稀土熔盐渣碳酸钠焙烧转型机理及浸出规律

Transformation mechanism and leaching performance of rare earth fluoride molten salt slag in the process of Na2CO3-roasting

借助反应热力学计算和动力学分析,研究碳酸钠焙烧稀土熔盐的转型机理和焙烧条件对稀土浸出的影响。研究结果表明:碳酸钠焙烧稀土熔盐渣反应的活化能(Ea)约为174.31 kJ/mol,受化学界面反应控制,温度升高可促进氟化稀土向氧化稀土转变;提高焙烧温度,延长焙烧时间,增加碳酸钠添加量均有利于提高稀土浸出率。稀土熔盐渣焙烧转化的优选条件如下:焙烧温度为700℃,反应时间为60 min,碳酸钠添加量为原料质量的30%。碳酸钠焙烧水洗除氟盐酸优溶可使熔盐渣中含稀土物在较低温度下发生物相转化,进而实现稀土的高效回收。

The transformation mechanism of rare earth fluoride molten salt slag(REFMSS)mixed with Na2CO3 in the roasting process and the effects of roasting conditions on rare earth(RE)leaching efficiency were investigated through thermodynamic calculations of reactions and the kinetic analysis.The results show that the activation energy(Ea)is about 174.31 kJ/mol,and the roasting process is controlled by interface chemical reaction.The transformation of rare earth fluoride to rare earth oxide(REO)is promoted at elevated temperature.Moreover,the increase of temperature,reaction time and Na2CO3 dosage is beneficial to RE leaching efficiency.The optimum roasting conditions for REFMSS are determined at 700℃,60 min,and Na2CO3 dosage with 30%mass fraction of raw material.Through the processes of Na2CO3 roasting,defluorination by washing and leaching by hydrochloric acid,the transformation of rare earth phases in REFMSS is achieved at lower temperature,which realizes the efficient recycle of RE.