A new principle of activation-analysis separations-X Substoichiometric determination of traces of gallium

A rapid method for the substoichiometric determination of gallium by neutron-activation analysis has been developed. After irradiation and dissolution of the test sample, gallium carrier is added and two preliminary separation steps are performed: the extraction into chloroform of cupferrates from 7N sulphuric acid and of diethyldithiocarbamates from 2-3N sulphuric acid. The pH of the remaining aqueous phase is then adjusted to 5.5, the solution extracted with a substoichiometric amount of 8-hydroxyquinoline in chloroform and the activity of the gallium hydroxyquinolate extract measured. A simultaneously irradiated gallium standard is treated in exactly the same way. From the activities of these two substoichiometric extracts the amount of gallium originally present in the test sample can be calculated. The method has been applied to the determination of 10(-6) to 10(-3)% of gallium in metallic aluminium and transistor-grade silicon.     

Electroreflectance spectra of polycrystalline gallium in alkali solutions

The electroreflectance spectra (ES) of polycrystalline gallium in alkali solutions have two bands of charge transfer (BCT) from adsorbed water molecules to metal. The energy of one band equals about 4.6 eV and is potential-independent, which points to the presence of water molecules with a zero charge transfer at the metal surface. The energy of the other is lower and drops with increasing potential, which points to the absence of decomposition of adsorbed water to OH_ groups. The plasma ES on gallium is determined largely by mechanism governing electromodulation of the concentration of the surface anion centers where the metal’s free electrons are scattered. The mechanism provides the ES intensity commensurate with that of the water BCT     

Methanol adsorption on the beta-Ga2O3 surface with oxygen vacancies: theoretical and experimental approach

Methanol adsorption on beta-Ga2O3 surface has been studied by Fourier transform infrared spectroscopy (FTIR) and by means of density functional theory (DFT) cluster model calculations. Adsorption sites of tetrahedral and octahedral gallium ions with different numbers of oxygen vacancies have been compared. The electronic properties of the adsorbed molecules have been monitored by computing adsorption energies, optimized geometry parameters, overlap populations, atomic charges, and vibrational frequencies. The gallia-methanol interaction has different behaviors according to the local surface chemical composition. The calculations show that methanol can react in three different ways with the gallia surface giving rise to a nondissociative adsorption, a dissociative adsorption, and an oxidative decomposition. The surface without oxygen vacancies is very reactive and produces the methanol molecule decomposition. The molecule is nondissociatively adsorbed by means of a hydrogen bond between the alcoholic hydrogen atom and a surface oxygen atom and a bond between the alcoholic oxygen atom and a surface gallium atom. Two neighbor oxygen vacancies on tetrahedral gallium sites produce the dissociation of the methanol molecule and the formation of a bridge bond between two surface gallium atoms and the methoxy group.     

Separation gallium-fer en presence d'edta

Macro- or microquantities of gallium can be separated from iron by precipitating the latter with sodium hydroxide in the presence of EDTA. Nearly all the gallium remains in solution. After the separation of iron, gallium is extracted with tributylphosphate from 3 N hydrochloric acid medium, and then re-extracted into water. Gallium is finally determined by precipitation with cupferron and ignition to the oxide, or for trace amounts of gallium, by colorimetric determination with rhodamine B. The method was checked with radioactive gallium and iron.     

On two alternative mechanisms of ethane activation over ZSM-5 zeolite modified by Zn2+ and Ga1+ cations

The activation of ethane over zinc- and gallium-modified HZSM-5 dehydrogenation catalysts was studied by diffuse reflectance infrared spectroscopy. Hydrocarbon activation on HZSM-5 modified by bivalent Zn and univalent Ga cations proceeds via two distinctly different mechanisms. The stronger molecular adsorption of ethane by the acid-base pairs formed by distantly separated cationic Zn2+ and basic oxygen sites results already at room temperature in strong polarizability of adsorbed ethane and subsequent heterolytic dissociative adsorption at moderate temperatures. In contrast, molecular adsorption of ethane on Ga+ cations is weak. At high temperatures dissociative hydrocarbon adsorption takes place, resulting in the formation of ethyl and hydride fragments coordinating to the cationic gallium species. Whereas in the zinc case a Br?nsted acid proton is formed upon ethane dissociation, decomposition of the ethyl fragment on gallium results in gallium dihydride species and does not lead to Br?nsted acid protons. This difference in alkane activation has direct consequences for hydrocarbon conversions involving dehydrogenation.     

