Separation and concentration of some platinum metal ions with a new chelating resin containing thiosemicarbazide as functional group

A new chelating ion-exchange resin containing thiosemicarbazide as functional group and based on macroreticular polystyrene-divinylbenzene (8%) has been prepared. Its sorption characteristics for palladium(II), platinum(IV), rhodium(III), ruthenium(III) and iridium(III) have been studied. These platinum metal ions can be quantitatively separated by sorption on this chelating resin and selective elution. The resin is highly stable in acid and alkaline solution.     

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).     

EPR spectroscopy of transformations of iridium(III) and iridium(IV) hydroxo complexes in alkaline media

Processes that occur in strong alkaline solutions of iridium(III) and iridium(IV) hydroxo complexes have been studied by EPR and electronic absorption spectroscopy. It has been demonstrated that dissolution of iridium compounds in alkaline solutions should be accompanied by a series of complicated transformations involving oxygen, which lead to the formation of several binuclear iridium(III, III), (III, IV), and (IV, IV) dioxygen complexes.     

Spectrophotometric determination of osmium(IV), iridium(IV) and platinum(iv) and separation and determination of palladium(II) and ruthenium(III) in the presence of other platinum metals, with oximidobenzotetronic acid as reagent

Oximidobenzotetronic acid is suggested as a reagent for the spectrophotometric determination of osmium(IV), iridium(III), iridium(IV), platinum(IV) and for separation and determination of palladium(II) and ruthenium(III) in the presence of other platinum metals. Iridium(III) and (IV) can be estimated when present together.     

The separation of rhodium and iridium by ion flotation

Mixtures of iridium(IV) and rhodium(III) as IrCl^2-₆ and RhCl^3-₆ are separated by ion flotation. The iridium(IV) is selectively floated from aqueous solutions of pH 2 and 0.05% Ce(IV) with either hexadecyltripropylammonium bromide (HTPAB) or hexadecyltributylammonium bromide (HTBAB). The rhodium(III) does not float under the same conditions. The floated iridium sublate is collected in n-butyl acetate without contamination by the unfloated rhodium. Data are presented also for the separation and recovery of the Ir(IV) and Rh(III) with the above surfactants, hexadecyltrimethyl-ammonium bromide (HTMAB) and hexadecyltriethylammonium bromide (HTEAB) from solutions of various sodium chloride and hydrochloric acid concentrations. The use of solvent sublation for recovering the floated iridium is examined. The separation is fast, practical, simple and does not require expensive reagents or apparatus. For these reasons, the separation of iridium and rhodium by ion flotation offers advantages over previous methods.     

Metal complexes of isonicotinic acid hydrazide

Complexes of platinum(IV), ruthenium(III), rhodium(III), iridium(III), gold(III), dioxouranium(II), zinc(II), cadmium(II), mercury(II) and manganese(II) with isonicotinic acid hydrazide were prepared and characterized on the basis of analytical, conductometric, magnetic susceptibility and spectral data. Platinum(IV) ruthenium(III), rhodium(III), iridium(III), dioxouranium(II) and manganese(II) form six-coordinate complexes while gold(III), zinc(II), cadmium(II) and mercury(II) form four coordinate complexes.     

Reactions of ruthenium(III), Rhodium(III) and Iridium(III) chlorides in molten nitrite eutectics

The reactions of ruthenium(III), rhodium(III) and iridium(III) chlorides in molten lithium nitrite—sodium nitrite, lithium nitrite—potassium nitrit and sodium nitrite—potassium nitrite eutectics were studied and compared with those of their first row congeners. Ruthenium(III) reacted to form hexanitroruthenate(II) with the evolution of nitrogen dioxide, whereas rhodium(III) and iridium(III) formed hexanitrorhodate(III) and hexanitroiridate(III), respectively. These complexes decomposed at higher temperatures to form ruthenium(IV), rhodium(III) and iridium(IV) oxides, respectively, with the evolution of nitrogen oxides. The stoichiometries of these reactions were established by thermogravimetry and the products were characterized by their IR, visible and UV spectra, and X-ray diffraction patterns.     

