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Kozlova S.A.,RAS Institute of Chemistry and Chemical Technology | Kirik S.D.,Siberian Federal University
Microporous and Mesoporous Materials | Year: 2010

The influence of different types of post-synthetic treatment (exposure at calcination, at boiling treatment in neutral, acidic and alkaline aqueous solutions, treatment in hydrofluoric acid) on the state of the silanol surface of the mesostructured mesoporous silicate materials MCM-41 and SBA-15 has been studied. The material alteration has been monitored by X-ray diffraction, IR-spectroscopy, thermal analysis and nitrogen adsorption. It has been shown that post-synthetic treatment changes the concentration of silanol groups on the material surface. The limit value has been established by experiment: about 3-4 OH/nm 2 for MCM-41 and 5-6 OH/nm 2 for SBA-15, with its excess resulting in the material destruction. The distribution of the re-formed Si-OH groups over the surface is of irregular focal nature. In spite of the destruction, the specific characteristics of the material (inner surface, volume, and lattice parameter) remain the same. The treatment type and medium content influence the material destruction rate, but not the limit density of the silanol covering. Based on the molecular model of MCM-41 and percolation theory an interpretation has been proposed due to the mechanism of fragmentary material decay. Fragments of the surface with the concentration of the OH-groups exceeding the limit eliminate from material because the concentration of OH-groups is correlated with concentrations of the broken silaxane bonds (Si-O-Si), which responsible for the surface connectivity. © 2010 Elsevier Inc. All rights reserved.

Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology
Acta Crystallographica Section B: Structural Science | Year: 2012

A revision is presented of the restrained Rietveld analysis of the crystal structure of magnesium perchlorate tetrahydrate, Mg(ClO 4) 2·4H 2O, recently published by Robertson & Bish [(2010), Acta Cryst. B66, 579-584]. The actual symmetry of the material is shown to be C2/m. The corrected structure model is refined by the derivative difference method [Solovyov (2004). J. Appl. Cryst. 37, 743-749], anisotropically for all non-H atoms and isotropically for two independent H atoms without restraints. © 2012 International Union of Crystallography Printed in Singapore - all rights reserved.

Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology
Chemical Society Reviews | Year: 2013

Ordered mesostructured mesoporous materials, combining nano-organization with atomic disorder, are both attractive and challenging objects of investigation by X-ray and neutron diffraction. The development of diffraction mesostructure analysis methods and their applications in studies on structural characterization, formation processes and physisorption phenomena in these advanced materials are summarized in this tutorial review. The focus here is on the techniques that allow extracting mesostructure parameters and peculiarities of density distribution in the materials from the Bragg reflection positions and intensities. The investigations of mesoporous silicates, their nonsilica replicas and composites are discussed including the combined use of diffraction with electron microscopy and physisorption. The small-angle scattering curve analysis, which is also an important methodology in the field, is out of the scope of this review. © The Royal Society of Chemistry 2013.

Grigorieva N.A.,RAS Institute of Chemistry and Chemical Technology | Fleitlikh I.Y.,RAS Institute of Chemistry and Chemical Technology
Hydrometallurgy | Year: 2013

The paper presents data on cobalt extraction from sulfate solutions with bis(2,4,4-trimethylpentyl)dithiophosphinic acid (HR) diluted with nonane and kerosene in the presence of electron donor additives (L). Trioctyl amine (TOA), trialkyl amine (TAA), trioctyl phosphine oxide (TOPO), trialkyl phosphine oxide (TAPO), tributyl phosphate (TBP), and n-octanol were used as additives. Using an electronic spectroscopy method, the interaction between cobalt loaded extracts (CoR2) and the additives was first studied. It was shown that, in the presence of the additives, cobalt oxidation decreased in the series TOA ≈ TOPO > TBP > n-octanol. This is due to a decrease in the HR activity in the presence of L as well as to the interaction between L and the initial cobalt complex resulting in the formation of mixed ligand complexes such as CoR 2â̂™ nL, where n = 1,2. Suggestions for prevention of cobalt oxidation in the organic phase containing bis(2,4,4-trimethylpentyl) dithiophosphinic acid are given. The degree of cobalt extraction decreases in the series HR + TOPO > HR ≈ HR + n-octanol ≠© 2013 Published by Elsevier B.V.

Kuz'Min V.I.,RAS Institute of Chemistry and Chemical Technology | Kuz'Min D.V.,RAS Institute of Chemistry and Chemical Technology
Hydrometallurgy | Year: 2014

Investigations into an assessment of the efficiency of the sorption of copper and nickel, from the pulps deriving from the leaching of low-grade sulfide ores (Kingashsky deposit, Russia) by hydrochlorination, using the chelating resin Purolite S930, were carried out. The recovery characteristics obtained for the process solution were compared to that for synthetic solutions. At pH 2.7-3.0, copper, nickel, and cobalt recovery, for long resin contact times, exceeds 99%. For pulps, compared to that for the synthetic solution, a significant decrease in the rate of metal recovery was observed which is presumably related to the influence of silicic acid. The sorption concentration constants for copper, nickel, and hydrochloric acid and the resin loss due to attrition were estimated. © 2013 Elsevier B.V.

