Study on the Extraction of Cerium(IV) from Nitric Acid Medium with tri-Isoamyl Phosphate

Abstract

This paper studied the extraction behavior of tri-isoamyl phosphate (TiAP)/n-dodecane as extractant for Ce(IV) in a nitric acid medium. In the study of extraction of pure Ce(IV) solution, the test results show that when the organic phase and the water phase ratio is 1: 1, the organic phase and the water phase are mixed and contacted for 90 s, and the pH value is 0-2.0, the extraction tends to be balanced, and the complexes formed by the extraction are theoretically deduced and obtained the theoretical molecular formula of the complex is Ce(NO3)4·nTiAP, where n is between 2 and 3; under this condition, the extraction rate of pure Ce(IV) can reach 99.45% after 16-stage countercurrent extraction test; the relative standard deviation is less than 2%. In the extraction of Ce(IV) solution containing other metal ions, the test results show that the extraction rate of 0.05 mol·L-1 TiAP/n-dodecane solution to the material liquid containing Ce(IV) 0.005 g·L-1 is about 64%. However, the experiment found that the extraction rate tends to decrease with the increase of the material liquid’s standing time. After 24 hours, the extraction rate is close to 0. Then, the experiment researched the influence of each metal ion component on the extraction after standing and obtained the metal. In the presence of ionic components, the extraction rate tends to decrease with the increase of the liquid standing time. Considering the strong oxidizing property of Ce4+ under acidic conditions, the experimental study of TiAP on Ce3+ and Ce4+ mixtures with different percentages. The results show that as the percentage of Ce3+ in the feed liquid increases, the extraction rate is in a downward trend, and the trend is consistent with the increase in the standing time on the extraction rate. The original liquid contains impurity Ce4+ is slowly reduced to Ce3+, which affects the extraction results. Studies have shown that TiAP of 0.05 mol·L-1 performs well for the extraction of Ce4+ in pure Ce(IV) solution; TiAP of 0.05 mol·L-1 is effective for extraction of Ce(III) solution of 0 ~ 5 mg·L-1. The effect of Ce3+ is not obvious; because Ce4+ is too oxidizing, when other metal ions studied are present at the concentration studied, it will accelerate the reduction of Ce4+ and affect the extraction results.