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.     

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.     

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.     

Synthesis and physicochemical properties of a biospecific carbon sorbent modified with lactic-acid oligomers

A method of lactic-acid (LA) polycondensation on a carbon sorbent, including sorbent impregnation and multistep thermal treatment with no catalysts or toxic solvents, is developed. This modification technique makes it possible to obtain materials with adjustable properties (molecular weight of the synthesized oligomer, amount of applied modifier, degree of screening of carbon-sorbent pores, etc.). The resulting sorbent samples were investigated using various physicochemical methods: ¹³С and ¹Н NMR spectroscopy, low-temperature nitrogen adsorption, differential thermal analysis, etc. It is established that the modifier concentration has an impact on the physicochemical characteristics of the studied carbon-sorbent samples. Of greatest interest is the carbon-sorbent sample impregnated with a 50% lactic-acid solution with subsequent thermal treatment. Its composition includes a high content of the modifier (biologically active substance with biospecific properties) and exhibits durable action.     

Optimization of Parameters of Synthesis of Carbon Sorbents Modified with Hydroxic Acids

Protection of Metals and Physical Chemistry of Surfaces - The synthesis of a carbon sorbent modified with lactic and glycolic acids using a vacuum rotary evaporator was carried out. The parameters...     

Synthesis of MWNT-based composite materials with inorganic coating

Multiwalled carbon nanotube (MWNT) based metal oxide composites were prepared by an impregnation method using organometallic compounds as precursor. Aluminium isopropoxide (AlIP), tetraethyl orthosilicate (TEOS), and tetraethyl orthotitanate (TEOTi) were used as inorganic sources and decomposed by hydrolysis on the surface of carbon nanotubes. The composites were subsequently investigated by transmission electron microscopy and their coverage was compared. A direct, solvent-free impregnation technique turned out to be the most successful for all organometallic compounds and provided homogeneous inorganic cover layer on the surface of purified MWNTs.     

Vapour phase polymerisation of pyrrole on cellulose-based textile substrates

Conducting textiles were prepared embedding polypyrrole in natural and man made cellulose-based fibres, such as cotton, viscose, cupro and lyocell, by means of in situ polymerisation. Chemical vapour phase deposition of polypyrrole is a suitable process for producing electro-conductive composites in two steps: (a) fabric impregnation with an aqueous solution of oxidant and dopant and subsequent drying; (b) exposition to pyrrole vapour and polymerisation.Comparative morphological and structural analysis was carried out on the conducting viscose prepared with both vapour and liquid phases processes and some significant differences in the structural, calorimetric and electrical properties were highlighted, due to the different methods of preparation. Vapour phase prepared fabrics show a high uniform polypyrrole coating on the fibre surface and its partial penetration inside the amorphous zones of the fibre bulk.WAXD analysis shows that the conducting fabrics preserve the crystalline structure of the cellulose matrix, while SAXS results evidence the presence of a nanoparticle dispersion of polypyrrole in the cellulose matrix. Polypyrrole–cellulose conducting composite textiles show good performances to light exposure and washing fastness tests.     

On The Enhancement of Wear Resistance of Hardened Carbon Tool Steel （AISI 1095） With Cryogenic Quenching

Many experimental investigations reveal that it is very difficult to have a completely martensitic structure by any hardening process. Some amount of austenite is generally present in the hardened steel. This austenite existing along with martensite is normally referred as the retained austenite. The presence of retained austenite greatly reduces the mechanical properties and such steels do not develop maximum hardness even after cooling at rates higher than the critical cooling rates.Strength can be improved in hardened steels containing retained austenite by a process known as cryogenic quenching.Untransformed austenite is converted into martensite by this treatment. This conversion of retained austenite into martensite results in increased hardness, wear resistance and dimensional stability of steel. Wear can be defined as the progressive loss of materials from the operating surface of a body occurring as a result of relative motion at the surface. Hardness, load,speed, surface roughness, temperature are the major factors which influences wear. Many studies on wear indicate that increasing hardness decreases the wear of a material. With this in mind, to study the surface wear on a surface modified (Cryogenic treated) steel material an attempt has been made in this paper. In this study as a Part -I Hardening was carried out on carbon tool steel (AISI 1095) of different L/D ratio with conventional quenchants like purified water, aqueous solution and Hot mineral oil. As a Part -II hardening was followed by quenching was carried out as said in Part- I and the hardened specimen were quenched in liquid Nitrogen which is at sub zero condition. The specimens were tested for its microstructure, hardness and wear loss. The results were compared and analyzed. The alloying elements increases the content of retained austenite hence the material used was AISI 1095 (Carbon 0.9%, Si 0.2%, Mn0.4% and the rest Iron)     

Sorption Properties of MIU-S Coal Sorbent in Relation to Nickel(II) Ions

Protection of Metals and Physical Chemistry of Surfaces - The physicochemical and sorption properties of MIU-S carbon sorbent have been studied. The studies were carried out on a model solution of...     

