Date of Award

1980

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

The purpose of this work was to study the ion flotation properties of the platinum group metals, develop methods for the quantitative recovery of the platinum metals from dilute solutions by ion flotation and investigate the feasibility of ion flotation for the group separation. The anionic chlorocomplexes of Pd(II), Ir(IV), Pt(IV), Au(III), Rh(III) and Ir(III) were floated from aqueous solutions with cationic surfactants of the quaternary ammonium type, RNR(,3)Br. The flotation behavior of each metal was determined with respect to variations of the surfactant primary, R, and secondary, R', chain lengths, the initial HCl concentration, the initial NaCl concentration, the initial surfactant concentration and the initial metal chlorocomplex concentration. Most of the surfactants prepared for this work floated the platinum metals; however, the maximum percentage of each metal floated varied significantly as the above parameters were varied. An increase in the percentage of all the metals floated was observed as the surfactant primary chain length was increased. As the surfactant secondary chain length was increased, the percentage of Au(III), Pd(II), Pt(IV) and Ir(IV) floated increased, but the percentage of Ir(III) and Rh(IV) floated significantly decreased. Furthermore, as the initial HCl or NaCl concentrations were increased, the percentage of each of the metals floated decreased regardless of the surfactant used for flotation. The percentage of Ir(III) and Rh(III) floated decreased to zero as the initial HCl or NaCl concentration was increased to 0.5 M. The percentage of Pd(II) floated decreased to zero as the initial HCl concentration was increased to 2.0 M. A general flotation selectivity sequence of Au(III) > Pd(II), Ir(IV), Pt(IV) > Ir(III) > Rh(III) was observed. Ion flotation enrichment ratios were calculated and compared to anion exchange distribution coefficients in order to verify the selectivity trends. Optimum ion flotation conditions were established for the recovery of Au(III), Ir(IV) Pt(IV) and Pd(II) from dilute solutions. A modified solvent sublation method was developed for quantitatively recovering the floated metals in n-butyl acetate. Procedures were developed for the single stage, batch ion flotation separation of several binary mixtures of the platinum metals. For these separations, conditions were adjusted in which one metal was selectively floated from the solution and recovered by a modified solvent sublation method in n-butyl acetate. Iridium and rhodium were separated by floating the Ir(IV) from aqueous solutions of pH 2.0 with hexadecyltri-n-propylammonium bromide (HTPAB). The Rh(III) was not floated by HTPAB. Both metals were quantitatively recovered after separation. Rhodium(III) and Ir(IV) were also separated with other surfactants from solutions of various NaCl and HCl concentrations. Platinum and iridium were separated by reducing the iridium to Ir(III) with hydroxylamine and floating the Pt(IV) with hexadecyltri-n-butylammonium bromide (HTBAB) from solutions of 0.1 M HCl. Iridium(III) was not floated with HTBAB from 0.1 M HCl solutions. Platinum(IV) and Ir(III) were also separated with other surfactants from solutions of various NaCl and HCl concentrations. Palladium(II) and Pt(IV) were partially separated from solutions of various initial HCl concentrations with all of the surfactant prepared for this work. Platinum(IV) was recovered free of Pd(II) from 2.0 M HCl solutions. Palladium(II) and Pt(IV) were quantitatively separated with HTBAB from 0.01 M NH(,3) solutions. The Pd(II) was converted to the cationic complex, Pd(NH(,3))(,4)('2+), by reaction with ammonia and was not floated by the cationic surfactants. The PtCl(,6)('2-) was unaffected by the ammonia and was floated by the surfactants. Palladium(II) and Pt(IV) were also separated with other surfactants from solutions of various ammonia concentrations.

Pages

163

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