含氟硫酸介质中伯胺N1923对Ce(Ⅳ)的萃取

Extraction of Cerium(Ⅳ) by Primary Amine N1923 from Sulfuric Acid Medium Containing Fluorine

铈(Ce)在轻稀土矿物中常与诸如F等多种其它元素伴生,针对矿物处理过程中得到的同时含有Ce(Ⅳ)和F^(-)等多组分复杂体系硫酸浸出液,从铈氟综合回收并丰富理论依据的角度出发,对伯胺N1923在含氟硫酸介质中Ce(Ⅳ)的萃取及反萃过程进行了研究。考察了酸度、萃取剂浓度、盐析剂浓度及温度对萃取过程的影响,采用斜率法初步讨论了反应机理。研究表明,预先质子化处理后的伯胺N1923在硫酸介质中可同时萃取Ce(Ⅳ)和F^(-),H_(2)SO_(4)浓度对Ce(Ⅳ)和F^(-)的萃取过程无显著影响。Ce(Ⅳ)的萃取率随水相中F^(-)浓度的增加而增大,萃取过程符合加合机理,其萃合物可表示为CeF(SO_(4))_(1.5)(RNH_(3)·HSO_(4))_(1.5)。通过考察不同温度下N1923对Ce(Ⅳ)的萃取分配比并计算相应的反应平衡常数及热力学参数,表明萃取过程为自发进行的、熵焓双驱动的放热反应。在含氟体系中,体积分数15%的N1923对Ce(Ⅳ)的饱和负载量为18.85 g/L,同时F^(-)的负载量为2.00 g/L。通过红外和核磁对萃合物结构分析可知部分萃合物间有多聚作用,硫酸根在萃合物中为双齿配位。此外,萃合物中的Ce(Ⅳ)可被含H_(2)O_(2)的硝酸反萃剂有效反萃,反萃率最高为90%,同时F^(-)几乎可以被完全反萃。

Cerium(Ce)usually exists in minerals with accompany of multiple elements,such as fluorine(F).To develop technologies and provide theoretical foundations for comprehensive recovery of Ce and F,the extraction and stripping process of Ce(Ⅳ)by primary amine N1923 in sulfuric acid medium containing fluorine was investigated.The effects of H_(2)SO_(4)acidity,extractant concentration,fluorine ion concentration and temperature on the extraction process were comprehensively investigated,meanwhile the extraction mechanism was discussed.It is shown that Ce(Ⅳ)and F^(-)can be extracted by primary amine N1923 in sulfuric acid medium at the same time,while the H_(2)SO_(4)acidity has no significant effect on the extraction.The extraction efficiency of Ce(Ⅳ)increases with the increase of F^(-)concentration in the aqueous phase and the extraction process conforms to the addition mechanism.Through investigating the extraction performance at varied temperatures,the reaction equilibrium constant and thermodynamic parameter are calculated,revealing that the extraction process is an exothermic reaction driven by both entropy and enthalpy.In the fluorine-containing system,the saturation loading capacity of N1923(volume fraction 15%)is 18.85 g/L for Ce(Ⅳ)and 2.00 g/L for F^(-).Fourier transform infrared(FT-IR)transmission spectroscopy and nuclear magnetic resonance(NMR)spectra of extracted complexes indicate that the complexes are partially polymerized and is bidentatally coordinated in the equilibrium extraction compound.In addition,Ce(Ⅳ)and F^(-)in the loaded organic phase can be effectively stripped using HNO_(3) containing H_(2)O_(2) as a stripping agent.The stripping rate of Ce(Ⅳ)can reach 90% and the F^(-)can be almost stripped thoroughly.