Acid Dissolution of a Texas Bentonite

109

Abstract--A correlation was made of crystallochemical data from 15 smectites with the half time of dissolution (to.~) in 6 N hydrochloric acid at 96~ From this the relation In to~ -3.95 -1.96 Fe w -2.30 Mg v~ was developed. It shows a remarkable dependence of the apparent dissolution rate of the octahedral layer of the smectites on the substitution of Fe 3+ and Mg 2+ for AI +3 in the octahedral position.

Section: Discussionmentioning

confidence: 99%

“…The kinetics and mechanism of dissolution of smecrites in HCI have been described by various authors such as Brindley and Youell (1951), Kar~ulin and Stubi6an (1954), Osthaus (1954Osthaus ( , 1956), Packter (1955), Granquist and Gardner-Sumner (1959), Fahn (1963), Turner (1964), Ci6el et al (1965), and many others.…”

Section: Introductionmentioning

confidence: 97%

Dissolution of Smectites in Hydrochloric Acid: II. Dissolution Rate as a Function of Crystallochemical Composition

Novak

1978

109

“…This was found to be the same for both octahedral and tetrahedral ions. Granquist and Sumner (1959) studied the various physical properties of an acid-treated Texas bentonite as a function of treatment time. They also observed a pseudo first-order kinetics.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Acid-Dissolution of Palygorskite (Attapulgite) and Sepiolite

Abdul-Latif

1969

Abstract-Palygorskite and sepiolite were digested with large excesses of hydrochloric acid at constant temperature for various periods of time. The reaction was found to be of first order with respect to the magnesium, aluminum and iron components in the clay and also with respect to hydrochloric acid concentration.The reaction rate constant for Mg is larger than for Fe, which is larger than for A|. Approximately one-third of the octahedral-type cations are extraneous, suggesting that only three of the five octahedral positions are filled. The reaction rate constant of Mg in sepiolite is about 240 times that for palygorskite. This may be an indication that sepiolite is less stable to chemical weathering than palygorskite.The activation energies for Mg, AI and Fe in palygorskite were found to be the same and equal to about 18.4 kcal per mole.Treatment of partially acid-digested palygorskite with magnesium ions under alkaline conditions resulted in an increase in the X-ray intensity of the 10.5 A spacing, suggesting some of the palygorskite was reconstituted.

“…The technique can be useful to determine if an element exists in more than one structural site in a given crystal structure (Brindley and Youell, 1951;Osthaus, 1956;Grandquist and Sumner, 1957). Together with other data, such as radiogenic argon retentivity, information about the structural nature of those sites can then be obtained.…”

Section: Introductionmentioning

confidence: 99%

K/Ar Systematics of an Acid-Treated Illite/Smectite: Implications for Evaluating Age and Crystal Structure

Aronson

Douthitt

1986

Abstract--On the basis of progressive acid dissolution the Thompson-Hower model states that mixedlayer glauconite/smectite and illite/smectite contain potassium in two structural sites: a mica-type K position (site 1) and a position of uncertain structural status more prone to dissolution (site 2). Site 2 was thought not to retain radiogenic argon (4~ Using extensive progressive acid dissolution and K/Ar studies on a sized illite/smectite (I/S), determining the amount of K in site 2 is shown to be somewhat more complicated than previously thought because the dissolution pattern depends on acid normality. More important, site 2 fully retains 4~and no age correction is thus necessary as is required by the Thompson-Hower model, further affirming the geochronologic value of iUite in mixed-layer clay. These data are also relevant to understanding the crystal and particle structure of I/S. Site 2 is probably a partly filled K interlayer that develops as an intermediate kinematic step on the way to being fully filled during the transformation of smectite to illite.