Surface area of kaolinite

No interaction between ferrihydrite and kaolinite was found at pH 9 because both compounds are negatively charged at this pH (Fig. 16.20b, c). Boiling kaolinite and montmorillonite in a Fe(N03)3 solution for 8 min resulted in clays containing up to ca. 55 mg oxalate soluble Fe/g clay. The BET surface area of kaolinite increased from 18 to 34 m /g and that of montmorillonite from 11 to 62 m g . Whereas kaolinite shows only a small decrease in > 10 pm pores, montmorillonite lost about half of its >10 pm pores even with the lowest Fe oxide content (6.6 mg ECq g clay). It has been speculated that in contrast to kaolinite, the Fe oxide, in the presence of montmorillonite, remained highly disorderd and active due to A1 and Si dissolved from... 

In an early study of the effect of calcination on the surface area of kaolinite, Gregg and Stephens (1953) found a small but progressive decline in the BET area over the temperature range 100-800°C. These results were in contrast to a 12% loss of structural water at 450°C. It was concluded that there was no detectable activation and that the crystallite structure was not broken up as a result of theimal dehydroxylation. 

XiE, Z., and J. V, Walther. 1992. incongruent dissolution and surface area of kaolinite. Geochim. Cosmochim. Acta 56 3357-63. 

Kaolinite is the most common mineral in this group and eonsists of stacks of 1 1 unit cells comprised of silica tetrahedral and gibbsite (Al) octahedral sheets. The stacks generally range from 0.05 to 2 pm in thiekness and ean attain thicknesses up to 4000 pm the stacks can range fi om 0.1 to 4 pm laterally. The specific surface area of kaolinite is of the order of 10 to 20 m /g of dry clay. 

Limited silica fines stabilization data indicated that increasing copolymer molecular weight from 100,000 to 1,000,000 daltons had, if anything, a negative effect on silica fines stabilization. At a molecular weight of 1,000,000 daltons, this copolymer appeared to be more effective in stabilizing silica fines than silica/kaolinite, calcite, or hematite fines. However, the results may be due in part to the larger particle size and lower surface area of the silica fines (see Table II). 

Adhesive force, non-Brownian particles, 549 Admicelle formation, 277 Adsorption flow rate, 514 mechanism, 646-647 on reservoir rocks, 224 patterns, on kaolinite, 231 process, kinetics, 487 reactions, nonporous surfaces, 646 surface area of sand, 251 surfactant on porous media, 510 Adsorption-desorption equilibria, dynamic, 279-239 Adsorption plateau, calcium concentration, 229... 

Materials. Na-Kaolinite A homoionic sample of kaolinite was prepared from a well-crystallized sample purchased from Source Clays, University of Missouri, using a standardized technique (14) which involved repeated washing with distilled water and by treatment with NaCl solutions to remove exchangeable ions such as Ca, and freeze-drying of the final product. Nitrogen specific surface area of this kaolinite was estimated to be 9.4nr/g and X-ray analysis showed the characteristic pattern of kaolinite. 

Our approach has been to study a very simple clay-water system in which the majority of the water present is adsorbed on the clay surfaces. By appropriate chemical treatment, the clay mineral kao-linite will expand and incorporate water molecules between the layers, yielding an effective surface area of approximately 1000 m2 g . Synthetic kaolinite hydrates have several advantages compared to the expanding clays, the smectites and vermiculites they have very few impurity ions in their structure, few, if any, interlayer cations, the structure of the surfaces is reasonably well known, and the majority of the water present is directly adsorbed on the kaolinite surfaces. 

As a function of their structural properties, clays interact differently with organic and inorganic contaminants. Two major groups of clay minerals are selected for discussion here (a) kaolinite, with a 1 1 layered structured aluminosilicate and a surface area ranging from 6 to 39 m g" (Schofield and Samson 1954) and (b) smectites with a 2 1 silicate layer and a total surface area of about 800m g" (Borchardt 1989). 

The adsorption isotherms in Figure 11.3 are of interest for several reasons. First, it may seem surprising that an assemblage of kaolinite platelets should give a reversible isotherm. The adsorbent had a specific surface area of 17 m2g-1, which would appear to correspond to a platelet thickness of c. 50 nm. The particle rigidity and the house-of-cards packing have probably resulted in the formation of a macro-porous aggregate, which accounts for the appearance of the reversible Type II isotherm. 

Kahr, G., and F. T. Madsen. 1995. Determination of cation exchange capacity and surface area of bentonite, illite, and kaolinite by methylene blue adsorption. Appl. Clay Sci. 

Using the value of the specific surface area of the kaolinite specimen prior to modification (70 m /g), the area occupied by each cation (1.2 nm ) and the amount of adsorbed modifier, we have estimated the thickness of the modifying layer covering the surface of the silicate, assuming that no defects exist in this layer. The resulting values, together with the experimental data on the Henry s constants and the differential heats of adsorption obtained as reported in [47] are listed in Table 10 for the two specimens considered. 