Pristine Points of Zero Charge of Gallium and Indium Oxides

Electrokinetic measurements and potentiometric titrations of indium oxide (commercially available reagent grade powder, washed with NaOH and HNO(3) to remove strongly adsorbed species) indicate the pristine point of zero charge to be pH 8.7. The isoelectric point at pH 9 was obtained for gallium oxide prepared in the same way. These values match the pristine point of zero charge of alumina, but they are much higher than the values reported for indium oxide and gallium oxide in the literature. Copyright 2001 Academic Press.     

Differential Pulse Polarographic Determination of Gallium and Niobium in Samples After Preconcentration of Their Quinolin-8-Olate Complexes on Microcrystalline Naphthalene

Abstract

Gallium and niobium react with quinolin-8-ol to form water insoluble complexes which are quantitatively adsorbed on microcrystalline naphthalene from the large volume of their aqueous solutions in the pH range of 3.5 - 8.2 and 6.2 - 9.4, respectively. After filtration, the metal complexes were desorbed with 10 ml of HCl (1M for Ga and 11 M for Nb) and determined by using a differential pulse polarograph (DPP). The dissolved oxygen is removed by adding a few milliliters of 4% NaBH₄ solution in the case of gallium. The detection limits are 0.04 ppm for gallium and 0.05 ppm for niobium at the minimum instrumental settings (signal to noise ratio = 2). The linearities are maintained in the concentration range 0.1 - 5.0 ppm for gallium and 0.4 - 6.0 ppm for niobium with correlation factors of 0.9997 and 0.9996 and relative standard deviations of 0.81 and 0.95%, respectively.

Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters such as the effect of pH volume of aqueous phase, reagent and naphthalene concentrations and the interference of a large number of anions and cations on the estimation of these elements were studied in detail. The method is found to be highly selective, fairly sensitive, rapid, simple and economical. It has been applied for the trace determination of gallium and niobium in various standard alloys and may be applied safely for the analyses of complex materials like environmental samples and ores.

     

Solvent extraction and separation of gallium, indium and thallium with N-benzylaniline

A simple and rapid method is proposed for the separation of tervalent gallium, indium and thallium by solvent extraction with N-benzylaniline in chloroform from different concentrations of hydrochloric acid. Thallium and gallium are extracted from 1M and 7.0-7.5M hydrochloric acid respectively. Indium is finally extracted from hydriodic acid. These metals in the final extracts are determined complexometrically. Interference from some cations can easily be eliminated by reduction with sulphite, followed by selective oxidation of thallium(I) to thallium(III) with saturated bromine water, and from others by the use of thioglycollic acid as a masking agent in the extraction of gallium and indium. Most common anions cause no interference. Log-log plots of distribution coefficients vs. concentration of amine for gallium, indium and thallium indicate a 2:1 limiting mole ratio of amine to these metals.     

Calorimetric study of the adsorption of air pollutants on alumina-supported tin and gallium oxides

The differential enthalpies of adsorption of air pollutants such as SO₂, NO₂, NO on aluminasupported tin and gallium oxides were measured by calorimetry coupled with isothermal volumetry. Whatever the amount of tin or gallium on alumina, the enthalpies of adsorption of SO₂ at low coverage were of the same order of magnitude or up to 50 kJ/mol lower than those of the support. The amount of SO₂ adsorbed decreased with increasing SnO₂ loading and increased with increasing Ga₂O₃ loading on the alumina. The differential enthalpies of adsorption of NO₂ are close to those on the support whatever the amount of tin or gallium (around 120–130 kJ/mol). NO is only reversibly adsorbed on the samples. The calorimetric data of ammonia adsorption are given for comparison.     

