Composition and properties of functional groups on surface of carbon sorbents modified by aminocaproic acid

The composition and properties of functional groups on the surface of carbon sorbents modified with aqueous solutions of aminocaproic acid of different concentrations were studied using physicochemical analysis methods: including acid-base titration, the Kjeldahl method, scanning electron microscopy, X-ray microanalysis, and X-ray photoelectron spectroscopy. The initial carbon sorbent was shown to have almost no functional groups on its surface. It was ascertained that the surface functionalization of carbon sorbent results in a change in microstructure and an increase in the amount of oxygen- and nitrogen-containing groups with increasing concentration of the modifying agent followed by its further polycondensation on the surface. According to the XPS data, the formation of the bond between aminocaproic acid and the carbon surface of sorbents occurs via a carboxylic group.     

Studies of the effect of surface modification of carbon sorbents by poly-N-vinylpyrrolidone using a complex of physicochemical and microbiological methods

The surface of the VNIITU-1 carbon mesoporous sorbent was modified with poly-N-vinylpyrrolidone characterized by antibacterial activity. Synthesis was carried out in two stages: (1) impregnation of the carbon sorbent by an aqueous solution of poly-N-vinylpyrrolidone with the molecular mass of 10000 g/mol; and (2) impregnation of the carbon sorbent by an aqueous solution of the (N-vinylpyrrolidone) monomer and initiator with their further polymerization in an inert atmosphere. Carbon sorbent samples were studied using a complex of physicochemical methods: scanning electron microscopy, infrared spectroscopy, low-temperature nitrogen adsorption, nuclear magnetic resonance, and thermogravimetry. It was found that the polymer obtained on the carbon surface is free of the initial toxic VP monomer. Microbiological tests of modified sorbents with respect to pathogenic and opportunistic microflora were carried out.     

Modification of carbon sorbent surface by poly-N-vinylpyrrolidone in application medicine

The surface of a VNIITU-1 carbon mesoporous hemosorbent is modified with poly-N-vinylpyrrolidone, which possesses its own antibacterial activity. The modification is performed in two steps: (1) impregnation of the monomer, N-vinylpyrrolidone, and the initiator in an aqueous solution and (2) polymerization in an inert atmosphere. The composition of products produced during polymerization reaction is analyzed by NMR ¹³C. The texture characteristics, the relief and the morphology, and the content of nitrogen in the initial and modified sorbents are studied by current physicochemical methods. Bench tests show that the contact with the modified sorbent leads to a decrease in the amount of Staphylococcus aureus bacterial cells and inhibition of their growth in comparison with the initial carbon sorbent.     

A mechanism of sorption of heavy metal ions from aqueous solutions by chemically modified cellulose

The effect of chemical modification on sorption properties of cotton cellulose with respect to Cu(II), Ni(II), and Fe(II) ions is studied. Modification was carried out through oxidation of cellulose with formation of dialdehyde cellulose, its further conversion to dialdoxime cellulose, and further to a sorbent with hydroxame acidic groups. The optimum conditions for cellulose modification were determined. The sorption capacitance of the modified sorbent is approximately twice as high as that of native cellulose; herewith, the time of establishment of equilibrium is reduced. The mechanism of chemisorption by modified cellulose is due to the presence of new sorption centers??hydroxame acidic groups??in the sorbent structure, alongside with ??-hydroxycarboxyl ones. The former, as opposed to the latter, form colored chelate complexes with heavy metal ions on the sorbent surface. Sorption isotherms are well described by the Langmuir model. The limiting sorption capacitance agrees with the amount of acidic groups of sorbents. This allows attributing such a sorbent to cationites and to interpret the mechanism of metal ion sorption from aqueous media by modified cellulose as ion exchange with the presence of -CHOHCOOH and -CONHOH functional groups.     

