Ultrafiltration of reconstituted skim milk in hollow fibers and plate-frame modules

Ultrafiltration was carried out using hollow fiber Fresenius F 60 module and Sartorius plate-frame laboratory ultrafiltration unit. Experiments were performed at constant concentration and in batch UF mode. Skim milk powder containing 33.4% total protein and 0.31% NPN was reconstituted in distilled water. The effect of transmembrane pressure, temperature, feed flow rate and reconstituted skim milk concentration on flux was investigated. With the increase of transmembrane pressure, flux of reconstituted skim milk powder by ultrafiltration steadily increased by all investigated temperatures (20, 40 55 degrees C) and all inlet flow rates. The difference in this effect among samples of various concentrations (8, 10 and 12% TS) was more expressed by lower temperatures, what could be ascribed to the more intense effect of higher RSM viscosity. The dependence of flux from temperature result in straight line, by all inlet flow rates and skim milk concentrations. By constant transmembrane pressure better flux was obtained by higher pH values of reconstituted skim milk (RSM). The experimental data are correlated satisfactorily by the Leveque's equation Sh = (Re Sc d/L)(003).