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Effects of Dissolution Conditions on the Recovery of Neodymium Phosphate from Waste Magnets



Author(s)

Hiroaki Onoda and Atsuya Iinuma

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DOI:10.17265/2161-6221/2022.1-3.002

Department of Informatics and Environmental Sciences, Kyoto Prefectural University, 1-5, Shimogamo Nakaragi-cyo, Sakyo-ku, Kyoto 606-8522, Japan

Neodymium-iron-boron alloy (Nd₂Fe₁₄B) is used in the manufacture of magnets. Neodymium is one of the rare earth elements and is therefore valuable. Recovery, reuse, and recycling of rare earth elements is necessary to protect this rare earth resource. Recently, a new method for recovering neodymium phosphate from iron-neodymium mixture solutions using a two-step precipitation method has been reported, avoiding the difficulties reported with previous methods. In this method, iron compounds were removed in Step I and neodymium phosphate was precipitated in Step II. This novel phosphate process was proposed because rare earth phosphate is the main component of rare earth ores. In this study, we dissolved actual waste magnets in various acids to obtain neodymium phosphate by this two-step precipitation process. The resulting precipitates were evaluated by XRD (X-ray diffraction), infrared spectroscopy, color hue, UV-visible reflectance spectra, Fe/Nd ratio, and recovery of neodymium and iron. The results showed that neodymium phosphate was selectively obtained by using nitric acid and hydrochloric acid. In particular, samples prepared with nitric acid showed no reddening due to iron compounds.

Rare earth recovery, phosphoric acid, precipitation.