Reactive Extraction of Citric Acid Using Tri-n-octylamine in Nontoxic Natural Diluents: Part 1—Equilibrium Studies from Aqueous Solutions

Use of cheap, nontoxic, and selective solvents could economically provide a solution to the recovery of carboxylic acids produced by the bioroute. In this regard in the present paper, reactive extraction of citric acid was studied. Problems encompassing the recovery of the acid ([H3A]aqo = 0.1–0.8) was solved by using tertiary amine (tri-n-octylamine, TOA) in natural diluents (rice bran oil, sunflower oil, soybean oil, and sesame oil). TOA was very effective in removal of acid providing distribution coefficient (D) as high as 18.51 (E% = 95 %), 12.82 (E% = 93 %), 15.09 (E% = 94 %), and 16.28 (E% = 94 %) when used with rice bran oil, sunflower oil, soybean oil, and sesame oil, respectively. Overall extraction constants and association numbers for TOA + rice bran oil, TOA + sunflower oil, TOA + soybean oil, and TOA + sesame oil were evaluated to be 35.48 (mol/l)−1.46, 29.79 (mol/l)−1.30, 33.79 (mol/l)−1.51, and 37.64 (mol/l)−1.65 and 1.46, 1.30, 1.51, and 1.65, respectively. Specific equilibrium complexation constants (KE(n/m)) were also predicted using mathematical modeling.