Hydrothermal and dry-heat fixation of K by soil clays and the effects on C.E.C., surface area and mineralogy

Clay Minerals ◽  
1971 ◽  
Vol 9 (2) ◽  
pp. 219-230 ◽  
Author(s):  
C. E. Davis ◽  
N. Ahmad ◽  
R. L. Jones
Keyword(s):  
Ion Exchange ◽  
Hydrothermal Reaction ◽  
Degree Of Crystallinity ◽  
New Mineral ◽  
Hydrothermal Conditions ◽  
Dry Heat ◽  
Surface Areas ◽  
Soil Clays ◽  
Dry Heating ◽  
Georgia Kaolinite

AbstractFixation of K by soil clays and selected reference clay minerals was induced by dry heat and hydrothermal procedures, at 100°C, 200°C and 380°C. Appreciable amounts were fixed at all temperatures. In the cases of the samples treated hydrothermally the amounts fixed increased with pressure.Fixation by dry heating at 380°C was significantly greater than at 100°C and 200°C respectively. Fixation under hydrothermal conditions increased in order 380°C > 200°C > 100°C.Reductions in cation exchange capacities (and surface areas) were associated with fixation, indicating that some fixation was due to ion exchange. Changes in mineralogy in some of the samples also support the conclusion that ion exchange was partly responsible for fixation. Some of the fixation under hydrothermal conditions was due to the formation of insoluble K-compounds - as for example the synthesis of a new mineral when one sample was treated.The lattice-iron content of the clays may have influenced their hydrothermal behaviour. Thus the Princes Town Clay ( > 7-5 % lattice-iron) and three nontronites (≫ 7-5 % lattice-iron) showed appreciable lattice collapse after hydrothermal treatment, while Wyoming bentonite and hectorite (<3-5%) lattice-iron) showed no collapse at all.The degree of crystallinity of the mineral may also have influenced its hydrothermal reaction. For example, the highly disordered soil kaolinite (St John's) was much more reactive than the more ordered Georgia kaolinite. Also, the more-ordered reference clays fixed relatively less K at 380°C than the less-ordered soil clays.

The Effect of Crystallinity of Nanoporous WO3 on the Intercalation and Deintercalation of Li+

2014 ◽  
Vol 1024 ◽  
pp. 128-131
Author(s):  
Ehsan Ahmadi ◽  
Mustaffa Ali Azhar ◽  
Dede Miftahul Anwar ◽  
Monna Rozana ◽  
Zainovia Lockman
Keyword(s):  
Ion Exchange ◽  
Constant Temperature ◽  
Annealing Time ◽  
Octahedral Coordination ◽  
Degree Of Crystallinity ◽  
Nanoporous Structure

Nanoporous anodic WO3 was annealed at three different times of 1h, 2h, and 3h at a constant temperature of 500oC. This was to investigate the intercalation and deintercalation behaviour of Li+ in this annealed nanoporous oxide. The as-anodised WO3 is amorphous and after annealing, monoclinic WO3 was observed with much higher degree of crystallinity when the time of annealing was increased from 1h to 3h. By electrodiffusion of Li+ in the nanoporous structure, an ion exchange between fully oxidized states (W6+) which is the octahedral coordination dominates (WO6) and Li+ could happen. This causes changing of the colour of the yellowish WO3 to bluish WO3.Li2O. This work showed the effect of annealing time on intercalation of Li+ ion with WO3, however crystallinity can play a good role for electron movement, it cause a decrease in Li+ ion interaction with WO3.

