A three-dimensional model was investigated for the measurement of mass diffusivity of CO2 in pure water and different nanofluids including silicon oxide, aluminum oxide, and titanium oxide with concentrations of 0.05, 0.1, and 0.2 wt%.. Different parameters such as temperature and the weight percentage of nanoparticles on CO2 diffusivity were investigated in COMSOL software and CO2 diffusivity was compared with experimental results. The modeling results reported that water was saturated with gas at 36,000 seconds, and the highest amount of absorbed gas occurred at 0.32 m and the results were validated with experimental data.