Effet du pH sur le rendement de récupération des acides carboxyliques par extraction liquide-liquide à partir des effluents aqueux

Abstract

waste water from food, pharmaceutical and chemical industries generate in large parts organic molecules with high added value that is the case of carboxylic acids. The liquid-liquid extraction by solvent remains the most appropriate method for removing such compounds from industrial effluents. The present work is to develop model equations to simulate the recovery yield of carboxylic acids by liquid-liquid extraction based on the reaction mechanism at the interface between phases. It was found that the pH has an inevitably affects on the selective separation of components in mixture containing several acids. An experimental validation of our models has been applied to the extraction of formic acid HCOOH 0.1 N content in aqueous solution. Three cases were identified: i) case or formic acid is alone in the aqueous solution, ii) formic acid in the presence of another carboxylic acid (benzoic acid C6H5COOH 0.025 N), iii) the acid is mixed with a weak base NH4OH 0.1 N; In each case, the values of extraction yield models were calculated and compared with experimental values.First time, when no pH change is made to the aqueous solution, it was noted that except in cases where the acid is the only constituent in solution, it can be extracted with good efficiency up to 46.6% it decreases to 37.4% if we introduce another carboxylic acid to the mixture and drop in the value of 3% in the presence of a weak base, the acid in the latter case can not be extracted. Second time, and when the pH varies over a wide range from 1.5 to 11, the acid, object of this study, can be extracted quantitatively and selectively for the three considered cases.