Dicaesium cobalt(II) dioxalate tetrahydrate [tetraaquabis("oxalato)cobalt(II)dicaesium(I)], Cs 2 Co II (C 2 O 4) 2 Á4H 2 O, has a layered structure and is isotypic with Cs 2 Mg(C 2 O 4) 2 Á4H 2 O. The unique Co atom shows octahedral coordination, with a mean CoÐO bond length of 2.084 A Ê. The Cs atom is irregularly coordinated by nine O atoms. Layers of CoO 4 (H 2 O) 2 octahedra, whose non-water O ligands belong to nearly planar bidentate oxalate groups, are separated by corrugated layers of Cs atoms. Medium-strong hydrogen bonds provide connections within the layer planes. All atoms are in general positions except the Co atom, which lies on a twofold axis. Comment As part of recent work on the crystal chemistry and topology of double metal oxalates (Kolitsch, 2004; Fleck & Kolitsch, 2004), the title compound has been prepared by crystallization from an aqueous solution at room temperature, and its crystal structure has been determined from single-crystal X-ray intensity data collected at 293 K. Cs 2 Co II (C 2 O 4) 2 Á4H 2 O is isotypic with Cs 2 Mg(C 2 O 4) 2 Á4H 2 O, the new structure type that was recently described by Kolitsch (2004). The title compound crystallizes in space group C2/c and exhibits a layered atomic arrangement. The asymmetric unit contains one unique Cs atom, one Co, two C, six O atoms and four H atoms. Only the Co atom is located on a special

The crystal structures of hydrothermally synthesized potassium scandium hydrogen arsenate(V), KSc(HAsO4)2, (I), and rubidium scandium diarsenate(V), RbScAs2O7, (II), were determined from single-crystal X-ray diffraction data collected at room temperature. Compound (I) represents a new microporous structure type, designated MCV-3, which is characterized by a three-dimensional framework of corner-sharing alternating ScO6 octahedra and HAsO4 tetrahedra. Intersecting tunnels parallel to [101] and [110] host eight-coordinate K atoms. There is one hydrogen bond of medium strength [O...O = 2.7153 (18) A]. Compound (II) is the first reported diarsenate with a KAlP2O7-type structure and is isotypic with at least 27 A(I)M(III) diphosphates. The average Sc-O bond lengths in (I) and (II) are 2.09 (2) and 2.09 (3) A, respectively. The K and Sc atoms in (I) lie on an inversion centre and a twofold axis, respectively. All atoms in (II) are in general positions.

The crystal structures of five new glycine (H2N–CH2–COOH) metal halogenide compounds were determined by single crystal X-ray diffraction. Three of them are monoclinic phases, GlycineCaCl2 · 3 H2O (space group P21/c, a = 9.964(2), b = 6.868(1), c = 13.959(3) Å, β = 104.11(3)°, R1 = 0.024), GlycineZnCl2 · H2O (space group P21/a, a = 7.868(1), b = 9.124(1), c = 10.645(1) Å, β = 103.51(1)°, R1 = 0.026) and Glycine2ZnCl2 · 2 H2O (space group C2/c, a = 14.444(1), b = 6.916(1), c = 12.968(1) Å, β = 117.90(3)° R1 = 0.033), two of them are orthorhombic phases Glycine3CeCl3 · 3 H2O (space group P212121, a = 4.788(1), b = 12.074(2), c = 30.949(6) Å R1 = 0.034) and Glycine2CaI2 · 3 H2O (space group Pca21, a = 13.059(3), b = 9.862(2), c = 22.724(5) Å R1 = 0.023). The atomic arrangements as well as aspects of the crystal chemistry of these compounds are presented.