Mikhlin Y.L.,RAS Institute of Chemistry and Chemical Technology | Karacharov A.A.,RAS Institute of Chemistry and Chemical Technology | Likhatski M.N.,RAS Institute of Chemistry and Chemical Technology
International Journal of Mineral Processing | Year: 2015

Atomic force microscopy (AFM) and force spectroscopy techniques have emerged as powerful tools for in situ studies of interactions between solid surfaces, reactants and air bubbles which are of fundamental importance for understanding the mechanisms and increasing the efficiency of froth flotation. Such studies, however, have very rarely involved real mineral sulfides and flotation collectors to date. Here, the tappingmode AFM, force spectroscopy with conventional silicon cantilevers, and ex situ XPS were used to characterize surfaces of single crystals of natural PbS and, for comparison, highly oriented pyrolytic graphite (HOPG) in pure water before and aftertheir pre-treatment in 0.1mMand 10mMpotassium n-butyl xanthate (KBX) solutions. ubmicrometer domains with the height about 3-8 nmwere observed on the PbS surfaceswith chemisorbed xanthate. The force-distance curvesmeasured upon retraction of the tip fromPbS andHOPG surfaces pre-treated in KBX solutions revealed the attraction forces, often with two sudden pull-off steps, acting at the separation distances longer than 100 nm.We attributed the soft domains to gas nanobubbles; the long-range attraction was explained in terms of the capillary forces induced by a vapor cavity arising between the tip and the hydrophobic substrates upon their disconnection, and coalescence of the cavity with the pre-existing nanobubbles. The role of these phenomena in flotation is briefly discussed. © 2015 Elsevier B.V. All rights reserved.

Kalyakin S.N.,RAS Institute of Chemistry and Chemical Technology | Kuz'Min V.I.,RAS Institute of Chemistry and Chemical Technology | Mulagaleeva M.A.,RAS Institute of Chemistry and Chemical Technology
Hydrometallurgy | Year: 2015

The use of binary extractants based on carboxylates and dialkylphosphates of secondary and tertiary amines and their mixtures for the separation of lanthanide (III) ions has been investigated. It is established that the solutions of these extractants in non-polar organic solvent extract lanthanide chlorides from aqueous phase according to the laws of binary extraction. The synergetic effect for the system of di-(2-ethylhexyl)carboxylate, caprinate of di-n-octylammonium and tri-n-octylammonium has been found. © 2014 Elsevier B.V. All rights reserved.

Tsyganova S.I.,RAS Institute of Chemistry and Chemical Technology
Wood Science and Technology | Year: 2013

In this work, different activated carbons were prepared from composites based on birch sawdust and coal-tar pitch by chemical activation with zinc chloride, phosphoric acid, and potassium hydroxide followed by carbonization. The influence of different chemical agents (ZnCl2, KOH, and H 3PO4), final temperature of carbonization and media on yield and structural properties of the carbonic product was studied. It was shown that chemical agents allow increasing yield of carbonic residue. Composite modification by H3PO4 or ZnCl2 facilitates the formation of molded porous carbonic residue during the carbonization process. However, addition of KOH to the composite leads to formation of powder-like carbonic residue having a specific surface area of 1,600 m2 g -1 at 800 C. It was established that all samples aged in air medium at 800 C have higher values of specific surface area in comparison with the same samples aged in argon medium at similar conditions. © 2012 Springer-Verlag.

Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2016

The structure of benzene:ethane co-crystal at 90 K is refined with anisotropic displacement parameters without geometric restraints from high-resolution synchrotron X-ray powder diffraction (XRPD) data using the derivative difference method (DDM) with properly chosen weighting schemes. The average C-C bond precision achieved is 0.005 Å and the H-atom positions in ethane are refined independently. A new DDM weighting scheme is introduced that compensates for big distortions of experimental data. The results are compared with density functional theory (DFT) calculations reported by Maynard-Casely et al. [(2016). IUCrJ, 3, 192-199] where a rigid-body Rietveld refinement was also applied to the same dataset due to severe distortions of the powder pattern attributable to experimental peculiarities. For the crystal structure of 2-aminopyridinium fumarate-fumaric acid formerly refined applying 77 geometric restraints by Dong et al. [(2013). Acta Cryst. C69, 896-900], an unrestrained DDM refinement using the same XRPD pattern surprisingly gave two times narrower dispersion of interatomic distances. © 2016 International Union of Crystallography.

Glaznev I.,RAS Boreskov Institute of Catalysis | Ponomarenko I.,RAS Institute of Chemistry and Chemical Technology | Kirik S.,RAS Institute of Chemistry and Chemical Technology | Aristov Y.,RAS Boreskov Institute of Catalysis
International Journal of Refrigeration | Year: 2011

Each specific cycle for adsorptive heat transformation (AHT) requires appropriate adsorbent which ensures the best realization of precisely this cycle. This paper addresses a synthesis of novel composite sorbents "CaCl2 confined to a meso-structured silicate SBA-15" with variable properties which appear to depend on the SBA pore size (8.1 and 11.8 nm). The equilibrium and dynamics of water sorption have been studied under typical conditions of isobaric stages of AHT cycle. Steep sorption isotherms are found, the pressure at which the sharp increase of water sorption is observed being higher in larger pores. This allows fine adjustment of sorbent properties to cycle boundary temperatures: the stronger water bounding by the salt confined to smaller pores results in the appropriate enhancement of the desorption and condensation temperatures. Comparison of the new composites with other adsorbents promising for AHT showed that mono-sized matrices are encouraging for both tailoring step-like sorption isotherms, managing the step position to fit given AHT cycle and fast water sorption. © 2011 Elsevier Ltd and IIR. All rights reserved.

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