The separation of platinum and iridium by ion flotation

The anionic chlorocomplexes of platinum(IV) and iridium(III) are separated by ion flotation from acidic, aqueous solutions with cationic surfactants of the type C₁₆H₃₃NR'₃Br, where R' is methyl, ethyl, n-propyl, or n-butyl. The PtCl₆^2-, which forms readily floatable salts with each of the surfactants, is selectively floated from the IrCl₆^3- and recovered after flotation in n-butyl acetate. The efficiency of the separation increases as the R' chain length increases and a quantitative separation is obtained with hexadecyltributyl-ammonium bromide (HTBAB) in 0.1 M HCl solutions. Since the flotation properties of Ir(IV) are similar to those of Pt(IV), hydroxylamine hydrochloride is used to reduce Ir(IV) to Ir(in) selectively in the presence of Pt(IV).     

The separation of iridium and ruthenium by ion flotation

Mixtures of iridium(IV) and ruthenium(III) as IrCl^2?₆ and RuCl^t—₆ are separated by ion flotation. Iridium (IV) is selectively floated from mixtures of the metal complexes in aqueous 1.0 M hydrochloric acid with hexadecylpyridinium bromide (HPB) and nitrogen. Ruthenium(III) does not float under the same conditions. In order to assess the usefulness of this procedure, the separation was also investigated with hexadecyltrimethylammonium bromide and hexadecyltripropylammonium bromide, from solutions of varying concentrations of sodium chloride, sodium nitrite and hydrochloric acid. Under optimal conditions at the 5 × 10^?5 M level, 78% of the iridium is recovered free of ruthenium, provided that excess of HPB and > 1 M chloride are present.     

The separation of palladium and platinum by ion flotation

Differences in the ion flotation properties of palladium(II) and platinum(IV) chloro complexes in aqueous solutions are used to achieve separations of these metals. The anionic chloro complex PtCl^2-₆ is floated selectively with cationic surfactants of the type, RNR'₃Br, from solutions of PdCl^2-₄ and various concentrations of hydrochloric acid. The palladium(II) does not float from solutions of ? 3.0 M HCl and the platinum(IV) floated from these solutions can be recovered free of palladium. However, the separation is incomplete as much of the platinum(IV) is also unfloated from these solutions. Quantitative separations are obtained by conversion of the palladium(II) to the cationic ammine, Pd(NH₃)₄²⁺ with aqueous ammonia prior to flotation. The anionic chloro complex of platinum(IV) is unaffected by the presence of ammonia and is floated quantitatively with the surfactant n-hexadecyltri-n-propylammonium bromide from 0.01 M ammonia solutions.     

Ion flotation studies of the chlorocomplexes of some platinum group metals

The anionic chlorocomplexes of Au(III), Pt(IV), Pd(II), Ir(IV), Ir(III) and Rh(III) can be floated from aqueous solutions with cationic surfactants of the type RNR'₃Br. The flotation behavior of each metal is reported with respect to variations of hydrochloric acid and sodium chloride concentrations, the R and R' chain lengths, initial surfactant concentrations and initial metal ion concentrations. The flotation behavior of the metals is compared to the anion-exchange selectivity coefficients and a flotation selectivity sequence of Au(III) > Pt(IV), Ir(IV), Pd(II) > Ir(III) > Rh(III) is generally observed. Nearly 100% of Au(III), Pt(IV), Ir(IV) and Pd(II) can be recovered from dilute solutions using the ion flotation procedures.     

Extraction of iridium with tetraphenylarsonium chloride and its flotation—spectrophotometric determination with rhodamine 6g

A sensitive flotation—spectrophotometric method, based on the ion-associate formed by the anionic chloride and chlorostannate(II) complex of iridium with the basic dye rhodamine 6G (R6G) is described. A sparingly soluble compound precipitates when the aqueous phase is shaken with di-isopropyl ether. The separated and washed compound is then dissolved in acetone. The molar absorptivity is 3.6 × 10⁵ l mol^-1 cm^-1 at 530 nm. Beer's law is obeyed. The component ratios in the isolated compound were determined, and the formula [(R6G⁺)₃IrCl₂(SnCl₃)^3-₄] · [(R6G⁺)(SnCl^-₃)] is proposed for the adduct. The effects of other noble metals were examined. The interferences of rhodium and platinum with the determination of iridium in the proposed method can be greatly decreased by a preliminary extractive separation of iridium into chloroform as a tetraphenylarsonium hexachloroiridate(IV) complex. Optimum conditions for the iridium extraction are reported.     

