Elucidating CO2 nanobubble interfacial reactivity and impacts on water chemistry.

Abstract Hypothesis Carbon dioxide nanobubbles can increase effective gas-transfer to solution and enhance buffering capacity given the stable suspension in water of CO2 gas within nanobubbles and the existence of larger gas/water interface. Experiments The physico-chemical properties and responses of CO2 nanobubbles were recorded at different generation times (10, 30, 50, and 70 min) and benchmarked against traditional macrobubbles of CO2 for the same amount of delivered gas. Effective concentration of CO2 was evaluated by measuring the buffer capacity (β). The size distribution of nanobubbles during the experiments was measured by Nanoparticle Track Analysis. Findings The mass transfer coefficient (KLa) showed a dramatically increase by 11-fold for the same volume of gas delivered when using nanobubbles. The β values obtained for nanobubbles were 7 times higher than that of traditional bubbles which can lead to significant source of CO2 availability by using the nanobubble method. Nanobubbles, consequently, undergo mass loss at higher pH corresponding to mass transfer process due to concentration gradient at the surrounding nanobubbles. This is the first report of CO2 nanobubbles buffer capacity evaluation.