Sepiolite formula

Attapulgite and sepiolite data plot on both sides of the neutral line.. The calculated structural formulas of these two clays are more subject to error than those of the sheet structure clays. As is suggested by their low cation exchange capacity octahedral sheets tend to approach neutrality. The amount of R3+ required to maintain neutrality is less if OH substitues for O2. ... 

Martin-Vivaldi, J.L. and Cano-Ruiz, J. 1955. Contribution to the study of sepiolite, 2. Some considerations regarding the mineralogical formula. Proc. Natl. Conf. Clays Clay Miner., 4th -Natl. Acad. Sci. Natl. Res. Counc., Publ., 456 166 172. 

To set up a more environmentally friendly process, it is mandatory to replace the caustic soda by solid bases. Many catalysts such as zeolites [2], alumina [3,4], sepiolite [5] and hydrotalcites [6,7] have been regarded as promising solid basic materials. Hydrotalcites, which are anionic clays, are the subject of this investigation. They are layered double hydroxides with the general formula [M(II)i.xM(III)x(0H)2].[A" x/n].mH20. The host layers are charged positively by replacement of divalent metal cations usually Mg ", Ni and... 

Fig. 2 Structural models and ideal formulae of sepiolite and palygorskite fibrous clays [26]...

Sepiolite has the ideal formula MggSii203o(OH)4 l2H20 substitution in both tetrahedral and octahedral positions is usually minor, and Mg fills not less than 90% of these positions thus, this material is clearly trioctahedral. Other elements have been sometimes reported in the octahedral centers, such as Fe(II/III), Ni(II), or Mn(II). 

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