DOCSLIB.ORG

Effect of Alkali Metal Hydroxides on the Morphological Development

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Effect of Alkali Metal Hydroxides on the Morphological Development Copyright © 2010 American Scientific Publishers Journal of All rights reserved Nanoscience and Nanotechnology Printed in the United States of America Vol.10, 1–13, 2010 Effect of Alkali Metal Hydroxides on the Morphological Development and Optical Properties of Ceria Nanocubes Under Hydrothermal Conditions View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by DSpace@IZTECH Institutional Repository Özlem Kepenekçi, Mehtap Emirdag-Eanes∗, and Mustafa M. Demir∗ Izmir Institute of Technology, Department of Chemistry, Gülbahçe köyü, Urla, 35430 I˙zmir, Turkey Nanocrystalline cerium(IV) oxide (CeO2, ceria) particles were produced via the hydrothermal treat- ment of cerium nitrate hexahydrate with various alkali metal hydroxides (MOH: M = Li, Na, K). Experimental conditions such as [MOH], reaction temperature, and reaction time were studied. Particle morphology as well as size of crystallites was precisely controlled by choice of experimen- tal conditions. While rod-shaped particles were obtained at 120 C, well-defined nanocubes were formed at higher temperatures regardless of the choice of MOH. Examination of particle growth kinetics, in the final stages of crystallization, showed that particle growth rate is controlled by two dif- ferent mechanisms. Grain boundary diffusion controls the particle growth in the presence of NaOH with an activation energy of 113.8 kj/mol and surface diffusion for LiOH ad KOH with the activation energy of 43.0–150.9 kj/mol, respectively. In addition, the particles exhibit strong violet and blue emissions at 400 nm and 370 nm. The former emission originates from excitation of a wide band gap of CeO2. The latter one is attributed to the trivalency of the cerium ion and appears to be sensitive to all the experimental conditions studied. Both extending reaction time and increasing temperature reduce the intensity of the 370 nm emission and increase the intensity of the 400 nm RESEARCH ARTICLE emission. Keywords: Ceria, Crystal Growth, Growth Kinetics, Nanoparticles, Semiconductor. 1. INTRODUCTION ceria particles.As a wet-chemical technique, the hydrother- mal process has attracted a lot of attention since desired Nanoscale semiconductor particles are of great interest due morphology can readily be produced at high purity by con- to their unique morphology dependent (size and shape) trolling parameters such as reaction time, reaction tem- physical properties.1–3 Therefore, synthetic methods have perature, concentration, and type of reactant.Previously, been developed to tailor the morphology of these parti- Yang et al.15 reported the synthesis of cube-shaped CeO cles making them useful in practical applications.In par- 2 starting from cerium(III) nitrate and NaOH at different ticular, there is an increasing interest in preparation of temperatures over 24 h.The authors studied the effect of cerium oxide (ceria) that has recently been used in various [NaOH] on the cubes and found that the size of the par- fields such as an oxygen ion conductor in solid-oxide fuel ticles increased as the concentration was increased.The cells4 and as an oxygen pump due to its high oxygen ion effect of pH on the crystallization of nanosized CeO was conductivity.5 Ceria has also received much attention in 2 16 the area of three-way catalysts6 as oxygen promoters and studied by Li W–H et al. It was claimed that the crys- 7 8 tallites synthesized in an acidic hydrothermal medium are in the area of catalysts for H2 production from fuels. Moreover, ceria has gained much attention for develop- larger and more monodisperse than the ones produced in ment of ultraviolet (UV) absorbent material, its absorption a neutral or alkaline medium.The effect of the counter- at about 400 nm being the strongest among all oxides.9 anions of cerium source on CeO2 nanostructures was inves- Several techniques including hydrothermal,10 11 reverse- tigated by Hu et al.17 They reported that the synthesized 12 13 − micellular, sonochemical, and those involving homoge- nanorods converted into cubes by addition of NO3 ions 14 − neous precipitation have been used for the preparation of under hydrothermal conditions.When NO 3 ions were present in the solution, the dissolution-recrystallization pro- ∗ − Authors to whom correspondence should be addressed. cess was largely improved.NO 3 ions act as both capping J. Nanosci. Nanotechnol. 