Representative data for soil minerals are presented in Table 2.Ill and 2.IV, taken from the publication of Greenland and Quirk (1962). Montmorillonite has the highest surface area, ranging up to 800 m /g. This means that a 10-g sample has an area of approximately two acres or four-fifths of a hectare. This is certainly an impressive value. Kaolinites have surface areas ranging between 10 and 40 m /g, whereas illites have values intermediate between montmorillonite and kaolin. Cation exchange capacities tend to vary directly with surface areas. Of course the importance of the surface area depends upon the activity of the surface, particularly toward water. 

Experiments were performed with analytically pure-grade kaolinite powder, crystalline muscovite, and talc in the form of mica. The powder (20 mg) was placed in an alumina crucible 4 mm high and 5.7mm in diameter and manually pelletized. The surface area of rectangular pieces of muscovite and talc (0.2-0.5 mm thick, side length 3-4 mm) was estimated with an MPB-2 optical microscope (x24). 

Later work showed similar adsorption-desorption behavior for NACs in clay types other than kaolinite. The adsorption constant was found to increase fairly uniformly for all tested NACs in the ratio of 1 6 12 (kaolinite iUite montmoril-lonite). This ratio is quite close to the relative surface areas of the three minerals illite and montmorillonite have 6 and 16 times more available surface area, respectively, than kaolinite (Haderlein, Weissmahr, and Schwarzenbach, 1996). This observation suggests that a similar EDA complexation mechanism controls the adsorption of NACs to these minerals as well. The authors also showed that TNT,... 

Conventional refractory grain alumina powders, kaolin, and Western bentonite can be used. Kaolin is preferred in amounts between 0.5 to 10% by weight of the sand. An example of a kaolin grade useful for this purpose is Freeport Kaolin Co. s Nusheen unpulverized kaolin material which consists of kaolinite particles with a specific surface area of about 16 m /g. 

The surface area of the kaolinite and the produced sample are obtained using nitrogen adsorption/desorption at 77 K (Fig.3). The lUPAC hysteresis analysis for both samples show types H4 and H3, respectively, as a result of capillary condensation in mesoporous structure. The hysteresis loop for kaolinite sample shows vertically inclined parallel branches at a pressure close to saturation. This is attributed to the existence of narrow slit-like pores. Those pores have opened more with hydroxide treatment and yielded a product with aggregates of plate-like pores (Fig. 4). The total pore volume of 0.0339 cmVg is obtained in comparison with the 0.016476 cmVg for the original kaolinite. The Single point surfaee area of the produced sample obtained at a relative pressure of 0.3 is 6.85 mVg. 

The amount of water retained varies directly in accordance with the surface area of the pores and indirectly with regard to the pore space. The specific surface of a particle is governed by its size and shape. For example, particles of clay have far larger specific surfaces than do grains of sand. As an illustration, a grain of sand, 1 mm in diameter, has a specific surface of about 0.002 m g-i, compared with kaolinite, which varies from approximately 10 to 20 m g-i. Hence, clays have a much higher specific retention than sands (Fig. 4.4). 

The properties of a material that determine its suitability as a filler and the properties it imparts to rubber are its grain-size, surface area of particles and surface activity of particles (i.e. the ability of the particle s surface to bond with the rubber matrix). These properties of clay minerals, especially kaolinite, and their appropriateness as fillers are explained below. 

The hydrated form of halloysite occurs in ( lindrical tubes of overlapping kaolinite sheets. The outside diameters of the tubes range frx)m 0.05 to 0.20 im, with a median value of 0.07 p,m, and range in length frx)m a fraction to several micrometres. The specific surface area of halloysite ranges from 35 to 70 (Mitchell, 1976). 

The specific immersion wetting enthalpies of kaolinite, illite, and their organo-philic derivatives were investigated in methanol and benzene in our earlier publications [35,37,38]. These data reveal that the heat of immersion in methanol is the highest in the case of the dialyzed hydrophilic mineral, and with increasing surface modification its value decreases. The comparison of immersion wetting enthalpies relative to unit mass of the adsorbent is justified only when the specific surface area of the adsorbent is constant. It is also known, on the other hand, that the value of liquid sorption capacity, is a function of surface modification 02 = where 2flm,2 is the hydrophobic surface area and a is the total... 

Silicagel R (Reanal, Hungary, analytical grade), silica powder (precipitated from commercial sodium silicate solution by alcohol and then dried and sieved. The Na content at the surface of the precipitated silica was 3.07 mmol per 100 g solid powder, determined poten-tiometrically.), silicates Sepiolite (Spain), Zeolite 13X (Linde, FRG), kaolinite (Zettlitz, FRG), illite (Fiizerrad-vany, Hungary), montmorillonite (Mad, Hungary), and vermiculite (South Africa). The specific surface areas of the adsorbents are summarized in Table 1. Their detailed description has been published [23—26]. 

---