Separation Of Light Rare Earth By Centrifugal Fractionation Extraction With Calix[8]arene Phosphate

Extraction and separation of high purity light rare earth without ammonia and nitrogen pollution is a difficult problem in recent years.Firstly,the synthesis and structure characterization of two extractants,de-tert-butyl calix[8]arene phosphate and de-tert-butyl calix[8]arene phosphate,were studied,and the synthesis conditions of p-tert-butyl calix[8]arene phosphate were optimized.The extraction performance of de-tert-butyl calix[8]arene phosphate for light rare earth ions La³⁺,Ce⁴⁺,Pr³⁺,Nd³⁺was analyzed,and an efficient extraction system was established.On this basis,the extraction and separation experiments of La³⁺&Ce⁴⁺and Pr³⁺&Nd³⁺mixed rare earth were carried out with p-tert-butyl calix[8]arene phosphate and de-tert-butyl calix[8]arene phosphate as extractants.The optimum separation conditions for La³⁺&Ce⁴⁺mixed rare earth and Pr³⁺&Nd³⁺mixed rare earth were obtained.On the basis of the above research,the separation of mixed rare earths by multistage fractionation extraction based on calix[8]arene phosphate was studied.The mathematical models of single-stage and multistage centrifugal fractionation extraction separation were constructed and validated by extraction experiments.Calix[8]arene phosphate was used as extractant to separate La³⁺&Ce⁴⁺and Pr³⁺&Nd³⁺mixed rare earth by centrifugal extraction fractionation extraction.This study provides theoretical basis and technical support for the pollution-free separation of light rare earth,and has broad application prospects.The main conclusions of this paper are as follows:?1?By analyzing the influence of reaction temperature and the solvent ratio of carbon tetrachloride to dichloromethane on the yield,the synthesis conditions of tert-butyl calix[8]arene phosphate were optimized,and the yield was increased from92.3%to 95.44%.?2?De-tert-butyl calix[8]arene phosphate was synthesized by substitution reaction.Its structure was characterized by IR,1H NMR and MS.?3?The extraction conditions such as pH value,extractant concentration,extraction ratio and extraction time were investigated.Under the optimum conditions,the extraction rates of La³⁺,Ce⁴⁺,Pr³⁺and Nd³⁺were 90.27%,98.09%,67.24%and78.91%,respectively.?4?The extraction conditions such as pH value,extractant concentration,extraction ratio and extraction time were investigated.Under the optimum conditions,the mixed separation factor of lanthanum and cerium for p-tert-butyl calix[8]arene phosphate was 5.972;the mixed separation factor of praseodymium and neodymium for p-tert-butyl calix[8]arene phosphate was 1.057;the mixed separation factor of lanthanum and cerium for de-tert-butyl Calix[8]arene phosphate was 1.44;and the mixed separation factor of lanthanum and cerium for de-tert-butyl calix[8]arene phosphate was 1.44.The mixed separation factor of ester to praseodymium and neodymium is 1.221.?5?Mathematical models of single-stage centrifugal separation and multi-stage centrifugal separation were established based on the mechanism of extraction separation reaction,equilibrium constants of complexation reaction,law of mass conservation and phase equilibrium equation,and simulated by using MATLAB software platform.Experiments and simulations show that the simulated predictions of multi-stage centrifugal extraction separation process based on centrifugal extractor are basically consistent with the experimental results.?6?Through simulation,prediction and optimization analysis,it was found that under the conditions of W/O=5 and W/F=1,when the extraction stage was 10,the purity of La³⁺in aqueous phase could reach 99.82%or more,using p-tert-butyl calix[8]arene phosphate as extractant.With de-tert-butyl calix[8]arene phosphate as extractant,multi-stage centrifugal fractionation was used to extract Pr³⁺and Nd³⁺mixed rare earth solution.When W/O=7,W/F=7,extraction stage was 30,f=30,purity of Pr³⁺in aqueous phase could reach 99%.