T. M. Korda

Extraction of palladium with thiacalix[4]arenes from nitric acid nitrate-nitrite solutions

Calix[4]arene 1, thiacalix[4]arenes 2(LH4), and calix[4]arenethioether 3 were compared in palladium extraction from nitric acid solutions; DPd for 2 was shown to be 2–3 orders of magnitude larger than for 1 at pH > 3 (comparable with 3) because of cation-exchange and coordination extraction of palladium. It was shown by extraction methods and IR spectroscopy that thiacalixarenes 2 extract complex species [PdnLmH4 − 2n] (m = 1, n = 1 and 2) and [(PdA2)nLmH4] (A = m = 1, n = 1–4) from nitric acid solutions at pH 3. Extraction constants for these palladium species that satisfactorily describe experimental data were calculated. As distinct from 3, thiacalixarenes 2 are promising for the combined extraction of palladium and silver from alkaline solutions and the selective extraction of fission palladium from nitric acid solutions. Phosphorylated at the upper rim thiacalixarenes 2 can be considered as bifunctional extractants for the separation of fission radionuclides.

ICP AES determination of platinum group elements and gold in collective extract and strip product solution in analysis of geological samples

ICP AES techniques for the determination of all platinum group elements (PGEs) and gold in extract and collective strip product solution have been developed on the basis of the interrelation between the main stages of the analysis. The ICP AES permissible contents of base metals interfering with the PGE and gold determination have been established. The extraction system (a mixture of p-alkyl aniline with petroleum sulfides in o-xylene or in the post-xylene fraction) is shown to be applicable to ICP and ensures a 10– to 20–fold concentration of PGEs and gold and the required (106) degree of decontamination of the extract from the matrix elements. A new two-step method for a collective back extraction of PGEs and gold with ammonia and thiourea solutions is proposed. The validity of the techniques is confirmed by the analysis of six standard samples and by the agreement of the results with those obtained by the independent ETAAS method. The techniques were tested on raw materials and copper-nickel plant products to determine all PGEs, including osmium, and gold over the range of their contents from 10−7 to 10−4%.

Thiacalix[4]arenes: Extraction of palladium and the electronic structure

The extractability of palladium nitro complexes with the charge state of sulfur and oxygen atoms in thiacalix[4]arenas in the cone and 1,3-alternate conformations are compared. The results of X-ray photoelectron and X-ray emission studies indicate the presence of considerable electron density on the bridging sulfur atoms, which is due to the contribution of the sulfur 3p AO to the upper occupied MOs of molecules. A series of changes in the electron density on sulfur atoms in the order calixarene thioethers > thiacalixarenes > dialkylsulfides ((C10H21)2S) > (C6H5)2S not completely coincide with changes in their extrability, which can be caused by different nature and stoichiometry of the formed palladium complexes.

Palladium(II) extraction by sulfur-containing calix[4,6]arenes from hydrochloric acid solutions

The comparison of the extraction properties of calixarenes, thiacalixarenes, and calix[4,6]arene thioethers showed that methyl(thiamethyl)calix[4,6]arenes 3a and 4a have the highest extraction abilities. These extractants rapidly and completely extract palladium from hydrochloric acid solutions; regarding distribution factors achieved in the kinetic mode, they three to four orders of magnitude exceed their monodentate analogue, octylbenzyl sulfide (OBnS). Approaches are considered to enhance palladium extraction via generating mixed palladium species in low-acidity solutions and via intramolecular catalysis by the protonated oxygen atoms of alkoxy groups in the lower rim. For 1 M HCl, the kinetic order of diluent effects on palladium extraction was established. The substitution of sulfur atoms for bridging CH2 groups was discovered to enhance palladium extraction by calix[4]arene thioether 3c.

JUSTIFICATION OF THE CHOICE OF AN EXTRACTION SYSTEM ON THE BASIS OF PETROLEUM SULFIDES FOR EXTRACTING FRAGMENT PALLADIUM

The article summarizes experiments performed on the extraction of palladium from spent nuclear fuels. Palladium extraction from high-level nitric acid solutions was performed using diesel fuels and petroleum sulfides. Petroleum sulfide extraction systems with aromatic solvents provided the highest selectivity for palladium. Experimental results for refinement of palladium after extraction are also summarized. 14 refs., 4 tabs.

Behavior of precious metals in extraction recovery and refining of fission product palladium

ConclusionThe experimentally determined total purification factors for palladium relative to silver (first cycle 102, second cycle >103) and rhodium and ruthenium (first cycle >104, second cycle >10) are greater than 105. In connection with the insufficient sensitivity of the atomic absorption method for monitoring and the relatively high value from the control run, we could not determine the true values of the purification factors in some operations of the second extraction cycle and for precipitation of palladosammine. The noted chemical aspects of the behavior of precious metals in extraction systems with petroleum sulfides lead to an estimate of the purification factors for palladium at the 108 level. In particular, the total purification factors increase by 10–100 times when the extraction is carried out in both cycles with W:O=10:1 (F=(W:O)/Dj, where j is the component to be separated [10]). Larger-scale laboratory testing of the proposed flow diagram for recovery and refining of palladium using Ag, Pd, Ru, Rh, and Sb will allow us to experimentally confirm that such estimates are realistic.

