(342e) 3D Printed Nanofiltration Composite Membranes with Reduced Concentration Polarisation

Concentration polarisation (CP) occurs when non-interacting solutes build up near the membrane-feed interface, resulting in a higher solute concentration than that in the bulk solution. This build up can induce water flux decline, reduce quality of produced water, increase power consumption and operating costs in membrane-based water treatment, including reverse osmosis (RO) and nanofiltration (NF) processes. There is an extensive literature on methods to reduce the impact of CP through modification of the membranes’ surface chemistry, structure, or a combination of the two. However, these measures have shown limited success since they also negatively impact membrane flux and, moreover, the uncertainty around their long-term stability and scalability has resulted in their low uptake by industry. Therefore, there is intense interest in methods that would effectively reduce CP without negatively affecting permeance and ensuring stable performance over time.

Here, we present an innovative approach to minimising concentration polarisation using 3D printed nanofiltration (NF) composite membranes consisting of a NF polydopamine-coated polyvinylidene fluoride (PVDF/PDA) selective layer on a 3D printed asymmetric wavy (patterned) support. The result is a wavy composite membrane with pure water permeance of 14 ± 2 LMH bar^-1 and molecular weight cut-off of ~550 Da, measured using a crossflow NF setup at a transmembrane pressure of 2 bar for Reynolds number (Re) of 700, using a range of dyes (rejection > 95% and mass balance >97% for all tests). The CP behaviour of the composite membranes was assessed by filtration of Congo red (CR) dye solution (0.01 g L^−1), showing that the wavy pattern significantly reduced the impact of CP compared to flat membranes, with a nearly tripling of the mass transfer coefficient and a 57% decline of the CP factor. Computational fluid dynamics showed that these significant performance improvements were due to improved hydrodynamics, with the maximum surface shear stress induced by the wavy structure (1.35 Pa) an order of magnitude higher than that of the flat membranes (0.18 Pa) at Re = 700. These results demonstrate that 3D printing is a viable technology route to reducing concentration polarisation in membrane nanofiltration applications.

References:

- Mazinani, S. et al., 3D printed nanofiltration composite membranes with reduced concentration polarisation. J Membrane Sci – 2022, https://doi.org/https://doi.org/10.1016/j.memsci.2021.120137.

- Al-Shimmery, et al., 3D printed composite membranes with enhanced anti-fouling behaviour. J Membrane Sci – 2019, https://doi.org/https://doi.org/10.1016/j.memsci.2018.12.058,

- Mazinani, S., et al., 3D Printed Fouling-Resistant Composite Membranes. ACS Appl Mater Interf – 2019,. https://doi.org/https://doi.org/10.1021/acsami.9b07764.

- Low, Z.-X., et al., Perspective on 3D printing of separation membranes and comparison to related unconventional fabrication techniques. J Membrane Sci – 2017. https://doi.org/http://dx.doi.org/10.1016/j.memsci.2016.10.006.