Kaolinite Formation mechanism

Kaolinite, on the other hand, has no structural counterpart among the igneous minerals. It is also the most widespread of the crystalline clay mineral. The most likely mechanism for kaolinite formation is the complete breakdown of feldspar or mica particles and the precipitation of kaolinite from Al(OH)3 and Si(OH)4 from the soil solution or from amorphous, less stable intermediates. 

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... 

Kaolinite is transformed into X-ray amorphous state when activated in air. According to authors [14,15], amorphization involves the destruction of bonds between tetrahedral and octahedral layers inside the package, till the decomposition into amorphous aluminium and silicon oxides. Other researchers [ 16,17] consider that amorphized kaolinite conserves the initial ordering of the positions of silicon atoms while disordering of the structure is due to the rupture of A1 - OH, Si - O - A1 bonds and the formation of molecular water. Endothermic effect of the dehydration of activated kaolinite is shifted to lower temperatures while intensive exo-effect with a maximum at 980°C still conserves. When mechanically activated kaolinite annealed at 1(X)0°C, only mullite (3Al20j-2Si0j) and X-ray amorphous SiOj are observed. In this case, the phase with spinel structure which is formed under thermal treatment of non-activated kaolinite is not observed thus, mechanical activation leads to the formation of other phases. 

It was demonstrated in [9] that mechanical activation of a mixture of Ca(OH)2 with AI2O3 (at molar ratio 1 4) in a vibratory mill results in partial interaction with the formation of calcium hydroaluminate 4Ca0-3Al203-H20. The authors [9] showed that mechanochemical synthesis of 3Ca0-Al203 H20 occurs starting from Ca(OH)2+Al(OH)3 and Ca(OH)2+ kaolinite mixtures during their activation at room temperature. 

Cordierite synthesis method based on mechanical activation of mixtures of hydrated oxides of calcium, aluminium and silicon, as well as natural hydrated compounds (talc, kaolinite and gibbsite), has been developed in [2, 3]. Mechanical activation of these mixtures does not lead to the formation of new phases but provides good mixing at the cluster level giving aggregates that form cordierite during the subsequent thermal treatment. 

Polyacrylamide (30% hydrolysed) is an anionic polymer which can induce flocculation in kaolinite at very low concentrations. Restabilisation occurs by overdosing, probably by the mechanism outlined in Fig. 7.32. Dosages of polymer which are sufficiently large to saturate the colloidal surfaces produce a stable colloidal system, since no sites are available for the formation of interparticle bridges. Under certain conditions, physical agitation of the system can lead to breaking of polymer-suspension bonds and to a change in the state of the system. 

Tardy, Y., and D. Nahon. 1985. Geochemistry of laterites, stability of Al-goethite, Al-hematite, and Fe -kaolinite in bauxites and ferricretes An approach to the mechanism of concretion formation. Am. J. Sci. 285 865-903,... 

This section reviews several of the methods that are used to categorize clays. First, the structure of clay minerals will be discussed. Next, the mechanism of formation for kaolinite will be reviewed followed by a description of the types of deposits in which clays are found. The section will end with a description of the types of clays used in the ceramics industry. 

As indicated in the Introduction, the condensation of formaldehyde into monosaccharides by basic catalysis has been known since the last century. The synthesis starts with the formation of glycolaldehyde which is a slow reaction and is responsible for the induction period observed in the condensation of formaldehyde to sugars. Once sufficient amounts of glycolaldehyde have been formed, an autocatalytic process ensues which transforms glycolaldehyde into glyceraldehyde and dihydroxyacetone, and then into all the possible tetroses, pentoses and hexoses. The principal mechanism is a base catalyzed aldol condensation, somewhat similar to the enzyme catalyzed biochemical transformations of sugars. A common mineral, kaolinite, has been found to be an efficient catalyst for this reaction. Ribose is indeed one of the important monosaccharides formed in this reaction. 

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