Mechanochemical, Sonochemical and Hydrothermal Activation of Niobium Pentoxide and its Catalytic Properties

Modification of niobium pentoxide with different dispersity via mechanochemical, ultrasound, hydrothermal and microwave treatments (MChT, UST, HTT, and MWT, respectively) has been studied. All types of treatment do not change of phase composition but leads to improvement (at HTT and MWT) or, on contrary, breaking of crystal structure (at MChT and UST) and variation of crystallite size and specific surface area. UV-Vis measurements display increase of absorption in visible region. As a result, modified samples show higher photocatalytic activity at degradation of rhodamine B under visible irradiation. Similarly, initial and modified Nb2O5 samples are catalysts for mechanochtmical and sonochemical destruction of the same dye. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3515

Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas

Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM-41 type and bimodal porous materials was studied

Synthesis and Photocatalytic Properties of Silver Niobate

The interaction between silver nitrate and niobium pentoxide has been studied under conventional thermal treatment (TT) as well as mechanochemical and sonochemical treatment (MChT and UST, respec-tively). The products of reaction have been investigated using XRD, DTA-TG, Raman spectroscopy, adsorp-tion of nitrogen. MChT and UST promote lowering the temperature of silver niobate (SN) formation. The formed SN possesses higher specific surface area and photocatalytic activity. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3527

High-pressure cryogelation of nanosilica and surface properties of cryosilicas

Silica cryogels (cryosilicas) in a powder state were synthesized with different concentrations of fumed silica A-300 (CA-300 = 5-20 wt.%), sonicated in aqueous suspension, then frozen at -14 oC at different pressures in a high-pressure stainless steel reactor (a freezing bomb), and dried in air at room temperature. To analyze the effects of low temperature and high pressure, samples were also prepared at -14 oC or room temperature and standard pressure. The structural and adsorption properties of the powder materials were studied using nitrogen adsorption, high-resolution transmission electron microscopy, infrared spectroscopy, thermogravimetry, low-temperature 1H NMR spectroscopy and thermally stimulated depolarization current. The structural, textural, adsorption and relaxation characteristics of high-pressure cryogel hydrogels and related dried powders are strongly dependent on the silica content in aqueous suspensions frozen at 1, 450 or 1000 atmospheres and then dried. The largest changes are found with CA-300 = 20 wt.% which are analyzed with respect to the interfacial behavior of nonpolar, weakly polar and polar adsorbates using low temperature 1H NMR spectroscopy

Модифікування та дослідження властивостей оксиду та оксигідроксиду олова (IV)

Чотири серії зразків оксиду та оксигідроксиду олова (IV) було модифіковано за допомогою меха- нохімічної та мікрохвильової обробки. Досліджено фізико-хімічні властивості всіх зразків за допо- могою рентгенофазового аналізу, диференційного термічного аналізу, методів дослідження порува- тої структури, електронної (UV-Vis) спектроскопії. Фотокаталітичні властивості дослідних зраз- ків вивчалися в реакціях фотодеструкції водних розчинів барвників (Cафранін Т, Родамін Б) при опроміненні у видимій області. Дослідження показали, що після проведення механохімічної обробки перших трьох серій зразків в атмосфері повітря питома поверхня знижується, а у воді залишаєть- ся майже незмінною. У результаті мікрохвильової обробки питома поверхня зростає, спостеріга- ється упорядкування кристалічної структури. В усіх випадках формується мезо-макропорувата структура. Усі зразки показали високу фото- каталітичну активність при фотодеструкції Родаміну Б та Сафраніну Т.Four series of tin (IV) oxide and oxo-hydroxide samples were modified by using microwave and mechanochemical treatments. Physical-chemical properties of all samples were studied by using the following techniques: XRD, differential thermal analysis, nitrogen adsorption-desorption, UV-Vis spectroscopy. The estimation of photocatalytic activity under visible irradiation was carried out by using degradation of textile dyes (safranin T, rhodamine B) in aqueous medium. Investigations have shown that a specific surface area decreases as a result of mechanochemical treatment of samples of the first three series in air, and remains almost unchanged after milling in water. The specific surface area increases and the crystal structure of the latter are improved as a result of microwave treatment. Meso-macroporous structure is formed in all cases. All samples showed high photocatalytic activity in the degradation of rhodamine B and safranin T

