Precious Metals Platinum, Palladium Separation And Enrichment

Platinum and palladium are two elements of platinum group metals, which belong to the precious metals. Their properties are so close, the separation of them is not easy, and the determinations are usually mutually disturbed.This paper have chosen a proper extraction system, tested the separation effect, explored the mechanism of the extraction, made the extractant reuse a reality and found appropriate methods for their determinations. The finished work as follows:(l)After reading a lot of related papers , chlorophosphonazoⅢ was chosen as the extractant , then the formation of the complex was studied. Its conditions is, in the H₂SO₄ solution, heating over 7min in boiling water and chlorophos-phonazoIII volume must reach 5.64×10^-7mol/10ugPd (Ⅱ) .After that, using chlorophosphonazoⅢ as the extractant, by experiments, absolute ethyl alcohol was chosen as the extraction solvent and ammonium sulphate as thesalting-out agent. The extraction system was established---absolute ethylalcohol -ammonium sulfate-water aqueous two-phase system. (2)Through the conditional experiments of absolute ethyl alcohol -ammonium sulfate-water aqueous two-phase system, its best experiment conditions were decided. That is: the volume ratio of absolute ethyl alcohol in solution is 30%, ammonium sulfate volume is not less than 5. Og, and the aqueous solution is 4mmol/10ml H₂SO₄ solution.(3)In the best conditions, the extraction maximum and the extraction rate were studied both in the platinum solution and in palladium solution. In the mixed solution, the extraction maximum of palladium and the content of platinum in raffinate were investigated. The results are: in the palladium solution, the extraction maximum is about 150ug/10ml and the extraction rate is nearly 100%;in the platinum solution, they are 380ug/10mland about 15%;in the mixed solution, the extracted maximum of palladium is about 150ug/10ml and the content of platinum in raffinate can reach 97%.(4)By the stripping of palladium, it was found that both HC1 and NH₃ ? H₂0 can be stripping agents, but the stripping effect of NH₃ ? H₂O is better, andthe extractant chlorophosphonazoIH can be reused if using NH3? H20 as the stripping agent.?Using continuous variation method and mole-ration method, the composition of the Pd-chlorophosphonazoIIIcomplex were determinated. That is chlorophos-phonazoIII '■ Pd=2 : 1. Associating related theories and reports, the structure of the complex was speculated and the mechanism of the extraction was explored. The conclusions is: the complexation reaction of palladium with chlorophosphonazoffi can produce complex anion, then the complex anion and protonated ethanol will form ion-association complex, this complex can be extracted into the ethanol phase.(6)The spectrometry determination of the Pd(II) extractive were studied in the present of absolute ethyl alcohol and ammonium sulfate. it was found that there is no influence if the blank is extracted by the same method. Therefore, the direct determination for the extractive was decided. (7)By experiments, it showed that absolute ethyl alcohol can increase the absorbance of Platinum over 0. 5 time and ammonium sulfate have no influence, so the spectrometry determination method for platinum was chosen, that is: determination of platinum in Pt (IV) -absolute ethyl alcohol-tin (II) chloride -bytyirhodamine B-PVA colour system.