The present invention relates to a method for the purification of an α-hydroxy acid on an industrial scale, in which the method involves: (a) subjecting an aqueous stream containing mainly α-hydroxy acid (1) to an extraction step, with the formation of an aqueous place containing mainly α-hydroxy acid (2), (b) concentrating the aqueous phase containing mainly α-hydroxy acid (2) by means of evaporation of water under reduced pressure, with the formation of a concentrated α-hydroxy acid solution in water (3), and (c) subjecting the concentrated α-hydroxy acid solution (3) to a crystallization, with formation of pure α-hydroxy acid (4), where (i) the concentrated α-hydroxy acid solution (3) is directly cooled in a melting crystallization device, and/or (ii) the concentrated α-hydroxy acid solution (3) is diluted with water and crystallization is brought about in one or more cooling crystallization devices and/or evaporative crystallization devices, and/or (iii) crystallization is brought about in one or more adiabatic crystallization devices.Cette invention se rapporte à un procédé pour purifier un acide α-hydroxy sur une échelle industrielle, ce procédé consistant: (a) à soumettre un courant aqueux contenant essentiellement de lacide α-hydroxy [1] à une étape dextraction, avec formation dune phase aqueuse contenant essentiellement de lacide α-hydroxy [2] (b) à concentrer la phase aqueuse contenant essentiellement de lacide α-hydroxy [2] par évaporation de leau à une pression réduite, avec formation dune solution dacide α-hydroxy concentrée dans de leau [3] et (c) à soumettre la solution dacide α-hydroxy concentrée [3] à une cristallisation, avec formation dacide α-hydroxy pur [4]. Dans cette invention, (i) la solution dacide α-hydroxy concentrée [3] est directement refroidie dans un dispositif de cristallisation par fusion, et/ou (ii) la solution dacide α-hydroxy concentrée [3] est diluée avec de leau et la cristallisation est effectuée dans un ou plusieurs dispositif
