A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, including the steps of contacting the gas stream with an aqueous composition including a substituted heteroaromatic compound having a six-membered heteroaromatic ring with from 1 to 3 nitrogen atoms in the heteroaromatic ring and at least one substituent wherein at least one of the substituents is of formula R.sup.1NH.sub.2 wherein R.sup.1 is selected from C.sub.1 to C.sub.6 alkylene and ethers of formula R.sup.2OR.sup.3 wherein R.sup.2 and R.sup.3 are C.sub.1 to C.sub.3 alkylene.

The invention provides a process for regenerating a liquid absorbent, comprising: contacting the liquid absorbent with a hydrophobic medium, wherein the liquid absorbent comprises at least one amine of Formula (I) and degradation product thereof comprising at least one imine of Formula (II), wherein each Ar is independently an aromatic group and each R is independently selected from hydrogen, an organyl group and NH.sub.2; and selectively extracting the degradation product into or through the hydrophobic medium.

##STR00001##

A redox flow acid-gas capture system includes an electrochemical cell including a cathode configured to contact a stream including an electroactive species in an inactive state and provide a reduced stream including the electroactive species in an active state, and an anode configured to contact an adduct stream including an adduct of an electroactive species and an acid-gas and provide an oxidized stream including the electroactive species in the inactive state and the acid-gas; an absorber configured to contact the reduced stream and the acid-gas and form the adduct stream including the adduct of the electroactive species and the acid-gas; and at least one of an oxygen stripper unit, or a degasser unit configured to provide a degassed stream including the electroactive species in an inactive state, and an acid-gas stream.