2010, Vol. 10, No. xx 1533-4880/2010/10/001/013 doi:10.1166/jnn.2010.3608 1 Effect of Alkali Metal Hydroxides on the Morphological Development and Optical Properties Kepenekçi et al. agent and an oxidizer during the formation of the CeO2 Spectrometer under excitation at 290 nm.All absorbance cubes.The influence of several other anions (such as Br −, and fluorometry measurements were done with the particles − 2− I , and SO4 ) was also investigated showing that the basic- suspended in deionized water.Due to the low dispersibility ity of the hydrothermal medium had a direct influence on of CeO2 nanoparticles in water, the samples were ultrason- the size and shape of the particles formed.However, there ically agitated for 10 min before measurement. is lack of information on how of alkali bases affect the structure and morphology of CeO2 particles.Such bases, also known as mineralizers, are used as a source of alkalin- 3. RESULT AND DISCUSSION ity for the crystallization of metal oxides and increase the 3.1. Structural and Morphological Characterization solubility of reagents to the levels sufficient for reactivity of CeO particles in a reasonable time.18 Here, we investigate the influence of 2 type and concentration of alkali base (LiOH, NaOH, KOH) Hydrothermal crystallization, in general, is based on a as well as reaction time and reaction temperature on the dissolution-precipitation mechanism of a precursor pre- particle morphology and crystal growth of CeO2 particles. pared from a metal salt using an alkaline solution as an X-ray diffractometry (XRD), scanning electron microscopy 19 oxygen source. In the particular case of CeO2,itwas (SEM), high resolution transmission electron microscopy claimed that the precursor is amorphous, and that crys- (HR-TEM), UV-vis spectroscopy, and photoluminescence talline CeO2 is obtained when a hydrothermal process is (PL) spectroscopy were utilized for characterization.We applied where the precursor is homogenously dissolved have demonstrated that the size and shape of the particles and subsequently reprecipitated.15 However, in this study, can be controlled through a combination of time and tem- we have demonstrated that the precursor is not amorphous perature; and the growth kinetics can be modulated by the and that the crystallization process begins during mix- type of metal hydroxides. ing of the reactant solutions at RT prior to hydrothermal treatment.Figure 1(a) presents the XRD pattern of a rep- 2. EXPERIMENTAL PROCEDURE resentative precursor prepared in the presence of NaOH. The reflections are well indexed for Ce2O3 •, CeO2 , 2.1. Experimental Method and as well as unreacted Ce(NO33 ♣.The presence of sharp reflections of both Ce O and CeO clearly suggests The cerium oxide nanocrystals were produced from the 2 3 2 that the precursor already contains the crystalline product reaction of 0.5 g cerium nitrate hexahydrate (Ce(NO33 · 6H2O) and a 10% solution of alkali metal hydroxide (MOH: M = Li, Na, K).The aqueous alkaline solutions were rapidly added to an aqueous solution of cerium nitrate inside a 23 mL teflon-lined stainless steel auto- CeO2 Ce O clave up to 50% of total available volume.The hydrother- 2 3 Ce(NO ).6H O mal reactions were carried out at various temperatures 3 2 from 120 Cto240C with the reaction times being var- iedfrom1hto24h.Each system was then allowed to cool to room temperature.The resulting particles were RESEARCH ARTICLE washed with 15 mL of water and separated by cen- (d) trifugation at 6000 rpm for 20 min.The particles were obtained by drying the precipitates at 60 C in air overnight. (c) Intensity/a.u 2.2. Characterization The crystal structure of the products was identified by (b) X-ray powder diffraction (XRD recorded on a Philips-X- perPro powder diffractometer with Cu K radiation of 0.15406 Å). The morphology of the CeO2 nanocrystals was observed by scanning electron microscope (SEM-Philips (a) XL-30S FEG, 5 kv) and transmission electron microscope 30 40 50 60 (TEM-FEI Tecnai F-20 microscope).The optical proper- 2θ ties were measured with a UV/VIS spectrometer (Var- Fig. 1. (a) X-Ray Diffraction pattern of precursor precipitated prior to ian Cary 50) equipped witha1cmquartz cuvette holder hydrothermal treatment.X-Ray Diffraction patterns of CeO 2 powders for liquid samples.Photoluminescence (PL) measurements synthesized at 240 C for 24 h in the presence of (b) KOH, (c) NaOH, were performed on a Varian Cary Eclipse Fluorescence (d) LiOH. 2 J. Nanosci. Nanotechnol. 10, 1–13, 2010 Kepenekçi et al. Effect of Alkali Metal Hydroxides on the Morphological Development and Optical Properties (Supplementary Fig.S1).When hydrothermal treatment is applied at 240 C for 24 h the signals of Ce(NO33 and Ce2O3 disappeared and the pure CeO2 phase was detected, regardless of the alkali base used.Particle mor- phology (size and shape) can be controlled by the type and concentration of MOH, reaction time, and reaction temperature. 3.1.1. Type of Alkali Base The effect of alkali metal hydroxides on the morphology of the precipitated CeO2 particles was examined.It was found that the formation and growth of CeO2 nanocubes were influenced significantly by the type of MOH used. The spectra (in Fig.1) labeled as b, c, and d refer to the CeO2 particles prepared in the presence of LiOH, NaOH, and KOH, respectively.All reflections in the spectra can be indexed to a face-centered cubic structure (JCPDS no 81-0792) with a lattice parameter of 5.412 Å.