火焰法制备螺旋碳纳米纤维及其亲水改性

目的利用乙醇火焰法制备螺旋碳纳米纤维,并考查不同表面改性方法对螺旋碳纳米纤维亲水性的影响。方法首先研究不同烧制时间、镍片-火焰距离、Sn Cl4溶液浓度对制备螺旋碳纳米纤维的影响,然后用水蒸气、聚乙烯吡咯烷酮K30(PVP)溶液以及氢氧化钠-浓硝酸溶液改性螺旋碳纳米纤维。通过扫描电镜、透射电镜、拉曼光谱仪、X射线衍射仪对所制备的螺旋碳纳米纤维进行表征,利用红外光谱分析、X射线光电子能谱分析和沉降实验评价不同改性方法的改性效果。结果随着镍片-火焰距离的增加,螺旋碳纳米纤维含量增加,均匀度逐渐下降;随着烧制时间的延长,螺旋碳纳米纤维的均匀度先增加后降低;Sn Cl4的浓度会影响碳纳米纤维的形貌和均匀度。制备均匀的螺旋碳纳米纤维的最佳条件为:73%Sn Cl4溶液,镍片-火焰距离1.5 cm,烧制9 min。通过红外光谱分析发现,三种改性方法都使螺旋碳纳米纤维表面接上亲水基团。沉降实验表明,PVP溶液和氢氧化钠-浓硝酸改性的螺旋碳纳米纤维在水溶液中静置48 h后的沉降率均为26.7%,而未改性的螺旋碳纳米纤维的沉降率为58.3%。结论通过乙醇火焰法可以制备出均匀的螺旋碳纳米纤维,其中烧制时间、镍片-火焰距离、Sn Cl4溶液浓度对制备的螺旋碳纳米纤维的形貌和均匀度影响很大,需要在特定的条件下才能制备出均匀的螺旋碳纳米纤维。通过三种方法对螺旋碳纳米纤维进行改性,发现PVP溶液和氢氧化钠-浓硝酸改性的螺旋碳纳米纤维的表面亲水性更好,其中PVP溶液改性操作简单,且对螺旋碳纳米纤维的形貌没有破坏,对于螺旋碳纳米纤维改性会更有利。     

Improvement of photocatalytic activity of high specific surface area graphitic carbon nitride by loading a co-catalyst

Graphitic carbon nitride(g-C_3 N_4) was synthesized by heating melamine and was then treated with sodium hydroxide solution under a hydrothermal condition to obtain g-C_3 N_4 with a large specific surface area(HSSA).HSSA shows higher photocatalytic activity for decomposition of acetaldehyde than that of original g-C_3 N_4. HSSA was modified with RuO_2 as a co-catalyst by the impregnation method. HSSA loaded with 0.05 wt% RuO_2 shows the highest photocatalytic activity for acetaldehyde decomposition under visible light(k = 455 nm).     

Carrier injection from polypyrrole coated gold electrode in pentacene field effect transistors

Carrier injection characteristics of conjugated polymer coated gold (Au) electrode were investigated. Using pentacene field effect transistors (FETs) with Au electrodes covered with polypyrrole (PPy) film deposited electrochemically from an aqueous electrolyte solution of HCl or PTSA (1 M) containing pyrrole monomer, transient microscopic optical second harmonic generation (TRM-SHG) measurements were carried out. Transfer characteristics of the transistors suggested that the injection of holes was assisted by the deposited polymer film improving the hole injection efficiency. The TRM-SHG results well supported the results of the electrical measurements, and we anticipate that polypyrrole could be a potential candidate as an electrode material in polymer electronics.     

Adsorption of phenol from aqueous solution by a hierarchical micro-nano porous carbon material

A hierarchical micro-nano porous carbon material (MNC) was prepared using expanded graphite (EG), sucrose, and phosphoric acid as raw materials, followed by sucrose-phosphoric acid solution impregnation, solidification, carbonization and activation. Nitrogen adsorption and mercury porosimetry show that mixed nanopores and micropores coexist in MNC with a high specific surface area of 1978 m2·g-1 and a total pore volume of 0.99 cm3·g-1. In addition, the MNC is found to consist of EG and activated carbon with...     

Effect of acidic surface functional groups on Cr（VI） removal by activated carbon from aqueous solution

The activated carbon with high surface area was prepared by KOH activation. It was further modified by H2SO4 and HNO3 to introduce more surface functional groups. The pore structure of the activated carbons before and after modification was analyzed based on the nitrogen ad-sorption isotherms. The morphology of those activated carbons was characterized using scanning electronic microscopy (SEM). The surface functional groups were determined by Fourier transform infrared spectroscopy (FTIR). The quantity of those groups was measured by the Boehm titration method. Cr(Ⅵ) removal by the activated carbons from aqueous solution was investigated at different pH values. The results show that compared with H2SO4, HNO3 destructs the original pore of the activated carbon more seriously and induces more acidic surface functional groups on the activated carbon. The pH value of the solution plays a key role in the Cr(Ⅵ) removal. The ability of reducing Cr(Ⅵ) to Cr(Ⅲ) by the activated carbons is relative to the acidic surface functional groups. At higher pH values, the Cr(Ⅵ) removal ratio is im-proved by increasing the acidic surface functional groups of the activated carbons. At lower pH values, however, the acidic surface functional groups almost have no effect on the Cr(Ⅵ) removal by the activated carbon from aqueous solution.     