Physicochemical and adsorption-structural properties of diatomite modified with aluminum compounds

A selective sorbent based on the diatomite of local origin modified with aluminum compounds has been studied by the methods of powder X-ray diffraction; FTIR; and differential thermal, adsorption-structural (BET), and chemical analyses. The surface modification of diatomite is carried out by heating it in an NaOH solution and its subsequent treatment with a solution of aluminum salt and ammonia. The amorphous surface silica partially dissolves during the treatment with NaOH and forms an aluminosilicate compound at the addition of an aluminum salt. The obtained material is deposited both on the surface of the diatomite and on the inner surface of the macro- and larger mesopores, which leads to the development of the specific surface area of 81.8 m²/g, which is 2.5 times larger than the corresponding value in the initial diatomite (37.5 m²/g). The precipitated aluminosilicate compound with the concentration equal to 0.34 g of Al/g of aluminosilicate contributes to the development of a porous structure in the treated diatomite, so the volume of the mesopores increases from 0.029 to 0.079 cm³/g and that of the micropores from 0.012 to 0.027 cm³/g. The qualitative changes in the composition of the obtained sorbent are confirmed by the emergence of new lines in the X-ray diffraction patterns, which are characteristic for aluminosilicates, and additional peaks in the infrared spectra corresponding to the stretching vibrations of Si-O-Al. The selectivity of the obtained adsorbent with respect to fluoride ions increases significantly, specifically, its adsorption capacity increases from 8.9 to 57.6 mg of F/g at the initial fluorine concentration equal to 0.15 mol/L.     

Effect of surface chemistry of carbon sorbents on high-performance liquid chromatography and mass-spectrometric analysis of amino acids

The work shows a complex approach to analyzing amino acids using carbon sorbents with different surface areas, including molecular-statistical calculations, high-performance liquid chromatography, and mass spectrometry with matrix-activated and surface-activated laser desorption/ionization (MALDI, SALDI). An analysis of the thermodynamic adsorption characteristics (TACs) of a series of proteinogenic amino acids and their isomers on graphitized thermal carbon black (GTCB) is carried out. A satisfactory correlation is established between experimental characteristics of amino-acid retention on the Hypercarb carbon sorbent and TACs of these particles calculated using the molecular statistics method. It is found in the identification of amino acids using the MALDI method in the chromato-mass-spectrometric modification in the off-line mode that the application of carbon sorbents as a support results in an increase in the intensity of the registered protonated molecular ions and adducts with alkali cations compared to a conventional experimental technique on a stainless-steel surface.     

Residual stress distribution in burnishing solution treated and aged 7075 aluminium alloy

The residual stress distribution in the surface region of solution treated and aged 7075 aluminium alloy workpieces that are orthogonally burnished under lubricated condition is determined using a deflection etching technique. The residual stress at the surface is low compressive and increase rapidly with an increase in depth beneath the burnished surface to a maximum compressive then decreases gradually with further increase in depth becoming vanishingly small tensile or compressive. The maximum residual stress and depth of the stressed region increase in burnishing speed, force and an increase, to some extent, in burnishing time. The results are interpreted qualitatively in terms of the variations in the amount of surface region deformation produced by changes in burnishing conditions.     

Investigation of the peculiarities of modification of carbon sorbent by lactic and glycolic acid with their subsequent polycondensation

A method of modification of carbon sorbents by copolymers of glycolic and lactic acids is developed. Control over the polycondensation process and adjustment of the synthesis conditions and parameters are done using the methods of NMR spectroscopy and thermogravimetric analysis. Optimal conditions for the modification of a carbon material are selected, allowing one to obtain predominantly the oligomers of glycolic and lactic acids. The surface shape and morphology, porous structure, elemental composition and composition of the functional groups, and mechanical strength of the carbon sorbent samples are investigated using a set of physicochemical methods. It is established that the adjusted conditions of polycondensation allow one to affix the modifying agent on the carbon sorbent.     

疲劳载荷对17CrNiMo6喷丸强化层残余应力与组织的影响

高强度渗碳钢17CrNiMo6常用喷丸强化工艺来改善抗疲劳性能,但疲劳载荷会使喷丸强化层的残余应力与组织发生改变,削弱了强化效果。采用X射线衍射方法研究了其残余应力、半高宽和残余奥氏体随疲劳载荷周次的变化规律,同时研究了喷丸前后表面形貌、硬度和组织的变化。结果表明,喷丸与二次喷丸强化层残余应力场在疲劳载荷前100周次内发生了应力松弛,松弛幅度分别为50%与33%,之后基本保持稳定。半高宽随载荷周次的增加分别下降了5%与7%,而残余奥氏体含量变化不大。此外,喷丸处理增加了材料表层残余压应力,细化了晶粒尺寸,使疲劳寿命提高了11%;二次喷丸可进一步增加材料表层残余压应力,细化晶粒尺寸并改善表面形貌使材料疲劳寿命提高了23%。因此在评估喷丸工艺强化效果,预测喷丸处理后零部件的疲劳寿命时,宜采用松弛后的残余应力作为衡量参数。     

