Pyrophyllite study

MacKenzie KJD, Brown IWM, Meinhold RH, Bowden ME (1985) Thermal reactions of pyrophyllite studied by high-resolution solid state Al and Si nuclear magnetic resonance spectroscopy. J Am Ceram Soc 68 266-272... 

The performance of clay materials (Halloysite, Pyrophyllite, Montmorillonite K-30) in the degradation of polystyrene (PS) was investigated in this study. The catalysts showed good catalytic activity for the degradation of PS with high selectivity to aromatics liquids. Styrene is the major product, and ethylbenzene is the second most abundant one in the liquid product. 

Marumo, K. (1989) Genesis of kaolin and pyrophyllite of the Kuroko deposit of Japan Mineralogical and geochemical studies. Geochim. Gosmochim. Acta, 53, 2915—2924. 

A linear correlation is obtained between bitumen extraction with the paddle mill and the adhesion tension against water saturated pyrophyllite. That the degree of water saturation of the pyrophyllite is important in explaining the difference between the 2 extraction processes indicates that it will be necessary to study each process in terms of the relevant adhesion tensions. These results demonstrate that adhesion tension is the most important parameter found to date in determining the degree of separation in the presence of surfactants. Measurements of adhesion tension between surfactant solutions and minerals similar to those found in tar sand may be of considerable value in studies of surfactant utility in both aqueous-surfactant, solvent-aqueous-surfactant and in situ extraction processes. In addition, if appropriate model situations can be developed, measurements of adhesion tension may be useful in upgrading bitumen-water-clay emulsions obtained by a variety of in situ and heavy oil recovery processes. 

Vidal, O. 1997. Experimental study of the thermal stability of pyrophyllite, paragonite and clays in a thermal gradient. European Journal of Mineralogy, 9, 123-140. 

It is instructive to compare the natural mineral assemblages with those in the simplified system which has been studied experimentally. The system muscovite-pyrophyllite is useful because it contains phases analagous to natural minerals. The system is dominated by two factors (1) the stability of the expandable phase (potassic beidellite) either alone or as a mixed layered phase (2) the stability of kaolinite in the presence of quartz. It appears from the data presented by Velde (1969) that the... 

Eggleston and Bailey (1967) published a study on dioctahedral chlorite and gave five examples of chlorites having a pyrophyllite-like layer and a brucite-like sheet (designated di/trioctahedral by the authors with the trioctahedral sheet including all species of chlorite with 5 to 6 octahedral cations per formula unit and dioctahedral 4 to 5 octahedral cations per formula unit). Identification of di/trioctahedral chlorites is indirectly accomplished. Eggleston and Bailey stated that identification depends on the intermediate value of c (060), on chemical analysis of impure material, and on the ideal compositions of the recrystallization products of static heating . The composition of one such chlorite for which they refined the structure is ... 

In addition to MC and MD simulations, several quantum-chemical studies of hydrated clay minerals with or without exchangeable cations in the interlayer space have been performed at the ab initio and semiempirical level of theory. The total energy of hydrated layered silicates (talc and pyrophyllite) without exchangeable counterions, the position and interactions of interlayer water... 

The formation of metal hydroxide surface precipitates and subsequent residence time effects on natural sorbents can greatly affect metal release and hysteresis. It has generally been thought that the kinetics of formation of surface precipitates was slow. However, recent studies have shown that metal hydroxide precipitates can form on time scales of minutes. In Figure 3.7 one can see that mixed Ni-Al hydroxide precipitates formed on pyrophyllite within 15 minutes, and they grew in intensity as time increased. Similar results have been observed with other soil components and with soils (Scheidegger et ak, 1998 Roberts et ak, 1999 Sparks, 2002, 2005). 

