Solvent Extraction of La(III) from Chloride Medium in the Presence of Two Water Soluble Complexing Agents with di-(2-ethylhexyl) Phosphoric Acid

The extraction of single La(III) from chloride medium with di-(2-ethylhexyl) phosphoric acid (P204) in the presence of two complexing agents, lactic acid (LA) and citric acid (H(3)cit), is investigated. The results show that separation factors (beta) between some light rare earths are higher than those in the conventional extraction systems under the same conditions, indicating that this system would be suitable for the extraction and separation. The equilibrium constants and thermodynamic functions, Delta H, Delta G, and Delta S, are calculated, and the cation exchange mechanism is also clarified by Fourier transform infrared (FTIR) spectroscopy. The recycling experiments also indicate that the two complexing agents can be effectively recycled, and the total chemical oxygen demand (COD) value in the raffinate is 65.84 mg/L, which meets the Emission Standards of Pollutants from Rare Earths Industry from the Ministry of Environmental Protection, People's Republic of China (2006). The results demonstrate that this system could be regarded as a promising green and effective separation technology