Load more

Recommended publications
  • Promotion Effects and Mechanism of Alkali Metals and Alkaline Earth
    Subscriber access provided by RES CENTER OF ECO ENVIR SCI Article Promotion Effects and Mechanism of Alkali Metals and Alkaline Earth Metals on Cobalt#Cerium Composite Oxide Catalysts for N2O Decomposition Li Xue, Hong He, Chang Liu, Changbin Zhang, and Bo Zhang Environ. Sci. Technol., 2009, 43 (3), 890-895 • DOI: 10.1021/es801867y • Publication Date (Web): 05 January 2009 Downloaded from http://pubs.acs.org on January 31, 2009 More About This Article Additional resources and features associated with this article are available within the HTML version: • Supporting Information • Access to high resolution figures • Links to articles and content related to this article • Copyright permission to reproduce figures and/or text from this article Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Environ. Sci. Technol. 2009, 43, 890–895 Promotion Effects and Mechanism such as Fe-ZSM-5 are more active in the selective catalytic reduction (SCR) of N2O by hydrocarbons than in the - ° of Alkali Metals and Alkaline Earth decomposition of N2O in a temperature range of 300 400 C (3). In recent years, it has been found that various mixed Metals on Cobalt-Cerium oxide catalysts, such as calcined hydrotalcite and spinel oxide, showed relatively high activities. Composite Oxide Catalysts for N2O One of the most active oxide catalysts is a mixed oxide containing cobalt spinel. Calcined hydrotalcites containing Decomposition cobalt, such as Co-Al-HT (9-12) and Co-Rh-Al-HT (9, 11), have been reported to be very efficient for the decomposition 2+ LI XUE, HONG HE,* CHANG LIU, of N2O.
    [Show full text]
  • Indium, Caesium Or Cerium Compounds for Treatment of Cerebral Disorders
    Europaisches Patentamt 298 644 J European Patent Office Oy Publication number: 0 A3 Office europeen des brevets EUROPEAN PATENT APPLICATION © Application number: 88305895.0 © intci.s A61K 31/20, A61K 31/28, A61K 33/24 @ Date of filing: 29.06.88 © Priority: 07.07.87 GB 8715914 © Applicant: EFAMOL HOLDINGS PLC Efamol House Woodbridge Meadows © Date of publication of application: Guildford Surrey GU1 1BA(GB) 11.01.89 Bulletin 89/02 @ Inventor: Horrobin, David Frederick © Designated Contracting States: c/o Efamol House Woodbridge Meadows AT BE CH DE ES FR GB GR IT LI LU NL SE Guildford Surrey GU1 1BA(GB) Inventor: Corrigan, Frank ® Date of deferred publication of the search report: c/o Argyll & Bute Hospital 14.11.90 Bulletin 90/46 Lochgilphead, Argyll PA3T 8ED Scotland(GB) © Representative: Caro, William Egerton et al J. MILLER & CO. Lincoln House 296-302 High Holborn London WC1V 7 JH(GB) © Indium, caesium or cerium compounds for treatment of cerebral disorders. © A method of treatment of schizophrenia or other chronic cerebral disorder in which cerebral atrophy is shown, is characterised in that one or more as- similable or pharmaceutically acceptable indium caesium or cerium compounds is associated with a pharmaceutically acceptable diluent or carrier. CO < CD 00 O> Xerox Copy Centre PARTIAL EUROPEAN SEARCH REPORT Application number European Patent J which under Rule 45 of the European Patent Convention Office shall be considered, for the purposes of subsequent EP 88 30 5895 proceedings, as the European search report DOCUMENTS CONSIDERED TO BE RELEVANT Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE ategory of relevant passages to claim APPLICATION (Int.