Topotactic route to synthesis of novel hydroxylated phases: I. Trioctahedral Micas

Clay Minerals ◽  
1986 ◽  
Vol 21 (2) ◽  
pp. 125-131 ◽  
Author(s):  
S. Komarneni ◽  
R. Roy
Keyword(s):  
Ion Exchange ◽  
Alkaline Earth ◽  
Water Molecules ◽  
Hydration Energy ◽  
Hydrothermal Conditions ◽  
Potential Applications ◽  
Clay Layers ◽  
First Time ◽  
Hydrolysis Of ◽  
Alkaline Earth Cations

AbstractK-depleted phlogopite mica was used as a topotactic precursor and treated with alkali (Li+, K+, , Rb+, Cs+), alkaline-earth (Mg2+, Ca2+, Sr2+, Ba2+) and trivalent (Al3+) cations under hydrothermal conditions of 200°C and 30 MPa pressure. K-, NH4-, Rb- and Cs-aluminosilicate micas were synthesised at 200°C in one day. The synthesis of Cs-aluminosilicate mica, with potential applications in the management of nuclear wastes, has been achieved for the first time by this approach. Ion exchange by Li+, Na+ and alkaline-earth cations under hydrothermal conditions did not produce anhydrous mica phases but resulted in hydrous phases with one or two layers of water molecules between the clay layers. The formation of hydrous phases may be attributed to the high hydration energy of the above cations compared to K+, , RB+ and Cs+. Ion exchange with Al3+ produced a chlorite-like phase because of the hydrolysis of Al3+ under these hydrothermal conditions. These studies are of relevance in the immobilization of wastes where hazardous ions can be fixed in highly stable insoluble phases like mica or chlorite.

Chivruaiite, a New Mineral with Ion-Exchange Properties

2008 ◽  
pp. 57-63
Author(s):  
Viktor N. Yakovenchuk ◽  
Sergey V. Krivovichev ◽  
Yurii P. Men’shikov ◽  
Yakov A. Pakhomovsky ◽  
Gregory Yu. Ivanyuk ◽  
...  
Keyword(s):  
Ion Exchange ◽  
New Mineral ◽  
Exchange Properties

Low Temperature Hydrothermal Synthesis of Nanophase BaTiO3 and BaFe12O19 Powders

1996 ◽  
Vol 457 ◽  
Author(s):  
Fatih Dogan ◽  
Shawn O'rourke ◽  
Mao-Xu Qian ◽  
Mehmet Sarikaya
Keyword(s):  
Particle Size ◽  
Hydrothermal Reaction ◽  
Average Particle Size ◽  
Reaction Times ◽  
Nanocrystalline Powders ◽  
Molar Ratio ◽  
Average Particle ◽  
Hydrothermal Conditions ◽  
Processing Variables ◽  
Xrd And Tem

ABSTRACTNanocrystalline powders with an average particle size of 50 nm has been synthesized in two materials systems under hydrothermal conditions below 100°C. Processing variables, such as temperature, concentration and molar ratio of reactants and reaction time were optimized to obtain particles of reduced size and stoichiometric compositions. Hydrothermal reaction takes place between Ba(OH)2 solution and titanium/iron precursors in sealed polyethylene bottles in the BaTiO3 and BaFe12O19 systems, respectively. While crystalline BaTiO3 forms relatively fast within a few hours, formation of fully crystalline and stoichiometric BaFei20i9 require considerably longer reaction times up to several weeks and strongly dependent on the Ba:Fe ratio of the precursors. The structural and compositional evaluation of the nanophase powders were studied by XRD and TEM techniques.

scholarly journals Investigation of Bioactive Glass-Ceramic 60SiO2-30CaO-10P2O5 Prepared by Hydrothermal Method

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Vuong Xuan Bui ◽  
Mai Quang Vo ◽  
Tien Anh Nguyen ◽  
Hoa Thi Bui
Keyword(s):  
Bioactive Glass ◽  
Hydrothermal Method ◽  
Reaction Temperature ◽  
Hydrothermal Reaction ◽  
Glass Ceramics ◽  
Degree Of Crystallinity ◽  
Apatite Phase ◽  
Powder Samples ◽  
Sbf Solution ◽  
The Degree Of Crystallinity

