Studies On Synthesis Of Bis-malonamides And Their Extraction Properties For U(?) And Th(?)

In the past 100 years,people's demand for energy has increased sharply,and various energy shortages and environmental problems have been exposed to us.Compared with other energy sources,nuclear energy is considered to be the most promising,clean and efficient energy source.In the process of nuclear fuel cycle,the reprocessing of spent fuel is very important,especially for the recovery of uranium and thorium.At present,the PUREX process which uses TBP as the extractant is a relatively mature process for spent fuel reprocessing.However,because of the defects of TBP,such as phosphorus and radiolysis,it is still necessary to find a more suitable and excellent extractant.In this experiment,we systhsized three bis-malonamides(TB-BisMA,TH-BisMA,TO-BisMA)with different carbon chains as extraction agents by using ethylenediamine,mitric acid,di-n-butylamine,di-n-hexylamine,di-n-octylamine and other raw materials.The structures of the intermediate product and the three extraction agents were characterized by NMR,IR and MS.The effects of extraction agent,extraction equilibrium time,diluent,acidity of metal ion solution,concentration of extraction agent and concentration of salting-out agent on extraction distribution ratio were studied by UV-VIS spectrophotometer.The results showed that the TH-BisMA can extracted U(VI)well when the diluent was kerosene,the aqueous acidity was 5.0M,and the extraction equilibrium time was 35 min.In this extraction condition,the extraction allocation ratio D was up to 113.47,which means that the extraction rate was up to 99.00%.The mechanism analysis showed that it was a neutral complexation extraction process,and the coordination ratio of TH-BisMA and U(VI)was 1.TH-BisMA can extracted Th(IV)well when the the diluent was xylene,the aqueous acidity was 5.0 M and the extraction equilibrium time was 40 min.The extraction allocation ratio was up to 43.10,that is,the extraction rate was up to 97.00%.In this process,we also compared and studied the extraction effect of TO-BisMA on U(VI)and Th(IV),and found that the optimal allocation ratio was 34.38 and 31.07 respectively,far less than the extraction effect of TH-BisMA.On this basis,we studied the extraction effects of the TH-BisMA and the TO-BisMA to Eu(?),and the best extraction rates were just 26.78% and 7.40% respectively,meaning the extraction effects were not ideal.It can be seen that the synthetic TH-BisMA can extract and recover U(VI)and Th(IV)in the reprocessing process of spent fuel well,and thus TH-BisMA has a great application prospect in the nuclear fuel cycle.