amorphous silica
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Nano Express ◽  
2022 ◽  
Shun-ichi Eto ◽  
Kazuma Higashisaka ◽  
Aoi Koshida ◽  
Kenta Sato ◽  
Mao Ogura ◽  

Abstract Due to their innovative functions, the use of nanoparticles in various industries has been expanding. However, a key concern is whether nanoparticles induce unexpected biological effects. Although many studies have focused on innate immunity, information on whether nanoparticles induce biological responses through effects on acquired immunity is sparse. Here, to assess the effects of amorphous silica nanoparticles on acquired immunity, we analyzed changes in acute toxicities after pretreatment with amorphous silica nanoparticles (50 nm in diameter; nSP50). Pretreatment with nSP50 biochemically and pathologically exacerbated nSP50-induced hepatic damage in immunocompetent mice. However, pretreatment with nSP50 did not exacerbate hepatic damage in immunodeficient mice. Consistent with this, the depletion of CD8+ cells with an anti-CD8 antibody in animals pretreated with nSP50 resulted in lower plasma levels of hepatic injury markers such as ALT and AST after an intravenous administration than treatment with an isotype-matched control antibody. Finally, stimulation of splenocytes promoted the release of IFN-γ in nSP50-pretreated mice regardless of the stimulator used. Moreover, the blockade of IFN-γ decreased plasma levels of ALT and AST levels in nSP50-pretreated mice. Collectively, these data show that nSP50-induced acquired immunity leads to exacerbation of hepatic damage through the activation of cytotoxic T lymphocytes.

2021 ◽  
Vol 21 (2) ◽  
pp. 170
Thet Mya Mya Sein ◽  
Ei Mon Aung

In this paper, Erianthus plant, a grass type of lignocellulosic biomass, is presented as an alternative source for the production of amorphous silica. Thermal treatment (combustion) of Erianthus plant under a controlled temperature of 600–900°C produces Erianthus Ash (EA). Then, silica powder was extracted from EA by the chemical extraction method. In this work, the effect of treatment temperature on the preparation of EA and extracted silica is studied. The EA samples and extracted silica are noted as EA600 – EA900 and Si600 – Si900 respectively with respect to the treatment temperature. To evaluate the effect of the concentration of NaOH solution on the purity of silica, NaOH solution (2–3 N) is verified in this work. The results revealed that the pure amorphous silica can be extracted using a 2.5 N NaOH solution from EA800. The percentage of amorphous silica with a purity of about 99% was confirmed by X-Ray Fluorescence (XRF).

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 7
Uyangaa Udaanjargal ◽  
Noriko Hasebe ◽  
Davaadorj Davaasuren ◽  
Keisuke Fukushi ◽  
Yukiya Tanaka ◽  

To understand how the climate system works in the continental interior, sediment cores that are approximately 30-cm long were taken from Olgoy, Boontsagaan, and Orog lakes, Mongolia. These cores were analyzed and compared with meteorological data (air temperature, precipitation, and wind) from climate stations in the study area. Comparison of metrological data from four stations shows similar climate fluctuations. When the temperature was high, less precipitation occurred in general. The sedimentary features measured in this study were water content, organic matter, carbonate, amorphous silica contents, whole and mineral grain size, and grain density. Excess 210Pb measurements were used to estimate sedimentary ages. According to principal component analysis (PCA), temperature correlates well to sediment characteristics in Olgoy Lake. Whole and mineral grain sizes are coarser when the temperature is high, while the amorphous-silica concentration is lower. A coarse grain size is interpreted to reflect low lake levels due to evaporation under high temperature with less precipitation. Amorphous silica may be from surrounding plants and reflects less vegetation when the temperature is high. However, in the recent 30 years, after the social system changed and overgrazing became a problem, the amount of amorphous silica has positively correlated with temperature on a short time scale. In the past 30 years, with less vegetation, amorphous silica has mainly come from weathered mineral particles. High temperature caused a thick, weathered mantle for each mineral particle, resulting in high amorphous-silica concentration. In Boontsagaan Lake, whole and mineral grain sizes are coarser when the wind speed is increased. Low precipitation correlates with a decrease in organic matter and an increase in carbonate and amorphous silica. In Orog Lake, it is difficult to establish an age model due to dried-up events. Some fluctuations in sedimentary characteristics may correspond to extreme events, such as earthquakes, and natural hazards, such as dzuds (harsh winters).

