Characterization of Adsorbed Iron in Montmorillonite by Mössbauer Spectroscopy

Diamant, Arik

doi:10.1346/ccmn.1982.0300108

Cited by 37 publications

(41 citation statements)

References 9 publications

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“…Similar behavior has been reported for Fe(II)-exchanged montmorillonite (Diamant et al 1982) and montmorillonite intercalated with dimethyltin(IV) complexes (Simopoulos et al 1988). It was also discussed by Breen et al (1992) in their study of the Sn(II)-clay interactions.…”

Section: Resultssupporting

confidence: 75%

Tin-Clay Complexes: A Mössbauer Study

Petridis

Bakas

1997

Clays and clay miner.

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Abstract--Divalent tin has been intercalated into montmorillonite by reacting partially hydrolyzed solutions of SnC12 under aerobic conditions at pH = 2.8 with aqueous dispersions of the smectite mineral.The precursor tin solution contains mainly the cationic trimeric ion Sn3(On)4 2 § which is shown to take part in the exchange reactions with the surface cations of the mineral. Variable temperature Mrssbauer spectroscopy was used in order to: 1) directly probe changes in the oxidation state and coordination environment of Sn 2 § in the process of intercalation; 2) examine the nature of tin atoms on the external surfaces and in the interlayer space of the clay platelets; and 3) study the dynamics of motion of tin atoms on the clay surfaces.The main conclusion from these studies is that about 75% of the Sn 2 § ions undergo extensive oxidation to the +4 state with concomitant hydrolysis and condensation that lead to the precipitation of SnO2 on the external surfaces of the clay. The rest of the Sn 2 § ions are introduced into the lamellar zone, as evidenced by the detailed Mrssbauer analysis of the dynamics of motion of tin atoms on the clay surfaces.

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Section: Resultssupporting

confidence: 75%

Tin-Clay Complexes: A Mössbauer Study

Petridis

Bakas

1997

Clays and clay miner.

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“…Our data suggest that the surface Sn polymer is weakly associated with surface water, and that the change in vibrational freedom of Sn near 210 K is associated with the melting of the latter, as noted by Anderson & Tice (1971). We can, however, find no rationale for the absence of a break in the In A vs. T curve for Fe3+-montmorillonite, in which the Fe 3+ ions were also believed to occur as an oxy/hydroxy coating on the surface of the clay (Diamant et al, 1982). Our results for the SnClz/kaolin system, which cannot have a significant contribution from an interlamellar species in intimate contact with water, also exhibit a discontinuity near 210 K. One possible explanation is that the Sn oxy/hydroxy polymers contain a greater amount of, or are in more intimate contact with, water than the corresponding hydroxyferric aggregates and that this water melts at a temperature close to that of water in the clay micropores.…”

Section: A(t) a Exp[-6ert/kod 2]mentioning

confidence: 78%

“…tightness of binding of the M6ssbauer atom within the system, which it might be anticipated would be greater for an interlayer than for a surface-bound species. Secondly, this vibrational freedom of the interlayer cation is greatly enhanced by the melting of associated water molecules at -210 K, and appears as a discontinuity at this temperature in plots of In A vs. temperature, T. This phenomenon has been used to distinguish interlayer from structural Fe in Fe2+'3+-exchanged montmorillonite (Diamant et al, 1982) and has been more fully treated by Simopoulos et al (1988) in their studies on dimethyltin(IV)-exchanged clay. Because the recoil free fraction,f, and the spectral area, A, are linearly related for "thin absorbers":…”