Behavior of nitrite forms of nitrosylruthenium on extraction and back extraction of heterometalic Ru/Zn complexes with trioctylphosphine oxide

The state of ruthenium in conjugated phases upon extraction of trans-[Ru(15NO)(15NO2)4(OH)]2− complex with tri-n-octylphosphine oxide (TOPO) in the presence of Zn2+ and subsequent back extraction with H15NO3 and NH3(concd.) solutions was studied by 15N NMR. Binuclear complexes [Ru(NO)(NO2)5−n(μ-NO2)n−1(μ-OH)Zn(TOPO)n] and [Ru(NO)(NO2)4−n(ONO)(μ-NO2)n−1(μ-OH)Zn(TOPO)n], where n = 2, 3, are predominant forms in extract. Kinetic restrictions for ruthenium extraction with TOPO solution in hexane and its back extraction with aqueous solutions of nitric acid and ammonia are eliminated in the absence of direct coordination of extractant to ruthenium. fac-Dinitronitrosyl forms [Ru(NO)(H2O)3(NO2)2]+, [Ru(NO)(H2O)2(NO2)2(NO3)]0 (3 and 6 M HNO3) and [Ru(NO)(H2O)(NO2)2(NO3)2]− (6 M HNO3) prevail in nitric acid back extracts. Equilibrium constant at ambient temperature (0.05 ± 0.01) was assessed for the coordination of second nitrate ion to nitrosylruthenium dinitronitrato complex. Complex species [Ru(NO)(NO2)4(OH)]2− and [Ru(NO)(NO2)3(ONO)(OH)]2− prevail in ammonia back extract.

Synthesis of gold nanoparticles stabilized with di-(2-ethylhexyl)dithiophosphoric acid and tris(2-aminoethyl)amine

Methods for preparing gold nanoparticles (NPs) surface-stabilized with di-(2-ethylhexyl)dithiophosphoric acid (DTPA) and tris(2-aminoethyl)amine (TAEA), which endow the nanoparticles with hydrophobic and hydrophilic properties, are described. In the case of DTPA, Au-NPs are first synthesized with surfactant shells by means of reducing [AuCl4]− with hydrazine in inverted micelles of oxyethylated Triton N-42 in a low-polarity medium of decane; then, the micelles are destroyed by polar chloroform in the presence of DTPA, which has a great affinity to gold due to its sulfur donor atoms and substitutes for the surfactant on the surface of the nanoparticles. In preparing hydrophilic nanoparticles, [AuCl4]− is reduced with solid NaBH4 directly in a nonaqueous solution of TAEA based on an ethanol and 2-propanol (3: 10) mixture. The nanoparticles are characterized by elemental analysis (for Au, C, H, N, and Na), X-ray powder diffraction, electronic absorption spectra, IR spectra, photon-correlation spectra, and transmission electron microscopy (TEM).

Extraction of palladium with acyclic analogs of thiacalix[4]arenes from nitric acid solutions

Abstractp-tert-Butylcalix[4]arene was compared with its acyclic analogs in palladium extraction from nitric acid solutions as mononuclear and poly(bi)nuclear complexes with participation of protonated molecules of podands and macrocycle. The extraction ability of podands is similar to that of macrocycle because of the same character of complexation (Pd: S = 1: 1) without formation of new chelates and lower than that of monodentate analog owing to formation of a square complex (Pd: S = 1: 2).

Rhodium and palladium joint extraction by dihexyl sulfide and alkylanilinium nitrate mixtures from nitrate solutions

We studied nonequilibrium distribution of inert rhodium(III) in extraction by dihexyl sulfide (DHS)and alkylanilinium nitrate mixtures from joint nitrate solutions of triaquatrinitrorhodium (0.1–4 g/L Rh) and palladium (0–2 g/L Pd). We discovered the effect of increasing rhodium recovery in the presence of palladium. This effect has a kinetic nature and arises from the fact that bis(alkyl sulfide) palladium(II) species catalyze the reaction between dihexyl sulfide and a rhodium intermediate based on alkylanilinium nitrate micelles. Depending on initial rhodium and palladium concentrations, the extraction system provides effective distribution factors for rhodium in the range DRh* = 8−300 and rhodium recoveries of 43–97% with ∼100% palladium recovery; single 5-min phase contact at 35°C ensures the 10-fold concentration of both metals in the extract. Our results are useful for developing processes for recovering fission rhodium from spent nuclear fuel.