Highly permeable and mechanically robust silicon carbide hollow fiber membranes

• Silicon carbide hollow fibers with a 1.8 mm outer diameter.
• High bending strengths of 30–40 MPa.
• Exceptionally high clean water flux of 50,000 L m−2 h−1 at 1 bar pressure difference.
• Optimized two-step thermal treatment is a key factor to obtain mechanically robust fibers.

Silicon carbide (SiC) membranes have shown large potential for applications in water treatment. Being able to make these membranes in a hollow fiber geometry allows for higher surface-to-volume ratios. In this study, we present a thermal treatment procedure that is tuned to produce porous silicon carbide hollow fiber membranes with sufficient mechanical strength. Thermal treatments up to 1500 °C in either nitrogen or argon resulted in relatively strong fibers, that were still contaminated with residual carbon from the polymer binder. After treatment at a higher temperature of 1790 °C, the mechanical strength had decreased as a result of carbon removal, but after treatments at even higher temperature of 2075 °C the SiC-particles sinter together, resulting in fibers with mechanical strengths of 30–40 MPa and exceptionally high water permeabilities of 50,000 L m−2 h−1 bar−1. Combined with the unique chemical and thermal resistance of silicon carbide, these properties make the fibers suitable microfiltration membranes or as a membrane support for application under demanding conditions.

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