摘要
稀土熔盐电解渣大都通过焙烧-酸浸工艺实现稀土回收,其中对于难处理的氟化稀土,基于固相固氟的思路,国内已有学者用氢氧化钙焙烧-盐酸酸溶的方式来实现稀土与氟的分离,但稀土浸出率仅为90%左右,其原因为焙烧产物CaF_(2)会溶于HCl导致酸浸液中除RE^(3+)外还有F^(-),二者重新结合为REF_(3)。Mg和Ca化学性质相似且MgF_(2)的溶度积比CaF_(2)小,则理论上MgF_(2)要比CaF_(2)更稳定。由此通过对钙剂和镁剂与稀土熔盐电解渣焙烧得到的CaF_(2),MgF_(2)的酸浸热力学和溶解行为进行研究,以便探明二者的溶解行为规律,进一步为焙烧-酸浸法选择合适的固氟试剂提供依据。由热力学分析结果可知,当0<pH≤3.2时,该范围内MgF_(2)比CaF_(2)先开始析出;pH在3.2~10.87范围内,MgF_(2)和CaF_(2)稳定存在且[Mg^(2+)]要低于[Ca^(2+)];当10.87<pH≤14时,MgF_(2)和CaF_(2)开始返溶生成Mg(OH)_(2(s))和Ca(OH)_(2(aq)),即MgF_(2)在酸中的稳定性更好且酸浸工序的pH=4~7为宜。当HCl浓度1 mol·L^(-1),液固比2∶1(mL/g),温度30~90℃,反应60 min后,CaF_(2)的溶解度变化为28.5~53.8 g·L^(-1),而MgF_(2)的溶解度变化仅为9.57~13.33 g·L^(-1),MgF_(2)在酸中的溶解效果整体要比CaF_(2)更差,说明MgF_(2)在酸中更加稳定即镁剂要比钙剂的固氟效果更佳。
The majority of rare earth molten salt electrolytic residue is recovered by roasting-acid leaching process.For rare earth fluoride which is challenging to handle,based on the concept of solid phase fixed fluorine,domestic scholars have used calcium hydroxide roasting-hydrochloric acid dissolution to achieve separation of rare earth and fluorine,but the leaching efficiency of rare earth is only approximately 90%.The reason is that the roasted product CaF_(2) dissolves in acid,resulting in the formation of F^(-) in addition to RE^(3+) in the pickling solution,and the two elements are recombined into REF_(3).In fact,the chemical properties of Mg and Ca are similar,and the solubility product of MgF_(2) is smaller than that of CaF_(2),so MgF_(2) is theoretically more stable than CaF_(2).Therefore,the thermodynamics and dissolution behavior of acid leaching of CaF_(2) and MgF_(2) obtained by calcination of calcium and magnesium and electrolytic residue of rare earth molten salt were studied to find out the law of dissolution behavior of CaF_(2) and MgF_(2),and further provide a basis for the selection of suitable fluorine fixation reagents by roasting-acid leaching method.According to the thermodynamic analysis results,when O<pH≤3.2,MgF_(2) begins to precipitate before CaF_(2).In the range of pH 3.210.87,MgF_(2) and CaF_(2) exist stably and[Mg^(2+)]is lower than[Ca^(2+)].When 10.87<pH≤14,MgF_(2) and CaF_(2) begin to redissolve into Mg(OH)_(2(s))and Ca(OH)_(2(aq)),that is,MgF_(2) has better stability in acid and the pH of the acid leaching process is 47.When the concentration of hydrochloric acid is 1 mol·L^(-1),the liquid-solid ratio is 2:1(mL/g),the temperature is 3090 C,and the reaction time is 60 min,the solubility of CaF_(2) is 28.5-53.8 g·L^(-1),and the solubility of MgF_(2) is only 9.5713.33 g·L^(-1).The solubility of MgF_(2) in acid is much smaller than that of CaF_(2),indicating that the fluorine fixation effect of magnesium is better than that of calcium.
作者
蒲婷
陈赞鸿
刘寅亮
张明辉
梁勇
Pu Tin;Chen Zanhong;Liu Yinlian;Zhang Minghui;Liang Yong(Jiangxi Provincial Key Laboratory of Green and Low Carbon Metallurgy for Strategic Nonferrous Metals,Faculty of Metallurgical Engineering,Jiangxi University of Science and Technology,Ganzhou 341000,China)
出处
《中国稀土学报》
北大核心
2026年第1期36-43,共8页
Journal of the Chinese Society of Rare Earths
基金
国家自然资源部稀土资源与环境重点实验室(2022IRERE305)
战略有色金属绿色低碳冶金江西省重点实验室江西理工大学(2024SSY11031)资助。