Evaluation of Se(IV) removal from aqueous solution by GMZ Na-bentonite: batch experiment and modeling studies

Bentonite has been studied extensively because of its strong sorption and complexation ability. In this work, the sorption of Se(IV) on purified GMZ bentonite was investigated under ambient temperature as functions of contact time, pH, Se(IV) concentration and co-existing ion Eu(III) using batch techniques. Sorption kinetics of Se(IV) was successfully described by the pseudo-second-order rate equation. The sorption amount of Se(IV) was strongly dependent on the solution pH, and a positive effect was observed on Se(IV) and Eu(III) co-sorption when these two elements existed in the same system under high surface coverage of sorbent. Double layer model was set up and used to quantitatively interpret the sorption experimental data collected in binary and ternary sorption systems. From the experimental results, one can conclude that GMZ bentonite may have good potentialities for immobilizing selenium in nuclear wastes.     

1-(2-氨乙基)吡咯烷树脂的合成及其对贵金属的吸附

研究了试剂摩尔比、反应温度、反应时间对1-(2-氨乙基)吡咯烷树脂合成的影响规律.此树脂的功能基含量2.74 mmol/g树脂,对Au(Ⅲ)、Os(Ⅳ)、Pt(Ⅳ)、Ir(Ⅳ)、Ru(Ⅲ)、Pd(Ⅱ)的吸附容量分别高达950、520、436、418、314、302 mg/g树脂.FT-IR、元素分析表征了树脂结构.测定了吸附速率曲线,配位比,表观吸附活化能△E_(Au)=6.4、△E_(Pt)=33.7kJ/mol.XPS研究了吸附机理.     

Solubility of Eu<Subscript>2</Subscript>(SeO<Subscript>3</Subscript>)<Subscript>3</Subscript> and sorption of Eu(III) onto TiO<Subscript>2</Subscript> in the presence of Se(IV)

Metal ions sorption can be significantly affected by the presence of other sorbates, especially of complexing ligands. In this study, the effect of Se(IV) on Eu(III) sorption onto TiO₂ at different pH and Eu(III) concentration was investigated. Se(IV) was found to enhance Eu(III) sorption as a function of Se(IV) concentration. Constant capacitance model was successfully used to interpret the sorption experimental data. The solubility product of Eu₂(SeO₃)₃ at ambient temperature was investigated to highlight the sorption mechanism of ternary sorption system. The pK _sp value of Eu₂(SeO₃)₃ was found to be 31.51 ± 0.95.     

Electron transfer dynamics of iridium oxide nanoparticles attached to electrodes by self-assembled monolayers

Self-assembled monolayers (SAMs) of carboxylated alkanethiolates (-S(CH(2))(n-1)CO(2)(-)) on flat gold electrode surfaces are used to tether small (ca. 2 nm d.) iridium(IV) oxide nanoparticles (Ir(IV)O(X) NPs) to the electrode. Peak potential separations in cyclic voltammetry (CV) of the nanoparticle Ir(IV/III) wave, in pH 13 aqueous base, increase with n, showing that the Ir(IV/III) apparent electron transfer kinetics of metal oxide sites in the nanoparticles respond to the imposed SAM electron transfer tunneling barrier. Estimated apparent electron transfer rate constants (k(app)(0)) for n = 12 and 16 are 9.8 and 0.12 s(-1). Owing to uncompensated solution resistance, k(app)(0) for n = 8 was too large to measure in the potential sweep experiment. For the cathodic scans, coulometric charges under the Ir(IV/III) voltammetric waves were independent of potential scan rate, suggesting participation of all of the iridium oxide redox sites (ca. 130 per NP) in the NPs. These experiments show that it is possible to control and study electron transfer dynamics of electroactive nanoparticles including, as shown by preliminary experiments, that of the electrocatalysis of water oxidation by iridium oxide nanoparticles.     

A field-induced poising technique for promoting convergence of standard electrode potential values of thermally oxidized iridium pH sensors

An electrochemical technique based on reversible charge ejection/injection is shown to be an effective procedure for bringing about the convergence of standard electrode potential values in a batch of thermally prepared iridium oxide pH sensors. Such a convergence simplifies electrode calibration procedures. The rationale for the technique and the results obtained are discussed in terms of adjustment of the proportions of iridium(III) and iridium(IV) oxides at the electrode surface.     

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.     

Role of hydrolysis in the sorption isolation of radionuclides from solutions

The sorption of hydrolized iron(III) and plutonium(IV) species by silica gel has been studied. It is shown that both mononuclear and polynuclear hydroxo complexes of iron(III) and plutonium(IV) display an increased and specific sorption activity in respect to silica gel.     

