Extraction Behavior of Amino Sulfonic Acid by Tertiary and Quaternary Amines

Based on a systematic investigation of the literature, p -aminobenzenesulfonic acid was selected as a typical solute to be separated from the dilute solution. An aliphatic, straight-chain amine, Alamine 336, and a chlorinated quaternary ammonium salt, Aliquat 336, were used as extractants. The effects of pH value, concentration of the extractant, type of diluents, and salt on the distribution coefficient, D, on extraction equilibrium were studied in the experiments. The results showed that protic, polar diluents were favorable for extracting p -aminobenzenesulfonic acid when Alamine 336 was used as the extractant, while the inert diluent was favorable when Aliquat 336 was used as the extractant. Salt existing in the aqueous phase apparently reduced the D of p -aminobenzenesulfonic acid. Meanwhile, the proton transfer and ion exchange in the extraction process were discussed. The extraction equilibria for both amines were described using the mass action law, and the results showed that the calculating data agree with the experimental data well. Further, the extraction behavior for other aminobenzenesulfonic, H, and DSD acids was investigated with Alamine 336 as the extractant in a wide pH region. The results showed that the extractant used for aminobenzenesulfonic acid depends on the requirement of the number of equilibrium stages and extraction yield.