A chemical reaction engineering model has been constructed to describe the extraction and recovery of bromine from a once-through seawater flow. The process uses a closed-loop circulation flow of air. This strips out free bromine from pre-chlorinated seawater in a packed column. Bromine liberated into the gas reacts with injected sulfur dioxide around a circulation loop to form liquid droplets containing product hydrobromic acid captured by mist elimination. Excesses of chlorine and sulfur dioxide compete for bromine and can reduce the recovery efficiency. Pseudo-homogeneous gas-phase kinetics accounts for simultaneous absorption and gas-liquid reaction of liberated bromine, excess chlorine, and injected sulfur dioxide. Re-circulating sulfur dioxide subsequently absorbs and reacts simultaneously with bromine and chlorine stripping. Parameter values are deduced for typical bromine recovery of 70%. The model can be used for optimizing the excesses of chlorine and sulfur dioxide.