Dissociative Adsorption of Water Molecules on Uncharged Surfaces of Indium(111) and Gallium

A possible mechanism of dissociative adsorption (DA) of water on the (111) surface of indium and liquid gallium is investigated within a cluster model for metal using a density functional method (B3LYP). The adsorption interaction of H and O atoms and OH group with these metals is studied. The free energy of DA of H₂ and O₂ molecules is calculated. An analysis of DA is performed both for the case of the metal/vacuum interface and with allowance made for solvation effects within a continuum approach. According to quantum-chemical calculations, DA of water on the In(111) surface is more thermodynamically probable than on gallium. In the case of indium, DA with the participation of a water dimer may have a smaller activation energy compared with DA of monomer H₂O_ads. The data obtained are used to interpret the experimentally observed nonmonotonous dependence of the work function for indium and gallium on the partial pressure of water vapor. The hypothesis about the origin of the absorption band in electroreflectance spectra for the gallium/aqueous solution interface as a result of the electron transfer from an adsorbed water molecule into the metal's conduction band is confirmed.     

电感耦合等离子体质谱法测定煤矸石中微量锗和镓

建立了测定煤矸石中微量锗和镓的电感耦合等离子体质谱法。煤矸石试样经高温灰化,用硝酸-氢氟酸-高氯酸-磷酸分解,以电感耦合等离子体质谱法测定其中的锗和镓。通过在线三通加入内标元素铑,消除非质谱干扰;通过选择干扰元素的异质同位素进行定量测定,采用数学公式在线校正,消除质谱干扰。与分光光度法进行比对,锗、镓测定结果的相对偏差为-0.63%~0.28%。克服了常规化学分析方法步骤繁琐、耗时长、工作量大的不足。该法测定结果的相对标准偏差小于3%(n=6),加标回收率为97.4%~102.5%。该方法具有检出限低、快速、简便、线性范围宽、多元素同时测定等优点,分析误差满足化学分析法的要求,可用于煤矸石中锗和镓的测定。     

Extraction and separation of gallium, indium and thallium with several carboxylic acids from chloride media

A method is proposed for the extraction and individual separation of trivalent gallium, indium and thallium with sec-octylphenoxy acetic acid (CA-12), sec-nonylphenoxy acetic acid (CA-100) and naphthenic acid (NA) from chloride media. The distribution equilibria of gallium (III), indium (III), thallium (III) and thallium (I) between carboxylic acids (CA-12, CA-100 and NA) dissolved in kerosene and acidic aqueous chloride media has been investigated as a function of the concentration of extractants and the concentration of hydrogen ion in aqueous phase. A possible mechanism of the extraction is discussed. The method permits rapid and precise individual separation of gallium (III), indium (III) and thallium (III), and is applicable to the analysis of alloy samples.     

交联镓皂石表面酸性及催化性能的研究

用水热法合成出两种不同镓含量的镓皂石，并用羟基铝低聚物对其进行了交联。对其表面酸性的考察发现，样品的酸量随嫁含量的增加而增大；样品均含有Ｂ酸和Ｌ酸中心，交联样品的Ｂ酸中心比交联前少。对样品催化性能的研究发现，催化活性与镓含量及酸量呈顺变关系。     

Chemical analysis of manganese nodules : Part II. Determination of uranium and thorium after anion-exchange separation

A method is described for the determination of uranium and thorium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, uranium is adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid. The effluent is evaporated and the residue is taken up in 7 M nitric acid—0.25 M oxalic acid; thorium is then isolated quantitatively by anion-exchange on Dowex 1 (nitrate form). Thorium is eluted with 6 M hydrochloric acid and determined spectrophotometrically by the arsenazo III method. Uranium is eluted from the resin in the chloride form with 1 M hydrochloric acid and then separated from iron, molybdenum and other co-eluted elements on a column of Dowex 1 (chloride form); the medium consists of 50% (v/v) tetrahydrofuran, 40% (v/v) methyl glycol and 10% (vv) 6 M hydrochloric acid. After removal of iron and molybdenum by washing the resin with a mixture of the same composition and with pure aqueous 1 M hydrochloric acid, the adsorbed uranium is eluted with 1 M hydrochloric acid and determined by fluorimetry. The method was used successfully for the determination of ppm-quantities of uranium and thorium in 60 samples of manganese nodules from the Pacific Ocean.     

