Characterisation of the sintering behaviour of Waelz slag from electric arc furnace (EAF) dust recycling for use in the clay ceramics industry

Waelz slag is an industrial by-product from the recovery of electric arc furnace (EAF) dust which is mainly sent to landfills. Despite the different chemical and mineralogical compositions of Waelz slag compared to traditional clays, previous experiments have demonstrated its potential use as a clay substitute in ceramic processes. Indeed, clayey products containing Waelz slag could improve mechanical and environmental performance, fixing most of the metallic species and moreover decreasing the release of some potential pollutants during firing. However, a deeper understanding of the complex phase transformations during its thermal treatment and the connection of this behaviour with the end properties is desirable in order to explain the role that is played by the Waelz slag and its potential contribution to the ceramic process. For this purpose, in the present study, the chemical, mineralogical, thermal and environmental behaviour of both (i) unfired powdered samples, and (ii) pressed specimen of Waelz slag fired up to different temperatures within the typical range of clay based ceramic production, has been studied. The effect of the heating temperature on the end properties of the fired samples has been assessed. In general, an increase of the firing temperature promotes sintering and densification of the products and decreases the open porosity and water absorption which also contributes to the fixation of heavy metals. On the contrary, an increase in the leaching of Pb, Cr and Mo from the fired specimens is observed. This can be attributed to the creation of Fe and Ca molybdates and chromates that are weakly retained in the alkali matrix. On the other side, at temperature above 950 °C a weight gain related to the emission of evolved gases is observed. In conclusion, the firing temperature of the ceramic process is a key parameter that affects not only the technical properties but also strongly affects the leaching behaviour and the process emissions.The authors gratefully acknowledge the financial support for this research by the BEFESA STEEL R&D, S.L.U. Company, Erandio, Biscay (España) and the framework of the Spanish Ministry of Science and Innovation Project (CTM 2009-11303 TECNO).Peer reviewe

Comparing conventional and microwave-assisted heating in PET degradation mediated by imidazolium-based halometallate complexes

The catalytic activity of two halometallate complexes based on imidazolium cations, (dimim)[FeCl4] (1) and (dimim)2[Fe2Cl6(μ-O)] (2), was evaluated in the glycolysis of polyethylene terephthalate (PET), either under conventional heating or microwave-assisted conditions. The two procedures led to the formation of bis(2-hydroxyethyl)terephthalate (BHET) as the major product with high yields, also allowing the isolation and structural characterization of a new polymorph. The influence of the halometallate structure on the catalytic activity was investigated, and additional experimental studies proved the involvement of both the imidazolium cation and metal anion in the reaction mechanism. The comparison of both approaches showed the advantages of the microwave methodology in terms of efficiency and time saving. Indeed, the use of ground PET and microwave heating provided quantitative yields of BHET. Under conventional heating conditions, the dinuclear iron complex gave a slightly lower yield than (dimim)[FeCl4] (74% vs. 77% for post-consumer PET) after 24 h of reaction. However, the microwave-assisted process led to comparable results in remarkably shorter reaction times (2 h). Interestingly, complex 2, containing the dipolar [Fe2Cl6(μ-O)]2− moiety, provided higher yields than 1 with the non-dipolar [FeCl4]− anion (77% vs. 69%). This behaviour has been rationalized on the basis of dielectric heating mechanisms (polarization and conduction), and it suggests a new approach towards obtaining more efficient catalysts by tailoring the catalytic species to be active in both heating mechanisms.Financial support from the Spanish Ministerio de Ciencia e Innovación (Projects MAT2014-55049-C2-R and MAT2016-75883-C2-1-P), Universidad del País Vasco/EuskalHerrikoUnibertsitatea (GIU17/50 and PPG17/37). Universidad de Cantabria (Proyecto Puente convocatoria 2018 financed by SODERCAN-FEDER)

Dynamics of AC susceptibility and coercivity behavior in nanocrystalline TbAl1.5 Fe0.5 alloys