    [Show full text]
  • Atomic Weights of the Elements 1995
    Atomic Weights of the Elements 1995 Cite as: Journal of Physical and Chemical Reference Data 26, 1239 (1997); https:// doi.org/10.1063/1.556001 Submitted: 02 May 1997 . Published Online: 15 October 2009 T. B. Coplen ARTICLES YOU MAY BE INTERESTED IN Atomic Weights of the Elements 1999 Journal of Physical and Chemical Reference Data 30, 701 (2001); https:// doi.org/10.1063/1.1395055 Journal of Physical and Chemical Reference Data 26, 1239 (1997); https://doi.org/10.1063/1.556001 26, 1239 © 1997 American Institute of Physics and American Chemical Society. Atomic Weights of the Elements 1995a) T. B. Coplen U. S. Geological Survey, Reston, Virginia 20192 Received May 2, 1997; revised manuscript received June 13, 1997 The biennial review of atomic weight, Ar~E!, determinations and other cognate data has resulted in changes for the standard atomic weight of 21 elements. The five most significant changes are: boron from 10.81160.005 to 10.81160.007; carbon from 12.01160.001 to 12.010760.0008; arsenic from 74.9215960.00002 to 74.9216060.00002; cerium from 140.11560.004 to 140.11660.001; and platinum 195.0860.03 to 195.07860.002. An annotation for potassium has been changed in the Table of Standard Atomic Weights. To eliminate possible confusion in the reporting of relative lithium isotope-ratio data, the Commission recommends that such data be ex- pressed using 7Li/6Li ratios and that reporting using 6Li/7Li ratios be discontinued. Be- cause relative isotope-ratio data for sulfur are commonly being expressed on noncorre- sponding scales, the Commission recommends that such isotopic data be expressed relative to VCDT ~Vienna Can˜on Diablo Troilite! on a scale such that 34S/32S of IAEA- S-1 silver sulfide is 0.9997 times that of VCDT.
    [Show full text]
  • Uptake of Nanoparticles of Cerium Oxide and Yttrium Oxide by Acanthamoeba Castellanii (Protozoa) and Daphnia Magna (Crustacea) James R
    Virginia Journal of Science Volume 62, 1 & 2 Spring 2011 Uptake of Nanoparticles of Cerium Oxide and Yttrium Oxide by Acanthamoeba castellanii (Protozoa) and Daphnia magna (Crustacea) James R. Palmieri1, Geneva Gehring, Catherine Minichino, and Shaadi F. Elswaifi Department of Microbiology, Infectious, and Emerging Diseases, Edward Via College of Osteopathic Medicine, 2265 Kraft Drive, Blacksburg, Virginia, USA 24060 ABSTRACT Currently, nanoparticles are synthesized and used at an unprecedented rate for industrial, medical, and research applications. The use of cerium oxide nanoparticles (CeONP) and yttrium oxide nanoparticles (YtONP) results in their spread as contaminants into the environment. Once in the environment, CeONP and YtONP can be taken up by organisms in the food chain where they may pose a public health risk. In this study we determine whether Acanthamoeba castellanii and Daphnia magna uptake CeONP or YtONP from their environment and thereby play a role in the transmission of the nanoparticles. Using electron microscopy, organisms exposed to the nanoparticles were examined. Our results indicate that the nanoparticles are associated with cell and organelle membranes. These findings have implications for the health risks associated with environmental contamination by CeONP and YtONP. INTRODUCTION In this study we determine whether protists and crustaceans play a role in the transfer of cerium oxide nanoparticles (CeONP) and yttrium oxide nanoparticles (YtONP) from the environment to other organisms within the aquatic food chain. Acanthamoeba castellanii, a common protist, and Daphnia magna, a planktonic crustacean, are important components in many aquatic ecosystems. Because acanthamoebae, such as A. castellanni, are aggressive feeders they consume inorganic and organic compounds from their environment, thereby serving as a link by transferring normally unavailable inorganic components to the food chain (Weekers et al.
