A Study on the Separation of Nitric Acid and Acetic Acid from Simulated Reprocessing Waste by TBP Extraction

The PUREX process is a key technology for spent fuel reprocessing, designed to selectively recover uranium and plutonium mainly through multiple chemical separation stages, minimizing high-level waste. Acetohydroxamic acid (AHA) enhances selectivity in this process but decomposes into acetic acid (HAc), which disrupts chemical equilibrium and reduces extraction efficiency. This study examines the extraction and separation of nitric acid (HNO₃) and HAc using 30% tributyl phosphate in organic kerosene (TBP-OK) under various conditions. Results show that 30%TBP-OK preferentially extracts HAc over HNO₃, especially in the low acid concentration range (HNO₃ < 1 mol/L, HAc < 0.2 mol/L). The selectivity coefficient drops from 3.05 in a 0.5 mol/L HNO₃-0.1 mol/L HAc system to 2.18 in a 1 mol/L HNO₃-0.2 mol/L HAc system. TBP forms stable 1:1 complexes with both acids, with equilibrium constants around 0.85 under typical conditions. Increasing TBP concentration enhances HNO₃ extraction, while phase ratio adjustments improve HAc separation. A 16-stage countercurrent extraction simulation confirms that optimizing these factors effectively separates HNO₃ and HAc, offering theoretical and technical support for refining the PUREX process.