An experimental study on the characteristics of bulk nanobubbles generated by CO2 hydrate dissociation

Bulk nanobubble is an extraordinary type of bubbles and has been widely used in various fields. Nevertheless, the characteristics of bulk nanobubbles generated by hydrate dissociation are still unclear. In this paper, we conducted a series of experiments to investigate the physicochemical characteristics and stability of bulk nanobubbles generated by CO2 hydrate dissociation. The results show that the dissociation of CO2 hydrate can generate stable bulk nanobubbles, which can exist in solution for a long period of time compared with ordinary bubbles. The interfaces of bulk nanobubbles in pure water showed a stronger electronegative property, suggesting the formation of an electric double layer around the nanobubbles. The nanobubble size increased with the rising of temperature and salt ion concentration, while decreased with the increase of pH value. For the absolute value of nanobubble Zeta potential, an inverse relationship with temperature, salt ion concentration, and pH value can be observed. The nanobubbles containing solution made the hydrate induction time significantly shortened and promoted the reformation of hydrates. Our findings would be helpful to thoroughly understand the characteristics of nanobubbles dissociation by the CO2 hydrate.