Abstract: A process for purifying an aqueous glyoxal solution comprising at least one acid by extractive acid removal, comprising i) mixing and dispersion of the aqueous glyoxal solution with an ion exchanger solution comprising a tertiary amine and an organic solvent, ii) phase separation and removal of the ion exchanger solution laden with the acid from the aqueous glyoxal solution, and iii) regeneration of the ion exchanger solution by contacting with a basic compound for neutralization of the acid and removal of the basic compound, iv) mixing and dispersion of the ion exchanger solution with water to obtain a dispersion of water and ion exchanger solution, v) Phase separation and removal of the aqueous phase from the ion exchanger solution in such a way that the content of the aqueous phase of the regenerated ion exchanger solution is <1% by weight, and recycling of the ion exchanger solution into step i).