Cellulose membranes with polyethylenimine-modified graphene oxide and zinc ions for promoted gas separation

Cellulose-based mixed-matrix membranes containing polyethylenimine-modified graphene oxide (PEI-GO) and Zn²⁺ ions were fabricated and used for gas separation. The incorporation of PEI-GO effectively hinders the crystallinity of regenerated cellulose, and PEI-GO was compatible with cellulose matrix and uniformly distributed within the matrix. X-ray photoelectron spectrum revealed the amino group on GO surface can effectively coordinate with Zn²⁺ ions in the membrane. The Zn²⁺ ions content in the membranes increased when increasing the PEI-GO addition. The optimum separation performance was achieved over the membrane with 17 wt‰ PEI-GO (RC-17) wiht the highest zinc content of 24.2 wt%. The corresponding permeability of CO₂ is as high as 268.9 Barrer, and the CO₂/N₂ and CO₂/CH₄ ideal selectivities could reach 48.9 and 57.4, respectively. The enhancement of CO₂ transportation was attributed to both the regulated microstructure of cellulose membrane by PEI-GO and the π-complexation mechanism of Zn²⁺ ions with CO₂ molecules. The prepared membranes would have a highly potential use in the field of CO₂ separation.