Applications of pore-expanded mesoporous silica. 7. Adsorption of volatile organic compounds

Three different varieties of mesoporous silicas were synthesized by varying the postsynthesis treatment of an as-synthesized ordered mesoporous material type MCM-41. The resulting materials consisted of a purely siliceous MCM-41, a pore-expanded MCM-41 (PE-MCM-41C), and a surfactant-laden pore-expanded MCM-41 (PE-MCM-41E) and were evaluated as adsorbents for two types of volatile organic compounds, i.e., chlorinated and aromatic hydrocarbons. Values of heat of adsorption and Henry's law constant were determined by pulse chromatography. Additionally, adsorption capacities were calculated with a dynamic method using breakthrough curves for single components in dry and humid environments. The surfactant-containing material exhibited good compatibility with chlorinated compounds in terms of heat of adsorption and efficiency in gaseous streams containing moisture. Purely siliceous mesoporous materials, i.e., MCM-41 and PE-MCM-41C, were more selective toward aromatic hydrocarbons but also gave rise to exceptionally strong adsorption.     

Preparation of a new ceramic microfiltration membrane from mineral coal fly ash: Application to the treatment of the textile dying effluents

New microfiltration membranes from mineral coal fly-ash material are obtained using ceramic method. Paste from mineral coal fly ash (obtained by calcinations at 800 °C of non-grinded mineral coal) is extruded to elaborate a porous tubular configuration used as supports. The support heated at 1125 °C, shows an average pore diameter and porosity of about 4.5 μm and 51%, respectively. The properties in terms of mechanical and corrosion resistances are very interesting. The elaboration of the layer based on fly-ash powder (obtained by sintering at 700 °C of a finely grinded mineral coal) is performed by slip-casting method. The heating treatment at 800 °C leads to an average pore size of 0.25 μm. The water permeability determined of this membrane is 475 L/h m² bar. This membrane can be used for crossflow microfiltration. The application to the treatment of the dying effluents generated by the washing baths in the textile industry shows an important decrease of turbidity (inferior to 1 NTU), of chemical oxygen demand (COD) values (retention rate of about 75%) and a total color removal. The performances in term of permeate flux and efficiency were determined and compared to those obtained using a commercial alumina microfiltration membrane. Almost the same stabilised permeate flux was obtained (about 100 L h⁻¹ m⁻²). So, it seems that the prepared membrane is suitable for such wastewater treatment.     

Catalytic nitroxidation of para-xylene over chromium oxide based catalysts

The synthesis of para-tolunitrile (PTN) and terephthalonitrile (TPN) by reacting nitrogen monoxide with para-xylene was studied in presence of three chromium oxide catalysts. The Cr₂O₃—Al₂O₃ catalyst was prepared under the form of aerogel or xerogel and shows excellent selectivities in nitriles along with good stability. However, the unsupported Cr₂O₃ catalyst showed much less performance and, in particular, produced no TPN. The beneficial action of alumina was explained in terms of stabilization of the Cr⁵⁺ species. Kinetic results seemed to indicate a redox-type mechanism of the reaction. Moreover the PTN was shown to be an intermediate in TPN formation.     

Physiological Demands during Construction Work

Notwithstanding the use of earthmoving equipment, cranes, and other machinery, physically strenuous and demanding tasks remain endemic to the construction industry. This research was motivated by the need to investigate the physical demands of construction work and to evaluate whether these physical demands are excessive. Physiological measures of energy expenditure, including oxygen consumption and heart rate data, were collected for 100 construction workers performing typical construction work. The average oxygen uptake for the measured construction activities was 0.82 L?min?1 (±0.22 L?min?1), and the average heart rate for the measured construction activities was 108 beats ?min?1 (±17 beats ?min?1). The measured data were evaluated against published guidelines for acceptable levels of physical performance in industrial settings indicating that a significant number of craft workers (20 to 40%) routinely exceed these physiological thresholds. The results clearly point to the need to promote and apply concepts of work physiology at the workplace to better the occupational health and safety of the construction workforce. This paper developed the foundation for further applied research regarding the physical demands of construction work.     

