Recovery of neodymium from an iron–neodymium solution using phosphoric acid

• Neodymium was recovered selectively from an iron–neodymium solution using phosphoric acid and ascorbic acid.
• The recovery ratio of iron decreased linearly with the concentration of ascorbic acid up to Asc/Fe = 0.5.
• The precipitates indicated the XRD pattern of neodymium phosphate after heating at 700 °C.
• An excess amount of phosphoric acid was required to obtain high recover ratios of neodymium.

The iron–neodymium alloy is generally used for magnets. Neodymium is one of the rare earth elements; since these elements are precious metals and therefore rare and expensive, recycling processes are often used to save costs. There are a few reported processes for the recycling of rare earth elements; however, these processes have disadvantages, including requirements for high temperatures and harmful gases. In this paper, a novel technique is presented to recover neodymium without the difficulties reported in previous methods. Because rare earth phosphates are main components of rare earth ore, a novel phosphate process is suggested in this work. The iron–neodymium solution was mixed with phosphoric acid solution and then adjusted to pH with sodium hydroxide solution. Ascorbic acid was added to the iron–neodymium solution to reduce ionic valence of iron. The precipitates were filtered off and dried. The ratio of neodymium and iron in precipitates and filtered solutions was estimated with an ICP method. As an ideal phenomenon, neodymium phosphate was filtered off, and the filtered solution contained all cationic iron. The ratios of Nd/Fe, P/(Fe + Nd), the concentration of ascorbic acid, and pH were varied to study the precipitation of neodymium compounds. In this work, over 99% of neodymium cation was recovered from an iron–neodymium solution using phosphoric acid and ascorbic acid. This novel process was observed to be useful for the recovery of neodymium, and may have applications in the recycling and recovery of other rare earth elements of interest.