The crystal structure of pyroaurite

Allmann, R.

doi:10.1107/s0567740868003511

Cited by 532 publications

(278 citation statements)

References 2 publications

(3 reference statements)

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“…The lines are explained in the text. The data are from the following references: (1) For single crystals: Allmann (1968Allmann ( , 1969) (pyroaurite and 'sjö grenite'); Arakcheeva et al calculated lines are strikingly similar to those from the regression analysis of the experimental data, which supports strongly the geometrical approach developed in this paper, together with the values determined for r(OH À (IV)) and the bond angle . The same value of is again appropriate with either trivalent ion, in agreement with the observation for the Ni-based systems; i.e.…”

Section: Layered Double Hydroxidessupporting

confidence: 71%

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The importance of proper crystal-chemical and geometrical reasoning demonstrated using layered single and double hydroxides

Richardson¹

2013

Acta Crystallogr Sect B

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Atomistic modelling techniques and Rietveld refinement of Xray powder diffraction data are widely used but often result in crystal structures that are not realistic, presumably because the authors neglect to check the crystal-chemical plausibility of their structure. The purpose of this paper is to reinforce the importance and utility of proper crystal-chemical and geometrical reasoning in structural studies. It is achieved by using such reasoning to generate new yet fundamental information about layered double hydroxides (LDH), a large, much-studied family of compounds. LDH phases are derived from layered single hydroxides by the substitution of a fraction (x) of the divalent cations by trivalent. Equations are derived that enable calculation of x from the a parameter of the unit cell and vice versa, which can be expected to be of widespread utility as a sanity test for extant and future structure determinations and computer simulation studies. The phase at x = 0 is shown to be an form of divalent metal hydroxide rather than the polymorph. Crystal-chemically sensible model structures are provided for -Zn(OH) 2 and Niand Mg-based carbonate LDH phases that have any trivalent cation and any value of x, including x = 0 [i.e. for -M(OH) 2 ÁmH 2 O phases].

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Section: Layered Double Hydroxidessupporting

confidence: 71%

“…6(d) suggests that there is a problem with the chemical composition assumed by Allmann (1968) for pyroaurite, i.e. x = 0.25.…”

Section: Substitution By Two Different Types Of Trivalent Cationsmentioning

confidence: 99%

The importance of proper crystal-chemical and geometrical reasoning demonstrated using layered single and double hydroxides

Richardson¹

2013

Acta Crystallogr Sect B

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“…Os valores dos parâmetros a e c foram obtidos segundo as Equações propostas por Debye-Scherrer. [22][23][24][25][26] O parâmetro c foi calculado através da multiplicação de d(003) em Å pelo índice 3, ou seja, c = 3d 003 . O parâmetro a foi calculado por meio da multiplicação de d(110) em Å por 2, isto é, a = 2d 110 .…”

