Preparation and characterization of monolithic alumina aerogels

Zu, Guoqing; Shen, Jun; Wei, Xiaojie; Ni, Xingyuan; Zhang, Zhihua; Wang, Jichao; Liu, Guangwu

doi:10.1016/j.jnoncrysol.2011.03.031

Cited by 164 publications

(87 citation statements)

References 24 publications

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“…The bands for -OH and H-O-H bonds were not observed at all for the α-Al 2 O 3 surface before any reactions (curve c 1 ). The bands of low wavenumbers of 759,630,652,617,554, and 465 cm −1 observed in the γ-Al 2 O 3 and α-Al 2 O 3 samples are attributed to a pseudoboehmite structure (Ren et al 2004;Zu et al 2011). After contact with propachlor, the observed spectra for γ-AlOOH (curve a 2 ) and γ-Al 2 O 3 (curve b 2 ) surfaces are nearly identical to their original states before any potential reactions occurred, except a small increase in band intensities.…”

Section: Fourier Transform Infrared Spectroscopymentioning

confidence: 92%

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

et al. 2012

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Purpose The aim of this study was to evaluate the roles of aluminum-based minerals, especially their surface Lewis acid sites (LASs), on the transformation and fate of chloroacetanilide herbicide contaminants when nucleophilic reagents are present. Materials and methods Batch experiments were used to study propachlor transformation processes under different reaction conditions. The surface bonding of aluminas before and after interacting with propachlor and dithionite were characterized by Fourier transform infrared (FTIR) spectra. The LASs on different aluminas, acting as the key role for accelerating the propachlor transformation, were analyzed by pyridine adsorption/FTIR spectroscopic technique. Results and discussion Rates of dithionite-initiated propachlor dechlorination were increased in the presence of aluminas. Transformation efficiencies of propachlor on different aluminas were found to be as γ-Al 2 O 3 >γ-AlOOH>α-Al 2 O 3 . A higher reaction temperature, higher pH, and higher alumina dosage can further increase the propachlor dechlorination rate.The addition of citric acid may block the active sites on alumina and reduce propachlor transformation by dithionite. FTIR and pyridine adsorption/diffuse reflectance Fourier transform infrared spectroscopy indicated that Al-S and Al-O bonds on the LASs of alumna play a key role in accelerating propachlor transformation. Conclusions LASs on alumina surfaces can effectively accelerate the propachlor transformation by dithionite. The strong electron accepting ability of LASs gives dithionite a favorable affinity to form surface sulfur compounds, which are stronger reductants and nucleophilic reagents for propachlor dechlorination. The intensities of LASs on alumina surfaces can be used to control the rate of propachlor transformation by dithionite.

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Section: Fourier Transform Infrared Spectroscopymentioning

confidence: 92%

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

et al. 2012

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“…For the film dried at the ambient temperature, three strong absorption bands-at 1,070, 620 and 482 cm -1 -are visible. This set of bands is typical for the structure of boehmite AlO(OH) [19]. Such structure is maintained for the coatings annealed at 300°C.…”

Section: Al 2 O 3 Filmsmentioning

confidence: 57%

Plasma enhanced aerosol–gel method: a new way of preparing ceramic coatings

Pietrzyk

Miszczak

Szymanowski

et al. 2013

J Sol-Gel Sci Technol

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The sol-gel process is widely used for the production of powders, coatings and bulk materials. However, being a wet-chemical technique, it has certain limitations related to properties of aqueous colloidal solution, especially when applied as a coating. The most frequently used methods, such as dip-and spin-coating, are difficult to apply onto more complex substrates. In these cases, the aerosol-gel deposition method can be regarded as the solution of this problem. In the present article, a novel plasma enhanced aerosol-gel method of coatings production is presented. A novelty of this method is based on an integration of the aerosol-gel deposition of thin films and their low temperature plasma treatment. Owing to the above, all stages of the coatings production processsubstrate preparation, film deposition, and its plasma treatment, can be carried out in a single reactor. The design and operational scheme of such device is presented in this work. Using this device, thin coatings were first deposited on substrates and then plasma treated. The effect of deposition and plasma discharge conditions on morphology and chemical structure of the films has been studied. It was found that plasma treatment had a substantial influence on all the examined properties of the aerosol-gel deposited coatings.

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“…Meanwhile, for a-Al 2 O 3 sample before any reactions (curve c 1 ), the abovementioned bands were not completely detected, which indicate no H-O-H and -OH bonds on the a-Al 2 O 3 surface before hydration. For the stretching vibration of bands at low wave numbers on g-Al 2 O 3 and a-Al 2 O 3 , i.e., the bands at 766, 656, 620, 615, 603, 562, 553, and 465 cm À1 , they are all attributed to the pseudoboehmite stretching [34,35]. After reacting with metolachlor, almost no changes were found for all the bands in the spectra for g-AlOOH (curve a 2 ) and g-Al 2 O 3 (curve b 2 ) except for the increase in very small intensities.…”

Section: Metolachlor Transformation Under Different Phmentioning

confidence: 99%

Heterogeneous Nucleophilic Transformation of Metolachlor by Bisulfide on Alumina Surface

Wei

Liu

et al. 2013

CLEAN Soil Air Water

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The present research elucidates the accelerating effect of alumina minerals on metolachlor transformation using sulfur nucleophiles and also determines the metolachlor transformation mechanisms in the heterogeneous reaction systems. Metolachlor transformation was first systematically investigated under different conditions. Then, the Fourier transform infrared (FTIR) spectra were used to characterize the changes in the surface bonds of the aluminas. The transformation products were qualitatively identified using LC/MS. The results showed that bisulfide can produce efficient metolachlor transformation rates, and the presence of the aluminas can further accelerate the transformation by achieving complete transformation in <21 days. In addition, a higher pH and higher bisulfide concentration are more favorable for metolachlor transformation. When normalized to the surface area, the metolachlor transformation rates were found to follow the order of a-Al 2 O 3 >g-AlOOH>g-Al 2 O 3 in the presence of different aluminas. FTIR results indicated that the enhancement of metolachlor transformation rates by bisulfide with aluminas can be attributed to the surface active nucleophiles on alumina surfaces formed through Al-S and Al-O bonds. The substitution of chlorine on the metolachlor followed the S N 2 mechanism by bisulfide with accelerated rate through mediating the heterogeneous reactions with aluminas.

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Preparation and characterization of monolithic alumina aerogels

Cited by 164 publications

References 24 publications

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

Dechlorinating transformation of propachlor through nucleophilic substitution by dithionite on the surface of alumina

Plasma enhanced aerosol–gel method: a new way of preparing ceramic coatings

Heterogeneous Nucleophilic Transformation of Metolachlor by Bisulfide on Alumina Surface

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