The extraction of trichlorostannato-rhodium complexes by polyurethane foam

 

Show simple item record

dc.contributor.advisor Koch, Klaus R en_ZA
dc.contributor.author Hall, Iris en_ZA
dc.date.accessioned 2016-10-14T06:27:19Z
dc.date.available 2016-10-14T06:27:19Z
dc.date.issued 1990 en_ZA
dc.identifier.citation Hall, I. 1990. The extraction of trichlorostannato-rhodium complexes by polyurethane foam. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/22135
dc.description.abstract Polyurethane foam (polyether based) has been found to efficiently extract rhodium from hydrochloric acid solutions containing stannous chloride. The amount of rhodium extracted is significantly influenced by inter alia temperature, acid concentration, the Sn(II):Rh mol ratio and the presence of alkali metal cations. The extraction efficiency is promoted by increased acid concentration and high Sn(II):Rh ratios. The presence of K⁺ inhibits the extraction of rhodium, while the effect of Li⁺ and Na⁺ is small. A series of model urethane compounds (diurethane podands and linear polyurethanes) have been synthesized and characterized. These model compounds allowed the direct determination of the extracted trichlorostannato·rhodium complex anions by ¹¹⁹Sn nmr spectroscopy. Conditions favouring the formation of [Rh(SnCl₃)₅]⁴⁻ were found to result in the extraction of increased amounts of rhodium. The predominant species in the urethane phase was identified as the hydrido complex, [RhH(SnCl₃)₅]³⁻, which is formed by protonation of [Rh(SnCl₃)₅]⁴⁻. The protonation reaction has been shown to be reversible. The ¹¹⁹Sn nmr study showed the formation of a new rhodium-hydrido complex formulated to be [RhH(SnCl₃)₄Cl]³⁻. In the presence of low tin(II) concentrations {Sn(II):Rh = 4:1}, [Rh(SnCl₃)₃Cl₃]³⁻ is predominantly extracted by the foam phase. Analysis of the acid-decomposed polyurethane foam phase by atomic absorption spectroscopy and of the model urethane compound phase by ⁷Li nmr spectroscopy, confirmed the extraction of alkali metal cations from aqueous solutions containing alkali metal salts. Our studies indicate that the polyether chains of polyuretha foam playa major role in the extraction process, and that the flexibility of the chains influences the efficiency of polyurethane foam as an extractant. The creation of cationic sites within the foam matrix, which facilitate the extraction of the rhodium-tin complex anions, is postulated to occur by protonation of the donor oxygen atoms as well as by chelation of cations such as H₃O⁺, Li⁺, Na⁺ and K⁺ by the polyether chains. A working model for the extraction of the trichlorostannato-rhodium complexes by polyurethane foam is proposed. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Chemistry en_ZA
dc.title The extraction of trichlorostannato-rhodium complexes by polyurethane foam en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Chemistry en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Hall, I. (1990). <i>The extraction of trichlorostannato-rhodium complexes by polyurethane foam</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Chemistry. Retrieved from http://hdl.handle.net/11427/22135 en_ZA
dc.identifier.chicagocitation Hall, Iris. <i>"The extraction of trichlorostannato-rhodium complexes by polyurethane foam."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Chemistry, 1990. http://hdl.handle.net/11427/22135 en_ZA
dc.identifier.vancouvercitation Hall I. The extraction of trichlorostannato-rhodium complexes by polyurethane foam. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Chemistry, 1990 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22135 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Hall, Iris AB - Polyurethane foam (polyether based) has been found to efficiently extract rhodium from hydrochloric acid solutions containing stannous chloride. The amount of rhodium extracted is significantly influenced by inter alia temperature, acid concentration, the Sn(II):Rh mol ratio and the presence of alkali metal cations. The extraction efficiency is promoted by increased acid concentration and high Sn(II):Rh ratios. The presence of K⁺ inhibits the extraction of rhodium, while the effect of Li⁺ and Na⁺ is small. A series of model urethane compounds (diurethane podands and linear polyurethanes) have been synthesized and characterized. These model compounds allowed the direct determination of the extracted trichlorostannato·rhodium complex anions by ¹¹⁹Sn nmr spectroscopy. Conditions favouring the formation of [Rh(SnCl₃)₅]⁴⁻ were found to result in the extraction of increased amounts of rhodium. The predominant species in the urethane phase was identified as the hydrido complex, [RhH(SnCl₃)₅]³⁻, which is formed by protonation of [Rh(SnCl₃)₅]⁴⁻. The protonation reaction has been shown to be reversible. The ¹¹⁹Sn nmr study showed the formation of a new rhodium-hydrido complex formulated to be [RhH(SnCl₃)₄Cl]³⁻. In the presence of low tin(II) concentrations {Sn(II):Rh = 4:1}, [Rh(SnCl₃)₃Cl₃]³⁻ is predominantly extracted by the foam phase. Analysis of the acid-decomposed polyurethane foam phase by atomic absorption spectroscopy and of the model urethane compound phase by ⁷Li nmr spectroscopy, confirmed the extraction of alkali metal cations from aqueous solutions containing alkali metal salts. Our studies indicate that the polyether chains of polyuretha foam playa major role in the extraction process, and that the flexibility of the chains influences the efficiency of polyurethane foam as an extractant. The creation of cationic sites within the foam matrix, which facilitate the extraction of the rhodium-tin complex anions, is postulated to occur by protonation of the donor oxygen atoms as well as by chelation of cations such as H₃O⁺, Li⁺, Na⁺ and K⁺ by the polyether chains. A working model for the extraction of the trichlorostannato-rhodium complexes by polyurethane foam is proposed. DA - 1990 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1990 T1 - The extraction of trichlorostannato-rhodium complexes by polyurethane foam TI - The extraction of trichlorostannato-rhodium complexes by polyurethane foam UR - http://hdl.handle.net/11427/22135 ER - en_ZA


Files in this item

This item appears in the following Collection(s)

Show simple item record