Section: Discussionmentioning

confidence: 99%

Mössbauer spectroscopic and thermogravimetric studies of tin-clay complexes

1992

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Complexes of SnCIJmontmorillonite have been prepared from solutions which contained 10, 20, 40 and 200 times the cation exchange capacity of the clay, resulting in complexes which contained 1.7, 1.6, 2.8 and 4-6 wt% of tin. Detailed thermogravimetric and variable temperature llgsn M6ssbauer spectroscopic studies of these complexes, both as prepared and following back exchange with Ca2+-ions, have shown that (i) the complexes are quite acidic in nature, and (ii) the majority of the Sn forms an oxy/hydroxy coating over the montmorillonite surface in which the vibrational freedom of Sn depends upon both the Sn content and the state of hydration of the coating. Adams (1987) has shown that layered silicates with small, highly charged cations residing on the exchange sites can impart considerable catalytic activity to the host structure. The small, highly charged cations polarize the water molecules held in the primary coordination sphere resulting in an acidic proton. Consequently, the clay acts as a solid source of protons and can efficiently catalyse a number of novel and industrially significant reactions such as the hydration of ethene (Atkins et al., 1983), the esterification of organic acids by alkenes (Ballantine et al., 1984) and the low temperature synthesis of tert-methylbutylether from 2-methylpropene and methanol (Adams et al., 1982). More recently, Ni 2+, Co 2+ and Cu e+-exchanged clays have proven to be efficient Diels-Atder cycloaddition catalysts (Adams et al., 1987).Recent investigations into the acidity and catalytic activity of a variety of cationexchanged clays (Breen et al., 1987; Breen, 1991a,b) have shown that when H +, A13+ and Fe 3 § reside on the exchange sites the acidity is predominantly Bronsted in nature, whereas Ni z+ and Co z+ ions result in predominantly Lewis acid centres. Only when the exchange sites are occupied by Cr 3+ is there a mixture of both Lewis and Bronsted acid sites. Clearly, the type of interlayer cation can have a profound influence on the nature of the acid sites and the resulting catalytic activity, insofar as Ni 2+ and Co 2+ are only effective acid catalysts at temperatures above 200~ whereas the other exchange forms referred to are active at temperatures below 100~To our knowledge, no previous attempts have been made to exchange Sn n+ (n = 2,4) cations between the layers of montmorillonite, although several groups have studied tin complexes on clays. Abdo et al. (1980) investigated a Sn-porphyrin complex sorbed on hectorite, Molloy etal. (1986) produced a high spacing intercalate using N-methyl-(3-triphenylstannyl)pyridinium iodide, and Petridis and co-workers (Simopoulos et al., 1988;Petridis et al., 1989) have studied the behaviour of cationic dimethyltin(IV) species 9 1992 The Mineralogical Society

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“…Upon Ca-saturation, however, both Fe 2+ doublets were removed (Figure 3b) confirming that the Fe 2 § was in the interlayer instead and at least two distinct interlayer sites are present. Diamant et al (1982) reported interlayer Fe 2 § in montmorillonite with values of $ = 1.04(3) and h = 3.12 (3) ram/see, which differ from those of~ = 1.09 (1) and (2) 4 (1) .... Li-CAL 0.208 (7) 0.506 (7) 0.27 (1) 10 (1) .... Na-KOE 0.192 (4) 0.516 (4) 0.27 (1) 21 (1) .... Ca-WOD 0.187 (7) 0.471 (7) 0.31 (1) 18 (1) .... Ut = untreated; Ca = Ca-saturated; Li = Li-saturated; Na = Na-saturated. 2 Fe3+ for SPO and MAN nontronites, Fe 2 § for BIN nontronite.…”

Section: Resultsmentioning

confidence: 99%

Structural Studies of Nontronites with Different Iron Contents by ⁵⁷Fe Mössbauer Spectroscopy

Cardile

Johnston

1985

Clays and clay miner.

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Abstract--The 57Fe Mrssbauer spectra of a series of untreated and Ca-saturated nontronites showed a predominant Fe a+ resonance which was computer-fitted with two Fe 3 § doublets defining iron in nonequivalent cis-FeO4(OH)2 octahedral sites. In most spectra a doublet indicating tetrahedral Fe 3. was fitted and in one untreated sample a doublet indicating interlayer Fe 3+ was identified. In a further untreated sample the interlayer iron was present as Fe 2+. Upon Ca-saturation the interlayer iron was displaced. It also appears that the interlayer iron was present in at least two different interlayer sites. From the computerfitted data it was clear that the interlayer cations have a significant effect on the MOssbauer resonances of iron in the two non-equivalent cis-octahedral and the tetrahedral sites of nontronite.

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Characterization of Adsorbed Iron in Montmorillonite by Mössbauer Spectroscopy

Cited by 37 publications

References 9 publications

Tin-Clay Complexes: A Mössbauer Study

Tin-Clay Complexes: A Mössbauer Study

Mössbauer spectroscopic and thermogravimetric studies of tin-clay complexes

Structural Studies of Nontronites with Different Iron Contents by ⁵⁷Fe Mössbauer Spectroscopy

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Characterization of Adsorbed Iron in Montmorillonite by Mössbauer Spectroscopy

Cited by 37 publications

References 9 publications

Tin-Clay Complexes: A Mössbauer Study

Tin-Clay Complexes: A Mössbauer Study

Mössbauer spectroscopic and thermogravimetric studies of tin-clay complexes

Structural Studies of Nontronites with Different Iron Contents by 57Fe Mössbauer Spectroscopy

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Structural Studies of Nontronites with Different Iron Contents by ⁵⁷Fe Mössbauer Spectroscopy