Self-Reactive Carbon Dioxide Absorbent with Sodium Carbonate-Based Hydrogel

Sodium carbonate is an abundant, low-cost, and low-hazard raw material widely used as a food additive and CO₂ absorbent in the food industry. However, its application in food packaging is limited because it is used in solid form, either in sachets or as a compounding ingredient in plastics. Solid sodium carbonate requires an external moisture supply for CO₂ absorption, with its performance dependent on moisture availability. This limitation hinders its commercialization in food packaging applications. We developed a sodium carbonate-based, self-reactive CO₂ absorbent hydrogel incorporating polyacrylic acid sodium salt (PAAS). This sodium carbonate hydrogel (SCH-PAAS) exhibits self-reactivity, eliminating the need for external moisture, and demonstrates a high CO₂ absorption capacity. PAAS incorporation facilitates the formation of a porous structure during gel solidification through reactions with CO₂. Increased PAAS content accelerates CO₂ absorption rates, particularly under low-temperature conditions (10 °C and 25 °C). Notably, absorption was faster at 10 °C than at 25 °C. The proposed SCH-PAAS exhibits a significantly enhanced absorption performance at low temperatures compared to conventional sodium carbonate-based materials, which exhibit reduced efficiency under such conditions. The increased gas–liquid contact area in SCH-PAAS makes it highly suitable for fresh food packaging applications, particularly under low temperatures.