The static and dynamic magnetic macroscopic properties of bulk and nanocrystalline TbAl1.5Fe0.5 alloys have been investigated. In bulk state, this alloy is understood as a reentrant ferromagnet. This is characterized by a ferromagnetic Curie transition at 114 K, as deduced from magnetization including Arrott plots, higher than that of TbAl2. The reentrance is found at lower temperatures, below 66 K, with a cluster glass behavior setting in, deduced from the magnetization irreversibility. This is accompanied by an abrupt increase in the coercivity from 0.08 kOe to 15 kOe at 5 K, with respect to the TbAl2 alloy. Room temperature Mössbauer spectroscopy confirms the paramagnetic state of such a bulk alloy. The spin dynamics within the disordered magnetic state is described by the AC-susceptibility which shows a Vogel–Fulcher law for the slowing down process. This is caused by a random anisotropy affecting the existing clusters. The production of milled TbAl1.5Fe0.5 alloys enhances the presence of magnetic disorder and results in the particle downsizing toward the nanocrystalline state (close to 10 nm). In this case, two frequency-dependent contributions exist, with different activation energies, one of them cannot be described by ideal spin glass nor blocking/unblocking (nanoparticle) processes. In addition, the coercivity reduces to 1 kOe with the decrease in the size as a consequence of the existence of single domain particles. The results are explained by the intricate interplay between exchange interactions and magnetocrystalline anisotropy with disorder and size effects. © 2012 Elsevier B.V.This work has been supported by the MAT2008-06542-C04 and MAT2011-27573-C04 projects.Peer Reviewe

An Oxalate Bridged Binuclear Iron(III) Ionic Liquid for the Highly Efficient Glycolysis of Polyethylene Terephthalate under Microwave Irradiation

An oxalate-bridged binuclear iron(III) ionic liquid combined with an imidazolium based cation, (dimim)2[Fe2Cl4(µ-ox)], was synthesized and characterized by a wide range of techniques. This halometallate ionic liquid was active in catalyzing the depolymerization of polyethylene terephthalate (PET) by glycolysis, under conventional and microwave-assisted heating conditions. Both methodologies were very selective towards the production of bis(2-hydroxyethyl)terephthalate (BHET). The employment of microwave heating proved beneficial in terms of time and energy saving when compared to the use of thermal heating. Indeed, dielectric spectroscopy studies revealed that the binuclear iron-containing ionic liquid exhibits an excellent heating response under an electromagnetic field. The catalyst provided quantitative conversions to BHET in the glycolysis of post-consumer PET bottles in only 3 h through microwave heating, as compared to 80 % conversion after 24 h under conventional heating

On the real catalytically active species for CO2 fixation into cyclic carbonates under near ambient conditions: dissociation equilibrium of [BMIm][Fe(NO)2Cl2] dependant on reaction temperature

An imidazolium based iron-containing ionic liquid [BMIm][Fe(NO)2Cl2] (BMIm = 1-n-butyl-3-methyl-imidazolium) has been synthesized for the first time and fully characterized employing a wide range of techniques. The iron-based containing ionic liquid was found to be an active catalyst for the cycloaddition of CO2 to epoxides, giving high conversions for various substrates under near ambient conditions. In addition, the catalytic system showed a good recycling performance for five consecutive reaction cycles. Key mechanistic studies demonstrated that a bifunctional catalytic system is generated in situ by the partial dissociation of the iron-based ionic liquid into [BMIm][Cl], which results in a very efficient catalyst without the need of any additive or co-catalyst. The metal center plays a role as Lewis acid and activate the epoxide group, and the chloride anion, as part of [BMIm][Cl] moiety, acts as nucleophile and leads to the ring opening through a nucleophilic attack on the less sterically-hindered Cβ. The process is favoured by an interaction via H-bonding between the substrate and the H–C2 of the imidazolium ring, as was demonstrated by additional experiments. Kinetic studies indicated that the process followed first-order kinetics with respect to epoxide concentration and proved the existence of a reversible coordination/de-coordination equilibrium in which the active species are generated from the [BMIm][Fe(NO)2Cl2] complex

Neutron Powder Diffraction study of the Magnetic Ionic Liquid Emim[FeCL4] and its deuterated phase

