Systems and methods are described for selectively removing an acid gas from a feed stream to reduce co-absorption of CO2. The system can include an absorber configured to contact at least a portion of the feed stream with a caustic solution or other basic solvents to produce a clean stream substantially depleted of the acid gas. To reduce co-absorption of CO2 by the caustic solution to less than 10% of the CO2 present in the feed stream, the absorber can be further configured to receive a driver gas that is substantially non-reactive with the caustic solution.