Improvement of dead-end filtration of biopolymers with pressure electrofiltration

Solid/liquid separation of biopolymers such as polysaccharides and proteins is still a problem not solved sufficiently on a technical scale. The main objective of the presented work was to set up a process strategy in order to improve the recovery of biopolymers by dead-end filtration. One aspect was the investigation of the influence of the pH value, ionic strength and pressure on the filtration kinetics of the dead-end filtration of the polysaccharide xanthan. pH value and ionic strength have an impact on the hydrodynamic radius and the zeta potential of biopolymers, and thus they have an impact on the filter cake structure and the filtration kinetics. The main focus was set on the enhancement of the filtrate flux by an electric field. This process, called pressure electrofiltration, leads to a drastic improvement of the filtration kinetics. The filtration time was thereby reduced from the range of hours down to minutes. Additionally another strategy was followed up, which aimed at an improvement of the specific filter cake resistance by changing process parameters like the pH and the ionic strength. These parameters influence the polymer-polymer and the polymer-water interactions and thus have an influence on the filter cake properties. Due to the great acceleration of the filtration kinetics the pressure electrofiltration serves as an interesting alternative to the cross-flow filtration and the precipitation with alcohol for the separation of biopolymers. (C) 2003 Elsevier Ltd. All rights reserved.