Sorption of palladium(II) from nitric acid solutions by silica modified with amino groups

The sorption of Pd(II), Ag(I), and Cu(II) from nitric acid solutions with silicas chemically modified with γ-(aminopropyl)trietoxysiloxane is investigated. It is assumed based on the investigation of solid phases by IR and X-ray photoelectron spectroscopy and thermogravimetry that the following processes occur during the sorption of palladium from nitric acid solutions: coordination of palladium atoms to nitrogen atoms of the functional group, interaction of palladium ions with the silica matrix, and the formation of polynuclear complexes. It is proposed to use a 5% solution of thiourea in 0.1 M HCl. It is determined that the establishment time of constant values of sorption in static conditions is as follows, min: 10 for Ag(I), 20 for Cu(II), and 30 for Pd(II). A sorbability series of ions from 2 M HNO₃ in identical conditions is as follows: A_Ag(I) > A_Pd(II) ? A_Cu(II). Silver ions are not sorbed from solutions with the concentration of HNO₃ < 1 M, which will create prerequisites for the separation of ions.     

Extraction of palladium (II) from nitric acid medium by imidazolium nitrate immobilized resin

Imidazolium nitrate functional groups (Im–NO₃) were anchored onto a polystyrene–divinylbenzene resin matrix, and investigated for the extraction of palladium (II) from nitric acid medium. The rate of extraction and distribution coefficient, K_d, mL/g, of palladium (II) were measured as a function of extent of functionalization, and concentrations of nitric acid, sodium nitrate and palladium nitrate. K_d values of palladium (II) show a maximum in 3.0 M–4.0 M nitric acid. Slope analysis of the distribution data obtained at various aqueous phase nitrate concentrations and resin phase exchanging capacity suggest the involvement of anion exchange mechanism for the extraction of palladium (II) from nitric acid medium. The ion exchange isotherm was fitted using Langmuir adsorption model and the apparent ion exchange capacity (b = 88 mg/g) was determined. The performance of the resin under dynamic conditions was evaluated by following a breakthrough curve and the data was fitted using Thomas model.     

Preparation of pure vanadium pentoxide by extraction using diisododecylamine

Diisododecylamine (DIDA) is shown to be an efficient agent for extracting vanadium(V) ions from weakly acidic (pH 5–6) sulfuric acid media. Its parameters are comparable with those for vanadium extraction by the well-known amine extracting agent TOA (tri-n-octylamine). The extraction of vanadium(V) ions by DIDA from the real shop leach liquors of vanadium slag with a vanadium concentration of 3.13–5.08 g/l is tested under laboratory conditions using the results obtained. Vanadium is reextracted from the organic phase by solutions of ammonia water (1: 1). The V₂O₅ samples prepared by the extraction technology are shown to satisfy the specifications of pure VnO-1 vanadium pentoxide.     

粗钯中银的分离

粗钯用硝酸溶解后 ,加入定量的氯化钠使银以氯化银沉淀析出 ,过滤除去氯化银。将滤液中的钯再次还原为粗钯 ,用二氯二氨络亚钯法进行提纯。在提纯过程的盐酸酸化阶段适当增加溶液中的盐酸浓度 ,使残余的银以[AgCl2 ] - 的形式经过滤洗涤去除 ,从而得到纯净的海绵钯。     

A solvent extraction study of silver(I), palladium(II) and mercury(II) with 2-tert-dodecylthiopyridine

2-tert-Dodecylthiopyridine was synthesized from 2-chloropyridine and tert-dodecanethiol in order to examine its extraction properties for various metals. It was found to have good selectivity for the extraction of palladium(II) and mercury(II) over platinum(II) and -(IV) and base metals from chloride media; silver(I) was found to be almost completely extracted from nitric acid (0.01–5 mol/dm³ HNO₃). Palladium(II) and mercury(II) were completely extracted from hydrochloric acid over the range 0.01–2 and 0.01–0.5 mol/dm³ HCl, respectively. The rate of extraction of palladium(II) from hydrochloric acid was much faster than when using dialkylsulfide and triisobutylphosphine sulfide extractants. An aqueous mixture of thiourea and hydrochloric acid was found to be effective as stripping solution for palladium(II). The extent of stripping was dependent on the concentrations of either thiourea or hydrochloric acid.     

