Determination Of Platinum, Palladium And Rhodium In Automobile Exhaust Catalysts

With the development of science and technology and the arising of the global environmental protection, thousands of automobile exhaust catalysts have been applied in vehicles to clean up automobile exhaust gases, which contribute to the increase of demand for noble metals and make them more and more expensive. Recently it becomes a highlight for the presis analysis of noble metals which is essemcial for reasearch, production and test, recycle process for noble metals catalysts.This dissertation consists of the following four chapters. In the first chapter, the recent development of the separation and enrichment technology, analysis methods and the application scope for noble metals were reviewed. In addition, the purpose and main content of the paper were proposed also.In chapter two, solvent impregnated resins(CL-TBP) have been formed by impregnating Amberlite XAD7HP with 34% tributyl phosphate as the extractant. Physical-chemistry adsorption, FT-IR and flame atomic absorption spectrometry (FAAS) characterization technology have been used to investigate the adsorption property of CL-TBP to Pt (IV) ion of noble metal. The influence of hydrochloric acid concentration, time for oscillations, reaction temperature, and coexistence ions to adsorption property of the resins also have been researched. It is showed that distribution ratio reaches to the max as hydrochloric acid concentration on 3.5mol/L. And the perfect time of oscillations is 10min. The optimal reaction temperature is 20℃near room temperature. The capacity of saturation adsorption of CL-TBP to Pt (IV) ion is 4.86mg/g, and the enrichment multiple for Pt is 200 in 50μg/L solution as recycle rate reaching 95%. Besides, this method has been used in the separation and enrichment process for Pt in synthetical automobile exhaust catalysts solution, in which Pt (IV) is separated successfully among Pd(II), Rh(III) and other base metal ions. The recovery assay results is among 90.89 % to 108.9% .In chapter three, the content of platinum, palladium and rhodium in automobile exhaust catalyst were detected by FAAS to investigate the different anslysis method for noble metals. In this work , in order to avoid the interference of spectral line of the nickel, the second sensitive wavelength (369.2nm) of rhodium was used as the detection wavelength. At the same time, the standard addition method was adopted to overcome the synergistic effects of the matrix elements. In which the range of linearity is from 0.5μg/ml to 20μg/ml; detection limit is 0.072μg/mL; relative standard deviation ranges from 1.8% to 2.7% and the recovery from 102.9% to 104.7%.For palladium detection, the working curve method produces good accurate and precise results,in which the range of linearity is from 0.1μg/ml to 15μg/ml; detection limit is 0.029μg/mL; RSD ranges from 0.8% to 2.5% and the recovery from 99.6% to 101.2%. After the separation for Pt in automobile exhaust catalysts, the result of platinum detection by FAAS method is favorable where RSD ranges from 5.8% to 7.5% and the recovery from 96.0% to 98.5%. Above all, the detection method for noble metals in automobile exhaust catalysts proved to be feasible for analysis process and recycle application.For chapter four, the primary investigation for noble metals analysis in automobile exhaust catalysts was carried through with X-ray fluorescence analysis(XRF) and polarographic catalytic wave(PCW) methods. In analysis process for noble metals by XRF, the samples should be prepared in powder in order to allay detection error. It is showed that XRF can be adopted as a good analysis method in quick detection of Pt and Pd, as its breakageless, rapid, simplify and highly roboticized character. It should be noted that XRF method can be used to analysis platinum and palladium but not rhodium with Rh target as diffraction source, and it can be a supplement for other methods. In addtion, PCW method was used to detection for rhodium, and this method is very sensitive to rhodium detection, in which detection limit is 10-11g/L, RSD ranging from 4.5% to 5.1%, respectively.