传统溶剂萃取法具有酸碱消耗大、含盐废水排放量大的缺点。以Ce的氧化还原为驱动力，根据P507对Ce(IV)和RE(III)的萃取能力不同，提出了一种新的反萃方法。研究了Ce(IV)在硝酸溶液中置换反萃轻稀土的反萃条件及机理。以Pr(III)作为轻稀土的代表元素探究了反萃相比、温度、反应时间、溶液酸度及Ce(IV)浓度、硝酸根浓度等因素对轻稀土反萃率的影响。结果表明，随着反应温度、时间及硝酸高铈铵溶液浓度增加，Pr反萃率不断增加，随着相比增大反萃率降低，使用0.56 mol/L硝酸高铈铵溶液反萃负载Pr的有机相，优化条件下Pr反萃率达98%，优于1 mol/L盐酸，该方法对轻稀土均有较好的反萃率。通过斜率法推测了萃合物形式及反应机理，FT-IR进一步验证了该机理。该反应为溶剂化机理，反萃前后有机相中组成分别为Pr(NO3)(HA2)2·(HA)和Ce(NO3)2A2。从FT-IR光谱分析可知，稀土元素置换了P-O-H中的H，并与P=O键配位，有机相中[NO3-]O的特征峰进一步证明了[NO3-]O参与反应。

The traditional solvent extraction leads to a large amount of acid-alkali consumption and saline wastewater discharge. Herein, a new strategy was proposed according to the different extraction ability of Ce(IV) and RE(III) with P507, driven by the oxidation and reduction of Ce. As one of the key procedure, the performance and mechanism of replaced stripping of light rare earth elements (LREEs) by Ce(IV) in nitrate solution was investigated in this study. Pr(III) was selected as the representative element of LREEs for the follow-up experiments. Several operational parameters such as phase ratio, temperature, reaction time, concentration of nitrate and Ce(IV) in aqueous feed, and acidity were investigated. Results indicated that the stripping efficiency of Pr(III) increased significantly with increasing temperature, reaction time and Ce(IV) concentration, while it decreased with the increase of phase ratio. The stripping efficiency of Pr(III) was 98% by 0.56 mol/L Ce(IV) under the optimal conditions, which was higher than that by 1 mol/L HCl solution. This method was generally applicable on the stripping of the other LREEs. The mechanism was explored by slope method and FT-IR spectrometric analysis. The solvation mechanism was carried out, and the key complexes in the organic phase before and after stripping were determined to be Pr(NO3)(HA2)2·(HA) and Ce(NO3)2A2, respectively. From the FT-IR spectrometric analysis, it can be concluded that the H in P-O-H was replaced by the rare earth, which was bonded with P=O. Nitrate was also involved in the reaction because of the presence of the characteristic peaks of nitrate.