Carbon dioxide absorption in 0.6 M piperazine (PZ)/4 M methyldiethanolamine (MDEA) was measured in a wetted wall contactor. The data were simulated using a model that accounts for chemical reactions and transport effects with the eddy diffusivity theory. PZ/MDEA blends absorb CO2 faster than monoethanolamine (MEA) or diethanolamine (DEA) blends with MDEA at similar concentrations. The reaction of PZ to form a monocarbamate is dominant at low loading (<0.14). The reaction of the monocarbamate to form dicarbamate is dominant at high loading. The absorption rate did not follow pseudo first-order behavior except at very low loading. All carbamate and dicarbamate formation reactions approached instantaneous behavior at high loading. The series resistance due to pseudo first-order reaction and instantaneous carbamate formation matched data throughout the entire loading range. A typical ammonia plant absorber was simulated at isothermal conditions using the rigorous model. Gas film limitations were dominant (>50%) only at the top of the absorber.