Separation of lanthanum and cerium on modified fly ash bed

The adsorption of lanthanum and cerium on modified fly ash bed has been studied. The effect of pH on the adsorption of both lanthanum and cerium by the bed material has been discussed. The exchange capacities of lanthanum and cerium have been determined. The method has been applied to monazite sand solution. The elution of both lanthanum(III) and cerium(IV) was studied using buffer and suitable eluting agent. The process is simple and may be considered as a low cost-methodology for separation of lanthanum and cerium.     

Radiochemical study of the separation of cerium(III) from lanthanum by solvent extraction using N-benzoyl-N-phenylhydroxylamine

The extraction of cerium(III) and lanthanum(III) by N-benzoyl-N-phenylhydroxylamine (N-BPHA) in chloroform has been studied in order to determine the composition and extraction constants of the extracted chelates. From the results obtained, the best conditions for the separation of cerium from lanthanum (separation factor about 200) have been predicted and experimentally verified.     

Simultaneous determination of lanthanum and cerium in mixed rare earths with p-acetylarsenazo by spectrophotometry

A new method has been developed for the simultaneous spectrophotometric determination of small amounts of lanthanum and cerium in the presence of large amounts of rare earth elements. Lanthanum (III) and cerium (III) were determined spectrophotometrically with p-acetylarsenazo as the color reagent in the chloroacetic acid medium at pH 3.1 by measuring the absorbances of the complexes at 670 nm. The remained rare earths were masked with ethylenediaminetetracetic acid and ethylenediaminetetracetic acid-zinc during the analysis. The optimum conditions for the simultaneous determination of lanthanum and cerium have been defined. The individual content of lanthanum (III) and cerium (III) were determined by varying the amounts of EDTA and EDTA-Zn used in the analysis and solving the simultaneous absorbance equations based on the Beer's law. The proposed method has been successfully applied to the determination of lanthanum and cerium in Longnan mixed rare earth oxides and other heavy rare earths without preliminary separation with satisfactory results. The relative errors of all analytical results of the method were not more than 2% with good precision. The procedure does not require separation of lanthanum, cerium and the other rare earth elements.     

Selective adsorption of cerium on activated charcoal from aqueous electrolyte solutions

The adsorption of cerium on activated charcoal has been studied as a function of shaking time, pH, concentration of adsorbate and temperature. The adsorption of cerium obeys Freyndlich and Langmuir isotherms. The influence of different cations and anions on cerium adsorption has been exmined. The adsorption of other metal ions on activated charcoal has been studied under specified conditions to check its selectivity for cerium adsorption. Consequently, cerium was removed from a mixture containing Ce, Ba, Sr, Ru, Cs, Cr, Nd, Pr and In. About 99% of the adsorbed cerium on activated charcoal can be recovered with 3M HNO₃ solution. A wavelelngth dispersive X-ray fluorescence spectrometer was used for measuring the cerium concentration.     

Studies on the adsorption behaviour of trace amounts of cerium on manganese dioxide from aqueous solutions in the presence of complexing agents

Adsorption behaviour of trace amounts of cerium on manganese dioxide has been studied as a function of pH (1–10) in the presence of EDTA, oxalate, citrate, tartrate, cyanide and thiocyanate ions. The influence of their concentration on the adsorption has also been investigated. Maximum adsorption of cerium has been noticed at pH6. Under specific conditions, adsorption of other metal ions has been measured for comparison. Low distribution coefficients are obtained for Cs(I) and Hg(II) in the presence of oxalate, and for Cr(III) in the presence of thiocyanate ions. Based on these data, separation of cesium, chromium and mercury from rare earths and cerium scavenging in natural water or in waste water treatment can be achieved.     

Adsorption of selected ions on hydrous cerium oxide

Hydrous cerium oxide was synthesized and laboratory study was conducted to address its applicability for decontamination of barium, strontium, molybdenum, europium, iodine, samarium and cesium ions from radioactive liquid wastes using radiotracer technique. The adsorption of Ba(II), Sr(II), Mo(II), Eu(II), I(I), Sm(III) and Cs(I) on hydrous cerium oxide has been investigated as a function of pH, concentration and temperature of the adsorptive solution and the result obtained show that these parameters affect the extent of adsorption. The ion-exchange capacity decreased at higher temperatures which could be due to decrease of active sites as well as hydrophilic properties of surface adsorbent. Hydrous cerium oxide shows relatively high adsorption in acidic and neutral media towards the radiotracers studied, which can be attributed to large hydrated radius and ion exclusion effect.     

