute and high solution concentration increases the thickness of the concentration polarization layer.