Bioactive glass-ceramics (BGCs) with the composition of 60SiO2-30CaO-10P2O5 (wt. %) have been synthesized by the hydrothermal method. The BGC samples were prepared at two reaction temperatures of 150 and 220°C, named BGC-150 and BGC-220. The XRD and FTIR analyses highlighted that the degree of crystallinity of BGCs increased linearly with hydrothermal reaction temperature. FE-SEM and TEM results indicated that the surface of BGC samples is covered by the nanosized particles which grow into larger sizes as a function of reaction temperature. The bioactivity of BGCs was investigated by the immersion of powder samples in the SBF solution. The results confirmed the dissolution and the interaction of BGC samples in the SBF solution which led to the formation of a new apatite phase on their surface.

Mineralogical composition of the clay fraction of two fluvio-glacial sediments from east Greenland

Clay Minerals ◽  
1980 ◽  
Vol 15 (2) ◽  
pp. 135-145 ◽  
Author(s):  
L. Petersen ◽  
K. Rasmussen
Keyword(s):  
Clay Fraction ◽  
Mineralogical Composition ◽  
Cold Climate ◽  
High Rate ◽  
Degree Of Crystallinity ◽  
Metamorphic Rocks ◽  
Glacial Sediments ◽  
East Greenland ◽  
Soil Clays ◽  
High Degree

AbstractThe < 2 µm fractions of two fluvio-glacial sediments from East Greenland have been analysed chemically and by XRD and Mössbauer spectroscopy. The bulk of each < 2 µm fraction consists of feldspars and micas (biotite) which are important constituents of the Precambrian igneous and metamorphic rocks of the area. Significant amounts of vermiculitic and smectitic minerals are also present. Compared with similar minerals present in Danish soil clays, the Greenland vermiculite and smectite are characterized by a high degree of crystallinity and it is concluded that these minerals have been formed from biotite through K release and lattice expansion. These processes appear to have proceeded at a sufficiently high rate to yield significant amounts of vermiculite and smectite despite the cold climate prevailing in the area.

scholarly journals Nanoscale Structural and Mechanical Analysis of Bacillus anthracis Spores Inactivated with Rapid Dry Heating

2013 ◽  
Vol 80 (5) ◽  
pp. 1739-1749 ◽  
Author(s):  
Yun Xing ◽  
Alex Li ◽  
Daniel L. Felker ◽  
Larry W. Burggraf
Keyword(s):  
High Temperature ◽  
Bacillus Anthracis ◽  
Exposure Time ◽  
Mechanical Analysis ◽  
Mechanical Stresses ◽  
Heat Inactivation ◽  
Content Type ◽  
Dry Heat ◽  
Wet Heat ◽  
Dry Heating

ABSTRACTEffective killing ofBacillus anthracisspores is of paramount importance to antibioterrorism, food safety, environmental protection, and the medical device industry. Thus, a deeper understanding of the mechanisms of spore resistance and inactivation is highly desired for developing new strategies or improving the known methods for spore destruction. Previous studies have shown that spore inactivation mechanisms differ considerably depending upon the killing agents, such as heat (wet heat, dry heat), UV, ionizing radiation, and chemicals. It is believed that wet heat kills spores by inactivating critical enzymes, while dry heat kills spores by damaging their DNA. Many studies have focused on the biochemical aspects of spore inactivation by dry heat; few have investigated structural damages and changes in spore mechanical properties. In this study, we have inactivatedBacillus anthracisspores with rapid dry heating and performed nanoscale topographical and mechanical analysis of inactivated spores using atomic force microscopy (AFM). Our results revealed significant changes in spore morphology and nanomechanical properties after heat inactivation. In addition, we also found that these changes were different under different heating conditions that produced similar inactivation probabilities (high temperature for short exposure time versus low temperature for long exposure time). We attributed the differences to the differential thermal and mechanical stresses in the spore. The buildup of internal thermal and mechanical stresses may become prominent only in ultrafast, high-temperature heat inactivation when the experimental timescale is too short for heat-generated vapor to efficiently escape from the spore. Our results thus provide direct, visual evidences of the importance of thermal stresses and heat and mass transfer to spore inactivation by very rapid dry heating.

