scholarly journals Green Synthesis of Hydrocalumite (CaAl-OH-LDH) from Ca(OH)2 and Al(OH)3 and the Parameters That Influence Its Formation and Speciation

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 672 ◽  
Author(s):  
Bianca R. Gevers ◽  
Frederick J.W.J. Labuschagné

Hydrocalumite is a layered double hydroxide (LDH) that is finding increased application in numerous scientific fields. Typically, this material is produced through environmentally polluting methods such as co-precipitation, sol-gel synthesis and urea-hydrolysis. Here, the hydrothermal green (environmentally friendly) synthesis of hydrocalumite (CaAl-OH) from Ca(OH)2 and Al(OH)3 in water and the parameters that influence its formation are discussed. The parameters investigated include the reaction temperature, reaction time, molar calcium-to-aluminium ratio, the morphology/crystallinity of reactants used, mixing and the water-to-solids ratio. Hydrocalumite formation was favoured in all experiments, making up between approximately 50% and 85% of the final crystalline phases obtained. Factors that were found to encourage higher hydrocalumite purity include a low water-to-solids ratio, an increase in the reaction time, sufficient mixing, the use of amorphous Al(OH)3 with a high surface area, reaction at an adequate temperature and, most surprisingly, the use of a calcium-to-aluminium ratio that stoichiometrically favours katoite formation. X-ray diffraction (XRD) and Rietveld refinement were used to determine the composition and crystal structures of the materials formed. Scanning electron microscopy (SEM) was used to determine morphological differences and Fourier-transform infrared analysis with attenuated total reflectance (FTIR-ATR) was used to identify possible carbonate contamination, inter alia. While the synthesis was conducted in an inert environment, some carbonate contamination could not be avoided. A thorough discussion on the topic of carbonate contamination in the hydrothermal synthesis of hydrocalumite was given, and the route to improved conversion as well as the possible reaction pathway were discussed.

2008 ◽  
Vol 14 (20) ◽  
pp. 6205-6212 ◽  
Author(s):  
Damien Dambournet ◽  
Gehan Eltanamy ◽  
Alexandre Vimont ◽  
Jean-Claude Lavalley ◽  
Jean-Michel Goupil ◽  
...  

2017 ◽  
Vol 1 (8) ◽  
pp. 1662-1667 ◽  
Author(s):  
Felix Rechberger ◽  
Gabriele Ilari ◽  
Christoph Willa ◽  
Elena Tervoort ◽  
Markus Niederberger

We present the nonaqueous sol–gel synthesis of crystalline SrTi1−xCrxO3 (x = 0, 0.3, 2, 5, 10%) nanoparticles and their processing into highly concentrated dispersions in ethanol by surface functionalization with 2-[2-(2-methoxyethoxy) ethoxy] acetic acid (MEEAA).


Catalysts ◽  
2017 ◽  
Vol 7 (12) ◽  
pp. 376 ◽  
Author(s):  
Liang Jiang ◽  
Yizhou Li ◽  
Haiyan Yang ◽  
Yepeng Yang ◽  
Jun Liu ◽  
...  

2005 ◽  
Vol 888 ◽  
Author(s):  
Chunhua Yao ◽  
Xipeng Liu ◽  
William M. Risen

ABSTRACTSmart composites based on ferromagnetic hybrid aerogels have been prepared. These novel materials change chemistry in response to light to form nanoparticles that react with compounds that are present in the environment of the aerogels. Thus, high surface area silica/functional polymer hybrid aerogels have been formed via sol-gel synthesis. They also can contain coordinated metal-ion species. They are reacted with Fe-precursors to form air stable ferromagnetic aerogels, which they are transformed into active particles themselves or by incorporation of additional metal ions. These active materials, which adhere to tissue, can be positioned magnetically within their environment. Once they are positioned, they can be transformed by UV light to form Au(0) nanoparticles which react with the molecules in their environment. The preparation and properties of these aerogels, their photochemistry and reaction with bio-molecules will be presented.


Author(s):  
Venkatachalam Chokkalingam ◽  
Boris Weidenhof ◽  
Wilhelm F. Maier ◽  
Stephan Herminghaus ◽  
Ralf Seemann

Droplet based microfluidics is used to perform sol-gel reactions. The chemicals are dispensed, mixed, and pre-processed inside a microfluidic device allowing for long operation times without any clogging. Using this approach and optimizing all reaction and processing parameters we generate mesoporous silica particles with a very high surface area of 820 m2g−1 and a narrow pore radius distribution of around 2.4 nm. To take full advantage of the possibilities offered by this microfluidic synthesis route, we produced platinum supported silica microspheres (as high as 7 mol. %) for heterogeneous catalysis.


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