Innovative dual-function system for efficient CO2 absorption and utilization: Local humidity swing fabric and microalgae-embedded hydrogel

Abstract

In this study, we explored the use of local humidity swing (LHS) adsorption technology for carbon dioxide (CO2) capture from air, leveraging its low energy consumption and cost-effectiveness. By employing a coating technique, we immobilized ion exchange resin (IER) particles on fabrics with different hydrophilicities. The coating, consisting of silk fibroin (silk) and glycerol, formed a thin membrane on the fabric surface, effectively immobilizing the IER particles. The results revealed that hydrophobic polyester fabric with an initial silk concentration of 2 wt% (2 %SF/Gly@IER-PF) exhibited superior CO2 adsorption capacity (11.07 ml/g at 10 % relative humidity) and stability at varying humidities (10–90 %) compared to the hydrophilic cotton fabric. By covering the 2 %SF/Gly@IER-PF with a hydrophilic, highly water-absorbing non-woven fabric, one-way moisture transfer between the two types of fabrics was made, significantly affecting the water content and the release of adsorbed CO2 within the SF/Gly@IER-PF, and CO2 adsorption/desorption cycles could be achieved by detaching and attaching the water-absorbing fabric from the 2 %SF/Gly@IER-PF. The SF/Gly@IER-PF-based LHS system was combined with a silk/alginate composite hydrogel containing live microalgae, forming a dual-function CO2 fixation system. The functionalized fabric efficiently captured CO2 from the air, which was subsequently utilized by the gel-immobilized microalgae. As a result, the microalgae showed a higher proliferation rate compared to the control hydrogel system without the attachment of SF/Gly@IER-PF. This demonstrates the potential application of the dual-function system in effectively reducing CO2 levels from the air.