Solvent extraction and separation of gallium(III), indium(III), and thallium(III) with tributylphosphate

A systematic study has been made of the solvent extraction behaviour of milligram amounts of gallium(III), indium(III), and thallium(III) with TBP from hydrochloric acid, and of thallium(III) from nitric acid, sulphuric acid and buffer solutions of different pH. The effect of the metal ion concentration, acid concentration, reagent concentration, salting-out agent, and diverse ions have been critically examined. A scheme for separation of gallium(III), indium(III), and thallium(III) from each other and for their determination is proposed.     

N503萃取镓及其机理的研究

镓的提取过去多采用中和、置换等老力法,其流程长,收率又低。近年来,溶剂萃取法显示出极大的优越性,因此,在镓的萃取分离方面国内外也给予了极大的重视,并已有综述^[1-3]。目前,从盐酸体系中萃取镓常用的工业萃取剂有:甲基异丁基酮(MIBK)^[4-7]、磷酸三丁酯(TBP)^[8-12]、三辛胺(TOA)^[13-17]等。但由于MIBK水溶性大、易挥发、TBP对聚氯乙烯萃取设备有严重的溶胀性、TOA的萃取选择性较     

COMPLEXES OF GALLIUM(III) WITH HYDROXYAROMATIC LIGANDS

Abstract

The equilibria between gallium(III) ion and selected hydroxyaromatic and dihydroxyaromatic ligands at 25°C, μ=0.100 M (KNO₃) have been determined. Potentiometric measurements on 1:1, 2:1, and 3:1 molar ratios of ligand to Ga(III) have been made as a function of degree of neutralization over the entire accessible ?log [H⁺] scale. Calculations were carried out so as to take account of competing hydrolytic reactions, and formation constants of gallium(III) with chromotropic acid, 8-hydroxyquinoline-5-sulfonic acid, 5-sulfosalicylic acid, and 1,2-dihydroxy-benzene-3,5-disulfonic acid were obtained. Stable hydroxo chelates do not form under the reaction conditions employed. The protonation constants of the ligands and the formation constants of the gallium chelates are discussed and compared with previously published work on these gallium chelates and on chelates of “analogous” metal ions such as those of Fe(III) and A1(III).     

Photometric determination of gallium with rhodamine b

Gallium is extractable as rhodamine B chlorogallate with benzene from 6M hydrochloric acid, and can be determined absorptiometrically or fluorimetrically in the extract. The interference of iron(III) is avoided by first separating gallium by extraction with isopropyl ether from hydrochloric acid solution containing titanous chloride. Traces of gallium can be determined in the presence of aluminium, indium, zinc, antimony, thallium, tungsten and other elements.     

Determination of traces of gallium based on stripping voltammetry with adsorptive accumulation

Trace levels of gallium can be quantified by linear-sweep voltammetry after absorptive preconcentration of the gallium/solochrome violet RS chelate on the hanging mercury-drop electrode. The interfacial and redox behaviors are evaluated by cyclic voltammetry. The adsorbed chelate yields two distinct reduction peaks that can be utilized to quantify gallijm. The effects of preconcentration time and potential, dye concentration, bulk concentration of gallium, and other variables on the chelate peaks are investigated. For a 2-min preconcentration time, the detection limit is 0.08 μg l^?1. With preconcentration for 60 s, calibration plots are linear for the range 0–16 μg ml^?1 gallium. Possible interferences by other trace metals and surface-active organic materials are investigated. Gallium added to samples of sea and rain water was quantified readily.     

Determination of gallium in an iron-aluminium matrix by solvent extraction and flame emission spectroscopy

Solvent extraction of gallium(III) into methyl isobutyl ketone from hydrochloric acid solutions containing titanium (III) sulphate provides a rapid method for separation of gallium from an iron/aluminium matrix and may be employed to eliminate the interference of these elements in the flame emission spectrometric determination of gallium.