METHOD FOR PURIFYING CONCENTRATED, AQUEOUS AND USED SOLUTIONS OF CHROMIC ACID, AND SOLUTIONS THEREBY PURIFIED

摘要

A method for purifying aqueous chromic acid solutions containing unwanted metal cations, wherein a base is added to the purified solution to precipitate out the unwanted cations; the precipitate thereby formed is separated from the aqueous phase, and the solution thereby purified is recovered. The method is characterized in that the solution to be purified is a used solution having a chromic acid concentration of at least twenty-five grammes per litre (25 g/l), and in that the base is added while maintaining the solution in an acid medium.