Development of bioactive materials based on surface chemistry

All bioactive materials developed up to 1990 were based on calcium phosphate. It was later revealed that materials that form bonelike apatite on their surfaces in the living body bond to living bone through the apatite layer, and that apatite formation on a material is induced by various functional groups on its surface. Based on these findings, bioactive titanium was prepared by forming sodium titanates on its surface via NaOH and heat treatments, and applied to an artificial total hip joint. Porous titanium metal able to exhibit osteoconductivity as well as osteoinductivity was prepared by forming anatase on its surface via NaOH, HCl and heat treatments. Various bioactive materials with different physical properties are expected to be derived from ceramics, metals and organic polymers by modifying their surfaces with functional groups effective for apatite nucleation.     

Sorption characteristics of needle-punch and modified materials

The use of bicomponent fibre in needle-punch materials and processing them on a calender results in materials that combine high sorption characteristics and mechanical strength. The optimum content of bicomponent fibre for obtaining fibre sorbents with high sorption capacity is 7–12% and the calendering speed is greater than 4 m/min. The size of the capillaries in the needle-punch materials formed during needle punching ensures that they are partially filled with liquids. __________ Translated from Khimicheskie Volokna, No. 1, pp. 41–43, January–February, 2007.     

Sorption of petroleum products by carbon sorbents

A comparative study of the adsorption of petroleum products by micro- and macroporous carbon sorbents was performed. For this purpose, four carbon sorbent samples prepared from various raw materials by various processing techniques were used. The pore structures and adsorption capacities of these sorbents for petroleum products were studied. It was found that the adsorption of petroleum products on porous and nonporous carbon sorbents occurred in different manners. In this case, macroporous sorbents with a weakly developed structure of sorbing micro- and mesopores exhibited a maximum capacity for petroleum products.     

Sorption of water vapor by various cellulosic materials

Conclusions The form of the dependence between the values of the water surface and the heat of wetting in processes of water vapor sorption by various cellulosic materials has been refined.The connection of water and thermal effects with the degree of crystallinity of cellulosic materials has been shown.Translated from Khimicheskie Volokna, No. 4, pp. 28–29, July–August, 1983.     

Sorption of palladium on carbon adsorbents from nitric acid solutions

Sorption recovery of palladium from nitric acid solutions on carbon adsorbents BAU, LKAU-7, ABG and UC has been investigated using model solutions with concentrations 8 × 10⁻⁴–8 × 10⁻³ mol/l for palladium and 1, 2 and 5 mol/l for nitric acid. The recovery degrees of Pd(II) depend on the concentration of palladium in contacting solutions as well as on the type of sorbent used. On average, they reach 60%–100% with the maximum in 1 M HNO₃ The palladium desorption by 10% thiocarbamide solution in 1M H₂SO₄ proceeds completely for the sorbent LKAU-7. The use of thiocarbamide solutions in 0.1 M NaOH increases the desorption of palladium from the sorbents BAU and UC up to 80%–85%     

Sorption kinetic studies of water vapour on activated carbon beds

Experimental measurements of the adsorption kinetics of water in activated carbon beds at different values of relative humidity have been made. The development of a simple theoretical model based on inter- and intra-particle mass transfer taking into account the thermal effects of sorption of water in activated carbon beds is described. The comparison of the model results with the experimental data is also presented. It is concluded that a single value of the estimated mass transfer coefficient can be used to reasonably predict the adsorption behaviour of water in activated carbon beds.     

Sorption of carbon tetrachloride in low-density polyethylene pellets

Unsteady-state conjugate sorption curves for carbon tetrachloride in low-density polyethylene (LDPE) pellets at temperatures between 40 and 70°C suggested there was a maximum in the diffusivity-concentration relationship at high values of concentration. The sorption curve at 70°C also displayed features characteristic of pseudofickian behavior, which was attributed to clustering of the penetrant at the high vapor acitivity corresponding to this temperature.     

Sorption kinetics of carbon dioxide onto rubidium carbonate

Rubidium carbonate was used as an adsorbent to capture carbon dioxide from gaseous stream of carbon dioxide, nitrogen, and moisture in a fixed-bed to obtain the breakthrough data of CO₂. Experiments were carried out at flow rates of carbon dioxide and nitrogen (5×10⁻⁶–35×10⁻⁶ m³/min), moisture (0.5×10⁻⁶–3.0×10⁻⁶ m³/h), amount of adsorbent (0.5×10⁻³–1.8×10⁻³ kg), mole fraction of carbon dioxide (0.03–0.22), and different sorption temperatures (323–353 K) at atmospheric pressure. The deactivation model in the non-catalytic heterogeneous reaction systems was used to analyze the sorption kinetics among carbon dioxide, carbonate, and moisture, employing the experimental breakthrough data that fit the deactivation model better than the adsorption isotherm models in the literature.     

