Diffusivity\nAnalysis of Liquid CO<sub>2</sub> and\nSaltwater under Deep Sea Conditions with the Dynamic Pendant Droplet\nVolume Analysis Method

Ocean already absorbed almost a third of global CO<sub>2</sub> emissions\nand offers huge CO<sub>2</sub> storage potential for widely deployed\nCCUS projects. Injecting and dispersing CO<sub>2</sub> in deep seawater\nis regarded as a promising method for accelerating the ocean sequestration\nprocess. The diffusion coefficient of CO<sub>2</sub> into deep seawater\nis of great value for determining the storage capacity. However, the\ncharacteristics of CO<sub>2</sub> diffusing into deep seawater are\nrarely studied. In this study, the diffusion coefficients of liquid\nCO<sub>2</sub> and seawater were measured using the dynamic pendant\ndroplet volume analysis (DPDVA) method under 5–20 °C temperature,\n6–20 MPa pressure and 3–4 wt % salinity. The results\nindicate that the diffusion coefficient increases with temperature\nand pressure and decreases with salinity. A total of 180 data points\nwere obtained in this study, of which 147 were deemed valid, with\nan experimental error of less than 6%. The range of diffusion coefficients\nwas found to be 3.53 × 10<sup>–10</sup>–7.36 ×\n10<sup>–10</sup> m<sup>2</sup>/s. This study is expected to\nfill the gap in the field of diffusion coefficient studies between\nliquid CO<sub>2</sub> and brine and support the assessment of CO<sub>2</sub> ocean storage capacity.