3D printed nanofiltration composite membranes with reduced concentration polarisation

Abstract

3D printed nanofiltration (NF) composite membranes with surface patterns minimising the impact of concentration polarisation (CP) are presented here for the first time. The membranes consist 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 Reynold number ( Re ) of 700, using a range of dyes (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 the 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. • Fabrication via 3D printing of NF composite membranes with surface wavy patterns. • Wavy composite membranes had a PWP of 14 ± 2 LMH bar − 1 and a MWCO of ∼550 Da. • Concentration polarisation was assessed by filtration of a Congo red solution. • The wavy structure led to a 57% lower CP and triple mass transfer coefficient. • Shear stress over the wavy structure is an order of magnitude higher than the flat one.