Designing Centrifugal Membrane Filters with uniform-pressure for UF/NF/RO separations

Abstract

A novel Ortho-Centrifugal Membrane Filter (O-CMF) was designed and assessed to tackle common issues in conventional laboratory centrifugal membrane filters, e.g. non-uniform transmembrane pressure and concentration polarization, and to ease membrane replacement. The O-CMF, manufactured by additive 3D printing in acrylonitrile butadiene styrene, with membrane area of 0.95 cm2, was designed to process a maximum liquid sample of 9 mL. It was tested with nanofiltration of aqueous solutions of NaCl, MgSO4, and lactose (concentrations of 1–20 g/L) at transmembrane pressures of 6–24 bar. Complementary Computational Fluid Dynamics (CFD) simulations, employing a custom solver from the open-source OpenFOAM-2306 c++ toolbox, were also run to seek insight of the O-CMF main features.The permeation experiments displayed minimal impact of concentration polarization. CFD simulations showed that concentration polarization is nearly uniform and that concentrate chamber is homogenized by centrifugal convection. The CFD permeate flux predictions, based on the osmotic pressure model, closely matched experimental data, and a correlation for predicting concentration polarization was also developed.The O-CMF device represents a substantial breakthrough in the technology of centrifugal membrane filters, consistently maintaining uniform transmembrane pressure and effectively minimizing concentration polarization. The device was evaluated using nanofiltration, but its pressure range is versatile enough to cover conditions suitable for both ultrafiltration and reverse osmosis operations. This adaptability extends its application across a variety of laboratory experiments, including sample concentration, hydraulic permeability tests, and membrane screening.