Comparison of chiral polyaniline carbon nanotube nanocomposites synthesized by aniline dimer-assisted chemistry and electrochemistry methods

We report herein aniline dimer-assisted chemistry and electrochemistry methods for synthesis of chiral polyaniline carbon nanotube composites. The negative charged carbon nanotubes were first dispersed into aqueous solution, and then aniline monomer, chiral inducing agent camphorsulfonic acid (CSA) and aniline dimer were added into above solution in sequence. Polymerization was initiated by adding oxidizing agent ammonium persulfate solution (chemistry method) or by inserting electrode with appropriate potential (electrochemistry method). Roles of CSA and aniline dimer in determining optical activity of the resulting polyaniline carbon nanotube nanocomposites were investigated in detail in this study. Effects of the carbon nanotube loading and the temperature on the optical activity of the resulting polyaniline carbon nanotube nanocomposites were also investigated. Two different methods (solution chemistry and electrochemistry) were compared in the synthesis of the chiral polyaniline carbon nanotube nanocomposites in this study.     

Preparation and mechanical properties of electrically conductive polypyrrole-poly(ethylene-co-vinyl acetate) composites

Electrically conductive polymer composite materials that possess good electrical and mechanical properties are prepared in two steps: first, a concentrated emulsion is generated by dispersing with stirring a toluene solution of pyrrole and a host polymer (poly(ethylene-co-vinyl acetate) or polyethylene) in a small amount of an aqueous solution of a surfactant (sodium dodecylsulfate); secondly, the oxidative polymerization of the monomer is carried out by introducing with stirring an aqueous solution of an oxidant (FeCl₃). After polymerization, flexible and stretchable conductive films can be obtained by hot-pressing the obtained composite powders. The conductivity of the composite exhibits a percolation threshold in the range 5–20 wt.% and reaches values as high as 5–7 S/cm. The mechanical properties of the composite films are determined by measuring the tensile strength as a function of elongation for various proportions of the conductive polymer in the composite and contents of vinyl acetate in the host polymer. Scanning electron microscopy (SEM) micrographs indicate that the hot-pressed materials possess a fluid-like morphology.     

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.     

Surface conductive films via polymerization on a liquid surface

Surface conductive crosslinked polybutyl acrylate (c-PBA) films were prepared in two steps. In the first step, a mixture containing the monomer of the conductive polymer (pyrrole or 3-methylthiophene) and the precursors of c-PBA (butyl acrylate, a crosslinking reagent, and the initiator 2,2′-azobisisobutyronitrile) was spread over the surface of a hot 2 wt.% poly (vinyl alcohol) aqueous solution, and allowed to polymerize. In the second step, the pyrrole or 3-methylthiophene containing c-PBA film was immersed into an iron chloride solution in ethyl acetate for the monomer present in the film to be oxidatively polymerized and to generate a conductive coating layer near the surface of the film. The highest conductivities achieved were 1 S/cm for polypyrrole and 18 S/cm for poly (3-methylthiophene). The effects of the oxidation polymerization time, the amount of monomer precursor of the conductive polymer, the concentration of the oxidant solution, and the extent of crosslinking of c-PBA were investigated.     

Electrochemical deposition of a carbon nanotube-poly(o-phenylenediamine) composite on a stainless steel surface

Electrodeposition of a nano-composite made of oxidized carbon nanotubes (CNTs) and a conductive polymer such as poly(o-phenylenediamine) (PoPD) on a stainless steel surface from aqueous solution was carried out by cyclic voltammetry. The presence of the CNTs enhanced the deposition of the PoPD and this enhancement was more significant in the presence of single walled carbon nanotubes (sCNT) by comparison to multi-walled carbon nanotubes (mCNT). Scanning electron microscope images indicated the incorporation of the CNTs in the PoPD layer. The nano-composite layer as well as the pure PoPD layer keeps the stainless steel in a passive state in acidic solution. The oxide film underneath the nano-composite layer is unique and showed high corrosion resistance in concentrated chloride solutions, which was confirmed by the presence of high contents of iron and chromium components. These findings suggest that the CNTs indirectly assist the passivation of the stainless steel by catalyic oxygen reduction and polymer oxidation process.     

活性炭及硅藻土对染料的吸附特性研究

采用活性炭、硅藻土、氢氧化镁改性硅藻土对1种阳离子染料和2种阴离子染料进行了吸附研究.BET液氮吸附法测定结果显示硅藻土改性后的比表面积增大而平均孔径降低;染料吸附结果表明:硅藻土改性后对天龙红(TR)及雷马素金黄(RGY)两种阴离子染料的吸附性能提高,而对阳离子染料亚甲基蓝的吸附性能降低;改性硅藻土对天龙红的吸附容量大于活性炭,而对雷马寨金黄及亚甲基蓝的吸附容量低于活性炭;采用准一级、准二级两种吸附动力学模型对染料的吸附动力学数据进行了拟合,结果显示改性硅藻土及活性炭的染料吸附过程更符合准二级动力学模型.