Experimental formation of chlorites from montmorillonite

337

135

Abstraet--A stable porous system consisting of montmorillonite cross-linked by Al-hydroxide oligomers was synthesized by reacting at room temperature an aqueous solution of such oligomers with a unit-layer dispersion of montmorillonite. The resulting cross-linked montmorillonite (AI-CLM) is a nonswelling material, showing basal spacings of 14.4 to 18.8/~, after air drying and between 14.2 to 18.0/~ after treatment at 119~ The basal spacing is found to depend on the age and OH/AI ratio of the Al-hydroxide solution, as well as on the relative amounts of the two reactants. A specific surface area of 160 m~/g and a diffraction pattern with a dominant basal spacing of 17.5 ]~ is obtained by using Al-hydroxide with OH/ AI = 1.85, aged for at least 5 days, and by applying an Al/montmorillonite ratio greater than 1.5 in the cross-linking process. The basal spacing of AI-CLM remains essentially unchanged after heating at 220~ while the specific surface area is not affected by heat treatment up to 480~Two possible configurations of Al-hydroxide oligomers, homogeneously distributed between parallel montmorillonite unit-layers, were considered in order to account for the basal spacing of 17.5-18.8/~, viz. (a) stacking of two oligomeric ring units in parallel orientation relative to the clay lamellae and (b) perpendicular orientation of individual oligomeric units.

Section: Description Of Relevant Systemsmentioning

confidence: 99%

Cross-Linked Smectites. I. Synthesis and Properties of Hydroxy-Aluminum-Montmorillonite

Lahav

1978

337

135

“…It has been applied particularly in attempts to develop chlorites or chlorite-like phases from montmorillonite by condensing hydroxide sheets between the silicate layers. Caill~re and Hrnin (1949) were pioneers in this type of study. Slaughter and Milne (1960) and Gupta and Malik (1%9) made more detailed studies along similar lines.…”

Section: Introductionmentioning

confidence: 99%

Hydroxy-Nickel Interlayering in Montmorillonite by Titration Method

Yamanaka

1978

115

Abstract--Nickel nitrate solution is potentiometdcally titrated (a) with montmorillonite, (b) without montmorillonite, in the nitrate solution. X-ray powder diffraction and chemical analyses are made of the products formed by the clay at various stages of titration. The pH values of the titration curve (a) are lower than those of curve (b) until the brucite-like hydroxynickel interlayer is more or less complete. The resulting product then closely resembles a chlorite. The preferential precipitation of hydroxide in the interlayer region is explained in terms of the acidic character of montmorillonite interlayers.Key Words---Chlorite, Interlayer, Montmorillonite, Nickel, Potentiometric. INTRODUCTIONVarious methods have been reported for preparing hydroxy interlayers in expanding layer silicates. These methods fall into two main groups: (i) a direct cation exchange method, (ii) a titration procedure. In method (i) the mineral, dispersed in water, is reacted with solutions containing hydrolyzed cations; after the exchange reaction, the excess cations are removed by centrifugation and washing. The method is applicable to cations which can be hydrolyzed extensively without precipitation of hydroxides. Examples are AI(OH)x and Fe(III)(OH)x in single or polymerized forms. Work prior to 1968 has been reviewed by Rich (1968); later studies include work by Sawhney (1968), Carstea et al. (1970, Herrera and Peech (1970), Brown and Newman (1973), Brindley and Sempels (1977).In method (ii), cations in an appropriate solution are added to the dispersed clay and the resulting clay + solution is then hydrolyzed by simple addition of alkali in a predetermined amount or by progressive titration. This latter procedure, which is used in the present work, is applicable to cations which can be hydrolyzed only slightly before precipitation occurs. It has been applied particularly in attempts to develop chlorites or chlorite-like phases from montmorillonite by condensing hydroxide sheets between the silicate layers. Caill~re and Hrnin (1949) were pioneers in this type of study. Slaughter and Milne (1960) and Gupta and Malik (1%9) made more detailed studies along similar lines. Attention was directed mainly towards intercalating Mg(OH)2 and Ni(OH)2 sheets between the silicate layers. The precise mechanism of the process has not been established but the general consensus is that the hydroxide is deposited on or sorbed by the silicate surfaces. In the present work, an attempt is made to follow the deposition of nickel hydroxide by potentiometric titration, with chemical and X-ray powder diffraction examination of the products formed at different stages of the process. The results lead us to conclude that the hydroxide-forming reaction takes place primarily with-

“…: Rich, 1968), and others at molar ratios between 1.5 and 3.75 and pHs from acid to slightly alkaline. Mg enters the hydroxy interlayers at high pHs (between 7 and 9) as was demonstrated by the experiment performed by Caillere and Henin (1949) where a Mg-hydroxy interlayer was precipitated in a montmorillonite, and confirmed by many natural examples. Chloritized montmorillonites are very common in alkaline soils of arid regions.…”

Section: Originmentioning

confidence: 68%

“…The unoriented X-ray diagrams (Table 2) can be compared with IIb chlorite polytype of Brown and Bailey (1962) and the treated montmorillonite of Caillere and Henin (1949) 9 There are many reflections (underlined in Table 2) that can not be assigned to a smectite powder pattern and are obviously chlorite-like, particularly two peaks in the 60 ~ 20 region (CuK~): 1.49 and 1.53 A. Outside of the chloritized horizon there is no such 1.53 ~_ reflection in the clay mineral fraction.…”

Section: Resultsmentioning

confidence: 99%

A Chloritized Montmorillonite from the Rio Chiflon Formation (TR) of Argentina

Bossi

1972

Abstract--X-ray, chemical, and genetic characteristics of a chloritized montmorillonite mineral species, found in The Rio Chifl6n Formation (La Torre, La Rioja, Argentina) are described. The mineral is associated with illite, montmorillonite, and chlorite, plus the non-clay associates analcite and hematite. The Rio Chifl6n Formation is of Upper Triassic age, and consists of red sandstones and siltstones representing poorly developed fluviatil cyclothems.Studies of the Li +, K + and Mg 2+ varieties of the clay, and solvation with glycerol or ethylene glycol have shown that the mineral is a smectite which behaves peculiarly with heating. Between 200 ~ and 600~ the mineral collapses gradually from a basal spacing of 13-10 A. Regular expansibility with ethylene glycol and glycerol is completely preserved (in the Li + and K + clays) up to a preheating of 400~ and partially preserved up to 600~ This behavior has been interpreted as caused by the presence of interlayer contaminants of a hydroxy-cation type. The interlayer cations may be AI, Mg, and Fe, (in this order).The environment of the Rio Chifl6n Formation has been evaluated in the light of well-known occurrences of intergradient clays in soils, and the presence of analcite and hematite. It is proposed that chloritization has taken place during a soil weathering process, under alkaline conditions with great availability of sodium during alternating dry-humid seasonal climates (oxidation conditions). The stability of the interlayer developed under these circumstances was increased during long burial and diagenesis.