Breaking Mass-Transfer Limits with an Innovative Spacer Design for Ultrafast Water Desalination

The world faces a growing scarcity of freshwater resources. Desalination and wastewater reuse have therefore become essential pathways toward a sustainable water supply. Ultrapermeable reverse osmosis offers great promise for improving water production efficiency. However, their performance is hindered in spiral wound modules by inadequate boundary layer mass transfer, which leads to aggravated concentration polarization (CP) and membrane fouling, making module redesign essential. Herein we employ a high-fidelity three-dimensional multiphysics model to quantitatively and systematically evaluate the critical role of an innovative feed spacer design for ultrafast water desalination. The results indicate that the bioinspired spacer design breaks the mass transfer limits of conventional designs, significantly enhancing the boundary layer mass transfer coefficient by 121% compared to a commercial spacer, with only a 54% increase in the pressure loss. The innovative spacer can achieve to sustain an ultrahigh water flux of 245 L m^-2 h^-1 (lmh) with a CP below 1.25. In contrast, the commercial spacer exhibits a substantially lower water flux (139 lmh), higher CP (1.36) and thus elevates the risk of membrane fouling under identical conditions. This spacer design offers a pathway toward sustainable freshwater production via ultrafast desalination, addressing water scarcity with a lower-carbon footprint.