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

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

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

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

Hydrothermal and mechanochemical synthesis of crystalline CaCO

Mechanochemical and microwave-assisted hydrothermal (MicroWave Treatment [MWT]) procedures were applied to prepare crystalline CaCO 3 . Mechanochemical process was carried out at different speeds of rotation (500 or 850 rpm/min), different duration times (30 or 60 min) and in the aqueous suspensions or in dry state. MWT synthesis was conducted in a saturated water vapour or under the layer of water. The crystalline and porous structures of the prepared samples as well as their morphology were investigated using N 2 adsorption, X-ray diffraction and scanning electron microscopy methods. As a result, the calcium carbonate samples in the form of calcite were obtained. The materials prepared by the mechanochemical route performed in the aqueous suspension are characterized by smaller crystallite sizes as compared to those obtained without the addition of water. The samples obtained hydrothermally have the largest size of crystallites. Powders prepared by energetical milling possess higher values of specific surface area in relation to the parameter for those synthesized hydrothermally. In the process of hydrothermal treatment, macroporous structure of the prepared materials is created. With the increasing specific surface area of the sample, the size of the crystallites decreased

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

On the utility of Transcarpathian Clinoptylolite in the adsorption of chloroform from aqueous solutions

The objective of the study was to determine the sorbing capacity of the transcarpathian clinophylolite ( Ukraine ) when applied to chloroform separation from aqueous solutions. Analyses and measurements included the chemical parameters and porosity of the mineral, as well as the effect of processing temperature, grain size distribution and pH ( of the agueous solution ) on the sorbing properties with respect to water and chloroform.The efficiency of chloroform sorption from the agueous solution ranged from 97 to 99%.This is an indication that the clinoptylolite has a great potential for being effectively used as a sorbend in the concentration of chloroform occuring in agueous solutions.The properties of the clinoptylolite make it applicable not only to analytical procedures,but also to water treatment