Dihexyl Sulfide Research Articles

Palladium Isolation and Purification from Nitrate Media: Efficient Process Based on Malonamides

ABSTRACTSolvents based on malonamides have been described to be very efficient and selective for liquid-liquid extraction of Pd(II) from nitrate media. The present study details the possibility to selectively extract Pd(II) over common metallic cations, Cu(II), Ni(II), Co(II), Zn(II), Nd(III), Fe(III) and Al(III) using N,N’-dimethyl,N,N’-dibutyltetradecylmalonamide (DMDBTDMA) in toluene. The lowest selectivity was obtained considering Fe(III) and Nd(III), the extraction of all other cations being negligible. Pd(II) distribution and selectivity regarding Fe(III) have been fine-tuned using the aqueous HNO3 concentration as the sole parameter, so that extraction, scrubbing and stripping steps can be simply designed without the need for other specific metal chelating reagents and/or aqueous media and without the extensive generation of aqueous effluents. DMDBTDMA was also benchmarked with other classical Pd(II) extractants such as tributylphosphate (TBP), dihexylsulfide (DHS), tetraoctyl diglycolamide (TODGA) and bis(2-ethylhexyl)sulfoxide (BESO) in toluene and in n-heptane. Overall, this study reveals that malonamides are very well positioned and should be considered for further processing of aqueous nitrate wastes containing Pd contaminated with common base metals.

Recovery of Platinum and Palladium from Spent Automobile Catalyst by Solvent-Impregnated Resins

ABSTRACTSeparation of platinum and palladium, using solvent-impregnated resin (SIR) impregnating di-hexylamine (DHA), di-n-octylamine (DOA), or di-hexyl sulfide (DHS), coated by polyvinyl alcohol crosslinked by glutaraldehyde, was investigated. Coating of the SIR successfully suppressed leakage of the extractant during adsorption. The coated SIR was applied to chromatographic recovery of the two metals and quantitative adsorption–elution was performed via the frontal analysis mode. The adsorption of Pt and Pd was achieved, while adsorption of the co-existing metals in the leaching solution was suppressed. Separation of Pt and Pd was achieved by employing sequential chromatography system together with the quantitative elution of Pt from DHA-SIR with the mixture of 0.5 mol/L thiourea and 0.5 mol/L HCl and that of Pd from DHS-SIR with the mixture of 0.1 mol/L thiourea and 0.5 mol/L HCl solution. Finally, elementary Pt was then obtained from the eluent of sequential chromatography system by simultaneous precipitation and reduction of Pt with sodium borohydride with 99.2% purity.

Triphenylphosphine sulfide-[C<sub>n</sub>mim][Tf<sub>2</sub>N]を用いた塩酸水溶液中における白金族元素の分配挙動

Although solvent extraction has been used in the recovery of rare metals from urban mines, some challenges remain. For example, large amounts of organic solvent are required for Pd (II) separation owing to the slow extraction kinetics of dihexylsulfide (DHS). This lengthens the separation process and increases the evaporation loss of diluents. In our previous work, we found that Pd (II) quickly separates from a hydrochloric acid medium using triphenylphosphine as a phosphorus-based extractant. In this work, we investigate the extraction and backextraction behavior of Rh (III), Pd (II), and Pt (IV) in a hydrochloric acid medium using the combination of triphenylphosphine sulfide (TPPS) and ionic liquids (ILs). Results show that the extraction mechanism of Pd (II) is based on the cooperative extraction effect of TPPS and ILs. Additionally, it was confirmed that the third phase during Pd (II) extraction was inhibited using TPPS-ILs. Furthermore, this study investigated the separation behavior of Rh (III), Pd (II), and Pt (IV) from a hydrochloric acid medium using TPPS-ILs as an extractant and a multiple back-extractant.

Reaction mechanisms of thioetherification for mercaptans and olefins over sulfided Mo-Ni/Al2O3 catalysts

