Microbubbles Loaded with Nickel Nanoparticles: A Perspective for Carbon Sequestration

This work reports a microfluidic study investigating the feasibility of accelerating gaseous carbon dioxide (CO₂) dissolution into a continuous aqueous phase with the use of metallic nickel (Ni) nanoparticles (NPs) under conditions specific to carbon sequestration in saline aquifers. The dissolution of CO₂ bubbles at different pH levels and salinities was studied to understand the effects that the intrinsic characteristics of brine in real reservoir conditions would have on CO₂ solubility. Results showed that an increased shrinkage of CO₂ bubbles occurred with higher basicity, while an increased expansion of CO₂ bubbles was observed with a proportional increase in salinity. To achieve acceleration of CO₂ dissolution in acidic brine containing high salinity content, the catalytic effect of Ni NPs was investigated by monitoring change in CO₂ bubble size at various Ni NPs concentrations. The optimal concentration for the Ni NPs suspension was determined to be 30 mg L^-1; increasing the concentration up to 30 mg L^-1 showed a significant increase in the dissolution of CO₂ bubbles, but increasing from 30 to 50 mg L^-1 displayed a decrease in catalytic potential, due to the decreased translational diffusion coefficient that occurs at higher concentrations. The optimal additive concentration of Ni NPs was tested with variations of solution at acidic and basic conditions and different levels of salinity to reveal how effectively the Ni NPs behave under real reservoir conditions. At the acidic level, Ni NPs proved to be more effective in catalyzing CO₂ dissolution and can sufficiently alleviate the negative impact of salinity in brine.