Investigation of the separation of small molecular organic acids from aqueous solutions via reactive extraction

The aim of this study is the investigation of the effect of various extractant and solvent combinations to the reactive extraction process, a promising technique used for the separation of small molecular organic acids from their aqueous solutions, to determine the optimum organic phase composition for the separation processes. Lactic acid, propionic acid, succinic acid, maleic acid, citric acid and oxalic acid are the organic acids that are under examination due to their economic worth. These carboxylic acids are recovered from their aqueous solutions by reactive extraction method using trioctylphosphine oxide which has low water solubility, high chemical stability, high boiling point and it is more environmentally friendly than the amine type extractants also they are recovered by using a secondary amine called dioctylamine and among the other amine extractants used in reactive extraction processes, there is a lack of study about the extraction of these acids with DOA in the literature. The experiments performed to determine the effect of alcohol, ketone and aliphatic hydrocarbon based solvents to the extraction capacity and to the extractive properties of the extractans used. Butanol, isoamyl alcohol, octanol, decanol, octane, decane, methyl isobutyl ketone, diisobutyl ketone, methyl ethyl ketone and diethly sabecate are solvents are consumed as the solvent respectively. In the experimental step the aqueous solutions of carboxylic acids with the concentration of eight percent by weight were prepared. The extraction experiments were performed at 298,15 K using organic phases prepared by mixing of TOPO and DOA with ten different solvents in different ratios. However, the separation of these acids using only pure solvents is also investigated. As a result of the experimental analysis, the quantity of the acid concentration in both organic and aqueous phase is found to calculate the values of distribution factor, extraction yield and loading ratio. It can be inferred from the results that an increase in the extractant concentration leads to an increase in the distrubution factor values but on contrary it leads to a decrease in the loading ratio values. In comparison with the results attained from the experiments performed using only pure solvents, introducing TOPO or DOA to the organic phase significantly enhanced the extraction yield. Furthermore, the separation of these acids from their aqueous solutions using DOA is given better results compared to the ones achieved using phosphor based extractant TOPO. Considering the organic phase mixture formed by the combinations of extractant and solvent, the most appropriate results with respect to extraction yield can be attained using DOA/MIBK for citric acid, DOA/MIBK for oxalic acid, DOA/DIBK for maleic acid, DOA/Butanol for succunic acid, DOA/Octanol for lactic acid and DOA/MIBK for propionic acid.