Method for isolating a carboxylic acid from an aqueous solution

Method for the recovery of carboxylic acid, said method comprising the steps of:

• a) subjecting an aqueous mixture comprising carboxylic acid and at least 5 wt. % dissolved magnesium chloride, based on the total weight of water and dissolved material in the aqueous mixture to a forward extraction step where the carboxylic acid is extracted from the aqueous mixture into a first organic liquid comprising at least 90 wt. % of an organic solvent, the organic solvent being selected from the group of C5-8 ketones, thereby obtaining an organic carboxylic acid solution and an aqueous waste liquid comprising magnesium chloride;
• b) subjecting the organic carboxylic acid solution to a back extraction step where the carboxylic acid is extracted from the organic carboxylic acid solution into an aqueous liquid to obtain a second organic liquid and an aqueous carboxylic acid solution whose concentration of carboxylic acids is higher than that of the aqueous mixture comprising carboxylic acid;
• and
• c) subjecting the aqueous waste liquid comprising magnesium chloride obtained in the forward extraction to a thermal decomposition step at a temperature of at least 300° C. to decompose the magnesium chloride to magnesium oxide and HCl,
• wherein the first organic liquid used in the extraction step a) comprises substantially no amine extractants, said amine extractants being amine compounds which form a complex with the carboxylic acid to be extracted.

Method for the recovery of carboxylic acid, said method comprising the steps of:

• a) subjecting an aqueous mixture comprising carboxylic acid and at least 5 wt. % dissolved magnesium chloride, based on the total weight of water and dissolved material in the aqueous mixture to a forward extraction step where the carboxylic acid is extracted from the aqueous mixture into a first organic liquid comprising at least 90 wt. % of an organic solvent, the organic solvent being selected from the group of C5-8 ketones, thereby obtaining an organic carboxylic acid solution and an aqueous waste liquid comprising magnesium chloride;
• b) subjecting the organic carboxylic acid solution to a back extraction step where the carboxylic acid is extracted from the organic carboxylic acid solution into an aqueous liquid to obtain a second organic liquid and an aqueous carboxylic acid solution whose concentration of carboxylic acids is higher than that of the aqueous mixture comprising carboxylic acid;
• and
• c) subjecting the aqueous waste liquid comprising magnesium chloride obtained in the forward extraction to a thermal decomposition step at a temperature of at least 300° C. to decompose the magnesium chloride to magnesium oxide and HCl,
• wherein the first organic liquid used in the extraction step a) is essentially free of amines, ethers, and alcohols, which means that these compounds, if present at all, are each present in an amount of less than 2 wt. %, calculated on the weight of the first organic liquid.