Extraction of Iridium(IV) by 1-(2-(2,4-Dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl)-1H-1,2,4-triazole from Hydrochloric Solutions

Extraction of iridium(IV) by 1-(2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-yl-methyl)-¹H-1,2,4-triazole from hydrochloric solutions was studied. Optimal extraction parameters were determined. The mechanism of iridium(IV) extraction in this system is ion exchange (3.0 mol/L HCl and τ_cont = 5 min). Electronic, ¹H NMR, ¹³C NMR, and IR spectroscopy and elemental analysis were used to determine the composition of the extracted compound.     

Flotation separation of hafnium(IV) from aqueous solutions

A simple, rapid method for the separation of hafnium from aqueous solutions has been investigated using^(175+181)Hf tracer. Cationic hafnium complex ions were floated from dilute acid solutions with sodium lauryl sulfate (SLS) and anionic hafnium complexes were floated from basic and oxalic acid solutions with hexadecyltrimethyl ammonium bromide (HTMAB). The conditions necessary for quantitative recovery of the metal and mechanisms of flotation are described.Author to whom correspondence should be addressed.     

Differential catalytic determination of iridium(IV) and rhodium(III) based on the oxidation of N-methyldiphenylamine-4-sulfonic acid

The kinetics of the oxidation of N-methyldiphenylamine-4-sulfonic acid with periodate ions was studied in weakly acidic solutions in the presence of iridium(IV), rhodium(III), and their mixtures. Oxidation rate constants were determined in the presence of individual catalysts and their mixtures. The synergetic effect of iridium(IV) and rhodium(III) on the rate of the indicator reaction was estimated; the range of catalyst ratios for the simultaneous determination of analytes was determined. The effect of some factors (oxidant nature and concentration, temperature, the ionic strength of solution, and interfering ions) on the rate of the indicator reaction in the presence of iridium(IV) and rhodium(III) mixtures was assessed. A procedure for the differential catalytic determination of iridium(IV) and rhodium(III) was proposed and tested in the analysis of artificial mixtures and a platinum concentrate of complex composition (KP-5).     

Foam Separation of Anions: Hydration,Entropy, and Selectivity

Abstract

A selectivity coefficient for the foam separation of Fe(CN)₆ ^4-, Ag(S₂0₃)₂ ^3-, Cr₂0₇ ^2-, Cr0₄ ^2-, S₂0₃ ^2-, HP0₄ ^2-, and I^? from solutions containing ethylhexadecyldimethylammonium bromide is related to the absolute partial molal entropy of each ion. The entropy, which correlates well with the degree of hydration, enables an estimate of the selectivity of an ion flotation or foam fractionation by a surfactant.     

The separation of tellurium(IV) from water and sea water by flotation with hydrated iron(III) oxide

A flotation separation is described for sub-microgram levels of tellurium(IV) from 1-1 samples of water and sea water. Tellurium(IV) is coprecipitated with hydrated iron(III) oxide at pH 8–9. The precipitate is floated with the aid of surfactant solutions and small nitrogen bubbles, separated and dissolved in dilute hydrochloric acid. Tellurium is then converted to hydrogen telluride with sodium tetrahydroborate and measured by atomic absorption spectrometry. Recovery of added tellurium (0.4 and 0.8 μg l^?1) was about 83%. The time required for the preconcentration is 30 rain per sample, including 15 rain stirring.     

Sensitive flotation-spectrophotometric determination of gold based on the gold(III)/bromide/rhodamine 6G system

A very flotation-spectrophotometric method based on the gold(III)/bromide/ tribromide/rhodamine 6G (R6G) system is described. In the presence of bromine, the dibromoderivative (R6G-Br) is formed. The gold compound is floated with di-isopropyl ether, washed with 1 M sulphuric acid and dissolved in methanol, and the absorbance of the solution is measured at 545 nm. The floated compounds is considered to be an adduct of the formula [(R6G-Br⁺)(AuBr^-₄)] · 12[(R6G-Br⁺)[Br^-₃)]. The apparent molar absorptivity is 11.4 × 10⁵] mol^-1 cm^-1. Important interference are Pd, Ag, Hg(II) and Tl(III), belong to the most interfering metals; after a preliminary extraction of gold from acidic bromide medium into di-isopropyl ether, only thallium(III) interferes significantly. The proposed method is applied to determining gold traces in a blister copper samle. Results obtained prove the good precision and accuracy of the method.     