Proprietes magnetiques de la phase Sr1,50La0,50MnO4

The crystallographic, electrical and magnetic properties of Sr_1,50La_0.50MnO₄ which has a K₂NiF₄-type structure show the existence of ferromagnetic clusters due to Mn³⁺Mn⁴⁺ short range ordering antiferromagnetically coupled.     

Directional alignment of MG63 cells on polymer surfaces containing point microstructures

MG63 cells cultured on regular arrays of point microstructures (posts and holes) are shown to preferentially align at certain angles to the pattern of the structures, at 0 degrees, 30 degrees, and 45 degrees in particular. The effect is found to be more pronounced for post rather than hole structures (although no significant difference is found for the angles the cells make to the holes or posts) and is thought to be due to the fact that the cells use the posts as anchorage points to hold themselves to the surface. It is also shown that cells preferentially align with the structures depending on the dimensions of the structures and the distance between neighboring structures. This is important when designing structured surfaces for cell-surface interaction studies for materials to be used in, for example, drug delivery or tissue engineering.     

Improvement of rheological properties of Algeria crude oil by addition of extra-light crude oil and a surfactant agent

Abstract

Effect of surfactant and extra-light crude oil addition on the rheological behaviors of an Algeria crude oil in order to improving its flowability were studied at low temperature. These rheological properties include steady flow behavior, yield stress and viscoelastic behavior. An AR-2000 rheometer was employed in all of the rheological examination tests. Results show that Toluene and extra-light crude oil addition causes a strong reduction in viscosity, the yield stress and can effectively increase of crude oil transport capacity. The toluene addition gets its best flow capacity and lowest viscosity at 6%. The extra-light crude oil addition obtains its best flow capacity and lowest viscosity at 50%. The viscoelasticity character of the crude oil has indicate a significantly influence by the addition of Toluene and extra-light crude oil.     

Rheological behavior of Algerian crude oil: effect of temperature and refined product

Abstract

The rheological behavior and its variation with temperature and refined product concentration of a crude oil sample coming from a quagmire of the separation station of Tin Fouye Tabankort oilfield/southern Algeria were investigated experimentally. The experiments were carried out at various temperatures (20, 30 and 50?°C) over the shear rate range of 0 to 700?s^?1 by using a controlled stress rheometer (AR 2000, TA Instrument). The results showed that the crude oil exhibit non-Newtonian of shear thinning behavior at low shear rate and Newtonian behavior at high shear rate and was adequately described by Casson and Herschel–Bulkley models. The rheological measurements through the steady flow test and viscoelastic behavior, including the storage modulus (G′), loss modulus (G″), and complex modulus (G*), has indicated that the rheological properties of the crude oil were greatly influenced by the temperature and the additive concentration.     

A methanol – Tolerant carbon supported Pt–Sn cathode catalysts

Carbon supported Pt–Sn bimetallic electrocatalysts with a Pt:Sn 90:10 atomic ratio were prepared by impregnation method and then heat treated at 300 and 500 °C under Helium atmosphere. The purpose of this work is to investigate the effect of tin addition to platinum for methanol tolerant oxygen reduction reaction. In this sense, structure and morphological properties of supported bimetallic catalysts were correlated to the catalytic performance. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterizations confirm the formation of Pt–Sn bimetallic electrocatalysts with a Pt single-phase material alloy and revealed an increase in the average particle size after heat treatment. The electrocatalytic activities of these samples for the oxygen reduction reaction (ORR) were examined in acidic medium using both a rotating disk (RDE) and a rotating ring disk (RRDE) electrodes. Compared with the Pt/C, Pt–Sn/C bimetallic catalysts show superior electrocatalytic activity towards ORR with an approaching four electron pathway leading to water formation. The specific and mass activity for ORR follow the order of Pt–Sn/C-500 ≈ Pt–Sn/C-300 > Pt–Sn/C > Pt/C. Furthermore, it is found that among the three Pt–Sn samples, Pt–Sn/C-500 exhibits the highest methanol tolerance. These experimental observations indicate that the addition of Sn into Pt is favorable to maximize the ORR performances of platinum and further the heat treatment is beneficial to improve the methanol tolerance behavior. On this basis, the novel Pt–Sn catalysts can be considered as potential candidates to be used as cathodes in Direct Methanol Fuel Cells.