Section: Espectroscopia Vibracional Na Região Do Infravermelho (Eiv)unclassified

Hidróxidos duplos lamelares à base de escória de alto forno

Rebelo¹,

Cunha²,

Corrêa³

2012

Quím. Nova

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Recebido em 14/4/11; aceito em 8/11/11; publicado na web em 13/1/12 LAYERED DOUBLE HYDROXIDES PRODUCED FROM BLAST FURNACE SLAG. Hydrotalcite like compounds (HT) were prepared by co-precipitation (Mg/Al = 3.5), using an acid solution with blast furnace slag and MgCl 2 .6H 2 O and aqueous solutions of NaOH. The following synthesis variables were investigated: temperature (30 and 45 °C) and pH (9 and 12). Depending of the temperature two systems were observed: Mg-Al-CO 3 (T = 30 °C); Mg-Al-Cl-CO 3 (T = 45 °C). An increase in the pH of synthesis and Mg 2+ concentration produced HTs well-crystallized and with greater values of all cell parameters. The study showed the potentiality of BFS in the synthesis of well-crystallized LDHs without the presence of other crystalline phases.Keyords: blast furnace slag; layered double hydroxides (LDHs); syntheses. INTRODUÇÃOA atual situação em torno da disposição de resíduos industriais tornou-se uma séria preocupação que ameaça o meio ambiente, a saú-de e a qualidade de vida. Quando os resíduos industriais são dispostos de maneira inadequada, causam graves problemas ambientais como contaminação das águas subterrâneas por lixiviação de metais tóxicos e emissões de material particulado para áreas vizinhas. A reciclagem de resíduos mostra-se como uma alternativa capaz de minimizar os impactos ambientais negativos decorrentes do processo produtivo. 1 A produção de aço gera uma série de resíduos industriais. Entre os vários tipos de resíduos, a escória de alto forno (EAF) tem atraído muita atenção, já que a sua produção ultrapassa a de qualquer outro resíduo. 1A indústria do aço no Brasil, representada por 14 empresas privadas, foi responsável pela produção, em 2010, de 32,9 milhões de toneladas de aço bruto, levando o país a ocupar a 9ª posição no ranking da produção mundial.2 De acordo com análises do Instituto Aço Brasil, a produção acumulada de janeiro a novembro de 2011 totalizou 34,9 milhões de toneladas de aço bruto e 27,3 milhões de toneladas de ferro-gusa, o que representa, em média, um volume total de 13,4 milhões de toneladas de escórias, oriundas do alto forno e da aciaria. 2A EAF é formada pela mistura entre a ganga do minério de ferro com as cinzas do coque ou carvão vegetal e do calcário, utilizado como fundente no processo de fabricação do ferro-gusa.3 Sua composição química é majoritariamente Ca, Si, Al e Mg, bem como uma pequena quantidade de Fe, Ti e Mn.3-5 O tamanho de suas partículas e estrutura variam em função da velocidade de resfriamento da EAF na água ou no ar. Ao ser resfriada bruscamente, a EAF adquire estrutura vítrea e forma granular, apresentando propriedades hidráulicas latentes; mas, se o processo empregado for o resfriamento lento, a escória cristaliza, formando um produto sem atividade hidráulica, constituído por silicatos e aluminossilicatos cálcicos. Nas escórias básicas (CaO/SiO 2 > 1) há predominância de melilitas (akermanita e gehlenita) e merwinita, enquanto que nas ácidas (CaO/SiO 2 < 1) ocorre principalmente wollastonita e anortita. 4,6,7 A E...

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“…Low-cost materials, in their natural and modified forms, have been also extensively studied as alternative adsorbents for dyes (Ahmad et al 2007;Gurses et al 2006). Among the different adsorbents, layered double hydroxides (LDHs), also known as hydrotalcite-like compounds or anionic clays, are promising waste scavengers, particularly for dye molecules (Allmann 1968). Recent studies showed that the use of LDHs for the retention of organic anions has given very good results (De Roy et al 1992;Lakraimi et al 2000).…”

Section: Introductionmentioning

confidence: 99%

Removal of Remazol Blue 19 from wastewater by zinc–aluminium–chloride-layered double hydroxides

et al. 2013

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Layered double hydroxides (LDHs), also called anionic clays, consist of cationic brucite-like layers and exchangeable interlayer anions. These hydrotalcite-like compounds, with Zn and Al in the layers and chloride in the interlayer space, were prepared following the coprecipitation method at constant pH. The affinity of this material for Remazol Blue 19, RB19 [2-(3-(4-Amino-9,10-dihydro-3-sulpho-9,10-dioxoanthracen-4-yl) aminobenzenesulphonyl) vinyl) disodiumsulphate], was studied as a function of contact time, pH of the solutions LDH dose and the RB19/[Zn-Al-Cl] mass ratio. It was found that 48 h is enough time for the equilibrium state to be reached with maximum RB19 retention at pH of 9 for an LDH dose equal to 100 mg and with an RB19/[Zn-Al-Cl] mass ratio higher than 3. The adsorption isotherm, described by the Langmuir model, is of L-type. The results demonstrate that RB19 retention on LDHs occurs by adsorption on external surface when RB19/[Zn-Al-Cl] mass ratio is equal or \3 and by both adsorption and interlayer ion exchange for ratios higher than 3. A mechanism for removal of RB19 anion has been confirmed by X-ray diffraction, IR spectroscopy and TG analysis (TG and DTG curves).

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The crystal structure of pyroaurite

Cited by 532 publications

References 2 publications

The importance of proper crystal-chemical and geometrical reasoning demonstrated using layered single and double hydroxides

The importance of proper crystal-chemical and geometrical reasoning demonstrated using layered single and double hydroxides

Hidróxidos duplos lamelares à base de escória de alto forno

Removal of Remazol Blue 19 from wastewater by zinc–aluminium–chloride-layered double hydroxides

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