Spectrofluorimetric determination of iridium(IV) traces using 4-pyridone derivatives

A new spectrofluorimetric determination of iridium(IV) with 3-hydroxy-2-methyl-1-phenyl-4-pyridone (HX) or 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) is reported. Iridium(IV) react with HX or HY and chelates were extracted into chloroform or dichloromethane. The organic phase showed fluorescence. The fluorescence measurements to quantify iridium were carried out in its fluorescent band centred at λ_ex=373 nm and λ_em=480 nm. Under optimal conditions, the calibration graphs were linear over the concentration range of 0.1-7.6 μg ml⁻¹ of iridium for Ir(IV)-HX and 0.1-5.8 μg ml⁻¹ for Ir(IV)-HY with a correlation coefficients of 0.999 and 0.992 and relative standard deviation of ±1.1%.The method is free from interference by Rh(III) and Pt(IV), which normally interfere with other methods. Iridium can be determined in the presence of 300-fold excess of rhodium(III) and 10-fold excess of platinum(IV).The method was applied successfully to the determination of iridium in some synthetic mixtures and mineral sample gave satisfactory results.     

Controlled-Potential Coulometric Determination of Iridium in Hexanitroiridate(III) with Microwave Sample Preparation

A procedure is proposed for determining 0.40 to 7.00 mg of iridium (RSD = 1–4%) in Ir(NO₂)^3- ₆. The procedure involved the fast conversion of Ir(NO₂)^3- ₆ into IrCl^2- ₆ by heating it with an HCl solution in a microwave oven and the controlled-potential coulometric determination of iridium using the Ir(IV)/Ir(III) redox system.     

Solvent Extraction Separation of Iridium(III) from Rhodium(III) by N-n-Octylaniline

The use ofN-n-octylaniline for the extraction of iridium(III) from malonate media is studied at pH 8.5. Iridium(III) extracted in the organic phase was stripped with 2.0 M hydrochloric acid and was determined spectrophotometrically by the stannous chloride–hydrobromic acid method at 385 nm. The extraction system is studied as a function of the equilibration time, diluent, reagent concentration and diverse ions. Experimental data have been analyzed graphically to determine the stoichiometry of the extracted species. It was found that the extraction of iridium(III) proceeds by an anion exchange mechanism and transforms into the extracted species [RR"NH₂ ⁺Ir(C₃H₂O₄)₂ ^–]_org. The method is simple, rapid, and selective and has been devised for the sequential separation of iridium(III) from rhodium(III), not only from each other, but also from other accompanying Platinum Group Metals (PGMs), Au(III), and base metals.     

Rhodium and iridium complexes of N-heterocyclic carbenes: Structural investigations and their catalytic properties in the borylation reaction

Bridged and unbridged N-heterocyclic carbene (NHC) ligands are metalated with [Ir/Rh(COD)₂Cl]₂ to give rhodium(I/III) and iridium(I) mono- and biscarbene substituted complexes. All complexes were characterized by spectroscopy, in addition [Ir(COD)(NHC)₂][Cl,I] [COD = 1,5-cyclooctadiene, NHC =  1,3-dimethyl- or 1,3-dicyclohexylimidazolin-2-ylidene] (1, 4), and the biscarbene chelate complexes 12 [(η⁴-1,5-cyclooctadiene)(1,1′-di-n-butyl-3,3′-ethylene-diimidazolin-2,2′-diylidene)iridium(I) bromide] and 14 [(η⁴-1,5-cyclooctadiene)(1,1′-dimethyl-3,3′-o-xylylene-diimidazolin-2,2′-diylidene)iridium(I) bromide] were characterized by single crystal X-ray analysis. The relative σ-donor/π-acceptor qualities of various NHC ligands were examined and classified in monosubstituted NHC-Rh and NHC-Ir dicarbonyl complexes by means of IR spectroscopy. For the first time, bis(carbene) substituted iridium complexes were used as catalysts in the synthesis of arylboronic acids starting from pinacolborane and arene derivatives.     

Separation of rhodium from iridium with sodium borohydride and standardization of rhodium(III) solutions

Of the platinum group metal separations, that of rhodium from iridium is the most difficult. The existing gravimetric methods are too lengthy or make use of organic reagents which ultimately need to be removed before iridium can be determined. The proposed method of separation is rapid, needs no pH control, and easy to carry out. Rh(III) ions are quantitatively reduced to Rh(0) by the action of aqueous sodium borohydride. The separation is best achieved in perchlorate medium in the presence of hydroxylamine. The separation is dependent on the concentration ratio of iridium to rhodium; if this is high, some iridium is co-precipitated; if low, the rhodium obtained is free from even spectrographic traces of iridium. A new method for standardization of Rh(III) solutions with sodium borohydride is proposed.     

