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Protein Fouling of Microfiltration Membranes in in-Line Modules

Dharmesh Kanani and Raja Ghosh. Chemical Engineering, McMaster University, 1280, Main Street West, Hamilton, ON L8S 4L7, Canada

In-line microfiltration membranes have found many applications in the biotech industry: ranging from sterilization of biological fluids to sample preparation for chromatography. The most appealing feature of these in-line (or syringe-type) filters is their disposable nature which facilitates ease of operation. Generally, syringe-type filters are used in a pseudo-constant flux mode, in which one would try to maintain a constant flow through the syringe filter by applying the needed pressure. Capacity or volumetric throughput of such a device is limited by fouling which causes the required transmembrane pressure (TMP) to increase significantly making it difficult to sustain the filtration process. Filtration through syringe-type holders is normally considered as dead-end filtration, and these processes are carried out at quite high fluxes. There have been very few systematic studies on fouling of microfiltration membranes by protein in the dead-end mode. These studies were generally carried out at constant pressure and the experimental data was modelled using blocking laws. The current work addresses the fouling of microfiltration membranes by proteins in syringe-type filter holders at very high fluxes, similar to those in syringe type of filtration applications. Fouling was studied using a pulsed injection technique, which allowed the measurement of membrane resistance before and after protein injection in a single experiment without the need for dismantling the membrane module. TMP time profiles were obtained for at different operating conditions. Part of the increase in membrane resistance due to protein fouling/deposition was found to be reversible even though the rejection of protein was negligible (indicating the absence of concentration polarization). The results obtained suggest that the reversibility was due to loosely held protein molecules on the membrane. Experimental data also seem to suggest the compressible nature of the deposited protein layer.