Pilot-scale press electrofiltration of biopolymers

Performing dead-end filtration of biopolymer dispersions remains an industrial problem, especially for large-scale biopolymer recovery and purification. Usually, alternative filtration processes such as cross-flow filtration is used for industrial scale biopolymer filtration. However, such filtration technology does not allow dewatering of the biopolymer dispersions up to high solids concentrations. Biopolymer solutions are usually highly viscous even at low concentrations which therefore complicates cross-flow filtration processes. Therefore, a significant need exists for a large-scale filtration technique which allows highly concentrated biopolymer dispersions to be dewatered. This work details the scaling-up of a pressurised dead-end membrane electrofiltration process to pilot-scale. This process has the potential to greatly improve the dewatering of biopolymer dispersions. In collaboration with an industrial filter plate manufacturer, a pilot-scale plate electrofilter was developed especially for biopolymer recovery. Within this filter an electric field is superimposed on a conventional pressurised filtration process. Thereby, on one of the two membranes, of the two-sided filter chamber, only a thin surface layer is formed, while on the opposite membrane, the charged biopolymers are deposited by electrophoretic migration.Additional to the construction and initial operation of the pilot press electrofiltration plant, the process is optimised and the influence of process parameters such as electric field strength and pressure were investigated. Using this pilot-scale electrofilter plate, filtration time could be reduced by greater than 90%, compared to a conventional press filter for the case study of xanthan polysaccharide dewatering from an initial concentration of 5 g/l. The final xanthan concentration after press electrofiltration was 220 g/l. Furthermore, filtration fractionation processes can clearly be improved with respect to their selectivity. This is shown for the case study of the filtration of a binary biopolymer mixture consisting of xanthan polysaccharide and bovine serum albumin (BSA) protein.