Extraction of gold(III) in hydrochloric acid solution using monoamide compounds

The extraction and separation properties of Au(III) using two monoamide compounds, N,N-di-n-octylacetamide (DOAA) and N,N-di-n-octyllauramide (DOLA), which have different side chain lengths attached to the carbonyl carbon (CH₃ for DOAA and n-C₁₁H₂₃ for DOLA), were investigated. The solvent extraction of some precious and base metals (Au(III), Pd(II), Pt(IV), Rh(III), Fe(III), Cu(II), Ni(II) and Zn(II)) in HCl solutions was carried out using DOAA and DOLA diluted with n-dodecane and 2-ethylhexanol. A good selectivity for Au(III) extraction with 0.5 M extractant is obtained at lower HCl concentrations (< 3.0 M) in both systems. The extractability of Au(III) with DOAA is greater than that with DOLA. In the 0.5 M DOAA–3.0 M HCl system, a third phase is formed when the Au(III) concentration in the initial aqueous phase is over 39 g/L. In contrast, third phase formation is not found in the 0.5 M DOLA–3.0 M HCl system, and its loading capacity of Au(III) is about 79 g/L. The Au(III) extracted in the organic phase is effectively back-extracted by 1.0 M thiourea in 1.0 M HCl solution in both systems, while some thiourea is precipitated using the organic phase containing 20 g/L of Au(III). The back extraction of Au(III) using water is poor in the DOAA system, but possible in the DOLA system.     

Carrier-mediated transport of uranium from phosphoric acid medium across TOPO/n-dodecane-supported liquid membrane

Present studies deals with the application of supported liquid membrane (SLM) technique for the separation of uranium (VI) from phosphoric acid medium. Tri-n-octyl phosphine oxide (TOPO)/n-dodecane is used as a carrier and ammonium carbonate as a receiving phase for the separation of uranium (VI) from the phosphoric acid medium. Throughout the study PTFE membranes are used as a support. The studies involve the investigation of process controlling parameters like feed acidity of phosphoric acid, carrier concentration and stripping agents. The effect of nitric acid and sodium nitrate in feed is also studied. It is found that there is negligible transport of uranium (VI) from pure phosphoric acid medium but it increases to very significant amount if 2 M nitric acid is added to feed phase. More than 90% uranium (VI) is recovered in 360 min using 0.5 M TOPO/n-dodecane as carrier and 1.89 M ammonium carbonate as stripping phase from the mixture of 0.001 M H₃PO₄ and 2 M of HNO₃ as a feed. The flux and permeability coefficient are found to be 9.21 × 10^− 6 mol/m² s and 18.26 × 10^− 5 m/s, respectively. Lower concentration of phosphoric acid with 2 M HNO₃ and higher concentration of carrier is found to be the most suitable condition for maximum transport of uranium (VI) from its low-level sources like commercial phosphoric acid.     

Influence of the crystalline microstructure on the diffusivity of hydrogen in palladium galvanostatic permeation and X-ray diffraction measurements

The influence of crystalline microstructure upon the apparent diffusion coefficient of hydrogen in Pd samples are reported. The apparent diffusion coefficient was measured by the galvanostatic permeation method (at 20°C), while the structure was characterized by X-ray diffraction measurements. Pd membrane electrodes of different thicknesses, l = 5 × 10⁻³cm and l = 10⁻²cm, were used. The structure of Pd membrane electrodes was changed by successive annealing and sequences of absorption and desorption of hydrogen accompanied by the α⇌β phase transition. Both the irreversible and reversible traps affect the mobility of hydrogen in Pd. The irreversible traps manifest in the variation of the apparent diffusion coefficient as a function of the average stationary bulk concentration of hydrogen, while the diffusion coefficient of the free hydrogen does not depend on the actual concentration of hydrogen in Pd. This is true provided that the average stationary bulk concentration of hydrogen is higher than the irreversible trap concentration. The diffusion coefficient of free hydrogen depends on the specific internal surface area according to McNabb-Foster-like equation. The value of the diffusion coefficient of hydrogen in single crystal of palladium was estimated, D₀ = (4.2 ± 0.3) × 10⁻⁷ cm²s⁻¹ (20°C).     

