Abstract: A method for regenerating alkaline solutions for pickling aluminum is provided, by which aluminum hydroxide is recovered. A pickling solution containing aluminum hydroxide, aluminate and a complexing agent and further additives is transferred from a pickling bath into a reactor section, which consists of at least one reactor where aluminum is precipitated as aluminum hydroxide. The pickling bath has a higher temperature than the reactor section. The process is operated so that the concentration of aluminate, alkali and gluconate as well as the temperature in the pickling bath, on the one hand, and the temperature gradient from the pickling bath to the reactor section, on the other hand, are adjusted so that the pickling solution in the pickling bath is undersaturated or metastably supersaturated with respect to precipitation of aluminum hydroxide, however, unstably supersaturated in the reactor section. A device for carrying out the process of the invention is also disclosed.