Electrophoretic deposition of carbon nanotubes and bioactive glass particles for bioactive composite coatings

The production of bioactive coatings consisting of 45S5 Bioglass^® and mutli-walled carbon nanotubes (CNTs) by electrophoretic deposition (EPD) was investigated. In addition to pure Bioglass^® coatings, the co-deposition and sequential deposition of Bioglass^® particles (size <5 μm) and CNTs on stainless steel substrates were carried out in order to fabricate bioactive, nanostructured composite layers. The optimal experimental conditions were determined using well-dispersed suspensions by means of a trial-and-error approach by varying the relevant EPD parameters: applied voltage and deposition time. SEM images demonstrated the successful fabrication of Bioglass^®/CNT composites by revealing their morphology and topography. The co-deposition of Bioglass^® particles and CNTs resulted in homogenous and dense coatings exhibiting the presence of well-dispersed CNTs placed in-between micron-sized Bioglass^® particles. This network of high-strength CNTs embedded in the glass layer could act as reinforcing element leading to higher mechanical stability of the coatings. The coatings obtained by sequential deposition offered a two-dimensional nanostructured fibrous mesh of CNTs covering the Bioglass^® layer thus providing a controlled (ordered) nano-topographical surface. This surface nanostructure has the potential to promote the attachment and growth of osteoblast cells and to benefit the formation of bone-like nanosized hydroxyapaptite crystals in contact with body fluids.     

Sorption of synthetic surfactants by “Policon” materials

The effect of the initial concentration of synthetic surfactant (SSF) in wastewaters on sorption was investigated, and Policon materials were recommended for use in the tertiary treatment stage where the concentration of SSF does not exceed 0.8 mg/dm³. It was noted that increasing the temperature of the effluents by 60° allows significantly extending the period of steady-state flow of the process and the depth of treatment remains high. The selectivity of Policon materials with respect to the SSF contained in synthetic detergents was investigated. The high efficiency of the materials in ultrafiltration of the components of synthetic detergents was demonstrated. __________ Translated from Khimicheskie Volokna, No. 4, pp. 48–51, July–August, 2007.     

Sorption of gold and silver on carbon adsorbents from thiocyanate solutions

Sorption recovery of thiocyanate gold and silver complexes on different carbon adsorbents has been studied using model solutions with concentrations 0.08-0.82 mmol/l and 0.16-1.06 mmol/l for gold and silver, respectively. The potassium thiocyanate concentration in these solutions was 0.25 mol/l and the pH of the contacting solution was ∼2. The degree of recovery exceeded 90% for gold and 80% for silver. The separate step-by-step desorption of thiocyanate gold and silver complexes was carried out by varying the initial concentration of thiocarbamide (desorption agent). The degree of recovery of noble metals can be increased up to 95% using basic thiocarbamide solutions (in 0.1-0.2 M NaOH) at the higher temperature of the process (up to 150 °C).     

Sorption of platinum and rhodium on carbon adsorbents from chloride solutions

Sorption recovery of platinum (II, IV) and rhodium (III) on different carbon adsorbents has been studied using fresh chloride model solutions with platinum and rhodium concentrations of 0.25–1.0 and 0.049 mmol/L, respectively. The concentration of hydrochloric acid in these solutions varied from 0.001 to 1.0 mol/L. The maximum recovery of platinum and rhodium was achieved with the carbon adsorbent based on charcoal (wood). This sorbent possesses the highest sorption ability to noble metals in medium acidic solutions (0.01–0.1 M HCl). However, the sorption from higher acid solutions (0.5–1.0 M HCl) proceeds on sufficiently high level as well (>80%). The use of thiocarbamide (10%) solutions in sulfuric acid (0.3 mol/L) as a desorption agent results in almost complete elution of rhodium (more than 95%), whereas platinum is retained in carbon adsorbent. This brings out some prospects for separation of these noble metals during their recovery from solutions of spent platinum–rhodium catalysts.     

