A Kinetic Study of Nitric Acid Extraction by Tri-n-octylamine

The importance of recovering nitric acid from wet-process phosphoric acid (WPA) has been growing due to the many advantages that nitric acid has over sulfuric acid for decomposing phosphate rock. Since tri-n-octylamine (TOA) shows good extraction and selectivity for nitric acid, basic research of this topic is required. In this study, the kinetics and mechanism of the extraction of nitric acid with tri-n-octylamine in kerosene has been studied at 25 degrees C, using a constant interfacial area cell with laminar flow. According to the results of this work, we find that the extraction process is controlled by the diffusion of nitric acid in the aqueous phase and by the chemical reaction taking place of the interface of both phases. The mechanism of the nitric acid extraction with TOA is revealed and the kinetic model is established.