Removal of mercury from natural gas by a new activated adsorbent from olive stones

This study was devoted to the valorization of a plant waste (olive stones): that is widely available in Mediterranean countries in order to remove mercury from natural gas. The raw material from olive stones was prepared by pyrolysis, chemical activation with phosphoric acid, and physical activation under steam. Two olive stone‐based granular activated carbons were prepared: one with the virgin stones, while the other was impregnated with sulphur. After treatment, the adsorbents obtained were characterized by determining the iodine number, the methylene blue index, and by estimating the porous properties by N₂ adsorption at 77 K. Thermogravimetric analysis and infrared spectroscopy analysis were carried out to determine the functional groups before and after mercury adsorption. An experimental study of vapour‐phase mercury adsorption by the activated carbons (virgin and sulphur‐impregnated) and a comparison with a commercial material (HGR) were performed. The comparison, made by analyzing the adsorption in a continuous mode, showed that the proportion of sulphur and the porosity were important for the removal of mercury. In the conditions used, the mercury adsorption on the ACs studied follows a physisorption mechanism. The results showed that granular activated carbon‐based olive stones (sulphur‐impregnated) are very efficient to remove mercury (with 2864 μg/g) and also less expensive than commercial activated carbon due to their local availability.     

Nanostructuring and Microstructuring of Materials from a Single Agropolymer for Sustainable MAP Preservation of Fresh Food

The main objective of the present work was to determine whether a single agropolymer [wheat gluten (WG)] could fit the modified atmosphere packaging (MAP) requirements of a range of six different fresh produce in key terms of oxygen permeation (Pe_O2) and CO₂/O₂ permselectivity (S) values. The required properties for optimal packaging of fresh fruits and vegetables were first evaluated using the Tailorpack MAP modelling software (UMR IATE, Montpellier, France) with packaging dimensions and respiratory and optimal atmosphere data as input parameters. Then, the modelled values obtained were compared with the properties of a range of WG composite films: monolayer self‐supported or multilayer at microscale or nanoscale, cast or thermoplasticised, with different formulations (percentage of plasticisers or nanofillers). The experimental gas transfer properties that could be covered by these materials ranged from 0.05 × 10^?10 to 2.00 × 10^?10 mol/m² s Pa for Pe_O2 and up to 18.0 for S. These ranges are much larger than conventional plastics that exhibit Pe_O2 from 0.10 × 10^?10 to 0.20 × 10^?10 mol/m² s Pa and S up to 4.5. It was demonstrated from a food‐requirements‐driven (Tailorpack modelling) and a multiscale film structuring (WG‐based composites) approaches, that transfer properties of WG‐based films would fit the requirements of the six selected fruits and vegetables better than conventional plastics. Copyright © 2012 John Wiley & Sons, Ltd.     

Tuning the crystallinity of thermoelectric Bi(2)Te(3) nanowire arrays grown by pulsed electrodeposition

Arrays of thermoelectric bismuth telluride (Bi(2)Te(3)) nanowires were grown into porous anodic alumina (PAA) membranes prepared by a two-step anodization. Bi(2)Te(3) nanowire arrays were deposited by galvanostatic, potentiostatic and pulsed electrodeposition from aqueous solution at room temperature. Depending on the electrodeposition method and as a consequence of different growth mechanisms, Bi(2)Te(3) nanowires exhibit different types of crystalline microstructure. Bi(2)Te(3) nanowire arrays, especially those grown by pulsed electrodeposition, have a highly oriented crystalline structure and were grown uniformly as compared to those grown by other electrodeposition techniques used. X-ray diffraction (XRD) analyses are indicative of the existence of a preferred growth orientation. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) confirm the formation of a preferred orientation and highly crystalline structure of the grown nanowires. The nanowires were further analyzed by scanning electron microscopy (SEM). Energy dispersive x-ray spectrometry (EDX) indicates that the composition of Bi-Te nanowires can be controlled by the electrodeposition method and the relaxation time in the pulsed electrodeposition approach. The samples fabricated by pulsed electrodeposition were electrically characterized within the temperature range 240?K≤T≤470?K. Below T≈440?K, the nanowire arrays exhibited a semiconducting behavior. Depending on the relaxation time in the pulsed electrodeposition, the semiconductor energy gaps were estimated to be 210-290?meV. At higher temperatures, as a consequence of the enhanced carrier-phonon scattering, the measured electrical resistances increased slightly. The Seebeck coefficient was measured for every Bi(2)Te(3) sample at room temperature by a very simple method. All samples showed a positive value (12-33?μV?K(-1)), indicating a p-type semiconductor behavior.     

Enhanced fluid flow through nanoscale carbon pipes

Recent experimental and theoretical studies demonstrate that pressure driven flow of fluids through nanoscale ( d < 10 nm) carbon pores occurs 4 to 5 orders of magnitude faster than predicted by extrapolation from conventional theory. Here, we report experimental results for flow of water, ethanol, and decane through carbon nanopipes with larger inner diameters (43 +/- 3 nm) than previously investigated. We find enhanced transport up to 45 times theoretical predictions. In contrast to previous work, in our systems, decane flows faster than water. These nanopipes were composed of amorphous carbon deposited from ethylene vapor in alumina templates using a single step fabrication process.