Fluorination reaction of UO_(3)and electrochemical preparation of UO_(2)

摘要

In this work,a technique was proposed to prepare UO_(2)from UO_(3)by the two processes of fluorination reaction of UO_(3)with NH_(4)HF_(2)and electrochemical reduction of UO_(2)^(2+)for the recycle uranium.The feasibility of fluorination reaction was firstly confirmed using thermodynamic calculation;then,the products were analyzed using XRD,Raman and fluorescence to be UO_(2)F_(2).The fluorination mechanism was inferred to be UO_(3)(s)+NH_(4)HF_(2)→(NH_(4))_(3)UO_(2)F_(5)→NH_(4)(UO_(2))_(2)F_(5)→UO_(2)F_(2).The redox behavior of UO_(2)^(2+)on W electrode was investigated by cyclic voltammetry and square wave voltammetry,which indicated that UO_(2)^(2+) was reduced to UO_(2)via a two-step single electron transfer with diffusion-controlled.The diffusion coefficient of UO_(2)^(2+) was calculated to be 6.22×10^(-5)cm/s.The disproportionation reaction of UO_(2)^(+) was observed,and the relationship between the disproportionation reaction and scan rate was discussed.Moreover,the electrochemical fabrication of UO_(2) was conducted by electrolysis at-0.8 V,and the product was analyzed by XRD,SEM and EDS to be UO_(2).ICP-AES results showed that the extraction efficiency of UO_(2) could reach 98.53%.