Hydrolysis of Acetals in Water under Hydrothermal Conditions.

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.

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Quantitative relationships between boehmite and γ-alumina crystallite sizes

Journal of Materials Research ◽

10.1557/jmr.2004.0200 ◽

2004 ◽

Vol 19 (5) ◽

pp. 1499-1503 ◽

Cited By ~ 11

Author(s):

J. Sánchez-Valente ◽

F. Hernández-Beltrán ◽

M.L. Guzman-Castillo ◽

J.J. Fripiat ◽

X. Bokhimi

Keyword(s):

Pore Diameter ◽

Lower Surface ◽

Order Kinetic ◽

Hydrothermal Conditions ◽

Structural Units ◽

Fresh Sample ◽

First Order ◽

Main Variable ◽

Crystallite Sizes ◽

Hydrolysis Of

Nanocrystalline boehmite obtained by limited hydrolysis of aluminum tri-sec-butoxide or aluminum chloride was aged under different conditions before being calcined above the dehydroxylation temperature. When aging was carried out under hydrothermal conditions, the condensation of the structural units obeyed a first-order kinetic law with apparent activation energy of 12.2 kcal/mol. Under dehydroxylation conditions, the boehmite fragmentation is accounted for by a simple power law that links its volume to that of the resulting γ-alumina. The main variable is the volatile compounds content (water for instance) in the fresh sample. In terms of texture, a better organization of the initial nanoparticles in the boehmite means a lower surface area and larger pore diameter in the corresponding γ-alumina.

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Biosynthesis of silver nanoparticles through tandem hydrolysis of silver sulfate and cellulose under hydrothermal conditions

Journal of Chemical Technology & Biotechnology ◽

10.1002/jctb.4259 ◽

2013 ◽

Vol 89 (12) ◽

pp. 1817-1824 ◽

Cited By ~ 3

Author(s):

Xianxue Li ◽

Tareque Odoom-Wubah ◽

Huimei Chen ◽

Xiaolian Jing ◽

Bingyun Zheng ◽

...

Keyword(s):

Silver Nanoparticles ◽

Hydrothermal Conditions ◽

Silver Sulfate ◽

Hydrolysis Of

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Synthesis of nano-sized boehmite by hydrolysis of aluminum chloride hexahydrate under hydrothermal conditions

Tsvetnye Metally ◽

10.17580/tsm.2017.02.08 ◽

2017 ◽

pp. 51-55

Author(s):

M. V. Batygina ◽

◽

N. M. Dobrynkin ◽

A. S. Noskov ◽

◽

...

Keyword(s):

Aluminum Chloride ◽

Hydrothermal Conditions ◽

Chloride Hexahydrate ◽

Aluminum Chloride Hexahydrate ◽

Hydrolysis Of

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Effect of Niobium on the Structure and Photoactivity of Anatase (TiO2) Nanoparticles

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2006.17948 ◽

2006 ◽

Vol 6 (3) ◽

pp. 762-770 ◽

Cited By ~ 12

Author(s):

Masanori Hirano ◽

Kazumasa Matsushima

Keyword(s):

Methylene Blue ◽

Photocatalytic Activity ◽

Solid Solutions ◽

Uv Light ◽

Anatase Tio2 ◽

Hydrothermal Conditions ◽

Niobium Content ◽

Uv Light Irradiation ◽

Adsorption Amount ◽

Hydrolysis Of

Anatase-type TiO2 nanoparticles doped with 0–30 mol% niobium were directly formed from precursor solutions of TiOSO4 and NbCl5 under mild hydrothermal conditions at 120–180 °C for 5 h using the hydrolysis of urea. When the niobium content increased from 0 to 30 mol%, the crystallite size of anatase increased from 8.5 to 19 nm. The band gap of anatase was slightly decreased by making solid solutions with niobium. Their photocatalytic activity and adsorptivity were evaluated separately by the measurement of the concentration of methylene blue (MB) remained in the solution after maintained in the dark or under UV-light irradiation. To form anatase-type solid solutions by doping 5–15 mol% niobium into TiO2 was effective for improvement of the photoactivity of TiO2. The photocatalytic activity (the photooxidation rate) and the adsorption amount of MB for the sample containing 15 mol% niobium became more than approximately nine times and six times as much as those of the hydrothermal anatase-type pure TiO2, respectively.

