Clays halloysite/kaolinites

The behaviour of M2D-C3-0-(E0)ra-CH3 over time (4 weeks) has been monitored by FIA-APCI-MS in the presence of Al(OH)3, CaC03 (calcite), FeO(OH) (goethite), Fe203 (hematite), halloysite, illite, kaolinite, sand, pumice, talc and Ti02 (anatase), and provides some useful comparative information regarding silicone surfactant behaviour in the presence of various solid media [10]. In general, the results indicated a dependence of parent molecule recovery on pH, with lower recoveries obtained with more extreme pH values (i.e. halloysite and sand, pH 3.7 and 4.8, respectively), consistent with the known pH instability of trisiloxanes under aqueous conditions [3,11,12,16]. In particular, the loss of the parent molecule was most rapid in the presence of the clay, halloysite, and is consistent with other reports of acceleration of silicone hydrolysis in the presence of acid clays [23-25]. Comparison of the recovery of M2D-C3-0-(E0) -CH3 in the presence of halloysite, kaolinite and illite clays (0.1%, 10 mg g-1) by FIA-APCI-MS is presented in Fig. 5.5.1 [10],... 

In view of the problems associated with the expanding 2 1 clays, the smectites and vermiculites, it seemed desirable to use a different clay mineral system, one in which the interactions of surface adsorbed water are more easily studied. An obvious candidate is the hydrated form of halloysite, but studies of this mineral have shown that halloysites also suffer from an equally intractable set of difficulties (JO.). These are principally the poor crystallinity, the necessity to maintain the clay in liquid water in order to prevent loss of the surface adsorbed (intercalated) water, and the highly variable morphology of the crystallites. It seemed to us preferable to start with a chemically pure, well-crystallized, and well-known clay mineral (kaolinite) and to increase the normally small surface area by inserting water molecules between the layers through chemical treatment. Thus, the water would be in contact with both surfaces of every clay layer in the crystallites resulting in an effective surface area for water adsorption of approximately 1000 tor g. The synthetic kaolinite hydrates that resulted from this work are nearly ideal materials for studies of water adsorbed on silicate surfaces. 

Allophane Allophane is an amorphous clay from natural soil it is a natural aluminosilicate originating from the transformation of volcanic ashes and glasses with weathering. Allophane exists for young volcanic soil and is progressively transformed into crystalline clays, halloysite, then into kaolinite... 

See also brick clays, china clay, FIRECLAY and the clay minerals halloysite, kaolinite, montmorillonite, etc. 

Figure 9. Dimensional changes on firing kaolinite (flint clay), halloysite, and montmoril-loniteJ ]...

Hydrothermal clay-silica deposits (kaolinite, halloysite, sericite, montmorillonite and silica) and zeolite deposits occur in Tertiary-Quaternary volcanic regions. These deposits are distributed in areas of epithermal gold mineralization. 

The percentage recoveries of M2D - C -> - 0 - (E 0 ) -CH3 over time in the presence of sand, soil and the clays kaolinite, halloysite and montmorillonite (0.1%, 10 mg g" -1) as determined by HPLC-APCI-MS methods are shown in Fig. 5.5.2 [10]. Validation of the data was obtained by parallel HPLC—LSD analysis (data not shown). 

The time (days) to 50% loss were sand (17) > kaolinite (4) > soil (3) > halloysite (1) > montmorillonite(< 0.1). The rate was most rapid for the solid media exhibiting extreme pH values (halloysite, montmorillonite), and highest for the intercalating clay, montmorillonite. The observed recovery from the soil sample (Te Kowhai) was intermediate to... 

One of the four compositional groups of clay minerals, the kandites include the minerals kaolinite, dickite, halloysite, and metahalloysite all have virtually the same composition. The first two minerals are common and widely used in the production of ceramics the latter two occur in tubular fibrous form. 

Clay (mineral) A group of fine-grained and platy aluminum silicate minerals. Kaolinite (ALSiiOs/OH ), montmorillonite ((Al,Mg)g(Si40io)4(OH)8-12H20), and halloysite (Al2Si205(0H)4-2H20) are common clay minerals. 

Hashimoto, 1. and 3ackson, M.L., 1960. Rapid dissolution of allophane and Kaolinite-Halloysite after dehydration. Clay and Clay Minerals, 7th Conf., pp. 102-113. 

DcSousa Santos, P., Brindley, G.W. and De Sousa Santos, H., 1965. Mineralogical studies of kaolinite-halloysite clays, 3. A fibrous kaolin mineral from Piedade, Sao Paulo, BrasiL Am Mineralogist, 50 619—628. 

Clay minerals Illite, kaolinite, halloysite, smectites, chlorites, Vermiculites, palygorskite, mixed-layer clays, etc. 

There are inconsistencies in the model for the calculation of activity products for the "clays. Exchangeable cations are disregarded for the low exchange capacity kaolinite, halloysite, chlorite, and moderate capacity illite. For certain expansible layer silicates and two zeolites, the logjo of the activity of selected cations is added into the sum of the activity products. 

Particularly attractive method for preparation of synthetic zeolite is recrystallization of natural aluminosilicates, such as kaolinite (halloysite), previously formed for elimination of plastic flow of highly thixotropic, pulverized zeolite. Some additional components of initial mixtures, such as texture modifiers (hard coal, lignite, cellulose, silica, aluminum oxide) are also introduced. They enrich the structure of zeolite adsorbent in transport pores and prevent an excessive compression of the clay material during the formation process. This results in an increase in product efficiency during the crystallization of zeolite phase. 

The admixture of clay mineral (halloysite) to carbonaceous deposit (as for waste materials) remarkably enriches the texture of mineral-carbon adsorbents in mesopores and leads to the decrease of magnitude of micropores volume with dimension of 0.4 - 2 nm. In the case of hard coal and kaolinite mixture this char contains the maximum sub- and micropores at the lowest content of mesopores. 

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