An Experimental Investigation of the Liquid–Liquid Extraction of Neodymium from Aqueous Solutions Using bis(2-Ethylhexyl) Phosphoric Acid

Rare earth elements (REEs) are indispensable to clean energy and advanced technologies, with neodymium (Nd) being critical for permanent magnets and high-performance devices. Therefore, efficient, and sustainable recovery of Nd(III) is essential. This study investigates the liquid-liquid extraction (LLE) of Nd(III) from aqueous chloride solutions using bis(2-ethylhexyl) phosphoric acid (D2EHPA) in toluene under batch conditions. Four parameters, aqueous pH (1.0–3.0), extractant concentration (0.15–0.60 mol L^–1), agitation rate (250–450 rpm) and residence time (5–20 min) were taken and varied in this study. The study used UV-Vis spectroscopy at 583 nm to quantify Nd(III), and FTIR confirmed the metal-extractant complex. The findings show that extraction efficiency increased sharply with pH, achieving around 55% at pH 2.0 and reaching equilibrium near 58% at pH 3.0. An extractant concentration of 0.45 mol L^–1 and agitation at 400 rpm for 15 min yielded optimal recovery while minimizing reagent use and processing time. Triplicate experiments demonstrated reproducibility with a mean relative standard deviation of around 3%. These findings establish a clear mechanistic and parametric understanding of Nd(III) transfer, contributing to conscious solvent extraction and a foundation for intensified processes.