scholarly journals Study of K-Feldspar and Lime Hydrothermal Reaction: Phase and Mechanism with Reaction Temperature and Increasing Ca/Si Ratio

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 46 ◽  
Author(s):  
Shanke Liu ◽  
Cheng Han ◽  
Jianming Liu
Keyword(s):  
Composite Material ◽  
Reaction Temperature ◽  
Inductively Coupled Plasma ◽  
Hydrothermal Reaction ◽  
Rietveld Method ◽  
Starting Material ◽  
Molar Ratio ◽  
Emission Spectrometry ◽  
Dissolution Mechanism ◽  
Hydrothermal Conditions

To elucidate the physicochemical properties of the artificial silicate composite material, K-feldspar and lime were reacted in mild hydrothermal conditions (different reaction temperatures and various K-feldspar/lime ratios). Formed phases were investigated using various techniques, such as X-ray powder diffraction, the Rietveld method, scanning electron microscopy (SEM), and inductively coupled plasma-optical emission spectrometry. The analysis revealed that tobermorite, grossular (hydrogarnet), alpha-dicalcium silicate hydrate (α-C2SH), amorphous calcium silicate hydrate, potassium carbonate, bütschliite, calcite, and calcium hydroxide formed with various conditions. Both the temperature and the Ca/Si molar ratio in the starting material greatly affected the formation of phases, especially the generation of tobermorite and α-C2SH. The substitution of H4O4 ↔ SiO4 proceeded with the increase of the Ca/Si molar ratio rather than the reaction temperature and the reaction time. More hydrogen was incorporated in hydrogarnet through the substitution of H4O4 ↔ SiO4 with the increase of the Ca/Si molar ratio in the starting material. Due to the properties of tobermorite as a cation exchanger and its potential applications in hazardous waste disposal, experimental parameters should be optimized to obtain better performance of the artificial silicate composite material from K-feldspar and lime hydrothermal reaction. The dissolution mechanism of K-feldspar was also discussed.

scholarly journals Correlations Between Alkali and Crystallinity in lyocell-Based ACF Probed with X-Ray Diffraction

2020 ◽  
Vol 58 (7) ◽  
pp. 495-500
Author(s):  
Young Min Jin ◽  
Joon Hyuk Lee ◽  
Sang Sun Choi
Keyword(s):  
Thermo Gravimetric Analysis ◽  
Thermal Characteristics ◽  
Degree Of Crystallinity ◽  
Bet Surface Area ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Potential Applications ◽  
Activated Carbon Fibres

This study examined the effect of alkalis on lyocell-based activated carbon fibres (ACFs) with high Brunauer-Emmett-Teller (BET) surface areas, using X-ray diffraction (XRD). Here, alkali treatments were conducted using 10 ~ 25 % NaOH and KOH on lyocell samples for 3 h at ambient room temperature. A secondary treatment with 4 % each of KOH and H3PO4 for an additional 3 h followed. An activated form of the samples was prepared by oxidation (stabilisation), carbonisation, and activation. The final ACF form of the samples showed a porous structure with high BET surface areas (> 1,000 m<sup>2</sup> g<sup>-1</sup>). A 25 % dosage of NaOH produced the highest BET surface area compared to other samples. In terms of crystallinity, a 15 % dosage of KOH was found to be the optimum dosage to secure the highest degree of crystallinity among all samples. Meanwhile, the NaOH was successfully shifted the samples into the most distinct form of cellulose II. 15 % NaOH was found to secure the most stable thermal characteristics, as determined via thermo-gravimetric analysis. The present work demonstrates the various physio-chemistries of ACFs prepared with different proportions and types of alkalis, leading to intriguing potential applications.

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