2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (widely known in the global hydrometallurgical industry as P507, PC-88A, SME 418, or HEHEHP) is an advanced acidic organophosphorus solvent extraction (SX) reagent.
This phosphonic acid monoester features an unsymmetrical chemical structure that balances strong metal-complexing power with exceptional selectivity, making it the foundational chemical engine for rare earth element (REE) separation and high-purity battery metal refining.
2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester also be named P507, the Technical Specifications as below:
CAS No.：14802-03-0
Molecular formula: C16H35O3P isomer
Molecular weight: 306.427
EINECS number: 238-865-3
Density: 0.95 g/ml
Vapor pressure: 0.085Pa at 25 ℃
Refractive index: 1.4400-1.4460
Flash point>100 ° C
Storage conditions: Store below+30 ° C
Solubility: soluble in toluene and ethanol
Form: Transparent liquid
Acidity coefficient (pKa): 3.1 [at 20 ℃]
Color: colorless to light yellow to light orange
PH value: 2.3 (10g/l, H2O, 20 ° C) (as an emulsion)
Water solubility: 5.95 μ g/L at 20 ℃
Boiling point>180 ° C (1013hPa) decomposes
Core Industrial Applications
A. Advanced Rare Earth Element (REE) Fractionation
In lanthanide metallurgy, separating adjacent rare earth elements (such as Neodymium/Praseodymium or Samarium/Gadolinium) is incredibly challenging due to the “lanthanide contraction,” which gives these elements nearly identical ionic radii.
The P507 Advantage: 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester exhibits significantly higher separation factors for these adjacent elements compared to standard D2EHPA. It is utilized in massive, multi-stage mixer-settler cascades to achieve product purities exceeding 99.99%.
B. High-Purity Cobalt-Nickel Separation
For electric vehicle (EV) battery chemistry supply chains, isolating cobalt (Co ion) cleanly away from vast nickel (Ni ion) background matrixes is critical.
At a precisely maintained acidic operational window (pH 4.0–5.0), this reagent forms stable, oil-soluble chelates with cobalt ions, leaving nickel fully rejected in the aqueous raffinate stream.
Operational Advantages & Challenges
Key Benefits:
High Hydrophobicity: Its dual 2-ethylhexyl branched alkyl chains ensure exceptionally low water solubility (0.05 g/L), minimizing organic entrainment losses into processing raffinate solutions.
Efficient Stripping Kinetics: Because its metal-complexation forces are thermodynamically milder than phosphinic alternatives (like DY272), stripping the loaded metals out of the organic phase requires lower concentrations of hydrochloric or sulfuric acid, cutting down chemical operating costs.
Carrier Miscibility: Completely miscible with standard aliphatic and low-aromatic hydrocarbon diluents (e.g., Escaid 110, 260# solvent oil).
By the way, our metal extractants as below, if you need, please feel free to ask us:
- P204 (D2EHPA or HDEHP) This is used for first step to remove impurity for laterite nickel ore.
- P507 non-ferrous metal extractant for copper, zinc, cobalt-nickel, cadmium, gold-silver, platinum group metals, rare earths and so on.
- DY272 Nickel cobalt separation extractant, it can take cobalt out from nickel cobalt solution, then leave pure nickel.
- DY984N copper solvent extraction reagent.
- QL256-2 Nickel Cobalt Manganese co extraction Extractant.
- DY316 Lithium extractant.
- DY319 high efficiency nickel cobalt co-extraction extractant for battery recycling, can take out nickel and cobalt together from Lithium battery electrolyte.
- DY366 Scandium extractant.
- DY377 efficient nickel and diamond separation extractant.
