Effective separation of neodymium and lanthanum by single-module hollow fiber supported liquid membrane with P507 as extractant

Rare earth elements (REEs) are commonly categorized into light (LREEs), medium (MREEs), and heavy (HREEs) groups. Separation between LREEs and MREEs or MREEs is relatively straightforward. However, isolating LREEs themselves is particularly challenging because of their similar ionic radii and identical charges. Traditional separation processes are hindered by drawbacks including low recovery rates for dilute REEs, poor selectivity, complex protocols, and environmental pollution. Consequently, developing a cleaner and more efficient method for LREEs separation is imperative. In this study, we employed a single-module hollow fiber supported liquid membrane (HFSLM) system with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507) as an extractant to concurrently extract and strip La3+ and Nd3+ from the mixed LREEs containing solutions. We also investigated the impact of flow rate, stripping solution acidity, feed solution pH, P507 concentration, Nd3+ concentration of feed solution, and the volume ratio between the feed and stripping solutions influence the extraction and stripping of LREEs, as well as the molar fractions of La3+ and Nd3+ in the solutions. Under optimal condition, the molar fraction of La3+ was 99.0% in the feed solution, whereas the molar fraction of Nd3+ reached 91.6% in the stripping solution. Furthermore, the experimental results demonstrated a consistent preference of P507-HFSLM system for extracting Nd3+ over La3+, and the underlying mechanism was thoroughly investigated. In summary, this study offers comprehensive insights and technical approaches for selective separation and purification of LREEs.