Self-clinkering carbon materials

Attention focuses on the production of carbon materials from nontraditional self-clinkering raw materials, both natural and synthetic. The properties of such materials are discussed.     

Sorption and diffusion of carbon dioxide in polyimide films

The sorption isotherms of carbon dioxide in a polyimide film sample were measured by a pressure decay method at 30, 40, 50, and 60°C and pressures up to 1.7 MPa. The mean permeability coefficients at the same temperatures were measured by a variable volume method at applied upstream pressures up to 3 MPa. The sorption equilibria at these temperatures were found to be well described in terms of a dual-mode sorption model. The pressure dependences of the mean permeability coefficients at these four levels of temperatures did not satisfactorily follow a dual-mode mobility model, but could be well simulated by a modified mobility model that both the Henry's law (D) and Langmuir (H) populations execute four kinds of diffusive movements such as D → D, D → H, H → D, and H → H. The diffusion coefficients of D → D, D → H, and combined H → H and H → D steps were determined by comparing the experimental permeability data with those predicted via this modified mobility model. The temperature dependences of such diffusion coefficients were consistent with Arrhenius-type equations within the covered temperatures.     

Sorption properties of multilayer carbon nanotubes produced from cotton

The sorption capacity of multilayer carbon nanotubes that have been synthesized by the mechanical activation of amorphous carbon produced from cotton is investigated. The sorptional efficiency of the carbon nanotubes depends on the storage time. The use of carbon materials derived from cotton as chelators is considered.     

Hardness of carbon materials

Data on the hardness of carbon materials obtained via conventional technologies are summarized. The data are compared with the structure characteristics and the properties of the carbon materials. Correlations of the structural characteristics and the properties of the carbon materials with their hardness have been revealed.     

Sorption and diffusion of supercritical carbon dioxide into polysulfone

Sorption and diffusion of supercritical carbon dioxide (SCCO₂) into polysulfone (PSF) from 313 K and 20 MPa to 333 K and 40 MPa were investigated in this study. A simple gravimetric method was used to measure the mass gain of SCCO₂ in PSF, and the Fick's diffusion model was applied to describe the desorption process. The sorption amount, the sorption diffusivity under supercritical states, and the desorption diffusivity at ambient conditions are presented. Comparisons of the sorption amounts and diffusivities of CO₂ for polymers of polycarbonate and PSF are discussed according to the interactions between gas and polymers. The morphology change and plasticization effect attributed to gas sorption in PSF were studied. Effects of glass‐transition temperature and yielding stress for PSF and other polymers were used to describe the difference in their diffusivities for the sorption and desorption processes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 474–482, 2004     

碳基吸附储氢材料

本文综述了活性炭、活性碳纤维、碳纳米纤维和碳纳米管的结构与储氢性能．活性炭只是在低温下才有好的吸附储氢性能,碳纳米材料吸附储氢对于工业应用还不成熟．活性碳纤维是一种可大规模生产且成本较低的微孔吸附材料,其作为储氢材料具有一定的工业前景．     

Sorption removal of oxygen by refractory materials from iron-nickel melts

Conclusions It is shown that it is possible in principle to carry out the sorption deoxygenation of a metal by refractories. A highly developed surface helps to provide a more complete sorption deoxygenation.Experimentally, periclase has better sorption properties than corundum.Most of the oxygen is removed from the melt in the first 5–10 min. The extent of the oxygen removal from the melt increases with an increase in its original concentration.Translated from Ogneupory, No. 3, pp. 22–24, March, 1984.     

Sorption kinetics of eight gases on a carbon molecular sieve at elevated pressure

The sorption kinetics of eight different molecules (O₂, N₂, Ar, CO, CO₂, SO₂, CH₄ and H₂) on a carbon molecular sieve was studied over a wide range of pressures up to 15 atm by using a volumetric method. The acentric factor was suggested as a potential factor to estimate the relative sorption rate. Since the apparent time constants of all the components showed much stronger dependence of pressure than those expected by the traditional Darken relation and the structural diffusion model, new models with the diffusion relation at the supercritical condition was proposed to predict the kinetic behaviors in the micropores. The proposed model successfully predicted the apparent time constant up to high pressure. In addition, the semi-empirical model that combined acentric factor with the proposed model was able to predict the strong pressure dependence accurately. However, since the strong adsorbates, CO₂ and SO₂, showed two-stage kinetic behavior with pressure, which was different from that of the other adsorbates. The kinetic behaviors of these molecules could be predicted by using two different sorption models.