A magnetic ionic liquid comprising 1-ethyl-3 methylimidazolium (Emim) cations and tetraclhoroferrate(III) (FeCl4) anions and its deuterated phase were synthetized and characterized magnetically. In both materials, the low temperature dependence of the magnetic susceptibility presents a maximum (around 4 K) related to an antiferromagnetic ordering, but the ordering temperatures are slightly shifted and the curves display different shapes. In addition, the magnetization of the deuterated phase tends to saturate at higher values than that corresponding to the non-deuterated analogue. A comparison of the neutron diffraction patterns above and below the magnetic transition clearly shows that the crystal and magnetic structures of these materials are different. Therefore, the present findings clearly prove that the magnetic exchange interactions that induce three-dimensional magnetic ordering are modified after the deuteration process.Part of this work was carried out at Institute Laue-Langevin (ILL) of Grenoble and was partially financially supported by MEC research project MAT2011-27573-C04

Pressure-induced charge ordering transition in CaMn7O12

We use high-pressure resistivity and single crystal x-ray diffraction at ambient and low temperature to investigate the charge ordering phase transition of CaMn 7 O 12 . We have found that at ambient temperature the Jahn-Teller distortion of the Mn 3 + O 6 octahedra rapidly decreases above 20 GPa, and vanishes at 28 GPa, when two Mn octahedral sites initially occupied by Mn 3 + and Mn 4 + become regular and equivalent as the result of a charge delocalization. Such a change correlates with a two orders of magnitude drop in the resistivity and a symmetry increase from the low-pressure rhombohedral R ¯ 3 phase to the cubic Im ¯ 3 structure, the same as one found at ambient pressure above 440 K. This yields the slope of the charge ordering phase boundary of d T c / d p ? ? 6 K/GPa. This result is further supported by the lack of a structural phase transition up to the maximum measured pressure of 30 GPa when the experiment is performed at 70 K. The satellite reflections of the structural modulation of the multiferroic phase of CaMn 7 O 12 observed at 70 K were found to hold up to 25 GPa with the structure keeping a constant modulation vector k = ( 0 0 0.925 ) with pressure. The average structure at 70 K does not show other indications of further phase transition.Y. Li and X. Du from Peking University are greatly acknowledged for growing and providing the CaMn7O12 crystals. D. Spahr and J. König from Goethe University are acknowledged for help with the single-crystal diffraction experiments. M.S. would like to acknowledge the financial support under the DFG-ANR Grant No. WI1232/41-1 and DFG GACR Project No. WI3320/3-1. V.M. and J.R.-F. thank the financial support from the Spanish Ministerio de Ciencia e Innovación (MICINN) for the Beatriz Galindo Program (BG20/000777) and for the Project No. PGC2018-097520- A-I00, respectively. DESY Photon Science is gratefully acknowledged. PETRA III at DESY is a member of the Helmholtz Association (HGF)

Synthesis of chiral iron-based ionic liquids: modelling stable hybrid materials

Five chiral iron-containing ionic liquids were synthetized from several chiral ionic liquids (CILs) based on different imidazolium cations. These novel compounds were prepared through an easy synthetic method involving mixing 1 equivalent of iron salt FeX3 (X = Cl or Br) and 1 equivalent of chiral ionic liquid. The soobtained chiral iron-based ionic liquids contain easily tunable imidazolium cations, which allow the preparation of a wide range of compounds within different functional groups and chiral moieties. These chiral iron-based ionic liquids have been fully characterized by a wide variety of techniques, including polarimetry, inductively coupled plasma optical emission spectrometry, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, magnetic susceptibility measurements, and UV-vis, attenuated total reflection Fourier-transform infrared and Raman spectroscopies. Such experiments confirmed the structure of these new materials, as well as their appealing properties. The combination of a chiral moiety with a haloferrate anion within the IL structure allows the formation of very stable and multifunctional compounds with promising chiral, magnetic, optical and acidic properties. The resulting chiral iron-based ILs exhibit great potential for use in a range of applications such as enantioselective catalysis or chiral recognition, to name a few.Ministerio de Ciencia e Innovación español - MAT2017-83631-C3-3-R y MAT2017- 89239-C2-(1,2)-PUniversidad del País Vasco/Euskal Herriko Unibertsitatea - GIU17/50 y PPG17/3