Determination of organic phase complexes formed on extraction of iron(III) from aluminium nitrate solutions with versatic 10

The extraction of Fe(III) from concentrated aluminium nitrate solutions by Versatic 10 in Escaid 110 was studied, using an AKUFVE system for the determination of extraction isotherms at constant pH values. The extraction data were analysed initially by classical slope analysis but this was found to be inadequate due to the complexity of the organic phase speciation. A statistical technique was then used to evaluate the compositions of the organic phase complexes by finding the best fits to the extraction data. Equilibrium constants governing the extraction of these complexes were calculated. Independent measurements of the amount of Versatic acid bound in the organic iron complexes were made by quantitative infrared analysis of organic extracts. Agreement between the statistical and infrared results was good. Complexes of the general form (Fe(OH)_3? V_n·sHV)_x were found, where n varied from 1 to 2 and s from about 0.5 to 2.5, with both decreasing as the iron loading in the organic phase was increased. Values of 2 or 3 were generally found for x, indicating the predominance of dimers and trimers.     

Synthesis and characterization of aluminum and AI/REE pillared clays and supported palladium catalysts for benzene oxidation

Volatile organic compounds (VOCs) are considered as a major pollutant in indoor and outdoor air.More stringent environmental regulations have been implemented in order to reduce the VOC emissions.One of the techniques available for destructive removal of VOCs is catalytic oxidation.In the present work,Al/Rare Earths (REE: Y,Ce,La,Pr and Nd) pillared clays (PILCs) were used to support 0.2 wt.% of palladium for the complete oxidation of low concentration of benzene.The supports and catalysts were characterized by XRD,N2 adsorp-tion/desorption,FTIR spectroscopy,HRTEM and H2-TPR techniques.The results indicated that after Al and Al/REE pillaring,the basal spac-ing,SBET,Amic and Vmic of Al and AlREE-PILC had a considerable increase compared with those of Na-mmt.Activity tests of deep oxidation of benzene showed that the catalytic activity of Pd catalysts supported on Al and AlREE-PILC were much higher than that on initial clays,which was due to the fact that optimized structure of PILCs,such as large basal spacing,high SBET and porosity,improved Pd dispersion and increased the active sites of Pd.Especially for Pd/AlCe-PILC,the temperature of complete oxidation was about 280 oC,exhibiting the highest catalytic activity.     

Precipitation transformation of rare earth sulfate into chloride with p-dodecylphenoxy carboxylic acids

Methods for transforming rare earth(RE) sulfate into chloride mainly include extraction process with organophosphonic mono-acids or aliphatic acids and precipitation process with ammonium bicarbonate(NH_4 HCO_3).In this paper,alkylphenoxy carboxylic acids(HAs) ofp-dodecylphenoxy acetic acid(HA-Ⅰ),pdodecylphenoxypropanoic acid(HA-Ⅱ) and p-dodecylphenoxybutyric acid(HA-Ⅲ),which were liquid at room temperature were synthesized and characterized.The precipitation mechanisms of RE elements with the HAs were investigated and the HA/RE molar ratios of the solid complexes were determined as3:1 by equi-molar series method which accord with the principle of charge balance.Applicability of HAs for the transformation of RE sulfate from concentrated sulfuric acid roasted RE concentrate into chloride via precipitation method was discussed.100% HA-Ⅱ was selected as the liquid organic precipitant without dilution of volatile solvent soracceleration of phase separation by phase-modifiers.The RE sulfate solution can be precipitated by HA-Ⅱ after neutralization with liquid NaOH and stripped with concentrated HCl at room temperature.High concentration of RE chloride of 218.1 g/L with low residue of sulfate radical of 0.536 g/L was obtained.The residual organic precipitant in the raffinate solution was tested to be lower than 8 mg/L at 25℃and the chemical oxygen demand(COD) in wastewater was less than 50 mg/L.     

Electrochemical behavior of cerium（IV） in a RTIL and its mixture with ethanol

A systematic study was carried out to explore the electrochemical behavior of Ce in room temperature ionic liquid（CnmimBr, where n=6, 8, 10） and mixture of C6 mimBr and ethanol by cyclic voltammetry. With increase in the number of carbon atoms on the alkyl substituent on methyl imidazolium cation, the electrochemical window of the ionic liquids was found to extend towards more negative potential value, as a result there was a possibility of reduction of Ce to lower oxidation states. The diffusion coefficient and activation energy for the diffusion were calculated in all the ionic liquids and one of their mixtures with ethanol. With increase in n value, the diffusion coefficient of Ce decreased due to increase in viscosity of the medium while the activation energy for the diffusion followed a reverse trend for C6 mimBr, C8 mimBr and C10 mimBr, respectively. The observations indicated that the nature of species of Ce might be different in room temperature ionic liquids（RTILs） from that present in their mixtures with ethanol.     