Ocena chemicznej degradacji wybranych właściwości gleb pod wpływem miedzi, cynku i wodoru

The concept of this study was based on the evaluation of the impact of copper (Cu), zinc (Zn) and hydrogen protons (H+) on selected chemical characteristics of two arabie soils: light loamy sand (No. 1) and silty soil (No. 2). The targeted chemical alterations of the soils concerned pH changes, water soluble forms of Cu and Zn and displaced alkaline cations as induced by Cu, Zn and H incorporation. Preliminarily, the amounts of exchangeable alkaline cations (ExAC = Ca + Mg + K + Na) were extracted by using l M CH3COONH4, pH 7.0 and these amounts were used for calculating amounts of Cu, Zn and H to be incorporated as follows: copper as CuSO4 o 5H2O, zinc as ZnSO4 o 7H2O and hydrogen in the form of HCl at spiking rates corresponding to 0, 5, 10, 30, 60, 100, 150, 200, 300, 400, 500 and 1000 % of ExAC. Treatments were incubated for 16 weeks at 18 Celsjus degree and kept at 75-85 % WHC (water holding capacity). Copper, zinc and hydrogen effects on soil chemical properties can be first observed throughout pH changes, which were more pronounced for H treatments as compared with Cu and Zn ones. The amounts of water extractable Ca (ie displaced) at Cu and Zn spiking rates of 1000 % ExAC are 25 and 21 times higher, respectively, for the soil No. l (light loamy sand), whereas for the soil No. 2 (silty soil), 44 and 38 times higher, as compared with the control treatment. The impact of H is intermediate and represents 24 and 35 times, for the soils No. l and No. 2, respectively. Results reported in the paper drive specific attention on the destructive effects of Cu, Zn and H, separately. The joint impact of these metals along with protons is the córę of agroenvirontnental concem. The chemical degradation established on the basis of water extractable alkaline cations (WEAC) follows the range: H > Cu > Zn.Koncepcja przedstawionych badań dotyczy oceny oddziaływania miedzi (Cu), cynku (Zn) i protonów (jonów wodorowych H+) na wybrane właściwości chemiczne dwóch gleb uprawnych: piaskugliniastego lekkiego (gleba Nr 1) i iłu pylastego (gleba Nr 2). Badane zmiany dotyczyły pH, wodorozpuszczalnych form Cu, Zn oraz kationów alkalicznych wypartych z koloidów glebowych pod wpywem wniesienia do obu gleb jonów Cu, Zn i H. Wymienne kationy alkaliczne (ExAC = Ca + Mg + K + Na] ekstrahowano uprzednio przy użyciu roztworu 1 M CH3COONH4 przy pH 7.0, a uzyskane dane służyły do obliczenia ilości Cu, Zn i H do wniesienia do gleb w postaci: miedź jako CuS0-4 o 5H2O, cynk - ZnSO4 o 7H2O i wodór w formie HCl. Dawki tych jonów odpowiadaty O, 5, 10, 30, 60, 100, 150, 200, 300, 400, 500 i 1000 % ExAC. Obiekty inkubowano przez 16 tygodni w temperaturze 18 °C oraz 75-85 % PPW (Polowej Pojemności Wodnej). Oddziaływania jonów Cu, Zn i H na chemiczne właściwości gleb ujawniły się najpierw poprzez zmiany odczynu, które były znaczące dla obiektów z jonem wodoru w porównaniu z obiektami z Cu i Zn. Wodnorozpuszczalne ilości Ca (tzn. wyparte) przy dawkach Cu i Zn wynoszących 1000 % ExAC są odpowiednio 25 i 21 razy większe dla gleby Nr 1 (piasku gliniastym lekkim), podczas gdy dla gleby Nr 2 (iłu pylastego), odpowiednio 44 i 38 w porównaniu z obiektem kontrolnym. Oddziaływanie jest natomiast pośrednie, czyli 24 i 35 większe, odpowiednio dla gleby Nr 1 i Nr 2. Wyniki przedstawione w pracy zwracają szczególną uwagę na destrukcyjne działania jonów Cu, Zn i H stosowanych oddzielinie. Łączne oddziaływanie obu metali wraz z protonami wywołuje negatywne skutki w ekosystemach poddanych antropopresji. Szereg degradacji chemicznej oparty na ilościach wodnorozpuszczalnych kationów licznych (WEAC) kształtował się następująco: H > Cu > Zn

