Absorbent aqueous composition containing a base and an azole for separating carbon dioxide from a gaseous effluent

An absorbent composition for absorbing the carbon dioxide contained in a gaseous effluent comprising the combination of a base B or a mixture of bases B with at least one compound R(NH)n in an aqueous solvent Z and/or the product obtained by reaction of said base B or of said mixture of bases B with said compound R(NH)n in said aqueous solvent Z, wherein:

• B is a base or a mixture of bases corresponding to one of the general formulae M(HCO3)x or M′y(CO3) or M″(OH)w, where M, M′, M″, which are identical or different, are chosen without distinction from:
• a monovalent cation such as lithium, sodium, potassium, rubidium or cesium,
• a quaternary ammonium cation corresponding to the general formula R1R2R3R4N+ wherein R1, R2, R3 and R4 are independently chosen from a hydrogen atom, a branched or unbranched, saturated or unsaturated aliphatic, substituted or unsubstituted, saturated or unsaturated alicyclic, substituted or unsubstituted, saturated or unsaturated heterocyclic, substituted or unsubstituted monoaromatic or polyaromatic hydrocarbon-based group containing between 1 and 20 carbon atoms, it being possible for R1, R2, R3 and R4 to be bonded in pairs by covalent bonds to form a heterocycle with 5 to 8 atoms,
• a divalent cation such as magnesium, calcium or barium,
• and wherein x, y, w are equal to 1 or to 2;
• R(NH)n is an unsaturated heterocyclic organic compound or a mixture of unsaturated heterocyclic organic compounds, wherein the radical R is an alicyclic, monoaromatic or polyaromatic, or heterocyclic group having at least one nitrogen atom, and n is between 1 and 20, preferably between 1 and 6, very preferably n is equal to 2 or 3;
• Z is essentially water or a mixture of solvents comprising water.