铈改性丝光沸石在甲醇胺化反应中的应用

研究了氨和甲醇以铈改性丝光沸石为催化剂,在常压固定床上选择性合成二甲胺的反应。考察了温度、氨醇比、甲醇液相空速等制备条件对催化剂的活性及二甲胺选择性的影响。     

钙蒙脱土吸附镧的影响因素及其应用

以钙基蒙脱土(Ca-MMT)为载体,研究其对镧(La)的吸附。 采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和元素mapping分析、傅里叶红外光谱(FT-IR)、BET、X射线荧光光谱分析(XRF)对其晶型结构、表面形态、比表面积、化学结构进行表征,考察了La的初始浓度、pH值、温度对Ca-MMT吸附镧性能的影响,考察了载镧钙基蒙脱土(Ca-MMT@La)的除磷效果。 结果表明:Ca-MMT投入量为10 g/L时,Ca-MMT的平衡吸附量随镧的初始浓度增加而增大,最大吸附量为49.62 mg/g;随着pH值增大,吸附能力增强,pH=6时为最佳pH吸附镧条件,吸附量为38.36 mg/g;随温度的升高,其吸附量先下降再上升,20 ℃吸附能力最大,吸附量为41.23 mg/g。 Langmuir等温吸附方程推断其吸附属于单分子层吸附。 Ca-MMT不具有吸附磷效果,而Ca-MMT@La对磷酸根有很强的吸附能力,吸附量为7.24 mg/g,除磷率为72.41%,其除磷率随含镧量增大而增大。     

Effect of rare-earth metals (Y,La, and Ce) on the corrosion and mechanical properties of aluminum-manganese alloy

Effect of some rare-earth metals (yttrium, cerium, and lanthanum) on the corrosion-electrochemical and mechanical properties of an aluminum-manganese alloy of eutectic composition (1.9% Mn) in a neutral medium was studied.     

Synthesis of La-incorporated chitosan beads for fluoride removal from water

In this study, lanthanum incorporated chitosan beads (LCB) were synthesized using precipitation method and tested for fluoride removal from drinking water. The effect of various parameters like complexation and precipitation time, lanthanum loading and ammonia strength on fluoride removal have been studied. It is observed that the parameters for the synthesis of LCB have significant influence on development of LCB and in turn on fluoride removal capacity. The optimal condition for synthesis of LCB includes lanthanum loading: 10 wt%, complexation time: 60 min, precipitation time: 60 min, drying temperature: 75 °C for 72 h. The maximum fluoride adsorption capacity of LCB was found to be 4.7 mg/g and negligible release of lanthanum ion was observed. XRD analysis shows the presence of lanthanum hydroxide and amorphous nature of LCB. SEM of LCB shows the presence of oval lanthanum hydroxide particles spread over the chitosan matrix. Fluoride adsorption capacity has been calculated by applying Langmuir and Freundlich isotherms. The comparative study suggests that LCB shows four times greater fluoride adsorption capacity than the commercially used activated alumina.     

Separation of <Superscript>139</Superscript>Ce using solvent extraction technique from La<Subscript>2</Subscript>O<Subscript>3</Subscript> target irradiated by 14.7 MeV protons

The radiochemical separation of no-carrier-added cerium from proton irradiated lanthanum was studied by solvent extraction using DEE, TBP and TPPO, the latter reagent being employed for the first time for separation of radiocerium from bulk of lanthanum. Distribution coefficients of cerium and lanthanum were investigated as a function of equilibrium time and concentration of HNO₃. A mixture of 0.05M K₂Cr₂O₇ and 0.1M H₂SO₄ was used as an oxidizing agent to improve the separation efficiency of cerium. A comparative study of the three extractants released that DEE is the best for separation of cerium from bulk of lanthanum oxide. The target was prepared by pressing. The production of ¹³⁹Ce of high radionuclidic purity and chemical purity via irradiation of lanthanum oxide target at MGC-20 cyclotron with protons of energy 14.5 MeV is described. The experimental yield was found to be 153 kBq/μA·h.     

Adsorption Studies of Radionuclides and Toxic Metal Ions on a Modified Mesoporous Lanthanum(III) Silicate

A new adsorbent, modified mesoporous lanthanum(III) silicate, has been prepared with various molar ratios of Si/La (10, 20, 40, 80) and cethyltrimethylammonium bromide (CTAB) as structure directing agent. XRD, nitrogen sorption, SEM, IR, thermogravimetry and sorption of radionuclides and toxic metal ions have been studied. The results show that adsorption amount of some element such as Pb(II) and Th(IV) has been increased significantly by incorporation of lanthanum ions in the framework of adsorbent. Separation of Co(II)‐Th(IV), Co(II)‐U(VI) and Mo(VI)‐U(VI) has been developed on columns of this adsorbent.     

