Synthesis of neodymium phosphate from iron-neodymium solution using sodium sulfite

Abstract

Iron-neodymium alloys are generally used for producing magnets. Neodymium falls under the class of rare earth elements, which are precious and expensive, and are thus often recovered by recycling processes as a cost saving measure. There are a few reported processes for the recycling of rare earth elements; however, these processes have disadvantages, including the requirement for high temperatures and the use of harmful gases. In this study, a novel technique for recovery of neodymium while circumventing the difficulties reported in previous methods is presented. Because rare earth phosphates are the main components of rare earth ore, a novel phosphate process is suggested in this work. In this process, an iron-neodymium solution was mixed with phosphoric acid solution and then adjusted to several different pH values using sodium hydroxide solution and nitric acid. The precipitates were filtered and dried. The ratio of neodymium to iron in the precipitates and filtered solutions was estimated by the inductively coupled plasma (ICP) method. As an ideal phenomenon, neodymium phosphate was filtered off and the cationic iron species were contained in the filtrate. The Fe/Nd and P/(Fe+Nd) ratios, concentrations of neodymium, iron, and phosphoric acid, and pH were varied to study precipitation of the neodymium compounds. The neodymium cation was recovered from the iron-neodymium solution using phosphoric acid. This novel process was demonstrated to be useful for the recovery of neodymium, and may find applications in the recycling and recovery of other rare earth elements of interest.