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Involvement of Intermediate Sulfur Species in Biological Reduction of Elemental Sulfur under Acidic, Hydrothermal Conditions

Applied and Environmental Microbiology ◽

10.1128/aem.03160-12 ◽

2013 ◽

Vol 79 (6) ◽

pp. 2061-2068 ◽

Cited By ~ 44

Author(s):

Eric S. Boyd ◽

Gregory K. Druschel

Keyword(s):

Elemental Sulfur ◽

Solid Phase ◽

Sulfide Concentration ◽

Hydrothermal Conditions ◽

Dialysis Tubing ◽

Biological Reduction ◽

Content Type ◽

Pore Sizes ◽

Production Of Hydrogen ◽

Hydrolysis Of

ABSTRACTThe thermoacidophile and obligate elemental sulfur (S80)-reducing anaerobeAcidilobus sulfurireducens18D70 does not associate with bulk solid-phase sulfur during S80-dependent batch culture growth. Cyclic voltammetry indicated the production of hydrogen sulfide (H2S) as well as polysulfides after 1 day of batch growth of the organism at pH 3.0 and 81°C. The production of polysulfide is likely due to the abiotic reaction between S80and the biologically produced H2S, as evinced by a rapid cessation of polysulfide formation when the growth temperature was decreased, inhibiting the biological production of sulfide. After an additional 5 days of growth, nanoparticulate S80was detected in the cultivation medium, a result of the hydrolysis of polysulfides in acidic medium. To examine whether soluble polysulfides and/or nanoparticulate S80can serve as terminal electron acceptors (TEA) supporting the growth ofA. sulfurireducens, total sulfide concentration and cell density were monitored in batch cultures with S80provided as a solid phase in the medium or with S80sequestered in dialysis tubing. The rates of sulfide production in 7-day-old cultures with S80sequestered in dialysis tubing with pore sizes of 12 to 14 kDa and 6 to 8 kDa were 55% and 22%, respectively, of that of cultures with S80provided as a solid phase in the medium. These results indicate that the TEA existed in a range of particle sizes that affected its ability to diffuse through dialysis tubing of different pore sizes. Dynamic light scattering revealed that S80particles generated through polysulfide rapidly grew in size, a rate which was influenced by the pH of the medium and the presence of organic carbon. Thus, S80particles formed through abiological hydrolysis of polysulfide under acidic conditions appeared to serve as a growth-promoting TEA forA. sulfurireducens.

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Formation mechanism of fine anatase crystals from amorphous titania under hydrothermal conditions

Journal of Materials Research ◽

10.1557/jmr.1998.0106 ◽

1998 ◽

Vol 13 (4) ◽

pp. 825-829 ◽

Cited By ~ 69

Author(s):

Kazumichi Yanagisawa ◽

Yuichi Yamamoto ◽

Qi Feng ◽

Nakamichi Yamasaki

Keyword(s):

Growth Rate ◽

Solid State ◽

Epitaxial Growth ◽

Deposition Process ◽

Hydrothermal Conditions ◽

Slow Growth Rate ◽

Amorphous Titania ◽

Two Stages ◽

Short Time ◽

Hydrolysis Of

Crystallization of amorphous titania prepared by hydrolysis of ethoxide was accelerated even by a small amount of water in the vapor phase. The existence of water promoted the change of localized structure of the amorphous titania to anatase structure, which resulted in acceleration of anatase nucleation. The anatase crystals grew in steam by solid-state epitaxial growth, but stopped growing in a short time. The growth of anatase crystals under hydrothermal conditions could be divided into the following two stages: the first stage with fast growth rate by the solid-state epitaxial growth and the second stage with slow growth rate by the dissolution and deposition process.

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