Kinetics of iridium(III) catalyzed oxidation of benzaldehyde and <Emphasis Type="Italic">p</Emphasis>-nitrobenzaldehyde by cerium(IV) in aqueous acidic medium

Oxidation of benzaldehyde and p-nitro-benzaldehyde by cerium(IV) sulphate in aqueous sulphuric acid is strongly catalyzed by iridium(III) chloride. The complex formed between cerium(IV) and the organic substrate in the first equilibrium step gives another complex in the presence of iridium(III), which ultimately gives the corresponding aromatic acids as the product of oxidation. The order of the reaction follows first-order kinetics at low concentrations to zero order at higher concentrations of both the oxidant and organic substrate. The rate is directly proportional to the concentration of catalyst, but decreases sharply with increasing H⁺ ions and cerium(III) concentrations, while change in ionic strength of the medium or the concentration of acetic acid and Cl⁻ ions has no effect on the rate.     

Reduction of iridium in solution

Iridium(IV) in solution may be reduced to metal via the intermediate Ir(I). Reduction of Ir(III) has not been detected. The current efficiency for metal deposition is low because: (1) The (IV)-(I) reduction is competing with the (IV) to (III) reduction, and hydrogen evolution in aqueous solution. (2) Ir(I) is very easily oxidised to (III), even by hydrogen. (3) Some iridium salts are not stable in the (IV) state (e.g. triaquotrichloroiridate in molar chloride).     

Synthesis of N-Methyl-2-Thioimidazole Resin and Its Complex Behavior for Noble Metal Ions

The functional group capacity and the percentage of functional group conversion of crosslinked polystyrene resin bearing N-methyl-2-thioimidazole (MTIR) synthesized under optimum conditions are as high as 4.08 mmol/g resin and 96.0%, respectively. The apparent activation energies of sorption of MTIR for Au(III) and Pt(IV) are 13.1 and 13.4 kJ/mol, respectively. The sorption behavior of MTIR for Au(III), Pt(IV), and Pd(II) obeys the Freundlich and Langmuir isotherms. The sorption capacities of MTIR for Au(III), Pt(IV), and Pd(II) are as high as 4.33, 2.12, and 2.33 mmol/g resin, respectively. Au(III), Pt(IV), and Pd(II) adsorbed on MTIR can be eluted quantitatively by the eluant. The resin can be regenerated easily and reused without an obvious decrease in the sorption capacity for Au(III) and Pd(II). The resin has high sorption selectivity for noble metal ions. Au(III) can be separated quantitatively in the presence of high concentrations of Cu²⁺, Fe³⁺, Ni²⁺, and Mn²⁺. The recovery of platinum from the spent industrial catalysts is 98.6% by MTIR. The preconcentration and separation of palladium and platinum from the anode deposits of electrolysis of crude copper have been investigated. The resin may have potential industrial uses.     

Bestimmung von iridiumspuren mit thiodibenzoylmethan mittels substöchiometrischer isotopenverdünnungs-analyse: Determination of traces of iridium with thiodibenzoylmethane by substoichiometric isotope dilution analysis

Determination of traces of iridium with thiodibenzoylmethane by substoichiometric isotope dilution analysisIridium(III or IV) reacts with thiodibenzoylmethane on heating at pH 6 to form a 1:3 complex, which can be concentrated by extraction into chloroform. Based on this reaction, a reproducible, selective determination of iridium is achieved by means of substoichiometric isotope dilution analysis, based on ¹⁹²Ir. The linear range is 1–11 nmol of iridium.     

Separation of rhodium and iridium by multiple fractional extraction

Mixtures of the chloro complexes of rhodium(III) and iridium(IV) were resolved by a nine stage multiple extraction technique. The solutes are partitioned in a hydrochloric acid-tributyl phosphate system. Rhodium is concentrated in the raffinate while iridium is concentrated in the extractant. 99% of the rhodium and 94% of the iridium are recovered free of the other metal. Experimental results agree reasonably well with the results predicted by a theoretical treatment of the distribution data.     

Sorption Purification of Scandium(III) To Remove Zirconium(IV) Impurity in Hydrochloric Acid Solutions

A study was made on separation of the Zr(IV) impurity from scandium(III) in hydrochloric acid solutions by sorption with KRF-20t-60 cation exchanger, including sorption kinetics and sorption under dynamic conditions. The sorbent regeneration with 5% ammonium fluoride or 10% potassium carbonate at 22°C was considered.