Extraction of Citric Acid and Maleic Acid from Their Aqueous Solutions Using a Phosphorus-Bonded Extractant, Tri-n-octylphosphineoxide, and a Secondary Amine, Dioctylamine

Abstract

The aim of this study is to investigate the extraction of citric acid and maleic acid from their aqueous solutions using different solvent–extractant mixtures in order to find the most effective composition for the extraction. Citric and maleic acids are chosen as the carboxylic acids due to their commercial worth in the industrial processes. Carboxylic acids are recovered from their aqueous solutions by reactive extraction, a promising liquid–liquid extraction technique, using trioctylphosphineoxide (TOPO), and a secondary amine called dioctylamine (DOA). TOPO has been chosen as an extractant since it has low water solubility, high stability, and it is more environmentally friendly than the amine-type extractants. For other amine extractants used in reactive extraction processes, there is a lack of study in the literature about the extraction of these acids with DOA. Extractants were dissolved in nine different solvents (butanol, decanol, octanol, isoamylalcohol, octane, decane, methylisobutylketone, and diisobutylketone) having different chemical structures. All experiments were carried out at 298.15 K. Comparisons of the results were made using the distribution coefficient (D), loading factor (Z), and the extraction yield (%E). It has been observed that a considerable amount of citric acid and maleic acid extraction was achieved using DOA (in the range of 13.95–99.19% and 31.94–99.41% according to the diluent used for citric acid and maleic acid, respectively) compared to that achieved with TOPO (in the range of 0.81–67.12% and 16.25–89.33% according to the diluent used for citric acid and maleic acid, respectively).