Influence of Kaolinite Clay Supplementation on Growth Performance and Digestive Function in Finishing Calf-fed Holstein Steers.

Two experiments were conducted to examine the influence of kaolinite clay supplementation (0%, 1%, or 2% diet dry matter [DM] basis) on characteristics of digestion (Trial 1) and growth performance (Trial 2) in calf-fed Holstein steers fed a finishing diet. In Trial 1, 6 Holstein steers (539±15 kg) with ruminal and duodenal cannulas were used to evaluate treatment effects on characteristics of digestion. Kaolinite clay supplementation decreased total tract DM digestion (linear effect, p<0.01) without effects (p≥0.10) on site and extent of digestion of organic matter, neutral detergent fiber, starch and N, or ruminal microbial efficiency. There were no treatment effects on ruminal pH, volatile fatty acids molar proportions or estimated methane production. In Trial 2, 108 Holstein steers (132.4±5.6 kg) were used in a 308-d study to evaluate growth performance and carcass characteristics. There were no treatment effects (p>0.10) on average daily gain (ADG) and gain efficiency (ADG/dry matter intake). Kaolinite supplementation tended (linear effect, p = 0.08) to increase dietary net energy (NE) during the initial 112-d period. However, the overall (308-d) effect of supplementation dietary NE was not appreciable (p>0.20). However, due to the inertness of kaolinite, itself, the ratio of observed-to-expected dietary NE increased with kaolinite supplementation. This effect was more pronounced (linear effect, p 0.03) during the initial 224 d of the study. Overall (308 d), kaolinite supplementation tended to increase (linear effect, p = 0.07) dietary NE by 3% over expected. Kaolinite supplementation did not affect carcass weight, yield grade, longissimus area, kidney, pelvic and heart fat, and quality grade, but decreased (linear effect, p = 0.01) dressing percentage. It is concluded that kaolinite supplementation up to 2% of diet DM may enhance energetic efficiency of calf-fed Holstein steers in a manner independent of changes in characteristics of ruminal and total tract digestion

Ice Formation on Kaolinite: Insights from Molecular Dynamics Simulations

The formation of ice affects many aspects of our everyday life as well as technologies such as cryotherapy and cryopreservation. Foreign substances almost always aid water freezing through heterogeneous ice nucleation, but the molecular details of this process remain largely unknown. In fact, insight into the microscopic mechanism of ice formation on different substrates is difficult to obtain even via state-of-the-art experimental techniques. At the same time, atomistic simulations of heterogeneous ice nucleation frequently face extraordinary challenges due to the complexity of the water-substrate interaction and the long timescales that characterize nucleation events. Here, we have investigated several aspects of molecular dynamics simulations of heterogeneous ice nucleation considering as a prototypical ice nucleating material the clay mineral kaolinite, which is of relevance in atmospheric science. We show via seeded molecular dynamics simulations that ice nucleation on the hydroxylated (001) face of kaolinite proceeds exclusively via the formation of the hexagonal ice polytype. The critical nucleus size is two times smaller than that obtained for homogeneous nucleation at the same supercooling. Previous findings suggested that the flexibility of the kaolinite surface can alter the time scale for ice nucleation within molecular dynamics simulations. However, we here demonstrate that equally flexible (or non flexible) kaolinite surfaces can lead to very different outcomes in terms of ice formation, according to whether or not the surface relaxation of the clay is taken into account. We show that very small structural changes upon relaxation dramatically alter the ability of kaolinite to provide a template for the formation of a hexagonal overlayer of water molecules at the water-kaolinite interface, and that this relaxation therefore determines the nucleation ability of this mineral

Influence of OH- concentration on the illitization of kaolinite at high pressure

The products of hydrothermal reactions of kaolinite at 300°C and 1000 bars were studied in KOH solutions covering an OH- concentration, [OH-], of 1M to 3.5M. XRD patterns indicated a notable influence of the [OH-] on the reaction. At [OH]≥3M, the only stable phase was muscovite/illite. The content of muscovite/illite was calculated from the analysis of the diagnostic 060 reflections of kaolinite and muscovite/illite. The results showed a linear dependence of kaolinite and muscovite/illite contents with [OH-]. 27Al MAS NMR spectroscopy revealed the formation of small nuclei of K-F zeolite at high [OH-]. Finally, modelling of the 29Si MAS NMR spectra indicated that the Si/Al ratio of the muscovite/illite formed was very close to that of muscovite, at least in the mineral formed at low [OH-]. In good agreement with the XRD data, the quantification of the reaction products by 29Si MAS NMR indicated a linear decrease of the kaolinite content with increasing OH- concentration.Dirección General de Investigación Científica y Técnica CTQ2007-63297Junta de Andalucía P06-FQM-0217