    [Show full text]
  • Corrosion Protection Mechanisms of Rare-Earth Compounds Based on Cerium and Praseodymium (WP-1618) Objective
    Corrosion Protection Mechanisms of Rare-Earth Compounds Based on Cerium and Praseodymium (WP-1618) Objective Hexavalent chromium containing coatings are widely used to protect U.S. military weapons systems from corrosion, yet present acute health and environmental hazards. This project focused on determining corrosion protection mechanisms for coatings that utilize rare-earth (RE) compounds instead of hexavalent chromium. Understanding the mechanisms by which RE compounds inhibit corrosion would reduce the risk of implementing environmentally friendly coating systems as chromate replacements. Technical Approach Two specific coating systems were examined; cerium-based conversion coatings (CeCCs) and epoxy polyamide primers containing praseodymium-based inhibitors. Prior to the start of the project, both coating systems had demonstrated corrosion protection that could meet current U.S. military requirements for aircraft. The approach taken in this project assumed that RE compounds are not inherently protective. Instead, the appropriate phase of a RE compound has to be incorporated into the proper type of coating to provide corrosion protection in specific environments. As part of the project, mechanistic models for corrosion protection were devised by fully characterizing the phases that were present in as-deposited coatings, the transport processes that occurred during corrosive attack, and the species that formed to passivate the substrates. Results Discovery of sub-surface crevices in substrates with CeCCs led to a significant change
    [Show full text]
  • Interactions of Lanthanides and Liquid Alkali Metals for “Liquid-Like” Lanthanide Transport in U-Zr Fuel
    Interactions of Lanthanides and Liquid Alkali Metals for “Liquid-Like” Lanthanide Transport in U-Zr Fuel THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Jeremy Payton Isler Graduate Program in Nuclear Engineering The Ohio State University 2017 Master's Examination Committee: Dr. Jinsuo Zhang, Advisor Dr. Marat Khafizov, Co-Advisor Copyrighted by Jeremy Payton Isler 2017 Abstract One of the major limitations in achieving increased burnup in metallic U-Zr nuclear fuel is Fuel-Cladding Chemical Interaction (FCCI). The migration of the fission product lanthanides from within the fuel to the peripheral is one of the major contributors to FCCI. A “liquid-like” transport mechanism proposes the lanthanide transport is aided by liquid cesium and liquid sodium in the pores of the fuel and at the fuel peripheral. The purpose of this thesis was to provide additional experimental evidence towards this proposed mechanism. This thesis investigated the interaction between the lanthanides and cesium and sodium, with a focus on the solubility of the lanthanides in these liquid alkali metals. First, a prediction of the solubility was calculated using the Miedema model. This prediction was then compared to the inversion crucible solubility experiment performed in this thesis. The solubility experiment studied the temperature and liquid-composition dependence of the lanthanides in liquid sodium, cesium and sodium-cesium mixtures. In addition, the solubility in mixtures shows the various alkali metals concentration effect on the solubility. With the results of differential scanning calorimetry (DSC) experiments, updated phase diagrams for sodium-neodymium and cesium-neodymium were obtained from the experimental data in this thesis.
