Capturing a target gas includes contacting a gas mixture including a target species with an aqueous solution including a buffer species, and transferring some of the target species from the gas mixture to the aqueous solution. The target species forms a dissolved target species in the aqueous solution, and the aqueous solution is processed to yield a first aqueous stream and a second aqueous stream, where the equilibrium partial pressure of the target species over the second aqueous stream exceeds the equilibrium partial pressure of the target species over the first aqueous stream. At least some of the dissolved target species in the second aqueous stream is converted to the target species, and the target species is liberated from the second aqueous stream. The target species can be collected and/or compressed for subsequent processing or use.