Modelling of zinc transport through a supported liquid membrane

The transport of zinc (II) from an aqueous solution containing zinc (II), iron (II), calcium (II) and magnesium (II) through supported liquid membrane using di-2-ethylhexyl phosphoric acid dissolved in kerosene as a mobile carrier was studied. The effects of temperature, rate of feed and stripping phase and concentration of stripping phase on the mass transfer coefficients of aqueous boundary layers and membrane were studied. A transport rate model has been derived taking into account diffusion through the feed side aqueous boundary layer, diffusion of carrier–zinc complex through the supported liquid membrane and diffusion through the stripping side aqueous boundary layer as simultaneous controlling factors. The mass transfer coefficient data of the side of the feed phase were correlated in the form of Sh = 0.0047 Re^1.349 Sc^0.3333. This correlation was used to calculate the mass transfer coefficient of the aqueous film at the side of the stripping phase. For some parameters and their levels, the mass transfer coefficients, k_f, k_m and k_s (m s^− 1), were calculated.     

Solvent extraction of some base and precious metals using 1,3,4-thiadiazole-2-nonylmercapto-5-thiol

This investigation is one of a series of studies in which the fundamental chemistry which underlies the extraction and separation of precious metals is considered. The title compound (TNSTH) was used as a solvent extraction reagent and shows some promise for extracting and separating the chloro-anions of Au(III) and Pd(II) from strong hydrochloric acid solutions (ca. 5 M). The distribution coefficients from such media were in the order of 10⁴. The title reagent may be used to separate the precious metals from each other. For example, the separation coefficients (i.e., ratios of distribution coefficients) for mixed solutions are 10⁶ for Au(III)/Rh(III) and Pd(II)/Rh(III); 145 for Au(III)/Pd(II); 180 for Pd(II)/Cu(I or II); 10⁶ for Pd(II)/Pt(IV). The time for half of the Pd(II) to be extracted is approximately 6 min, which is acceptable for a commercial process. The title reagent provides a means of separating precious metals from base metals as the latter, with the exception of copper, are not extracted. In the case of copper, the extraction is as Cu(I) rather than Cu(II). The stoichiometry of the Pd(II) extraction is Pd:TNSTH is 1:1.5. Some additional information concerning the nature of the complexes formed by the title compound and chloro-anions in alcoholic solution indicates that Cu(TNST), Ag(TNST), Pd(TNST)₂, and RhCl₃(TNST)₂ are formed. Most of the metals, with the notable exception of rhodium(III) and iridium(IV), can be stripped using a thiourea/HCl solution. The reagent TNSTH appears to be a chelating agent with donor N and S atoms.     

Preparation of hybrid perovskite-type Li0.33La0.56TiO3 by adding ionic liquids

Perovskite-type Li_0.33La_0.56TiO₃ (LLTO) shows greater advantages than organic liquid electrolytes to be used in all-solid-state lithium-ion batteries with high energy densities. Ionic liquid [BMIM][BF₄] was used to improve the properties of Li_0.33La_0.56TiO₃ by attrition milling in this study. The microstructure, crystallinity and lithium-ion conductivity of the samples were measured by scanning electron microscopy (SEM), X-ray diffraction (XRD), and impedance spectroscopy (IS). The total ionic conductivities of the samples LLTO + x wt% [BMIM][BF₄] increase upon adding [BMIM][BF₄] and the maximum conductivity reaches 4.71 × 10⁻⁴ S/cm when x = 12.5 wt%. The enhancement of the total conductivity is ascribed to the bridging role of the ionic liquid among grains, as evidenced by the low activation energy of 0.17–0.25 eV and the SEM observation. The Li⁺ transference numbers of the hybrid samples are all lower than that of the pure LLTO, indicating the existence of electronic conductions. The hybrid material with a mixed conductivity and good stability in the atmosphere can find uses in all-solid-state lithium-ion batteries to improve the interface contact between electrolytes and electrodes.     