Tailoring the physical properties of hybrid magnetic quinuclidine-based plastic compounds via weak interactions

Herein we explore the opportunities arising from combining bicyclic amine cations with halometallate anions to build organic–inorganic hybrid materials. We will use the crystal engineering approach in these materials, focusing on the tuning of the organic cation, which is mainly responsible for obtaining both new plastic states at high temperature and electrical behaviour below the plastic temperature. Precisely, this work explores the influence of the ketonization of the bicyclic quinuclidine molecule (C7H13N)+, which, combined with the tetrachloroferrate(1-) anion, gives the compound (3-oxoquinuclidinium)[FeCl4]. Interestingly, crystallization in the presence of humidity is enough to obtain an isostructural hydrate phase of formula (3-oxoquinuclidinium)[FeCl4]·H2O. Although the organic–inorganic layered structure is the same in both compounds, the three-dimensional magnetic ordering disappears after the intercalation of crystallization water molecules. A heat treatment above 400 K allows the removal of water obtaining the non-hydrate phase. Finally, the temperature evolution of the electric and magnetic behaviour will be compared with other previously reported hybrid organic–inorganic materials built with tetrachloroferrate ions and quinuclidinium-based cations.Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del País Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P, MAT2017-83631-C3-3-R and MAT2017-86453-R) is acknowledged. The authors gratefully acknowledge technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). The paper is (partly) based on the results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona and Institute Laue-Langevin (ILL) in Grenoble (Proposals 5-31-2673 and 5-12-358)

Incommensurate crystal structure, thermal expansion study and magnetic properties of (dimethylimidazolium)2[Fe2Cl6(μ-O)]

A thorough characterization of the title compound, (dimim)(2)[Fe2Cl6(mu-O)], consisting of a (mu-oxido)-bridged binuclear iron(III) complex and 1,3-dimethylimiazolium (dimim) cation, has been performed using a wide range of techniques. The room temperature disordered crystal structure of this compound transits to an incommensurately modulated crystal structure at 100 K; to our knowledge, the first one found for an imidazolium halometallate complex. The crystal structure was solved in the superspace group P (1) over bar(/alpha/beta/gamma)0 with modulation vector q = 0.1370(10) 0.0982(10) 0.326(2) at 100 K. Variable temperature synchrotron powder x-ray diffraction showed the presence of satellite peaks in addition to the main diffraction peaks up to 208 K. Furthermore, a thermal expansion study was performed with this technique from 100 to 383 K (near of its melting point) adressing questions about the nature and consequences of the ion self-assembly of this (mu-oxido)-bridged binuclear iron(III) complex, as well as the molecular motion of the imidazolium cation within the crystalline structure as a response to the temperature effect. Finally, we present a deep magnetic study based on magnetic susceptibility, magnetization and Mossbauer measurements, where the strong antiferromagnetic exchange coupling detected is due to the occurrence of a mu-oxido bridge between the Fe(III), giving rise to an intra-dimeric antiferromagnetic exchange coupling of -308 cm(-1).Financial support from Universidad de Cantabria (Proyecto Puente convocatoria 2018 funded by SODERCAN_FEDER), Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (GIU17/50 and PPG17/37) and Ministerio de Economia y Competividad (MAT2017-89239-C2-(1,2)-P). The authors gratefully acknowledge Technical and human support provided by SGIKer (UPV/EHU, MINECO, GV/EJ, ERDF, and ESF). Dr. Israel Cano thanks financial support from the European Community through a Marie Skodowska-Curie Individual Fellowship (IF-EF; Programme/Call: H2020-MSCA-IF-2015; Proposal No: 704710-Sdchirnanocat). C2TN authors acknowledge the FCT (Portugal) support through the UID/Multi/04FeCl49/2013 project. The paper is (partly) based on results of experiments carried out at the ALBA Synchrotron Light Source in Barcelona