Liu Youwei, Zhong Yuan, Lei Xiang, Wang Jinliang
School of Metallurgical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, China.
Yichun Lithium New Energy Industry Research Institute, Jiangxi University of Science and Technology, Yichun 336000, China.
Materials (Basel). 2024 Nov 27;17(23):5807. doi: 10.3390/ma17235807.
We conducted a mechanistic and experimental study on zinc fluoride roasting for the recovery of NdFeB waste to address the difficulties faced during this pyrometallurgical recovery process, such as the high dependence on the quality of raw materials, the high energy consumption involved in roasting transformations, and the low added value of mixed rare earth products. Thermodynamic calculations showed the feasibility of fluorinating rare earths in NdFeB waste, and one-factor experiments were performed. The results showed that at a roasting temperature of 850 °C, a reaction time of 90 min, and 100% ZnF addition, the fluorination rate of rare earths could reach 95.69%. In addition, after analyzing the mesophase composition of a clinker under different roasting temperature conditions, it was found that, when the roasting temperature exceeded 850 °C, the fluorination rate of rare earths was reduced, which was consistent with the thermodynamic results. On this basis, response surface methodology (RSM) was used to carry out experiments to investigate in depth the effects of various factors and their interactions on the fluorination rate of rare earths, which provides a sufficient experimental basis for the recovery of NdFeB waste via fluorination roasting. The results of this study show that ZnF addition had the greatest influence on the rare earth fluorination reaction, followed by roasting temperature and roasting time. According to the optimization results of the model, the optimal roasting conditions were determined as follows: 119% ZnF addition at 828 °C, a roasting time of 91 min, and a rare earth element fluorination rate of 97.29%. The purity of the mixed fluorinated rare earths was as high as 98.92% after leaching the roasted clinker with 9 M hydrochloric acid at a leaching temperature of 80 °C, a liquid-solid ratio of 4 mL/g, and a leaching time of 2.5 h. This study will lay the foundation for promoting the application of pyrometallurgical technology in the recycling of NdFeB waste.
我们针对氟化锌焙烧回收钕铁硼废料开展了一项机理与实验研究，以解决该火法冶金回收过程中面临的难题，比如对原材料质量的高度依赖、焙烧转化过程中的高能耗以及混合稀土产品附加值低等问题。热力学计算表明了对钕铁硼废料中的稀土进行氟化的可行性，并进行了单因素实验。结果显示，在焙烧温度为850℃、反应时间为90分钟且氟化锌添加量为100%的情况下，稀土的氟化率可达95.69%。此外，在分析不同焙烧温度条件下熟料的中间相组成后发现，当焙烧温度超过850℃时，稀土的氟化率降低，这与热力学结果一致。在此基础上，采用响应面法（RSM）进行实验，深入研究各种因素及其相互作用对稀土氟化率的影响，为通过氟化焙烧回收钕铁硼废料提供了充分的实验依据。本研究结果表明，氟化锌添加量对稀土氟化反应的影响最大，其次是焙烧温度和焙烧时间。根据模型的优化结果，确定了最佳焙烧条件如下：氟化锌添加量为119%，焙烧温度为828℃，焙烧时间为91分钟，稀土元素氟化率为97.29%。在80℃的浸出温度、4 mL/g的液固比以及2.5小时的浸出时间下，用9M盐酸浸出焙烧后的熟料后，混合氟化稀土的纯度高达98.92%。本研究将为推动火法冶金技术在钕铁硼废料回收中的应用奠定基础。