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This study aims to investigate the physical and chemical characterization of six fly ash samples obtained from different municipal solid waste incinerators (MSWIs), namely grate furnaces, rotary kiln, and fluidized bed reactor, to determine their potential for CO2 and thermochemical energy storage (TCES). Representative samples were characterized via simultaneous thermal analysis (STA) in different atmospheres, i.e., N2, air, H2O, CO2, and H2O/CO2, to identify fly ash samples that can meet the minimum requirements, i.e., charging, discharging, and cycling stability, for its consideration as TCES and CO2-storage materials and to determine their energy contents. Furthermore, other techniques, such as inductively coupled plasma optical emission spectroscopy, X-ray fluorescence (XRF) spectrometry, X-ray diffraction (XRD), scanning electron microscopy, leachability tests, specific surface area measurement based on the Brunauer–Emmett–Teller method, and particle-size distribution measurement, were performed. XRF analysis showed that calcium oxide is one of the main components in fly ash, which is a potentially suitable component for TCES systems. XRD results revealed information regarding the crystal structure and phases of various elements, including that of Ca. The STA measurements showed that the samples can store thermal heat with energy contents of 50–394 kJ/kg (charging step). For one fly ash sample obtained from a grate furnace, the release of the stored thermal heat under the selected experimental conditions (discharging step) was demonstrated. The cycling stability tests were conducted thrice, and they were successful for the selected sample. One fly ash sample could store CO2 with a storage capacity of 27 kg CO2/ton based on results obtained under the selected experimental conditions in STA. Samples from rotary kiln and fluidized bed were heated up to 1150 °C in an N2 atmosphere, resulting in complete melting of samples in crucibles; however, other samples obtained from grate furnaces formed compacted powders after undergoing the same thermal treatment in STA. Samples from different grate furnaces showed similarities in their chemical and physical characterization. The leachability test according to the standard (EN 12457-4 (2002)) using water in a ratio of 10 L/S and showed that the leachate of heavy metals is below the maximum permissible values for nonhazardous materials (except for Pb), excluding the fly ash sample obtained using fluidized bed technology. The leachate contents of Cd and Mn in the fly ash samples obtained from the rotary kiln were higher than those in other samples. Characterization performed herein helped in determining the suitable fly ash samples that can be considered as potential CO2-storage and TCES materials.

Arsenates with arsenic in octahedral coordination are very rare. The present paper provides an overview of all known M(+) arsenates(V) containing octahedrally coordinated arsenic (M(+) = Li, Na, K, Rb, Cs, Ag) and the crystal structures (determined from single-crystal X-ray diffraction data) of the following seven new hydrothermally synthesized members belonging to six different structure types, four of which are novel: LiH(2)As(3)O(9), LiH(3)As(2)O(7), NaHAs(2)O(6)-type KHAs(2)O(6), KH(3)As(4)O(12) and isotypic RbH(3)As(4)O(12), CsAs(3)O(8) and NaH(2)As(3)O(9)-type AgH(2)As(3)O(9). The main building unit of these compounds is usually an As(4)O(14) cluster of two edge-sharing AsO(6) octahedra sharing two apical corners each with two AsO(4) tetrahedra. The different connectivity between these clusters defines the different structure types. The novel CsAs(3)O(8) structure, based on a derivative of the As(4)O(14) cluster, is the most condensed of all these M(+) arsenates, with an O/As ratio of only 2.67 compared with values of 2.75-3.5 for the remaining members. This is achieved through polymerization of the cluster derivatives to infinite chains of edge-sharing AsO(6) octahedra. The ([4])As/([6])As ratio drops to only 0.5. All but two of the protonated title compounds show protonated AsO(6) octahedra. Hydrogen bonds range from very strong to weak. An analysis of bond-length distribution and average bond lengths in AsO(6) octahedra in inorganic compounds leads to an overall mean As-O distance for all known AsO(6) octahedra (with R factors < 0.072) of 1.830 (2) A.

