Extraction of Nitric Acid Using Tri- n -butylphosphate: A Study on Understanding and Thermodynamic Modeling

The extraction was investigated for the H2O/HNO3/TBP/isane system using a combined experimental, computational, and data-driven approach, enabling a transition from molecular-scale modeling to process development based on spectroscopy and chemometrics. Batch experiments were conducted to measure the distribution of H2O and HNO3 between the aqueous and organic phases. Infrared spectra of the organic phases were recorded to elucidate the H2O and HNO3 speciation. Molecular dynamics simulations provided a molecular-scale description of the system, allowing the identification of six predominant species in the organic phase using graph theory. These results were used as inputs for the principal component analysis deconvolution of the infrared spectra. The species were grouped into three principal components, allowing for the distinction of three distinct spectra. A thermodynamic model was then developed, taking into account these data to fit both the speciation data acquired through IR spectroscopy and the distribution data. A very good agreement was observed between the experimental and calculated data.