Abstract  Electrokinetic soil remediation has been proven to remove heavy metals and polar organics from low hydraulic conductivity subsurface environment. In this study, carboxymethyl-beta-cyclodextrin (CMCD) was used as a carrier to assist electrokinetic treatment for removal of low polarity organic contaminants from soils (2.2% organic carbon content). Naphthalene and 2,4-dinitrotoluene (2,4-DNT) were selected as the test compounds. The results from columns experiments showed that 46 and 43% of naphthalene and 2,4-DNT, respectively, were removed using 0.01 N NaNO(3) flushing solution with 40 V electrical potential while 70 and 72% of naphthalene and 2,4-DNT were removed using 2 g/L CMCD solution. Naphthalene and 2,4-DNT removal was enhanced to 83 and 89%, respectively, by using 2 g/L CMCD with 40 V electrical potential. Findings from this study also demonstrated that cyclodextrin assisted electrokinetics can enhance the removal rate of naphthalene and 2,4-DNT. Electric potential applied has more influence on the contaminant removal than the amount of CMCD used. Higher voltage application caused increase in the removal rate of naphthalene and 2,4-DNT, and appeared to be one of the critical factors in obtaining higher contaminant removal while increasing CMCD solution concentration above 2 g/L appeared to have little effect on the contaminant removal.

Abstract  Single-walled carbon nanotubes (SWCNTs) derivatized with cobalt phthalocyanine (CoPh) were applied onto screen-printed graphite electrodes (SPEs) to be used for the low-potential electrochemical oxidation of thiocholine (TCh). Covalent attachment of CoPh to SWCNTs via stable sulfonamide bonds was confirmed by Raman/FT-IR spectroscopy and thermogravimetric analysis (TGA) coupled with FT-IR detection. The resulting modified SPE surfaces (CoPh-SWCNT-SPEs) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) with the redox probe [F(3)(CN)(6)](3-/4-). Detection of TCh was accomplished using cyclic voltammetry and amperometry; a lower overpotential (100 mV vs. Ag/AgCl pseudoreference electrode) was obtained using CoPh-SWCNT-SPEs as compared to unmodified SPEs and SPEs modified with non-functionalized SWCNTs (SWCNT-SPEs). The linear range for TCh detection was 0.077-0.45 mM, with a sensitivity of 5.11 x 10(-1) mu A mM(-1) and a limit of detection of 0.038 mM according to the 3 s/m definition. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Gold electrodes were functionalized with an electropolymerized matrix of Au nanoparticles modified with 2-mercaptoethanesulfonic acid. 3-mercaptophenyl boronic acid and p-aminothiophenol. The resulting nanostructured electroconductive matrix was used as support for the oriented immobilization of horseradish peroxidase to construct a reagentless amperometric biosensor for H2O2. The electrode, poised at 0.0 mV, exhibited a rapid response within 8 s and a linear calibration range from 5 mu M to 1.1 mM H2O2. The sensitivity of the biosensor was determined as 498 mu A/M cm(2). and its detection limit was 1.5 mu M H2O2 at a signal-to-noise ratio of 3. The electrode retained 95% and 72% of its initial activity after 21 and 40 days of storage at 4 degrees C. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  The highly dispersed and ultrafine carbon-supported Pd nanoparticles (Pd/C) catalyst is synthesized by using an improved precipitation-reduction method, which involves in Pd(II) -> PdO center dot H(2)O Pd(0) reaction path. In the method, palladium oxide hydrate (PdO center dot H(2)O) nanoparticles (NPs) with high dispersion is obtained easily by adjusting solution pH in the presence of 1,4-butylenediphosphonic acid (H(2)O(3)P-(CH(2))(4)-PO(3)H(2), BDPA). After NaBH(4) reduction, the resulting Pd/C catalyst possesses high dispersion and small particle size. As a result, the electrochemical measurements indicate that the resulting Pd/C catalyst exhibits significantly high electrochemical active surface area and high electrocatalytic performance for formic acid electrooxidation compared with that prepared by general NaBN(4) reduction method. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Pyrite (FeS(2)) oxidation in modem sedimentary environments is neither a purely chemical nor purely microbial process, but it is significantly enhanced by the activity of microorganisms that use reduced forms of iron and sulphur in their metabolisms. On the early Earth, where oxygen levels were thought to be <10(-5) of the present atmospheric level and chemical oxidants scarce, such biological mediation may have been critical in the redox cycles of iron and sulphur. Here, we show that detrital sedimentary pyrite grains in a similar to 3.4 billion-year-old sandstone were colonised by microbial communities. The detrital pyrite comes from the basal quartz arenite member of the 3.43-3.35 Ga Strelley Pool Formation (SPF) in the East Strelley greenstone belt of the Pilbara Craton, Western Australia Rock chips and petrographic thin sections of black sandstones occurring on two ridges close to the SPF type locality of Strelley Pool were investigated using optical microscopy, SEM, TEM. laser Raman and NanoSIMS. The detrital pyrite grains exhibit laminated carbonaceous coatings of early Archean age, with localised enrichments of nitrogen that are interpreted as the in situ remains of biofilms growing on these nutrient-rich minerals. Pyrite surfaces contain spherical pits, chains of pits and channels that are morphologically distinct from abiotic alteration features. The pits and channels are widespread, have a clustered distribution typical of microbial colonisation, and are closely comparable to biologically mediated microstructures in the younger rock record and those created by extant Fe- and S-oxidising microbes in the laboratory. They are thus interpreted as trace fossils formed by the attachment of bacteria to the pyrite surfaces. A nano-layer and discreet nano-grains of secondary mineral precipitates, namely Fe-oxides belonging to the magnetite-maghaemite group, attest to pyrite oxidation. These are intimately associated with the biofilms and trace fossils, and are interpreted to represent the fossilised mineral products of biologically mediated pyrite oxidation. These data extend the geological range of microbes capable of metabolising reduced Fe and/or S compounds back to the early Archean and indicate that pyrite-rich sedimentary rocks provide promising targets in the search for extraterrestrial life. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  Grand canonical Monte Carlo (GCMC) simulation is used to investigate the performance of poly(vinyl alcohol) (PVA) membrane in separating the azeotropic water/ethanol mixture (95.57. wt% ethanol) over a wide range of pressures (10-1000. kPa), temperatures (298-338. K) and PVA polymerization degrees (100-1000). By calculating the sorption isotherms and the ethanol-to-water separation factors, we observe that the water/ethanol adsorption amount and separation factor decline slowly with the increase of temperature; as the polymerization degree rises, both of adsorption amounts first increase and then decrease, while the separation factor changes adversely. Concepts such as fractional free volume (FFV) and hydrogen bonding interactions are analyzed to explain the observation. As the polymerization degree increases, the FFV changing trend is similar to the one mentioned in the discussion of adsorption amount, but their inflexions are different. Hydrogen bonding interaction successfully explains this variation. We further deduce that the fact that the change of adsorption amount results from a transition from cooperation to competition between FFV and hydrogen bonding interactions. The optimal operating conditions for separation are 298. K and 101.325. kPa. Under this condition, the PVA membrane (polymerization degree 1000) has a separation factor of ∼80 for the water/ethanol azeotropic mixture, which means that the concentration of ethanol can be refined to 99.96. wt% and anhydrous ethanol is possible to be obtained by PVA membrane separation. © 2010 Elsevier B.V.

