<p>This study investigates the deoxidation rate of blister copper (Cu) using hydrogen (H₂) – argon (Ar) and H₂ gas bubbling. By introducing an H₂ – Ar mixed gas through a submerged lance, the deoxidation reaction occurs at the reaction interface during the rise of gas bubbles. Experiments were conducted at 1473&#xa0;K, with a total gas flow rate of 0.5 × 10⁻⁵ to 1.5 × 10⁻⁵ m³·s⁻¹ and an initial H₂ partial pressure of 0.2 to 1.0&#xa0;atm. The deoxidation rate equation of Cu melt was derived based on the two-film model, considering the mass transfer of dissolved oxygen (O) through the liquid boundary layer and the counter-diffusion of H₂ and H₂O through the gas boundary layer. Additionally, the change in the mass transfer resistances under different reaction conditions was analyzed to investigate the transition of the rate-controlling step. The derived model for the Cu deoxidation rate was validated against the experimental results and showed good agreement. The rate-controlling step successively changed from mass transfer in the gas boundary layer of H₂ to mixed-rate control phase and finally to a mass transfer of O in the liquid boundary layer. Under the conditions used in this study, a lower H₂ partial pressure increased deoxidation efficiency in the latter stage by promoting more complete H₂ consumption within individual bubbles.</p> Graphical Abstract <p></p>