Performance of Organic Salts as Salting-Out Media on Recovering Nicotine from Water

Three degradable organic salts, sodium formate (NaCHO2), sodium succinate (Na2C4H4O4), and sodium citrate (Na3C6H5O7), were evaluated for the extraction of nicotine from aqueous solutions by forming two-phase systems. The detailed phase diagrams, including the binodal curves and tie-lines, were experimentally determined at 298.15 K and atmospheric pressure by the cloud point method. The three empirical equations including Merchuk, Pirdashti, and Hu models gave a perfect correlation of the experimental binodal data, and the reliability of liquid-liquid equilibrium data was evaluated using the Othmer- Tobias and Bancroft equations. It could be found that all adopted organic salts promoted the expansion of two-phase regions and had a high partition yield for nicotine extraction from water. The relative tendency of the anions to form aqueous two-phase systems being C6H5O73- > C4H4O42- > CHO2- was consistent with their valence order, which could be explained by the Gibbs hydration free-energy theory. Furthermore, the salting-out ability of salt anions was also in accordance with the parameter order (Na3C6H5O7 > Na2C4H4O4 > NaCHO2) of the calculated effective excluded volume. Increasing the temperature from 298.15 to 318.15 K and the pH value from 8.0 to 11.0 at 298.15 K was conducive to the two-phase formation of the ternary nicotine + Na3C6H5O7 + water system to increase the distribution coefficients and recovery percentages of nicotine. Computational thermodynamics of cloud point indicated that the more negative Gibbs free energy with temperature promoted the desolvation of nicotine to migrate preferentially to the top phase. It was concluded that degradable organic salts would be effective for nicotine extraction at an industrial scale.