Rare earth elements are one of the most essential ingredient of modern technological applications. The extraction and recovery of rare earths from primary resources generates huge overburden, which adversely affect the environment. The spent Neodymium-Iron-Boron (NdFeB) magnet can be a potential secondary resource of rare earths through urban mining and recycling. In the earlier studied hydrometallurgical processes for the recovery of rare earths from spent NdFeB magnet, use of concentrated acids during leaching, discharge of acidic effluents and involvement of energy intensive oxidation roasting operations (500–950 °C) found as the major drawbacks of the processes. In view of high energy consumption and environmental concern, the present paper is focused on the development of an energy efficient process for the recovery of rare earths from spent NdFeB magnet. In this study, conventional oxidation roasting-acid leaching method was adapted to a lower temperature chlorination roasting-water leaching process by reducing the roasting temperature to 300 °C. In the process, ammonium chloride (NH₄Cl) was used as chloridizing agent. The thermodynamic feasibility for selective chlorination of rare earths in the presence of NH₄Cl was studied using FactSage and Thermo Gravimetric- Differential Thermal Analysis (TG-DTA). In order to determine the most suitable chlorination roasting condition, the effect of different parameters such as temperature, NH₄Cl dosage and roasting time were studied in detail. The roasted products were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and chemical analysis. The rare earths were quantitatively and selectively recovered at the most suitable chlorination roasting condition (300 °C, 3 times of stoichiometric amount, 3 h) followed by water leaching. From the leach solution, rare earth oxide of 99.2% purity was produced. The leach residue containing 96.4% Fe₂O₃ was obtained as a by-product of the process. The lower chlorination roasting temperature and shorter roasting time (300 °C, 3 h) make the process more energy-efficient. The process with zero effluent discharge is easily scalable and environment-friendly.

稀土元素是现代技术应用中最重要的成分之一。从主要资源中提取和回收稀土会产生巨大的负担，对环境造成不利影响。废钕铁硼磁体可以通过城市采矿和回收利用成为潜在的稀土二次资源。在较早研究的从废NdFeB磁体中回收稀土的湿法冶金工艺中，浸出过程中使用浓酸，酸性废水的排放以及涉及能量密集型氧化焙烧操作（500-950°C）的发现是其主要缺点。流程。鉴于高能耗和对环境的关注，本文的重点是开发一种从废NdFeB磁铁中回收稀土的节能工艺。在这项研究中，通过将焙烧温度降低到300°C，将传统的氧化焙烧酸浸出方法应用于较低温度的氯化焙烧焙烧水浸出过程。在此过程中，氯化铵（NH₄ Cl）的作为氯化剂。使用FactSage和热重差热分析（​​TG-DTA）研究了在NH ₄ Cl存在下对稀土进行选择性氯化的热力学可行性。为了确定最合适的氯化焙烧条件，不同参数如温度，NH _4的影响详细研究了Cl的添加量和焙烧时间。烘焙产品通过X射线衍射（XRD），扫描电子显微镜-能量色散X射线光谱（SEM-EDS）和化学分析进行了表征。在最合适的氯化焙烧条件下（300°C，化学计量的3倍，3 h）对稀土进行定量和选择性回收，然后进行水浸。从浸出溶液中，制得纯度为99.2％的稀土氧化物。作为该方法的副产物，获得了含有96.4％Fe ₂ O ₃的浸出残余物。较低的氯化焙烧温度和较短的焙烧时间（300°C，3小时）使该过程更加节能。零废水排放的过程易于扩展且对环境友好。