Synthesis and characterization of neodymium phosphate powder resulted from neodymium loaded-HDEHP organic solutions by a stripping–precipitation process using a Lewis type cell

The solvent extraction process of neodymium(III) from aqueous solution by di(2-ethylhexyl) phosphoric acid (HDEHP) in kerosene has been performed as a first step to accomplish the homogeneous precipitation of neodymium phosphate by stripping from an organic metal loaded HDEHP solution using phosphoric acid solutions. In this study, stripping–precipitation approach was proposed to synthesize powders of neodymium phosphate using a modified Lewis cell. The effects of extractant, organic phase, neodymium concentration, stripping phase, phosphoric acid content and temperature were separately investigated. The neodymium precipitate was characterized by X-ray diffractometry, scanning electron microscopy, particle size measurement, thermogravimetric analysis and infrared spectroscopy. The results showed that the powder precipitated with 3 M H3PO4 showed more regular and slightly larger particles than those obtained by 5 M H3PO4 while the precipitate with 8 M H3PO4 gave highly agglomerated particles. Increasing the HDEHP concentration from 0.25 M to 0.75 M gave an increase of the particle size of the precipitate. As the temperature increases (10–45 °C), the formed particles appeared to be more crystalline and smaller in size.

Pre-extracted neodymium was stripped from an organic loaded HDEHP solution using phosphoric acid solutions. Increasing the HDEHP concentration from 0.25 M to 0.75 M gave an increase of the particle size of the precipitate.Figure optionsDownload as PowerPoint slideResearch highlights
► Pre-extracted neodymium was stripped from an organic loaded HDEHP solution using phosphoric acid solutions.
► Stripping–precipitation approach was proposed to synthesize powders of neodymium phosphate.
► The powder precipitated with 3 M H3PO4 showed more regular particles and slightly larger than those obtained by 5 M H3PO4.
► Increasing the HDEHP concentration gave an increase of the particle size of the precipitate.