Influence of Thermal Treatment on Kankara Kaolinite

In this work, the influence of thermal treatment on the structure of Kankara kaolinite was studied for the first time, using X-ray diffractogram (XRD), EDX, NanoSEM, FTIR-Attenuated Total Reflectance, DTA/TGA and BET surface area measurements. The treatment temperatures applied represents the peak of the transformation stages. The results show that surface area decreases with increase in temperature of treatment, while its crystal structure was transformed from the native kaolinite structure via the amorphous metakaolin to the typical mullite/crystobalite structure though with some unidentifiable peaks. The morphological studies showed that Kankara kaolinite is composed of nano-platelets of about 30nm thickness and in bundles of between 1 – 3 µm thicknesses with some marked variations/reductions as the treatment temperatures increases. The DTA/TGA result shows that the kaolinite undergoes dehydroxylation at 528.560C while been converted to metakaolin with a weight loss of about 14.4%. The presence of the characteristic OH, Al-OH, Si-OH and Si-O-Al bands were confirmed with the ATR studies which also showed the disappearance and subsequent appearance of new bands as the treatment temperature increased, this also affected the surface area and pore sizes of the transformation products

Mineralogical characterisation and processing of some industrial minerals from Uganda

This report describes the mineralogical characterisation and processing of several industrial minerals collected by Dr DJ Morgan in October 1991 during a visit to Uganda (Visit report WG/91/31R). The industrial minerals included raw materials (see Table 1) from African Ceramics Ltd (Mutaka kaolin, feldspar and ball clay) and samples collected by the Geological Survey and Mines Department Uganda (the remaining kaolin, talc and diatomite). The aim of this study was to assess their quality for various applications, especially ceramic manufacture. This work was carried out as part of the DDA/BGS project "Minerals for Development"

Acidity of edge surface sites of montmorillonite and kaolinite

Peer reviewedPreprin

Evaluation of some ceramic clays from Zambia

This reports details the technical evaluation of ceramic clays collected during visits to Zambia in 1990 and 1991 by the author (Clive Mitchell). The clay samples included: Choma kaolin (Southern Province), Twapia kaolin (Copperbelt Province), Kapiri Mposhi kaolin (Central Province), Masenche clay (Northern Province), Leula clay, Misenga clay and Chikankata clay (Southern Province). The Choma kaolin was asessed to be an excellent source of ceramic-grade kaolin. The Twapia and Kapiri Mposhi kaolin are not suitable due to poor fired clour. The Masenche, Leula and Misenga clays were assessed to only be suitable for craft pottery or structural clay products such as bricks and tiles. The Chikankata clay has potential for use in the manufacture of clay stoves however further testing is required to confirm its suitability for this use

Discovery of halloysite books in a ~270,000 year-old buried tephra deposit in northern New Zealand

As part of a wider study examining the geomechanical properties, especially sensitivity, of sequences of Quaternary pyroclastic and associated deposits and buried soils in the landslide-prone western Bay of Plenty area near Tauranga, eastern North Island, we examined the mineralogy of a pale pinkish-grey tephra deposit directly beneath non-welded, siliceous Te Ranga Ignimbrite (~2 m thick) in a ~25 m high cutting at Tauriko.http://www.smectech.com.au/ACMS/ACMS_Conferences/ACMS21/ACMS%202010%20Abstracts/ACMS%202010%20S1A6_Wyatt%20et%20al%20(Lowe).pd

Microscopic Mechanism and Kinetics of Ice Formation at Complex Interfaces: Zooming in on Kaolinite

Most ice in nature forms thanks to impurities which boost the exceedingly low nucleation rate of pure supercooled water. However, the microscopic details of ice nucleation on these substances remain largely unknown. Here, we have unraveled the molecular mechanism and the kinetics of ice formation on kaolinite, a clay mineral playing a key role in climate science. We find that the formation of ice at strong supercooling in the presence of this clay is twenty orders of magnitude faster than homogeneous freezing. The critical nucleus is substantially smaller than that found for homogeneous nucleation and, in contrast to the predictions of classical nucleation theory (CNT), it has a strong 2D character. Nonetheless, we show that CNT describes correctly the formation of ice at this complex interface. Kaolinite also promotes the exclusive nucleation of hexagonal ice, as opposed to homogeneous freezing where a mixture of cubic and hexagonal polytypes is observed