Gas permeability and permselectivity properties of ethylene vinyl acetate/sepiolite mixed matrix membranes

• Ethylene vinyl acetate (EVA)/sepiolite mixed matrix membranes were prepared.
• Surface modification of sepiolite established hydrogen bonding with EVA.
• Mechanical properties were enhanced as a result of hydrogen bonding.
• Permeability, CO2/CH4, and CO2/N2 selectivity improved by sepiolite addition.
• O2/N2 selectivity values did not change after the addition of sepiolite.

Ethylene vinyl acetate (EVA) mixed matrix membranes (MMMs) were prepared by incorporating fibrous sepiolite modified by 3-aminopropyltrimethoxysilane (3-APTMS). Gas transport through the prepared MMMs was investigated in detail. Permeabilities of O2, CO2, CH4, and N2, gases were significantly increased by the addition of 3 wt.% of sepiolite. At the same sepiolite loading, the CO2/CH4 and CO2/N2 selectivity of the MMMs at 5 bar were respectively enhanced by 9% and 28.2%, while the O2/N2 selectivity did not notably change and their values remained nearly constant around 2.5–3. The enhanced permeation was attributed to the decreased crystallinity percentage, confirmed by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC). Moreover, XRD results and microscopic images demonstrated that sepiolite fibers were uniformly dispersed in the EVA matrix due to the presence of hydrogen bonding between amino groups of modified sepiolite and carbonyl groups of EVA. Also, upon the incorporation of 3 wt.% sepiolite, the tensile strength and elongation at break were simultaneously enhanced by 46% and 76%, respectively.