皮江法炼镁还原渣用作燃煤固硫剂的试验研究

我国是一个贫油富煤的国家,且高硫煤所占比重很大,煤炭燃烧产生的SO2是导致酸雨形成的主要原因,我国镁工业每年排出大量的镁还原渣,镁渣中含有大量的碱金属氧化物,完全可以用作燃煤的固硫剂。本文通过实验室的实验,试图证明镁还原渣用过燃煤固硫剂的可行性,并初步探索出最佳的固硫条件。     

Regulation of sorption processes in natural nanoporous aluminosilicates. 3. Impact of electromagnetic fields on adsorption and desorption of formaldehyde by clinoptilolite

The effect of electromagnetic fields on the adsorption–desorption properties of natural zeolites is a new direction in the theory of physical and chemical processes associated with the surface characteristics of aluminosilicates. The influence of two types of fields, an ultrahigh-frequency electromagnetic field (UHF EMF) and a weak pulsed magnetic field (WPMF) is considered. Modes for treatment of natural zeolite (clinoptilolite) and its activated forms for the most effective sorption of formaldehyde, water, and a mixture thereof were found. It was shown that the preadsorption activation of zeolite in a UHF EMF enhances the selectivity of water vapor sorption, whereas treatment of the sorbent in a WPMF largely affects the selectivity of the absorption of formaldehyde vapors. The decreased desorption of formaldehyde as a result of activation of the mineral in a UHF EMF, as well as complete absence of formaldehyde desorption when a WPMF was used as an activator, was detected.     

Drying of liquidized products of pyrolysis on composite sorbent CaCl<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: Statics,dynamics, and modeling

Our investigation on the equilibrium of water sorption by composite sorbent CaCl₂/Al₂O₃ in a model system based on benzene and its use for the dynamic drying of liquidized products of pyrolysis is reported. To describe the dynamics of drying, a mathematical model has been developed that has been used to estimate the operating parameters of an industrial drying plant for liquidized products of pyrolysis.     

Application of amorphous brush-plated

The results obtained during industrial trials have shown that the service life of hot work dies can be increased by 33 to 180% using the brush plating technique to prepare amorphous coatings. The coatings possess a much higher hardness, lower friction coefficient at room and elevated temperatures, good scale resistance in addition to higher surface finish, compared to uncoated dies, and thus improve the tribological performance of the dies. In this work, a study of the crystallization process, its kinetics, and the hardness variations of the coatings has been made. According to the data obtained, it can be considered that the main reason for the success of amorphous brush-plated coatings is that, during the operation, crystallization and precipitation takes place instantaneously, which results in a strong secondary hardening effect, thus leading to an increase in the red hardness of the surface layers of dies, therefore ensuring higher thermal wear resistance of the dies.     

Sorption properties of fullerene-modified activated carbon with respect to metal ions

The prospects of modying of the activated carbon with microamounts of fullerenes, which can enhance its adsorption capacity with respect to metal cations by a factor of 2.5–5, are illustrated. The analysis of experimental data makes it possible to assume that silver ions are reduced on the carbon sorbent surface to metal silver, lead cations are sorbed due to the donor-acceptor interaction, and the copper ion sorption may lead to both the cation reduction to metal copper and the formation of complexes with different ligands preferentially with those containing an amino group. Original Russian Text ? V.V. Samonin, V.Yu. Nikonova, M.L. Podvyaznikov, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 204–206.     

Formation and Properties of Electron- and Ion-Conducting Layers of N-Substituted PVC Derivatives Grafted onto Active Carbon

Protection of Metals and Physical Chemistry of Surfaces - A systematization is presented of studies of carbon sorbent functionalization based on chemical modification of the active carbon surface...     

