Preparation of biomass-based gas separation membranes from biochar residue obtained by depolymerization of lignin with ZSM-5 to promote a circular bioeconomy.

Reuse of biochar residues after lignin degradation will not only save costs but also reduce the pollution, protect and improve the environment. In this study, biochar residue (BR) after peanut shell lignin selective depolymerization on ZSM-5 were recycled, and characterized by Scanning Electron Microscopy, Surface area & pore size distribution analyzers, Thermogravimetric Analysis. Subsequently, a series of hybrid matrix membranes were prepared using ethyl cellulose as the matrix and biochar residue after depolymerization under different reaction conditions as the filler. The separation performance of BR/EC membranes for CO ₂ /CH ₄ mixed gas and CO ₂ /N ₂ mixed gas was measured. The results showed that the gas separation membranes prepared with biochar residue (3 h, 300 °C) as filler had good gas separation characteristics. The resulting mixed-matrix membrane exhibited a permeability of 66.00 Barrer for CO ₂ and selectivities of 9.97 for CO ₂ /CH ₄ . Meanwhile, the resulting mixed-matrix membrane exhibited a permeability of 79.53 Barrer for CO ₂ and selectivities of 20.01 for CO ₂ /N ₂ . Both exceed the upper limit of known pure EC membranes. Therefore, the use of biochar residue after ZSM-5 depolymerization as a filler for gas separation membranes is a feasible way. Furthermore, the membrane is well stabilized, proving its good potential for industrial applications.
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