Supercritical CO2–EtOH expanded liquid processing to produce tailored PEEK-WC membranes

Abstract

Supercritical CO₂ expanded ethanol is used to induce a phase separation process for one-step preparation of porous skinless membranes from a modified poly(etheretherketone). The process takes the advantage of the flexibility of the procedure that is also timesaving and greener than traditional phase separation methods. Skin-less membranes with modular structures have been obtained, combining different processing parameters, including SC-expanded liquid composition, polymer concentration, temperature and pressure. Kinetics and thermodynamics that control the phase separation have been analyzed in relation to diffusivity and solvent power of the SC-expanded liquid. Combining the different processing parameters, open structures with high void volume fraction and high degree of interconnectivity have been obtained, as confirmed by a very low resistance to mass transfer. Nitrogen fluxes up to 350 L cm⁻² min⁻¹ have been measured through membranes prepared at 250 bar, 35 °C, and 10% w/w.