分层取样方式对碳酸氢铵沉淀法生产碳酸稀土过程混合RECl3溶液理化指标检测结果的影响研究

稀土的提取与分离需要经过硫酸焙烧、水浸、萃取、反萃和碳沉等一系列过程,其中混合RECl₃溶液是稀土产业线中的重要中间产品,该混合稀土溶液的REO浓度、配分、密度等理化指标是评价混合RECl₃溶液产品质量的主要参数。针对一定存储条件下的混合RECl₃溶液,按照国家标准分析方法,结合X射线荧光光谱法(XRF)、电感耦合等离子体原子发射光谱法(ICP-AES)和重量法等手段,对该溶液中的REO浓度、配分、密度等项目进行检测,研究分层取样方式对3项理化指标的影响及变化规律。通过不同存放时间的变化因素绘制混合RECl₃溶液中REO浓度、密度的变化曲线,得出混合RECl₃溶液的存放时间越长,不同层面取样时这两个指标检测结果差异越大的结论;浅析了混合RECl₃溶液取样深度变化对检测结果的影响因素,对混合RECl₃溶液从表层到底层按照均匀间隔取样进行检测,得出REO浓度和密度的检测结果呈递增趋势,配分的检测结果呈轻稀土含量减少、重稀土含量增加的趋势等结论;研究了混合RECl₃溶液中REO浓度范围差异与存放一定时间内REO浓度的变化趋势,得出REO质量浓度小于50 g/L或大于250 g/L时,其检测结果变化缓慢,REO质量浓度在100～200 g/L时,其检测结果变化快速的结论。深入剖析了分层取样方式影响检测结果的基础理论,此研究可用于指导用于稀土应用产品的混合RECl₃溶液的质量控制,对规范混合RECl₃溶液的取样操作具有重要的指导意义。

Investigation on effect of the stratified sampling mode on determination results of physical and chemical index of mixed RECl3 solution produced during rare earth carbonate production by ammonium bicarbonate precipitation method

The extraction and separation of rare earths require a series of processes such as sulfuric acid roasting, water leaching, extraction, back extraction, and ammonium bicarbonate precipitation. Among them, the mixed RECl₃ solution is an important intermediate product in the rare earth industry line. The physical and chemical indexes of mixed rare earth solution, including rare earth oxide (REO) concentration, the ratio of single rare earth to the total rare earth, and density, are the key parameters to evaluate the quality of mixed RECl₃ solution products. According to the national standard analysis methods and other approaches including X-ray fluorescence spectrometry (XRF), inductively coupled plasma atomic emission spectrometry (ICP-AES) and gravimetry, the effect of the stratified sampling mode on the determination results of REO concentration, the ratio of single rare earth to the total rare earth, and the solution density in mixed RECl₃ solution stored under certain environmental condition was investigated. The changing curve of REO concentration and density was plotted by varying the storage time. It was found that the difference of determination results of samples with different stratified sampling mode increased with increasing the storage time of mixed RECl₃ solution. The influence factors of sampling depth of mixed RECl₃ solution on the determination results was briefly discussed. The mixed RECl₃ solution was sampled at uniform intervals from surface to bottom for determination. The results of REO concentration and density showed an increasing trend. While the ratio of light rare earth to the total rare earth showed a decreasing trend, and the ratio of heavy rare earth to the total rare earth showed an increasing trend. The variation trend of REO mass concentration with REO concentration range difference in mixed RECl₃ solution within certain storage time were investigated. It was shown that the determination results of REO concentration changed slowly when its mass concentration was less than 50 g/L or higher than 250 g/L. When REO mass concentration was in range of 100-200 g/L, the determination results of REO concentration changed fast. The basic theory for the influence of stratified sampling mode on determination results was deeply analyzed. This study could be used to guide the quality control of mixed RECl₃ solution in rare earth production industry. It had important guiding significance for normalizing the sampling operation of mixed RECl₃ solution.