Determination of lanthanum with n-benzoyl-n-phenylhydroxylamine

N-Benzoyl-N-phenylhydroxylamine is proposed for the gravimetric determination of lanthanum, at pH 6.4–7.2. The precipitates can be weighed directly or ignited to the oxide. By suitable pH adjustment, many metals can be separated from lanthanum, which can then be determined in the filtrates. Interferences of Ni, Cu, Zn and Fe(II) are masked with cyanide. About 99.5% of cerium can be separated from lanthanum by precipitating cerium(IV) at pH 4.8–5.2.     

Catalytic properties of complex oxide coatings on foamed nickel

Effect of the Ni/NiO composite support on the properties of catalytic systems based on cerium oxide and lanthanum manganite with various dopants was studied.     

Oxygen isotopic exchange between carbon dioxide and some molybdates or rare-earth elements

The oxygen exchange between C¹⁸O₂ and the normal molybdates of cerium, lanthanum, praseodymium and neodymium has been studied within the temperature interval 300–500°C. The specific rates and activation energies of exchange for these molybdates were found to have similar values. The reactivity of oxygen in the molybdates studied was shown to be close to the reactivity of oxygen in MoO₃     

La séparation du scandium,du lanthane et de l'yttrium

The behaviour of scandium on a resin column has been studied and an efficient separation of scandium, lanthanum and yttrium has been effected using citric acid at different pH's. The hysteresis phenomenon which accompanies the adsorption of scandium and its importance for calculations, based on the theory of levels, are discussed.     

Complexation reactions between lanthanum,gadolinium, and ytterbium and reagents of Arsenazo III group on the surface of fibrous materials loaded with a Chelex 100 ion exchanger

The complex formation reaction between La(III), Gd(III), and Yb(III) with Arsenazo III, Arsenazo M, and Chlorophosphonazo III after adsorption on polyacrylonitrile fiber loaded with an ion exchanger with iminodiacetate groups Chelex 100 has been studied. The influence of medium acidity, duration of the contact of the solution with the adsorbent, the presence of masking agents, and the concentrations of ions on the analytical signals of complexes in the solid phase has been investigated. It has been shown that there is a possibility to perform sorption-spectroscopic determination of the total concentration of the indicated elements using Chlorophosphonazo and the sum of lanthanum and gadolinium with Arsenazo M after adsorption from malonic acid solutions.     

The effect of metallic cations on the electrophoretic properties of a pretreatedHevea latex

High-ammonia latex concentrate prepared from doubly-centrifuged fieldHevea latex was exhaustively dialysed to remove any residual water-soluble non-rubber constituents. The electrophoretic mobilities of the dialysed latex in the presence of various metallic cations were investigated as a function of electrolyte concentration. The mobility decreased with increasing concentration of the cations Na⁺, Ba²⁺, Mg²⁺ and Ca²⁺ in a manner consistent with the effect of simple electrolyte on compression of the electric double layer. Anomalous behaviour was noted for the divalent ion copper, in that it reversed the charge of the latex particles at a concentration even lower than that of uranyl ions. Multivalent cations (lanthanum, cerium and thorium) had a profound influence on the latex particles where very low charge reversal concentrations were observed. It is believed that strong adsorption of hydrolysed species from the metallic ions was responsible for reversing the charge of the originally negative latex particles. These experiments indicated that the efficiency with which the cations reversed the charge of the latex particle surface was in the order: lanthanum > cerium > copper > thorium > uranyl > calcium > magnesium > barium > sodium. The number of cation binding sites on the latex particle surface and the chemical free energies of cation adsorption were calculated. It was found that the interaction of the latex particle with the hydrolysable metallic cations was much more stronger than that with the simple divalent cations and that this intercation was comparable to that of biological surfaces.     

电感耦合等离子体原子发射光谱法测定稀土钢中微量镧、铈

采用稀王水溶解样品,选择La408.672 nm、Ce456.236nm为分析线,建立了电感耦合等离子体原子发射光谱法(ICP-OES)测定稀土钢中微量镧、铈的方法。结果表明,各元素校准曲线线性良好,相关系数可达0.99999;方法测定范围为：0.0001%～0.10%。检出限为：镧0.00002%,铈0.00006%。按照实验方法测定标样中镧、铈,结果的相对标准偏差RSD(n=8)为2.18%、1.68%。     

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry-I. Cerium, neodymium and lanthanum matrices

The present paper deals with spectral interferences from cerium, neodymium and lanthanum on prominent lines of scandium, yttrium and rare earth elements (REE). The “true detection limit” criterion was used for rational wavelength line selection as proposed by boumans and vrakking [Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. Analysis lines selected for cerium and neodymium matrices suffered both wing and line interferences. In the case of a lanthanum matrix, it is possible to choose mostly analysis lines that are free of line interference and negligible wing interference. The high degree of spectral interferences with a cerium or neodymium matrix significantly worsens the true detection limits. This article is an electronic publication in Spearochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.