Cellulose interactions with CO₂ in NaOH(aq): The (un)expected coagulation creates potential in cellulose technology

Upon the search for a suitable processing method for cellulose, the dissolution in NaOH(aq) presents a real green potential, including its ability to sorb environmental CO₂(g) affecting dissolution. Here, CO₂(g) was delivered in a controlled way to the cellulose/NaOH(aq) system during the in-situ analysis with FTIR, pH and temperature meters, resulting in efficient coagulation of cellulose. Surprisingly, the coagulation occurred with a minimal loss of alkalinity. This was considered an effect of a specific interaction between the dissolved polymer and gas, resulting in the introduction of carbonate species, highly influential in the coagulation process. The process repeated at 25 °C and 5 °C suggested a strong influence of temperature. The conversion routes of the CO₂(g) coagulant were also related to the dissolved state of the polymer. The recovered cellulose appeared competitive with EtOH recovery in terms of structure. The presented finding put a perspective on the utilisation of both the coagulation process and final materials in cellulose technology.