Precise sulfonation degree control enables high-performance SPEEK membranes for energy-efficient air dehumidification

Membrane dehumidification provides an energy-efficient alternative to conventional methods (e.g., condensation and adsorption), addressing high energy consumption and operational limitations of traditional technologies for selective water vapor removal. This study engineered sulfonated poly(ether ether ketone) (SPEEK) membranes with precisely tunable sulfonation degrees (DS = 45%-75%) by optimizing reaction time, temperature, and sulfuric acid concentration. Systematic evaluation revealed that increasing DS significantly enhances membrane hydrophilicity by promoting the formation of interconnected ionic clusters, as validated by spectroscopic and morphological analyses. The SPEEK membrane with DS = 75% achieved a peak dehumidification efficiency of 52.4% and water vapor permeability of 1.61 × 10 −5  kg m −2  s −1 , outperforming the DS = 45% membrane by 10.5% in efficiency. Performance was further optimized under operational conditions of 0.2 MPa pressure and 27 °C temperature gradient, which mitigated concentration polarization. These results demonstrate that DS-controlled SPEEK membranes offer a scalable, energy-saving solution for industrial gas dehumidification, with potential applications in air conditioning, pharmaceutical manufacturing, and microelectronics processing.