The thioetherification reaction of 1-butanethiol and 1-hexene dissolved in n-hexane was investigated over sulfided Mo-Ni/Al2O3 catalysts. The experimental results showed the catalysts have good catalytic performance for thioetherification reaction, but the isomerization and hydrogenation reactions of olefins over the catalysts can inhibit thioetherification reaction. As reaction temperature increases, the isomerization and hydrogenation reactions of olefins increase rapidly, however, the inhibition of thioetherification reaction also increases. The sulfur distribution and molecular structures of sulfur compounds in the products were analyzed by the gas chromatograph with sulfur chemiluminescence detector (GC-SCD) and the gas chromatograph/mass spectra spectrometry (GC/MS). Two possible routes of thioetherification reaction could be observed. At low temperature, the major pathway involves a direct addition of 1-butanethiol to the terminal carbon of double bond of 1-hexene. In this mechanism, the main product is anti-Markovnikov adduct. At a higher temperature, the CS bond of 1-butanethiol can be subsequently cleaved, and the adsorbed -SH species can be formed on the catalysts. On the same time, abundant 1-hexene can be absorbed on the catalysts, as well. Therefore, the adsorbed SH species can then recombine with adsorbed 1-hexene to form new hexyl-mercaptans, which can continue to produce another kind of thioether (di-hexyl sulfide) with adsorbed 1-hexene. Similar with the first reaction route, the thioether of the anti-Markonikov adduct still dominates in the product.

Selective Recovery of Platinum Group Metals from Spent Automobile Catalyst by Integrated Ion Exchange Methods

Selective recovery of platinum group metals (PGMs), such as Pd, Pt, and Rh, from spent automobile catalyst has been investigated by integrated ion exchange method using dihexyl sulfide (DHS) impregnated resin and commercial weak anion exchange resin (Diaion WA-21) as adsorbents. Batchwise adsorption revealed that the DHS impregnated resin possesses the selective adsorption ability for Pd and WA-21 possesses selectivity for all PGMs, especially Rh. Chromatographic separation of Pd with column packed with DHS impregnated resin can be selectively achieved. The chromatographic separation of Pd and Pt with a column packed with WA-21 is effectively progressed, while that of Rh is insufficient yield due to a slow adsorption rate. Separation of Rh from other two PGMs can therefore be achieved by switching the eluent. Both adsorbents show almost no adsorption abilities for other heavy metals containing in the spent automobile catalyst. Sequential chromatographic operation of the column packed with DHS impregnated resin followed by the column packed with WA-21 can be finally achieved to recover mutual PGM from leaching solution of spent automobile catalyst.

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.

Kinetics of rhodium extraction from nitric acid solutions with a mixture of dihexyl sulfide and alkylanilinium nitrate

The manifold enhancement of the rhodium extraction efficiency from nitric acid solutions of triaquatrinitrorhodium is discovered with the use of two-component mixed extractants based on alkylaniline (AA), dihexyl sulfide (DHS), dihexyl sulfoxide (DHSO), tributyl phosphate (TBP), and oxime ACORGA P5100. A mixture of unimolar solutions of alkylanilinium nitrate and DHS is found to be the most efficient extractant: at 35°C, this mixture quantitatively extracts rhodium within 5 min from aqueous solutions containing 0.06 to 3 mol/L HNO3. The extraction kinetics are studied. The following two-stage extraction mechanism is substantiated: the equilibrium of formation of a colloidal-chemical intermediate involving [Rh(H2O)3(NO2)3], HNO3, and (BHNO3)p (an associated form of the alkylanilinium salt) and the reaction of the intermediate with DHS (the rate-controlling stage).

Dihexyl sulfideによる塩酸溶液からのPd (II)およびPt (IV)の抽出とSulfideの劣化について

Extraction of Pd(II) and Pt(IV) with dihexyl sulfide (DHS) from chloride solutions, and the degradation of DHS to dihexyl sulfoxide (DHSO) were investigated in this study. When Pt(IV) exists in aqueous solution to be extracted, the extraction of small amounts of Pt(IV) causes the oxidation of DHS to DHSO as well as the reduction of Pt(IV) to Pt(II). The presence of DHSO in organic phase results in the formation of insoluble substances with metals ions such as Sn(IV), Fe(III), Si(VI), Zn(II) and Pt(IV) at the interface between the organic and aqueous phases. The appearance of the insoluble substances is due to the low solubility both in aqueous and organic phases. The insoluble substance is decreased by the addition of the modifier like alcohols. In the extraction of metal ions, the repeated operation of extraction and stripping of metal ions with DHS increases the amount of DHSO. The extraction of Pt(IV) is increased, when the contact time is extended and when the concentration of Pd(II) is lower in the extraction operation of Pd(II) and Pt(IV) by DHS. It is considered that the oxidation of DHS takes place by the following reaction. H2PtCl6 + 3DHSorg + H2O →PtCl 2·(DHS)2, org + DHSOorg + 4HCl