Abstract  Ordered mesoporous carbon supported MgO (Mg-OMC) materials were synthesized by the carbonization of sulfuric-acid-treated silica/triblock copolymer/sucrose/Mg(NO3)(2) composites. In the current approach, triblock copolymer P123 and sucrose were employed as both structure-directing agents for the self-assembly of rice husk ash silica solution and carbon precursor. Sulfuric acid was used to cross-link P123 and sucrose in the as-synthesized composites in order to improve the carbon yield. The synthesized Mg-OMC was characterized by X-ray diffraction, N-2 adsorption-desorption isotherm method, X-ray photoelectron spectroscopy, scanning electron microscope equipped with energy dispersive X-ray analysis and transmission electron microscopy. The thermal stability of Mg-OMC was verified by CO2-temperature programmed desorption, which confirmed the chemisorption of CO2 on MgO. The CO2 adsorption capacity of Mg-OMC-1 was observed to be 92 mg/g of sorbent which is comparable with that of the well established CO2 sorbents. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  1m3 of methane hydrate can be decomposed into a maximum of 216m3 of methane gas under standard conditions. Conversely, such a large volume of methane hydrate can be utilized to store and transport a large quantity of natural gas. When methane hydrate is formed artificially by simply reversing its process of natural generation, the amount of methane gas consumed owing to hydrate formation is fairly low which would be problematic for its massive synthesis and application. In this study, experiments are carried out with the goal of increasing the amount of gas consumed by adding two kinds (CM-95 and CM-100) of multi-walled carbon nanotubes (MWCNTs) to pure water, where the physical length of CM-95 is much shorter than CM-100. When the 0.004wt.% CM-95 MWCNT solution is compared with pure water, the gas consumption rate almost triples indicating its effect in hydrate formation. Also, the CM-95 MWCNTs decreased the hydrate formation time to a greater extent than the CM-100 MWCNTs at a low subcooling temperature.

Abstract  Three different types of nanofluids were prepared by dispersing gamma-Al2O3, TiO2 and CuO nanoparticles in a 0.5 wt% of carboxymethyl cellulose (CMC) aqueous solution. Thermal conductivity of the base fluid and nanofluids with various nanoparticle loadings at different temperatures were measured experimentally. Results show that the thermal conductivity of nanofluids is higher than the one of the base fluid and the increase in the thermal conductivity varies exponentially with the nanoparticle concentration. In addition to increase with the nanoparticle concentration, the thermal conductivity of nanofluids increases with the temperature. Neural network models were proposed to represent the thermal conductivity as a function of the temperature, nanoparticle concentration and the thermal conductivity of the nanoparticles. These models were in good agreement with the experimental data. On the other hand, the Hamilton Crosser model was only satisfactory for low nanoparticle concentrations. (C) 2010 Elsevier Ltd. All rights reserved.