Recyclable bio-based polylactic acid gas-liquid membrane contactor for carbon capture process

Abstract

The need for sustainable and carbon-neutral technologies is growing due to ambitious climate goals and the depletion of non-renewable resources. Carbon capture and utilization (CCU) is emerging as a key approach to closing the carbon cycle, with membrane-based CO₂ absorption reducing energy demands during the capture process. However, conventional membranes rely on fossil-based polymers and toxic solvents, raising concerns about their environmental impact. This study introduces a bio-based membrane contactor for CCU applications, utilizing polylactic acid (PLA), a renewable and sustainable biopolymer. The influence of polymer concentration, molecular weight, crystallinity, solvent type, and recycling on membrane morphology and CO₂ capture performance was investigated. The PLA membranes exhibited asymmetric morphologies ranging from finger-like to sponge-like structures. Higher polymer concentration and molecular weight increased sponge-like morphology, while solvents with stronger solvating power promoted finger-like structures. Interestingly, initial polymer crystallinity did not influence membrane morphology, but crystallinity induced during synthesis supported sponge-like structures. Membranes made with high molecular weight PLA and wide finger-like morphologies demonstrated stable CO₂ capture performance (2.36 × 10^-⁵ m³/m²·s), comparable to commercial PVDF membranes (2.47 × 10^-⁵ m³/m²·s). Furthermore, recycled membranes retained CO₂ capture performance over five cycles (2.04 – 2.26 × 10^-⁵ m³/m²·s). This study highlights the potential of bio-based membranes to enable energy-efficient and circular CO₂ capture, taking significant steps toward greener, more sustainable CCU technologies.