I.I. Effect of Residence Time on Desorption Some researchers found that trace elements [Ni, Pb, As(V)] reacted with metal oxides and pyrophyllite over longer times resulted in either irreversible or reversible sorption mechanisms. Violante et al. (2003) studied the effect of residence time on the sorption of Zn onto ferrihydrite in the presence of Cu. As Cu has a greater affinity than Zn for tire surfaces of ferrihydrite, Cu was added from 1 to 336 hours after Zn at a Zn/Cu molar ratio of 2. Zinc sorption increased, particularly when Cu was added 6 to 336 hours after Zn. A possible explanation of these findings is that trace elements initially sorbed on the surfaces of variable-charge minerals slowly form precipitates with time. As discussed before, sorption is considered to be the predominant sorption mechanism responsible for trace element uptake on mineral surfaces within the first few hours, while surface precipitation is considered to be a much slower process, occurring on a time scale of hours to days (McBride, 1994 Scheidegger et al., 1997 Sparks, 1999 Borda and Sparks, Chapter 3, this volume). Clearly, Cu added many hours or days after Zn addition cannot replace Zn ions that have formed precipitates on the surfaces of the ferrihydrite. 

In another series of MD simulations of TCE on clay mineral surfaces, the clay mineral pyrophyllite, an uncharged, 2 1, dioctahedral phyllosilicate, was constructed using experimental data (Lee Guggenheim, 1981). We chose pyrophyllite for study because it has the same structure as the smectites, but it is a neutral clay and the interlayer space is thus devoid of the hydrated counterions that would typically be present to complicate simulations. 

Elzinga E, Peak D, Sparks DL (2001) Spectroscopic studies of Pb(II)-sulfate interactions at the goethite-water interface. Geochim Cosmochim Acta 65 2219-2230 Elzinga E, Sparks DL (1999) Nickel sorption mechanisms in a pyrophyllite-montmorillonite mixture. J Colloid Interface Sci 213 506-512... 

The reason for presenting this hypothetical analysis of the Al203-Si02-H20 system is that just such a study was made by Zen (1961) of seven pyrophyllite deposits in... 

The kaolinite mineral species studied are kaolinite, kaolinite d (disordered kaolinite), dickite and nacrite. These polytypes have been described by Bailey (1963) on the basis of sense and degree of displacement of 1 1 layers and the position of vacant octahedral positions in the layer sequence. For the hydrated kaolinitic minerals, we have used the terminology of Keller and Johns (1976) which is based on endellite as the completely hydrated species and halloysite as the partly or completely dehydrated species. The polytypes of chlorite have been described by Bailey and Brown (1962) and Hayes (1970). In Fig. 8.3b it is shown that montmorillonite, the mixed-layer clays and illite are located between pyrophyllite without interfoliar charge and the dioctahedral... 

Other studies in this field for which the SIESTA approach has been used include the study of cation distributions in phyllosilicates like pyrophyllite, beidellite and several smectites and ilhtes [149], a study of the (001) surface of galena [150] and the combined theoretical-experimental study of the structure oh the high-pressure monoclinic phase II of cristobalite [151]. 

Nickel sorption on pyrophyllite, kaolinite, gibbsite, and montmorillonite at pH 7.5 results in formation of Ni-nucleation products from solutions which are undersaturated with respect to the thermodynamic solubility product of Ni(OH)2(s). An important finding of the study of Scheidegger et al. (16) is that the structural environment of Ni in all Ni sorption samples is similar. There is also an obvious similarity among the spectra of the Ni sorption samples and the spectrum of takovite, suggesting the presence of Ni phases of similar structure (Table II). 

Similar process was also used to develop yttrium aluminum garnet (Y3AI5O12, YAG) transparent ceramics with nanosized grains [52], In this study, a high-pressure cell was used, where disk samples were placed in a capsule made of NaCl, both to ensure the quasi-hydrostatic compression of the sample and prevent its contact with the graphite heater. The whole structure was then contained in the pyrophyllite high-pressure cell. The sample temperature in the high-pressure cell... 

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