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Polytetrafluoroethylene (PTFE) porous membranes are widely used for high-temperature filtration.

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This study reveals the first attempt to apply PTFE hollow fiber membranes for removing ultrafine particles in PM2.5.

Membrane wetting is the main obstacle for carbon dioxide (CO2) capture on long-term operation. In order to understand wetting, polytetrafluoroethylene (PTFE) hollow fiber membranes were fabricated through paste extrusion, stretching, and sintering processes. CO2 capture performance over 180 days was performed. It indicates no obvious deterioration of CO2 flux over 180 days. Subsequently, further investigation was performed through immersion of PTFE hollow fiber membranes in different absorbent solutions. Results of Fourier transform infrared (FTIR) spectroscopy, energy-dispersive spectroscopy (EDS), and variations of membrane weight showed the PTFE polymer kept good stability in the absorbent solutions over 24 weeks. Scanning electron microscopy (SEM) images indicated the pore sizes of the PTFE hollow fiber membranes did not markedly enlarge during immersion, which was proved by pore size distributions. Contact angle measurements indicated no obvious reduction (8° reduction) in the membrane hydrophobicity over 24 weeks. Values of the contact angle relied on the surface tension values of the absorbent solutions. AFM images showed that immersion imposed a negative influence on the roughness values, which was the same order as the contact angle. The results suggested that none of the absorbent molecules entered the interior of the PTFE polymer. PTFE hollow fiber membranes may be a promising alternative for CO2 capture on long-term operation.

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The immobilization of photocatalysts is considered an effective approach to solve the problem of the difficult recycling of powdered nanocatalysts after photocatalytic degradation.