Extraction of rhodium and iridium with 4-(non-5-yl) pyridine

The extraction of rhodium and iridium with 4-(non-5-yl)pyridine (NP) was investigated. The rate of rhodium extraction increases with increasing concentration of NP and chloride ions. Spectroscopic studies indicate that the extracted species is an ion pair, RhCl^3?₆ 3HNP⁺. Under the conditions of optimum Rh extraction ([Cl^?]=3.7 M, [NP]=0.3 M, [H]=0.08 M), iridium is also extracted by NP with similar efficiency in the form of IrCl^3?₆ 3HNP⁺. The use of hypophosphorous acid to labilize rhodium results in a better extraction of rhodium without significantly changing the extraction of iridium. The efficiency and kinetics of the rhodium extraction improve with increasing chloride concentration. For [Cl^?] ? 3.7 M, [H₃PO₂]=2.5 M, [NP]=0.3 M and Ph ≈ 1.6, 82% of rhodium is extracted in 4 min and 95% in 30 min.     

Rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide: Syntheses,structures, and spectral characteristics

The syntheses and spectral (IR, UV-VIS, XPS, and ¹H and ¹³C NMR) characteristics of the rhodium(III), palladium(II), and platinum(II) complexes with 2-(2-hydroxybenzoyl)-N-methylhydrazinecarbothioamide (HBMHCTA) are described. The coordination of HBMHCTA to the central metal ion and its intraligand rearrangement in the complex formation of rhodium(III) ions are studied. The structure of the mixed-ligand complex [Pd(H₂L)PPh₃] is determined by X-ray diffraction analysis.     

Ion flotation behaviour of thirty-one metal ions in mixed hydrochloric/nitric acid solutions

The ion flotation of 31 metal ions in hydrochloric/nitric acid solution with the cationic surfactant cetylpyridinium chloride was investigated. A 25-ml portion of 0.27-2.87 x 10(-4)M metal ion and 1.8-6.0 x 10(-4)M cetylpyridinium chloride solution in 0.17-3.4M acid mixture ([HCl]:[HNO(3)] = 2.4:1) was subjected to flotation in a cell, 22.5 cm high and 4.0 cm in diameter, for 5 min, with nitrogen bubbles. Ir(IV), Pt(IV), Ge(IV), Sn(IV), Bi(III), Au(III), Tl(III), Pd(II) and Sn(II) were floated from solution in 95-100% yield; Ru(III), Rh(III), Ir(III), Hg(II), Ag(I) and Tl(I) were partly floated, while Cr(VI), Ti(IV), Zr(IV), Ga(III), In(III), Fe(III), Sb(III), Al(III), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), CD(II) and Pb(II) were floated with less than 20% yield. The flotation behaviour of these metal ions in the mixed acid system was compared with that in hydrochloric acid. The flotation is more efficient in the mixed acid system.     

Study on Determination of Trace Copper by Spectrophotometry after Flotation Separation Using Microcrystalline Adsorption System

The paper presents a novel method for the flotation separation of Cu²⁺ using microcrystalline adsorption system prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of NH₄SCN and octadecyl trimethyl ammonium bromide (OTMAB), various salts on the flotation yield of Cu2+ have been investigated to select the optimum experimental conditions. The possible flotation separation mechanism of Cu²⁺ was discussed. The results showed that under the optimum conditions, octadecyl trimethyl ammonium bromide cation (OTMAB⁺) reacted with SCN^‐ to produce the microcrystalline matter (Ms‐M) of (OTMAB⁺·SCN^‐), the water‐insoluble ternary association complex of [Cu(SCN)₄] (OTMAB)₂ which produced by Cu²⁺ and SCN^‐, OTMAB⁺ was quantificationally adsorbed on the surface of Ms‐M of (OTMAB²⁺·SCN^‐) and was floated above water phase, the liquid‐solid phases were formed with clear interface. In this condition, K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Fe²⁺, Mn²⁺, Ni²⁺, Cd²⁺ and Co²⁺ could not be floated. Therefore, Cu²⁺ was separated completely from the above metal ions. A new method of determination of trace copper by flotation separation was established. The proposed method has been successfully applied to the determination of Cu²⁺ in plating waster water, and the results agreed well with AAS method. The recoveries were 93.3%～107.8%, and the RSD was 1.9%～2.1%.