Dyes catalytic degradation using modified tin(IV) oxide and hydroxide powders

Mechanochemical modification of low-dispersed SnO 2 and high-dispersed SnO(OH) 2 powders with specific surface area 6 and 198 m 2  g −1 have been studied. The crystal, porous, and electronic structure of obtained products, as well as their photocatalytic activity under visible light in the process of dyes degradation has been investigated. It has been established that high-dispersed powder is porous and poorly crystalline. Its specific surface area decreases after milling. On the contrary, low-dispersed powder is almost nonporous and well crystallized. Its specific surface area increases but degree of crystallinity reduces as a result of milling. Milling of both powders in water leads to formation of meso-macroporous structure. The narrowing of band gap and increase of adsorption of visible light occur after modification of low-dispersed sample. As a result, photocatalytic activity of milled powders under visible irradiation significantly increases. Maximal activity showed high-dispersed sample milled in air and water

Solid phase extraction of explosives on Ni-doped carbosils prepared by mechanochemistry

The article presents the application of two sets of Ni-doped carbosils in the solid phase extraction of explosives. The adsorbents were prepared by two different methods. The first set of carbosils was obtained by mechanochemical deposition of potato starch and nickel salt on the surface of silica gel, and subsequent carbonization. The second set of carbosils was obtained from the same precursors and under quite similar conditions, i.e. with the exception of mechanochemical deposition of potato starch replaced by the gelation step. The prepared adsorbents were applied in solid phase extraction of explosive nitrate esters, and nitroaromatics from aqueous solutions. The adsorption and desorption steps were evaluated separately. It was found that textural properties, influenced by carbon deposit and nickel content, have a large impact on the solid phase extraction results. The recovery rates obtained onto carbosils prepared by mechanochemical method are approximately thrice as high as those observed for carbosils prepared by gelation method. It was shown that the composites with moderate nickel content can be used as effective materials for extraction both of aliphatic and aromatic explosives

Thermal and calorimetric investigations of titania–silica composites

The paper presents the studies of effects of TiO 2 amount differentiation on the structural and thermal properties of titania–silica complex oxides prepared by chemical vapor deposition of TiCL 4 onto the Si-40, Si-60, and Si-100 silica gels. The mesoporous materials, characterized by a varied pore structure with highly developed surface and large pore volume, were obtained. The porous structure of materials under investigations was characterized by the low-temperature nitrogen adsorption–desorption method as well as by power spectral density calculated from the calorimetric investigations of water confined in the pores. Moreover, the thermodesorption of water using the quasi-isothermal thermogravimetry was used to characterize their thermal and surface properties. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent–water interfaces were calculated. It was stated that the increase of titania content causes a gradual decrease of specific surface area and has a significant effect on the porous structure formation. The water thermodesorption from the surface proceeds in few stages because of the porosity created by TiO 2 . The decrease in the total surface free energy (Δ G Σ ) can be observed with the increasing TiO 2 content. The largest Δ G Σ value at the adsorbent/strongly bound water interface is exhibited by the adsorbents of Si-100 series. The lowering of the freezing/melting points of water contained in the pores of the studied materials is strongly connected with their porous structure