    [Show full text]
  • Roles of Lanthanum and Cerium in Grain Refinement of Steels During
    metals Review Roles of Lanthanum and Cerium in Grain Refinement of Steels during Solidification Yunping Ji 1,2, Ming-Xing Zhang 3 and Huiping Ren 1,2,* 1 School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China; [email protected] 2 School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China 3 School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072, Australia; [email protected] * Correspondence: [email protected]; Tel.: +86-472-595-2289; Fax: +86-472-595-4368 Received: 15 October 2018; Accepted: 25 October 2018; Published: 30 October 2018 Abstract: Refinement of as-cast structures is one of the most effective approaches to improve mechanical properties, formability, and surface quality of steel castings and ingots. In the past few decades, addition of rare earths (REs), lanthanum and cerium in particular, has been considered as a practical and effective method to refine the as-cast steels. However, previous reports contained inconsistent, sometime even contradictory, results. This review summaries the major published results on investigation of the roles of lanthanum or/and cerium in various steels, provides reviews on the similarity and difference of previous studies, and clarifies the inconsistent results. The proposed mechanisms of grain refinement by the addition of lanthanum or/and cerium are also reviewed. It is concluded that the grain refinement of steels by RE additions is attributed to either heterogeneous nucleation on the in-situ formed RE inclusions, a solute effect, or the combined effect of both. The models/theories for evaluation of heterogeneous nucleation potency and for solute effect on grain refinement of cast metals are also briefly summarized.
    [Show full text]
  • Three Related Topics on the Periodic Tables of Elements
    Three related topics on the periodic tables of elements Yoshiteru Maeno*, Kouichi Hagino, and Takehiko Ishiguro Department oｆ physics, Kyoto University, Kyoto 606-8502, Japan * [email protected] (The Foundations of Chemistry: received 30 May 2020; accepted 31 July 2020) Abstaract: A large variety of periodic tables of the chemical elements have been proposed. It was Mendeleev who proposed a periodic table based on the extensive periodic law and predicted a number of unknown elements at that time. The periodic table currently used worldwide is of a long form pioneered by Werner in 1905. As the first topic, we describe the work of Pfeiffer (1920), who refined Werner’s work and rearranged the rare-earth elements in a separate table below the main table for convenience. Today’s widely used periodic table essentially inherits Pfeiffer’s arrangements. Although long-form tables more precisely represent electron orbitals around a nucleus, they lose some of the features of Mendeleev’s short-form table to express similarities of chemical properties of elements when forming compounds. As the second topic, we compare various three-dimensional helical periodic tables that resolve some of the shortcomings of the long-form periodic tables in this respect. In particular, we explain how the 3D periodic table “Elementouch” (Maeno 2001), which combines the s- and p-blocks into one tube, can recover features of Mendeleev’s periodic law. Finally we introduce a topic on the recently proposed nuclear periodic table based on the proton magic numbers (Hagino and Maeno 2020). Here, the nuclear shell structure leads to a new arrangement of the elements with the proton magic-number nuclei treated like noble-gas atoms.
    [Show full text]
  • Direct Comparison of Covalency in Thorium(IV)- and Cerium(IV)-Imido Complexes † § † § † ‡ § † Thibault Cheisson, , Kyle D
    Communication Cite This: J. Am. Chem. Soc. XXXX, XXX, XXX−XXX pubs.acs.org/JACS Multiple Bonding in Lanthanides and Actinides: Direct Comparison of Covalency in Thorium(IV)- and Cerium(IV)-Imido Complexes † § † § † ‡ § † Thibault Cheisson, , Kyle D. Kersey, , Nolwenn Mahieu, , , Alex McSkimming, † † † Michael R. Gau, Patrick J. Carroll, and Eric J. Schelter*, † P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States ‡ Departement́ de Chimie, ENS Paris-Saclay, UniversitéParis-Saclay, 94235 Cachan, France *S Supporting Information generate the anilide complex [Th(NHArF)(TriNOx)] (3)by ABSTRACT: A series of thorium(IV)-imido complexes fl F protonolysis with 3,5-bis(tri uoromethyl)aniline (Ar NH2, was synthesized and characterized. Extensive experimental Scheme 1). and computational comparisons with the isostructural cerium(IV)-imido complexes revealed a notably more Scheme 1. Syntheses of the new Th(IV)-Imido Complexes covalent bonding arrangement for the CeN bond compared with the more ionic ThNbond.The thorium-imido moieties were observed to be 3 orders of magnitude more basic than their cerium congeners. More generally, these results provide unique experimental evidence for the larger covalent character of 4f05d0 Ce(IV) multiple bonds compared to its 5f06d0 Th(IV) actinide congener. hemical bonding in lanthanide and actinide compounds C pushes our understanding and description of metal− ligand interactions. Fundamental understanding of these metal−ligand bonds redefines comprehension of the elements, even 150 years after the disclosure of the periodic trends, and contributes to new applications in reactivity.1 This knowledge from https://pubs.acs.org/doi/10.1021/jacs.9b04061.
