Abstract:The kinetics of the bis(2-ethylhexyl) phosphate (HDEHP) extraction of lanthanum and cerium were investigated in a lactic acid complex system. The effects of stirring speed, specific interface area, temperature and concentration of different solution components on the extraction rate were studied using a constant interface cell device. When the stirring speed was 130-180 r/min, the extraction reaction rate was mainly controlled by the chemical reaction, and increased with increasing the specific interface and temperature. The extraction kinetics shows that the extraction reaction conforms to a pseudo-first-order reaction, and the mass transfer process occurs at the interface between the organic and liquid phases rather than in the bulk phase. The Gibbs free energy of the extraction reaction ΔG<0, indicating that the reaction can proceed spontaneously, while the calculation of the apparent activation energy shows that HDEHP is more likely to combine with cerium during extraction.

Key words: lanthanum; cerium; mechanism; extraction kinetics; Lewis cell