Ирина Сергеевна Медянкина ◽  
Владимир Михайлович Скачков ◽  
Лилия Александровна Пасечник

Предложен способ получения высокодисперсного аморфного кремнезема из отходов обогащения низкотитанистых ванадий содержащих титаномагнетитов АО «ЕВРАЗ Качканарский ГОК» - хвостов мокрой магнитной сепарации. Применение раствора гидрофторида аммония ( NHHF) позволяет практически селективно извлечь кремний в раствор в виде гексафторосиликата аммония. Степень извлечения кремния раствором 1,0 - 2,5 мас.% NHHF за 6 часов составляет 46%. Диффузионный процесс выщелачивания кремния из ХММС описывается кинетическим уравнением 1 -(1 -а) = 0,0043• exp(-5230/RT)-г . Аморфный кремнезем SiO, полученный золь- гель методом из фторидного кремнийсодержащего раствора, имеет высокоразвитую поверхность S = 320 м/г, рассчитанный из средней плотности «белой сажи» размер частиц составляет d = 10 нм. Увеличение концентрации NHHF до 20 мас.% приводит к повышению растворимости кремния, а также других компонентов хвостов мокрой магнитной сепарации, которые являются нежелательными примесями в конечном продукте SiO. В целом показана перспективность гидрохимического выщелачивания кремнийсодержащих промышленных отходов - хвостов мокрой магнитной сепарации слабыми растворами гидрофторида аммония для синтеза чистого аморфного SiO. A method for producing amorphous silica from the enrichment wastes of low-titanium vanadium containing titanomagnetites of JSC «EVRAZ ZSMK» - wet magnetic separation tailings is proposed. The use of a NHHF solution makes it possible to practically selectively extract silicon into the solution in the form of ammonium hexafluorosilicate. The extraction of silicon with 1,0 - 2,5 wt.% NHHF solution for 6 hours reached 46%. The diffusion process of the silicon extraction is described by the kinetic equation 1 - (1 - a) = 0,0043 • exp(-5230 / RT)• t . Amorphous silica obtained by the sol-gel method from a fluoride silicon-containing solution has a highly developed surface 320 m/g, the particle size calculated from the average density of «white carbon black» is of 10 nm. The increase in concentration to 20 wt. % NHHF leads to the rise of the silicon solubility and of other tailings components, which are unwanted impurities in the final product. In general, it is shown that the hydrochemical leaching of silicon-containing industrial waste - tailings with weak solutions of ammonium hydrofluoride is promising for the synthesis of pure amorphous silica.

2021 ◽  
Yinan Xu ◽  
Nicole LiBretto ◽  
Guanghui Zhang ◽  
Jeffrey Miller ◽  
Jeffrey Greeley

Amorphous, single site, silica-supported main group metal catalysts have recently been found to promote olefin oligomerization with high activity at moderate temperatures and pressures (~250°C and 1 atm). Herein, we explore the molecular-level relationship between active site structures and the associated oligomerization mechanisms by developing amorphous, silica-supported Ga3+ models from periodic, first-principles calculations. Representative Ga3+ sites, including three- and four-coordinated geometries, are tested for multiple ethylene oligomerization pathways. We show that the three-coordinated Ga3+ site promotes oligomerization through a facile initiation process that generates a Ga-alkyl intermediate, followed by a Ga-alkyl-centered Cossee-Arlman mechanism. The strained geometry of a three-coordinated site enables a favorable free energy landscape with a kinetically accessible ethylene insertion transition state (1.7 eV) and a previously unreported β-hydride transfer step (1.0 eV) to terminate further C-C bond formation. This result, in turn, suggests that Ga3+ does not favor polymerization chemistry, while microkinetic modeling confirms that ethylene insertion is the rate-determining step. The study demonstrates promising flexibility of main group ions for hydrocarbon transformations and, more generally, highlights the importance of the local geometry of metal ions on amorphous oxides in determining catalytic properties.

ACS Omega ◽  
2021 ◽  
Cheng Li ◽  
Xiaoqing Wang ◽  
Anjie Yang ◽  
Peng Chen ◽  
Tianxiang Zhao ◽  

2021 ◽  
Vol 12 (2-2021) ◽  
pp. 253-260
O. A. Timoshchik ◽  
E. A. Shchelokova ◽  
A. G. Kasikov ◽  
M. V. Bryukhanova ◽  

The sorption of vanadium (V) and nickel (II) from aqueous solutions on amorphous silica obtained from metallurgical slags of the Kola MMC is considered, and the optimal conditions for the metal sorption process are determined. It is established that the maximum sorption of metals is achieved at pH 2.0–4.0, at a temperature of 40 °C and a process time of 60 minutes for nickel and 90 minutes for vanadium.

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