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Hydrotalcite

About: Hydrotalcite is a research topic. Over the lifetime, 6188 publications have been published within this topic receiving 135483 citations.


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TL;DR: The basic salts of this system were prepared and their structures and physico-chemical properties were studies by electron microscopy, chemical analysis, X-ray powder diffraction, thermal analysis, and acidity-basicity measurements as mentioned in this paper.
Abstract: The basic salts of this system were prepared and their structures and physico-chemical properties were studies by electron microscopy, chemical analysis, X-ray powder diffraction, thermal analysis, i.r. absorption spectra, BET absorption, and acidity-basicity measurements. The salts were found to be new compounds analogous to hydrotalcite. They can be expressed by the formula; [M 2+ M 3+ (OH)2(x+y))]y+ [A 1 − , Az2- · mH2O]-(z1 + 2z2) where M2+ and M3+ denote di- and trivalent cations, A− and A2− denote mono- and divalent anions, respectively, and y = z1 + 2z2; z1 ≫ z2. The structures consist of positively charged Cd(OH)2-like basic layers and intermediate layers formed from anions and water molecules with the solid solution of divalent cation (M2+) and trivalent cation (M3+) being formed in the range of 0.6 > x/(x + y) > 0.9. The anions of Cl−, NO 3 − and ClO 4 − are easily substituted by CO 3 2− . A large part of the NO 3 − makes a monodentate-type bond and the ClO 4 − a bridge-type bond.

933 citations

Journal ArticleDOI
TL;DR: Ahstraet et al. as discussed by the authors used coprecipitation followed by hydrothermal treatment between 150 ~ and 250~C. Based on the structural formula [Mgl_xAlx(OH)~lX+l(COz)x/2 �9 mH20] x-, pure solid solutions were formed in the range Al/(Al + Mg) = 0.2 to 0.33, where m = (1 - 3x/ 2).
Abstract: Ahstraet--Hydrotalcite solid solutions were prepared by coprecipitation followed by hydrothermal treatment between 150 ~ and 250~C. Based on the structural formula [Mgl_xAlx(OH)~lX+l(COz)x/2 �9 mH20] x-, pure solid solutions were formed in the range Al/(Al + Mg) = 0.2 to 0.33, where m = (1 - 3x/2). Maximum crystallite size was achieved by hydrothermal treatment between 180 ~ and 200~ with x = 0.337 to 0.429. Crystal strain was also minimized at these values of x. The adsorption c~pacity for Naphthol Yellow S increased as x increased and reached a maximum (1.56 x 10 6 moles/m 2) when x = 0.287, a value eight times larger than that of Mg(OH)~. A weak endothermic DTA peak at about 350~ is probably due to the loss of structural water in the main layer of the structure. On calcination between 400 ~ and 700~ only periclase was detected, probably containing A1 in solid solution. Hydration of the calcined product resulted in the reconstruction of the original hydrotalcite structure.

812 citations

Journal ArticleDOI
TL;DR: A number of approaches to the synthesis of a class of anionic clay minerals (M a 2+ M b 3+ (OH) 2 a +2 b (X − ) 2 b · x H 2 O; M 2+ = Mg, Ni, Co, Zn, Cu, etc., M 3+ = Al, Cr, Fe, Sc; m 2+ /M 3+ ∼ 1−5; X − = water and base stable anion; x = 0−6) have been sumarized.

772 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of temperature of precipitation, total metal cations concentration, of the molar fraction M(III)/M(III) + M(II) in solution on the composition and on the crystallinity degree of the samples has been investigated.
Abstract: Hydrotalcite-like anionic clays of general formula [M(II)1–xM(III)x(OH)2]x+[CO32–x/2]x– · m H2O with M(III) = Al and M(II) = Mg, Ni, Zn have been prepared by precipitation of the hydroxycarbonates from the “homogeneous” solution after the thermally induced hydrolysis of urea. The effect of the temperature of precipitation, of the total metal cations concentration, of the molar fraction M(III)/M(III) + M(II) and of the molar fraction urea/M(II) + M(III) in solution on the composition and on the crystallinity degree of the samples has been investigated. The optimum conditions are reported to obtain micro-crystalline powders with a narrow distribution of particle size in a short time with a simple procedure. The compounds obtained have been characterised for chemical composition, thermal behaviour, particle-size distribution and BET-surface area. In addition, the crystal structure of Mg0.67Al0.33(OH)2 (CO3)0.165 · 0.4 H2O has been refined by X-ray diffraction powder methods. The carbonate form has been converted into the chloride form by letting gaseous HCl flow over the hydrotalcite-like compounds, heated at 150 °C. The exchange of Cl– anions with some alkoxide anions in the presence of the respective alkanols has been investigated. The exchange reaction was driven by the segregation of NaCl crystals poorly soluble in alkanols and led to the co-intercalation of the alkoxide ions together with the alkanol with the formation of a bi-layer of extended alkyl chain in the interlayer region of the Mg-Al hydrotalcite. The intercalation compound, washed with water, produces a hydrotalcite with Cl– and OH– as balancing anions.

616 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023162
2022314
2021189
2020254
2019365
2018427