V_8C_7-Fe基表面复合材料的铸造烧结过程和耐磨性研究

应用 SEM和 XRD研究了铸造烧结过程中 V8C7- Fe基表面复合材料组织结构的变化 ,用 MM2 0 0磨损实验机研究了 V含量对 V8C7- Fe基表面复合材料耐磨性能的影响。结果表明 ,随着含 V量的提高 ,表面复合材料的硬度越高 ,耐磨性能越好。     

镀铝温度对渗铝层/基体界面空洞生长动力学的影响

采用不同的镀铝温度在20碳钢上制备了不同厚度的热浸镀铝层,通过测量热浸镀铝层厚度以及高温氧化后渗铝层/基体界面空洞平均直径和形核数量随氧化时间的变化,研究了镀铝温度对渗铝层/基体界面空洞生长的影响。结果表明:随镀铝温度升高,镀铝后的表面层厚度减小,合金层厚度增加;在高温氧化期间,渗铝层/基体界面空洞的生长速度随镀铝温度的升高而减小,其变化规律与热浸镀铝后表面层厚度随镀铝温度的变化规律相一致;界面空洞平均深度随镀铝温度升高而增加,其变化规律与热浸镀铝后合金层厚度随镀铝温度的变化规律相一致;界面空洞增量随氧化时间的延长先增加而后逐步减少,且镀铝温度越高,空洞形核速度越小。分析了镀铝温度对界面空洞生长的影响机制。     

Low-pressure,high-temperature siliconizing of tungsten-I

The study of surface siliconizing of tungsten ribbons by low pressure (10^–3 to 10^–6 Torr) and high temperature (800 to 1200°C) heterogeneous decomposition of SiH₄ shows a competition between silicon deposition on the surface and its diffusion in the metal Coatings of W₅Si₃ and WSi₂ are formed which grow parabolically or linearly depending on deposition and temperature conditions; their thickness has been determined without destroying the ribbon by measuring the variations of the electrical conductivity with the quantity of silicon introduced. The activation energy of the inter diffusion coefficients, the composition and resistivity of the phases, and the surface parameters corresponding to the surface evolution (monochromatic and total emissive powers) have been determined for the different compounds. The decomposition kinetics of SiH₄ were also determined.     

Inverse gas chromatography for identification of poly(ethylene glycol adipate) and tripropionitrilamine on the surface of polymeric sorbent

Identification of the adsorption of poly(ethylene glycol adipate) (PEGA) and tripropionitrilamine (TPA) on styrene-divinylbenzene porous polymer was performed with the use of the inverse gas-chromatography method in finite concentration. PEGA and TPA were applied in quantities ω = 10^?6?10^?3 mass fractions. As test sorbates n-propanol, n-butanol, and n-hexane used. The adsorption isotherm and the values of specific retention volumes were calculated via the Glueckauf method. It was found that the dependence of the retention volumes on the sorbate concentration in gas phase of the studied samples is well approximated by a power function corresponding to the Freundlich isotherm. The possibility of detecting PEGA and TPA on the surface of sorbent through the A coefficients of a power function was shown, and a linear dependence between the A values and negative logarithm of ω was also found, making it possible to quantitatively determine TPA and PEGA on the surface of a sorbent.     

A study of the adsorption of silver nanoparticles by high-performance liquid chromatography

The method of high-performance liquid chromatography has been used to study the adsorption of stable silver nanoparticles, which were obtained by radiation-chemical synthesis in reverse micellar solutions of H₂O + Ag⁺/Aerosol OT/isooctane composition. Adsorption was conducted on polar and nonpolar sorbents. It has been determined that almost all nanoparticles are retained on nonpolar sorbent C18; however, their binding is not strong. After accumulation of a particular amount of nanoparticles, they leave a column with effluent. It has been shown that the adsorption and optical properties of silver nanoparticles almost do not change after the adsorption-desorption cycle on C18. It has been determined that, on polar silica gel, the adsorption of silver nanoparticles proceeds less intensely (fewer than half of the particles move to the near-surface layer of the sorbent; however, their interaction with surface is very strong and they were not desorbed. For nanoparticles and the molecules of the micelle-forming agent Aerosol OT, adsorption isotherms have been plotted. Based on the obtained results, possible mechanisms of adsorption of nanoparticles on the surface of polar and nonpolar sorbents have been considered.