Salts of the basic amino acid l-arginine are potential co-promoters and blending components for the conventional solvents used in carbon dioxide-based separations. This study defines the contribution of arginine salts to equilibrium carbon dioxide absorption at co-promoter concentrations (less than 1 M) and high pressure. Experimentally determined carbon dioxide loadings in aqueous potassium and sodium salt solutions of l-arginine show a positive relationship with pressure (range: 110–4110 kPa); but a negative behaviour with an increase in temperature (range: 303.15–363.15K) and solvents concentrations (range: 0.25–0.75 M). The experimental results are correlated by the Kent-Eisenberg and the explicit models, with an average absolute deviation of 10.72% and 5.03%, respectively. The regressed parameters of both models allow satisfactory estimation of the carbon dioxide loadings in arginine salt solutions at other process conditions. Comparison with piperazine and monoethanolamine shows that l-arginine salts have a better carbon dioxide absorption capacity at high pressure.