The extraction of hafnium (IV) by some organophosphorus reagents in the presence of two mineral acids

Extraction of hafnium (IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids of constant total acidity 2, 4, 6 and 8 M and c_Hf ? 4 × 10^?4mol l^?1. The organic phase consisted of solutions of various acidic or neutral organophosphorus reagents including di-n-butylphosphoric acid, di-n-amylphosphoric acid, di-n-octylphosphoric acid, n-decylphenylphosphonic acid, tri-n-butylphosphine oxide, tri-n-octylphosphine acid (TOPO), tri-n-phenylphosphine oxide, and tri-n-butylphosphate (TBP); or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. Pronounced synergic extraction of hafnium occurs only with organophosphorus reagents from aqueous phases whose acidity is not lower than 3 M (HClO₄ + HNO₃) or 5 M (HClO₄ + HCl). The synergic effect was not affected markedly by variation of the initial concentration of hafnium in the range 1 × 10^?8 ?4 × 10^?4 mol l^?1, but it decreased with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H⁺ ions. No synergism was observed for the extraction of hafnium from mixtures of perchloric and sulphuric acids. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.     

Influence of surface Ce/Zr ratio on formation of κ-Ce2Zr2O8 superstructure and its application in three-way catalysis

Ceria-zirconia based(CZ) materials are still a crucial component of three-way catalysts(TWCs) now.Compared with traditional cubic or tetragonal phase,CZ material with pyrochlore-type κ-Ce₂Zr₂O₈ phase shows an excellent oxygen storage capacity,and thus is examined as a promising material for developing TWCs.Considering the remarkable surface Ce/Zr ratio change during the κ-Ce₂Zr₂O₈ formation,we investigated the effects of surface C...     

X-ray study of the martensitic transformation in an indium-thallium alloy

Single crystal X-ray measurements of the temperature dependence of the lattice parameters of In_0.73Tl_0.27 between 25 and 300 K were performed in order to search for a pretransformation tetragonal phase above the f.c.c.-f.c.t. martensitic transformation at 165 K, as previously found for FePd by Seto et al. [H. Seto, Y. Noda and Y. Yamada, J. Phys. Soc. Japan57, 3668 (1988); 59, 965 (1990)] and in order determine, in conjunction with ultrasonically measured room temperature elastic data, the parameters of the Landau free energy for the O_hD_4h proper ferroelastic transformation. The mechanical stability limit of the cubic phase and the third and fourth order elastic moduli depend on thermal cycling through the transformation, but their ratio and the transformation temperature T₀ remained constant. In the as-grown state of the crystal all model parameters are consistent with those measured ultrasonically by Brassington and Saunders [Proc. R. Soc.A387, 289 (1983)]. The directly measured volume change at T₀ was found to be negative, consistent with the positive pressure coefficient of T₀ for In_0.77Tl_0.23 [G. A. Saunders, J. D. Comins, J. E. Macdonald and E. A. Saunders, Phys. Rev.B34, 2064 (1986)]. No pretransformation tetragonal phase about T₀ was found.     

CO32-型TOMAC自碱性溶液中萃取硫代亚砷酸

针对含砷烟尘碱浸液砷分离问题,提出CO32-型TOMAC有机相萃取硫代亚砷酸的方法.以碱浸液的模拟料液为研究对象,经硫化预处理后,测定有机相饱和萃取容量并初步探索萃取机理.考察有机相组成、相比、萃取时间及萃取温度对砷萃取分离效果影响,结果表明：有机相组成为30%CO32-型TOMAC+15%仲辛醇+磺化煤油;水相料液组成为0.5 mol/L NaOH +9.69×10-2mol/L AsIII;在室温及相比为VO/VA=1/l的条件下,AsIII单级萃取率为85.3%.经4级逆流萃取,萃余液中AsIII浓度可降至1.34×10-3 mol/L以下,萃取率可达98%以上,达到了碱性溶液有效脱砷的目的.     

The extraction of zinc(II) from sulphate and perchlorate solutions by di(2-ethylhexyl)phosphoric acid dissolved in Isopar-H

The extraction of zinc from sulphate and perchlorate solutions at constant ionic strength, by di(2-ethylhexyl)phosphoric acid, DEHPA, in Isopar-H has been studied at 25°C as a function of metal and DEHPA concentrations. The distribution data have been analyzed both graphically and numerically, using the computer program LETAGROPDISTR [33]. The results showed that the species extracted into the organic phase have the composition ZnA₂HA and ZnA₂H₂A₂ for both perchlorate and sulphate systems. The formation constants for each system are given in Table 2. An estimate of the formation constant of ZnSO₄ in aqueous phase was obtained from the extraction data in sulphate solutions.