Enhancing Gas Separation Performance of Polyvinyl Alcohol Membranes through Cyclodextrin-Based Additives: An Experimental Study on Permeability and Selectivity Analysis

Polyvinyl alcohol (PVA)-based membranes modified with cyclodextrins (CDs) and rotaxanes were developed to overcome the permeability-selectivity trade-off in gas separation. This study demonstrates that α-CD incorporation (۲–۱۰ wt%) in PVA significantly enhances CO₂/CH₄ selectivity (up to ۲,۸۹۸) and CO₂ permeability (۵۷.۸ Barrer), attributed to the molecular sieving effect of α-CD’s cavity diameter of ۴.۷–۵.۳ Å, as supported by kinetic diameter alignment. Illustrating the classic trade-off, increasing α-CD content from ۲% to ۱۰% boosted selectivity from ۲۸۹ to ۲,۸۹۸, while permeability decreased from ۵۷.۸ to ۲۸.۹۸ Barrer (a permeance drop from ۰.۴۸ to ۰.۲۴ GPU). In contrast, γ-CD-modified membranes achieve exceptional O₂/N₂ selectivity (۱,۱۰۸) due to their larger cavity diameter ۷.۵–۸.۵ (Å), while rotaxane nanotubes create non-selective transport pathways, yielding ultrahigh N₂ permeability (۵۶.۰۳ Barrer) but inverted O₂/N₂ selectivity (۰.۲۳). The distinct transport mechanisms—solution-diffusion dominance in CD-PVA systems versus pore-flow in rotaxane-modified membranes—were validated through permeation tests and structural characterization. α-CD membranes show promise for biogas upgrading (CO₂/CH₄ selectivity >۲,۸۰۰), whereas γ-CD variants excel in oxygen enrichment. Rotaxane-modified membranes enable high-flux applications like inert gas production. This work advances the design of tunable membrane materials by correlating additive topology (CD cavity size, rotaxane nanotubularity) with gas separation performance, offering pathways to address industrial challenges in CO₂ capture, O₂/N₂ separation, and hydrocarbon purification.

کلیدواژه ها:

Membrane ، Gas separation ، Polyvinyl Alcohol (PVA) ، Cyclodextrin (CD) ، CO۲ ، CO₂/CH₄ separation ، Molecular Sieving ، Permeability-selectivity analysis