Selective preparation of neodymium phosphates from iron mixed solution by two-step precipitation

Abstract

Abstract Neodymium iron boron alloy, Nd2Fe14B, is used in the manufacture of magnets. Neodymium is one of the rare earth elements, so it is valuable and expensive. In order to protect this rare earth resource, it is required to collect, reuse, and recyle rare earth elements. Recently, a new method for recovering neodymium phosphate from mixed solutions has been reported, avoiding the difficulties reported by previous methods. Since rare earth phosphate is the main component of rare earth ore, this new phosphate process was proposed. Neodymium phosphate was precipitated selectively from iron-neodymium mixed aqueous solution by 2 step processes with pH adjustments in this work. With this method, it was possible to separate neodymium and iron without using high temperatures or specialized equipment. The optimum conditions were determined by evaluating precipitation by yield, Fe/Nd ratio, hue, UV–visible reflectance spectra, X-ray diffraction, and infrared spectroscopy. In step I where pH was adjusted using sodium hydroxide, iron hydroxide was precipitated. Then, phosphoric acid was added, and the pH was further adjusted to obtain a neodymium phosphate precipitate as step II. The optimum conditions of this separation method were clarified.