Recovery of aconitic acid from simulated aqueous effluents of the sugar-cane industry through liquid-liquid extraction

The recovery of carboxylic acids from the by-products of sugar-cane treatments by the technique of solvent extraction has been studied, in order to reduce environmental pollution and in view of the possible uses of aconitic acid in the food-processing and chemical industries. The liquid-liquid extraction process can be considered as an alternative to the classical precipitation method for the separation of aconitic acid from dilute aqueous effluents. In this work, the selected solvent was composed of a mixture of an extractant (tributylphosphate) with a diluent (dodecane). The concentration of tributylphosphate in the mixture of extractant and diluent, the composition of the initial aqueous solution and its pH, as well as the mass: solvent ratio were found to influence the equilibrium of distribution of the carboxylic acid between the organic and the aqueous phases. With a solvent composed of a mixture of tributyphosphate (70 vol%) + dodecane (30 vol%) and a mass:solvent ratio of 5, the percentages of aconitic acid extracted by the solvent were higher than 98% (mass%) whatever the composition of the initial aqueous solution. After the extraction step, the regeneration of solvent could be easily obtained by stripping of solute from the organic phase with a basic aqueous solution. This preliminary study showed the possibilities of the method for use in industrial processes.