Comparative Study of CO₂ Dissolution in Aqueous Media for Applications in Bioelectrochemical Systems

In alignment with the Sustainable Development Goals (SDG 13: Climate Action and SDG 7: Affordable and Clean Energy), the urgent need to mitigate the high atmospheric level of carbon dioxide (CO₂) has lead research toward sustainable carbon capture and utilization technologies. Bioelectrochemical systems (BESs), especially microbial electrosynthesis (MES), have emerged as promising technology for converting CO₂ into value-added products with the assistance of the electroactive microbial metabolisms. However, the efficiency of MES remains constrained by the inherently low solubility and limited mass transfer of CO₂ in aqueous systems, which minimizes the availability of CO2 for microbial uptake and conversion. This study investigates the CO₂ dissolution behavior in various aqueous media—deionized (DI) water, reverse osmosis (RO) water, tap water, phosphate-buffered saline (PBS), PBS with anode additives, and microbial growth media including acetogen and sulfate-reducing bacteria formulations. Carbon dioxide (CO₂) dissolution was observed through changes of pH and conductivity to examine dissolution efficiency and media stability. Based on results achieved, this study highlights DI and RO water enhances CO₂ uptake but lack of buffering leads to pH stability, while PBS-based medium not only offers superior pH stability but also effectively support CO₂ dissolution, making them more suitable for long-term operation in microbial electrosynthesis systems. These findings provide crucial insights for selecting optimal aqueous environments to enhance CO₂ dissolution and support the design of more robust, efficient MES systems for future carbon-neutral technologies.