The Mechanism Study Of Rare Earth From Chloride Medium With Synergistic Systems Of The Acidic Phosphorus-containing Extractant

The separation and purification of rare earth mainly used the method of solvent extraction at present. The system of P507-HCI has been widely used in the rare earth separation industry. However, problems of stripping existed in the extraction of the medium and heavy rare earth elements using P507. Compared with P507, the balance aqueous phase acidity of Cyanex272was lower, and the rare earth ions are readier for stripping. Therefore, the synergistic system of P507and Cyanex272which applied for the extraction of heavy rare earth elements may improve the stripping ability and reduce the acid and alkali consumption. When P507was used to separate light rare earth elements, the extraction ability decreased with the increase of the aqueous phase acidity and the saponification was needed which brought serious ammonia-nitrogen waste water pollution. P204has a higher balance aqueous phase acidity and bigger extraction ability comparatively with P507. So the synergistic system of P507and P204which applied for the extraction of light rare earth elements may improve rare earth separation and achieve non-saponification extraction separation. This paper has studied the mechanism of P507-Cyanex272system and P507-P204system. The mainly results are as follows:(1)The mechanism of P507-Cyanex272synergistic system aimed at heavy rare earth elements Y3+、Tm3+has been studied. The system of P507-Cyanex272shows synergistic effect. The maximum synergistic effect (R) was obtained at a composition of the molar ratio of P507to Cyanex272to be1:1and R increased with the increase of aqueous equilibrium pH. The chloride ion affected on the extraction with P507or Cyanex272alone, with one chloride ion involving in the extracted complexes. RE3++2H2B2(o)+Cl←�'RECl(HB2)2(o)+2H+However, no effect of chloride was found on the extraction with their synergistic system, mainly because of the steric hindrance and competition coordination. RE3++2H2A2(o)+H2B2(o)←�'RE(HB2)(HA2)2(o)+3H+(2) The mechanism of P507-P204synergistic system aimed at light rare earth elements Nd3+、Sm3+has been studied. The system of P507-P204shows synergistic effect. The maximum synergistic effect (R) was obtained at a composition of the molar ratio of P507to P204to be3:2and R increased with the increase of aqueous equilibrium pH. The chloride ion affected on the extraction with P507or P204alone, with one chloride ion involving in the extracted complexes. RE3++2H2L2(o)+Cl←�'RECI(HLZ)2(o)+2H+However, no effect of chloride was found on the extraction with their synergistic system. RE3++2H2L2(o)+H2A2(o)←�'HRE(HA2)(HL2)2(o)+3H+(3) The rule of extraction separation of high concentration P507and/or P204extracting Nd3+、Sm3+in sulfuric-hydrochloric acid has been studied. The system of P507-P204showed evident synergistic effect. The separation coefficient βSm/Nd increased with the increase of balance aqueous phase acidity. At the same aqueous equilibrium pH, βsm/Nd of P507-P204system is the biggest. Therefore, in the sulfuric-hydrochloric acid medium, the synergistic system P507-P204not only had evident synergistic effect, but aslo had bigger than the one of single extractant P507or P204.