光照射下における微量の高分子量アミンを含むジヘキシルスルフィドによる塩酸溶液からの白金（ＩＶ）の抽出

Extraction of platinum (IV) from hydrochloric acid solutions by using dihexylsulfide (DHS) containing micro amount of trioctylmethylammonium chloride (TOMAC) was investigated under irradiation of light. Although the complex of Pt (IV) with DHS is not formed by the extraction, on this extraction system, Pt (IV) was extracted quantitatively by DHS because (TOMA)2PtCl6 complex activated by irradiation of ultraviolet rays acts as catalyst. The stoichiometric composition of the DHS complex formed in the organic phase was deduced to be PtCl4DHS. Therefore, the following equilibrium equations are proposed: PtCl62 -(aq) + 2TOMAC (org) ⇔ (TOMA)2PtCl6(org) + 2Cl- (aq) (TOMA)2PtCl6(org)→hv(TOMA) 2PtCl6*(org) (activated complex) (TOMA)2PtCl6*(org) + 2DHS(org) ⇔ PtCl4 · 2DHS(org) + 2TOMAC(org) . In the equilibrium reactions, it was found that Pt (IV) in the complex is not reduced to Pt (II). The examination of diluent effects proved that aromatic diluents with electron-donating groups, such as m-xylene and toluene, promote the activation of TOMAC-Pt (IV) complex, whereas aromatic diluents with electron-accepting groups, such as chlorobenzene and nitrobenzene, and aliphatic diluents, such as hexane and dodecane, suppress that activation. Furthermore, it was found that from the examination of effects of high molecular-weight amine, the catalytic effect of amine-Pt (IV) complexes depends on their activated degree by irradiation of ultraviolet rays, which is promoted by electron-donating groups of amines, and ability of replacement between the chlorine atoms coordinated to Pt (IV) in the activated complex and DHS, which is affected by steric hindrance of amines.

Comparative Studies on the Solvent Extraction of Pd(II) Using Alkane-1,ω-diyl Bis(O,O-diisobutyl phosphorodithioate)s

Abstract A series of new bis-type derivatives of O,O-diisobutyl phosphorodithioate, namely, the alkane-1,ω-diyl bis(O,O-diisobutyl phosphorodithioate)s (ADBDiBPDT), were synthesized for use in the solvent extraction of precious metals. These compounds having the general formula (i-BuO)2P(S)S(CH2)nS(S)P(Oi-Bu)2, have considerable selectivity for extraction of Pd(II) over Au(III), Ag(I), and Pt(IV) when extracted from 0.1 M (1 M = 1 mol dm−3) perchlorate, nitrate, and chloride media. The extractability of individual metal ions increases with the increase in the length of the alkane-1,ω-diyl chain (n = 1—4), joining the two phosphorodithioate groups in the bis-structure. The extraction of palladium(II) from 1.0 M chloride solution at pH 3 in 1,2-dichloroethane (DCE) proceeds through the formation of either a 1 : 2 (n = 1) or a 1 : 1 (n = 2,3,4) palladium-ligand complex involving ligand displacement in PdCl42− species. When compared with the monofunctional triisobutylphosphine sulfide (TIBPS) and dihexyl sulfide (DHS), the new reagents were found to provide higher Pd(II) extraction and better extraction selectivity, under identical conditions. The higher members of the ADBDiBPDT series acting as bidentate ligands are also characterized by better stripping properties compared with those of the monodentate sulfur ligands. The metal loading capability, the extraction constants, and the kinetic properties of palladium extraction using these reagents are discussed.

SOLVENT EXTRACTION OF MERCURY(II) WITH SOME SULFUR-CONTAINING EXTRACTING REAGENTS

ABSTRACT A few novel kinds of sulfur-containing extracting reagents, i.e. 2-ethyl-2-(isobutylthiomethyl)butanethiol (EIBTMBT), 3,3-diethylthietane (DETE) and 3,3-di-butylthietane (DBTE), were synthesized to investigate their extraction behaviors for mercury(II) from acidic chloride media at 303 K and compared with that of di-hexylsulfide (DHS), a conventional sulfur-containing extracting reagent. 1,2-dichloroethane was used as a diluent for all reagents. Mercury(II) was found to be extracted with DETE and DBTE according to solvation reaction mechanism as 1:2:2 metahchloride ion:reagent complexes as well as with DHS as follows: The evaluated extraction equilibrium constants for DETE and DBTE were virtually the same, i.e. Kc = 2.3, regardless of the Length of the alkyl radicals and, surprisingly, less than that for DHS (Kc =7.3). On the other hand, it was found to be extracted with EIBTMBT as a 1:2 metal:reagent chelate according to the following extraction reaction:

Peculiarities of the reactions of autohydrogenolysis of organosulfur compounds in the presence of MAlCl4

The reactions of hydrogenolysis of representatives of various classes of organosulfur compounds (hexyl mercaptan, dihexyl sulfide, dihexyl disulfide, thiophene, and concentrates of sulfides isolated from diesel fuel) in the presence of MAlCl4 (M= Li, Na, K) was studied. High degrees of conversion of sulfur-containing compounds in hydrogenolysis reactions are achieved at substantially low temperatures (150–250°C). The reactions of elimination of sulfur from organosulfur compounds with the formation of H2S occur with the participation of hydride ions, formed in the process; in this case the solvent performs the function of a proton donor. In liquid conversion products the presence of aromatic hydrocarbons is detected. The scheme of occurrence of the coupled reactions occurring in the presence of MAlCl4 is cited.

Determination of129I and127I in human thyroid blocks containing mercury as a preservative

A solvent extraction techniques has been developed to separate iodine from mercury contained in thyroid tissues for the determinations of129I and127I in human thyroid blocks by neutron activation analysis. The tissue samples are digested with a mixture of 5 ml HCl and 1 ml HNO3 in a round-bottomed flask fitted with a condenser running with cold water to avoid any loss of iodine. Iodine is extracted into 0.1 M dihexyl sulfide solution in xylene leaving the majority of the mercury in the aqueous phase. Iodine is adsorbed on activated charcoal packed in quartz tubes either by heating the xylene containing iodine in the presence of oxygen or by heating the aqueous solution obtained after back extracting iodine from xylene using a saturated sulfur dioxide solution. Iodine is desorbed from the charcoal and trapped into a quartz ampule which is sent for neutron activation.

Extraction equilibria of gallium(III) and thallium(III) with dihexyl sulfide from hydrochloric acid.

The extraction equilibria of gallium(III) and thallium(III) from hydrochloric acid with dihexyl sulfide (DHS=S) in 1, 2-dichloroethane were measured at 303 K to examine the effects of the concentrations of hydrochloric acid and dihexyl sulfide. The stoichiometric relation of the extraction reaction of gallium(III) was found to be: GaCl3+S→←;GaCl3S;Ke, Gawhere the equilibrium constant was evaluated as Ke, Ga=1.9×102dm3/mol. Extraction of thallium(III) was found to be expressible by the following two stoichiometric relations for low and high concentration regions of hydrochloric acid, respectively. TlCl3+H++Cl-- + 2S→←HTlCl4; Ke, T1 TlCl3+2H++2Cl-+S→←H2TlCl5S; Ke, T1where the equilibrium constants were evaluated as Ke, T1 = 4.0×106 (dm3/mol)4 and Ke, T1=1.6×105 (dm3/mol)5.

Solvent extraction of palladium with dihexyl sulfide.

The mechanism of palladium extraction from aqueous ammonium chloride solutions with dihexyl sulfide in toluene was investigated at 303 K from the viewpoints of extraction equilibrium and kinetics. The result of a loading test suggests that palladium is extracted as a 1:2 metal-reagent complex. The concentration dependencies of the reactant species were examined using a stirred transfer cell with a constant interfacial area to investigate the extraction rate mechanism. The observed extraction rate was reasonably explained in terms of a simple reaction scheme involving complex formation between the intermediate complex adsorbed at the interface and a free extractant molecule dissolved in the aqueous phase as the rate-determining step.

EXTRACTION EQUILIBRIUM OF MERCURY(II) WITH A SULFUR-CONTAINING CARBOXYLIC ACID.

ABSTRACT The extraction behaviors of mercury(II) with dihexyl sulf ide(=DHS), 1,2-bis (hexylthio) ethane ( = BHTE) and ∝-butylthiolauric acid(= ∝-BTLA) from nitric acid and hydrochloric acid were compared at 30 ° C. It was found that in the case of the extraction from nitric acid, mercury(II) is almost quantitatively extracted by these extractants except DHS and that in the case of that from hydrochloric acids, the extractability for mercury(II) of these extractants was in the order:BHTE > DHS > ∝-BTLA. Further detailed studies were conducted in order to investigate the extraction behavior of ∝-BTLA for mercury(II) from chloride medium. It was clarified that ∝-BTLA does not behave as a cation-exchange extractant but as a solvating extractant owing to the strong affinity of a sulfur atom in ∝-BTLA to mercury(II), and that mercury(II) is extracted according to the following solvation mechanism by ∝-BTLA. Extraction equilibrium constant was evaluated as Ke=5.5(dm3/mol).