Potassium indium bis[hydrogen arsenate(V)], KIn(HAsO 4 ) 2 , rubidium indium bis[hydrogen arsenate(V)], RbIn(HAsO 4 ) 2 , and caesium indium bis[hydrogen arsenate(V)], CsIn(HAsO 4 ) 2 , were grown under mild hydrothermal conditions (T = 493 K, 7-8 d). KIn(HAsO 4 ) 2 adopts the KSc(HAsO 4 ) 2 structure type (space group C2/c), while RbIn(HAsO 4 ) 2 and CsIn(HAsO 4 ) 2 crystallize in the space group R3c and are the first arsenate representatives of the RbFe(HPO 4 ) 2 structure type. All three compounds have tetrahedral-octahedral framework topologies. The M + cations, located in voids of the respective framework, are slightly disordered in RbIn(HAsO 4 ) 2 . In KIn(HAsO 4 ) 2 , there is a second Katom position with a very low occupancy, which may suggest that the K atom can easily move in the channels extending along [101]. Chemical contextMetal arsenates often form tetrahedral-octahedral framework structures that frequently show potentially interesting properties, such as ion conductivity, ion exchange and catalytic properties (Masquelier et al., 1990(Masquelier et al., , 1994a(Masquelier et al., ,b, 1995(Masquelier et al., , 1996(Masquelier et al., , 1998Mesa et al., 2000;Ouerfelli et al., 2007a Ouerfelli et al., ,b, 2008 PintardScré pel et al., 1983;Rousse et al., 2013). In the course of a detailed study of the system M + -M 3+ -As-O-(H) by hydrothermal syntheses, a large variety of new arsenate(V) compounds and structure types were found (Kolitsch, 2004; Schwendtner, 2006; Schwendtner & Kolitsch, 2004a,b, 2005,b,c,d, 2017a.The three new title compounds belong to the family of hydrogenarsenate compounds with the general formula M + M 3+ (HAsO 4 ) 2 . Including the three compounds reported here, nine compounds with this general formula are known. They crystallize in four different structure types. KIn(HAsO 4 ) 2 is a further representative of the KSc(HAsO 4 ) 2 structure type (Schwendtner & Kolitsch, 2004a), which is also adopted by AgGa(HAsO 4 ) 2 and AgAl(HAsO 4 ) 2 (Schwendtner & Kolitsch, 2017c (Schwendtner & Kolitsch, 2017c). The asymmetric unit contains one K, one In, one As, one H and four O atoms (Fig. 1a). The slightly distorted InO 6 octahedra share corners with six HAsO 4 tetrahedra, thus forming a three-dimensional anionic framework with narrow channels parallel to [110] and [101] (Fig. 2a,b) which host the K atoms. There are two K-atom positions (K1 and K2), at a distance of 2.653 (15) Å from each other. The K1 position is located on an inversion centre and has a refined occupancy of 0.976 (2), while K2, which lies between two K1 positions, is located on a twofold axis (like the In atom) and has a refined occupancy of 0.024 (2). Both K-atom positions show a [4 + 4]-coordination with average K-O bond lengths of 2.949 and 3.016 Å for K1 and K2, respectively (Table 1). This is slightly longer than the reported average K-O bond length for lations after Gagné & Hawthorne (2015) show bond-valence sums (BVSs) of 0.99 valence units (v.u.) for K1 and 0.85 v.u. for K2, indicating an 'underbonded' charact...

The crystal structures of hydrothermally synthesized alpha-, (I), and beta-caesium scandium bis[hydrogen arsenate(V)], (II), both CsSc(HAsO4)2, have been determined from single-crystal X-ray diffraction data collected at room temperature. The dimorphs are both characterized by a three-dimensional negatively charged framework of corner-sharing alternating ScO6 octahedra and HAsO4 tetrahedra. The charge-balancing Cs+ cations are located in a system of three intersecting tunnels in (I) and in tunnels parallel to the a axis in (II). Strong to weak hydrogen bonds reinforce both frameworks. The average Sc-O bond lengths are 2.098 and 2.094 A, respectively. Compound (I) is triclinic and isotypic with (NH4)Fe(III)(HPO4)2, alpha-A(I)V(III)(HPO4)2 (A is NH4 or Rb) and alpha-(NH4)(Al(0.64)Ga(0.36))(HPO4)2. Compound (II) is monoclinic and isotypic with (H3O)Fe(III)(HPO4)2, beta-A(I)V(III)(HPO4)2 (A is NH4 or Rb), CsIn(HPO4)2 and RbSc(HPO4)2. Both (I) and (II) represent the first arsenate examples of their structure types. The Cs and Sc atoms in (I) lie on inversion centres. In (II), all atoms are in general positions. A brief overview is presented of the six structure types shown by A(I)M(III)(HXO4)2 compounds (X is P or As).