    [Show full text]
  • USE of CERIUM OXIDE (Ceo2)
    Global NEST Journal, Vol 17, No 3, pp 536-543, 2015 Copyright© 2015 Global NEST Printed in Greece. All rights reserved USE OF CERIUM OXIDE (CeO2) NANOPARTICLES FOR THE ADSORPTION OF DISSOLVED CADMIUM (II), LEAD (II) AND CHROMIUM (VI) AT TWO DIFFERENT pHs IN SINGLE AND MULTI-COMPONENT SYSTEMS CONTRERAS A.R.1 1Department of Chemical Engineering, Escola d’Enginyeria CASALS E.2 Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain PUNTES V.2,3 2Institut Català de Nanotecnologia KOMILIS D.1 Campus de la Universitat Autònoma de Barcelona SÁNCHEZ A.1,*, 08193 Bellaterra, Spain FONT X.1 3Institut Català de Recerca i Estudis Avançats Passeig Lluís Companys, 23, 08010 Barcelona, Spain Received: 16/05/2015 Accepted: 17/05/2015 *to whom all correspondence should be addressed: Available online: 24/08/2015 e-mail: [email protected] ABSTRACT Cerium oxide (CeO2) nanoparticles (NPs) were used for the removal of cadmium (II), lead (II) and chromium (VI) ions in single aqueous solutions and in solutions with mixtures of the three metals. The adsorption studies were carried out at pH 5 and 7 using a systematic factorial experimental design that considered the metal concentration from 1 mg l-1 to 10 mg l-1 and NP concentration from 0.064 g l-1 to 0.640 g l-1. The highest adsorption capacity was obtained in the removal of lead (II) (128.1 mg g-1), followed by cadmium (II) (93.4 mg g-1) and finally chromium (VI) (34.4 mg g-1). Data were fitted to a polynomial function obtaining the best reduced models.
    [Show full text]
  • Periodic Table 1 Periodic Table
    Periodic table 1 Periodic table This article is about the table used in chemistry. For other uses, see Periodic table (disambiguation). The periodic table is a tabular arrangement of the chemical elements, organized on the basis of their atomic numbers (numbers of protons in the nucleus), electron configurations , and recurring chemical properties. Elements are presented in order of increasing atomic number, which is typically listed with the chemical symbol in each box. The standard form of the table consists of a grid of elements laid out in 18 columns and 7 Standard 18-column form of the periodic table. For the color legend, see section Layout, rows, with a double row of elements under the larger table. below that. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that. The rows of the table are called periods; the columns are called groups, with some of these having names such as halogens or noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences. Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table.
    [Show full text]
  • Separation of Radioactive Elements from Rare Earth Element-Bearing Minerals
    metals Review Separation of Radioactive Elements from Rare Earth Element-Bearing Minerals Adrián Carrillo García 1, Mohammad Latifi 1,2, Ahmadreza Amini 1 and Jamal Chaouki 1,* 1 Process Development Advanced Research Lab (PEARL), Chemical Engineering Department, Ecole Polytechnique de Montreal, C.P. 6079, Succ. Centre-ville, Montreal, QC H3C 3A7, Canada; [email protected] (A.C.G.); mohammad.latifi@polymtl.ca (M.L.); [email protected] (A.A.) 2 NeoCtech Corp., Montreal, QC H3G 2N7, Canada * Correspondence: [email protected] Received: 8 October 2020; Accepted: 13 November 2020; Published: 17 November 2020 Abstract: Rare earth elements (REE), originally found in various low-grade deposits in the form of different minerals, are associated with gangues that have similar physicochemical properties. However, the production of REE is attractive due to their numerous applications in advanced materials and new technologies. The presence of the radioactive elements, thorium and uranium, in the REE deposits, is a production challenge. Their separation is crucial to gaining a product with minimum radioactivity in the downstream processes, and to mitigate the environmental and safety issues. In the present study, different techniques for separation of the radioactive elements from REE are reviewed, including leaching, precipitation, solvent extraction, and ion chromatography. In addition, the waste management of the separated radioactive elements is discussed with a particular conclusion that such a waste stream can be
    [Show full text]