Use of Surfactants to Enhance the Removal of PAHs from Soil

The efficiency of soil remediation is often limited by the low aqueous solubility of Polycyclic Aromatic Hydrocarbons, PAHs. Surfactants can then be used to enhance the removal of PAHs from soils. The dissolution of pure solid deposit of benzo(a)pyrene, B(a)P, has shown that cationic surfactants are the most efficient to increase the aqueous solubility of B(a)P, when compared to neutral or anionic surfactants. In this paper we compare by using soil suspension washings, the efficiency of two surfactants (i) a cationic surfactant, the benzyldimethyl dodecylammonium bromide, BDDA, and (ii) a neutral one, the t-octylphenoxypolyethoxy ethanol, triton X-100. The losses of surfactant, by adsorption on soil or precipitation, were measured together with the release of B(a)P, chosen as a model molecule, representative of all the PAHs. The efficiency of surfactants used in blend was then compared to the efficiency of surfactants alone.     

Entropic effects in carbon nanotubes-templated crystallization of Poly(3-alkyl thiophenes,P3HT,P3OT)

A significant increase in polymer crystallinity is reported in composites of carbon-nanotubes (CNT) and Poly(3-octylthiophene-2,5-diyl), P3HT and Poly(3-octylthiophene-2,5-diyl), P3OT; Differential scanning calorimetry (DSC) reveal an increase from about 40% crystallinity of the native P3HT to ∼62% in composites containing 25 wt% MWNT. A similar behavior is observed in P3OT with ∼68% crystallinity, a double crystallization peak and higher melting temperature than the native polymers. The effect is unique to CNT and is not induced by fullerenes or graphene layers. High-resolution transmission electron microscopy, (HRTEM) of CNT-polymer dispersions reveal chains stacked upon the CNT in an elongated, stretched conformation. Following a detailed molecular study by Bernardi et al. and the HRTEM observations the DSC results are attributed to a CNT-mediated entropic effect: due to their intrinsic, 1D cylindrical shape the CNT impose an increased conjugation length on chains adsorbed and stacked upon dispersed CNT. Crystallization thus commences from a heterogeneous mixture of native chains and chains with a longer persistence length (higher effective rigidity) and consequentially a lower effective height of the entropic barrier for crystallization. The findings offer a new insight into the origins of CNT-induced polymer nucleation.     

Structural Studies and Valence Band Splitting Parameters in Ordered Vacancy Compound AgGa7Se12

The threefold absorption in the fundamental absorption region of the ternary chalcopyrite AgGa₇Se₁₂, an ordered defect compound of AgGaSe₂, is analyzed to elucidate the three closely spaced band gaps in its valence band due to the lifting of degeneracy of the Γ₁₅ level. Hopfield’s quasi cubic model is employed to extract the crystal-field and spin–orbit splitting parameters and the linear hybridisation of orbitals model for evaluating the percentage contribution of Ag d-orbital and Ga and Se p-orbitals to the p–d hybridization of orbitals. The observed optical properties are correlated with the structural parameters like deformation parameter, anion displacement and anion–cation bond lengths that are deduced from X-ray diffraction data. The compound films for the studies are prepared by a modified form of Gunther’s three temperature technique and the compositional analysis was done by energy dispersive analysis of X-rays. X-ray photoelectron spectroscopy confirms the compound formation while atomic force microscopic technique was used for surface morphological analysis. The electrical resistivity of these n-type semi-conducting films is assessed to be ~5 Ωm and the films are found to be photosensitive.     

A Langrangian Study of Solids Suspension in a Stirred Vessel by Positron Emission Particle Tracking (PEPT)

A technique of Positron Emission Particle Tracking (PEPT) was used to obtain information on the flow behavior of coarse particles suspended in pseudoplastic liquids agitated by axial‐hydrofoil Lightnin impellers A320 and A410. PEPT enables the position of a 600 μm radioactive particle tracer inserted inside one of the suspended particles to be detected many times per second and its full trajectory followed inside the vessel. Particle trajectory analysis yielded information on particle circulation, velocity distribution, and spatial occupancy. The minimum speed for complete particle suspension, N_js, was also determined. The well‐known Zwietering correlation failed to predict the measurements by a substantial margin, suggesting that it is inadequate for viscous non‐Newtonian liquids.     

Model oxide-supported metal catalysts: energetics,particle thicknesses,chemisorption and catalytic properties

Many industrially important catalysts consist of late transition metal particles supported on the surfaces of oxide materials. Our studies of such systems using model catalysts consisting of metal films vapor deposited onto the surfaces of single-crystalline oxides are reviewed here. Systems studied include Cu on ZnO, Pt on ZnO, Au on TiO₂ and Cu, Ag and Pb on MgO. A unique adsorption microcalorimeter was developed to measure directly the energetic stability of the metal atoms on the oxide surfaces and the adhesion energy at the metal/oxide interface, which clarify the structural and chemisorption properties of the ultrathin metal particles. The structure of the oxide surface and the metal particles was elucidated by low-energy electron diffraction (LEED), low-energy ion scattering spectroscopy (ISS), angular-resolved X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The electronic character of the metal particles was revealed by XPS, Auger electron spectroscopy (AES), band-bending and work function measurements. Sintering rates were measured by temperature-programmed ion scattering spectroscopy (TPISS). The chemisorption properties of these particles and their catalytic reactivity were monitored by mass spectroscopy and temperature-programmed desorption (TPD).     

Rubber modification of low temperature cure cyanate ester matrices and the performance in glass fabric composites

Low temperature cure cyanate ester resin systems were developed and modified with epoxy‐terminated butadiene acrylonitrile rubber (ETBN) and impregnated into woven glass fabric. Mode I and mode II interlaminar fracture toughness values of the cured laminates were evaluated as a function of rubber concentration. Mode I fracture toughness increased to almost twice that of the unmodified system, while mode II fracture toughness remained essentially unchanged. Composite samples were subjected to aging experiments in water and the absorption/desorption behavior was investigated as was the effect on thermal performance. The presence of rubber was found to reduce the rate of matrix deterioration but also caused a substantial increase in water uptake. It was found that although the addition of rubber to the matrices decreased the unconditioned (dry) T_g all specimens showed the same reduction in T_g, after equilibrium water absorption.     

Scintillation from Eu2+ in Nanocrystallized Glass

A Eu²⁺-doped SiO₂–Al₂O₃–CaO–CaF₂ glass was prepared and converted into a transparent glass ceramic by heat treatment. The crystalline phase and its size were determined by X-ray diffraction and a transmission electron microscopy. The scintillation of Eu²⁺ ions in both glass and ceramic under X-ray excitation was investigated and compared with that in a single-crystal scintillator.     

In situ observation of dynamic elastic modulus in polypyrrole actuators

Polypyrrole is a leading conducting polymer actuator, but the factors that influence its performance when actuated under load in devices (such as the polymer stiffness) are not yet fully understood. To this end, we have probed the dynamic elastic modulus of polypyrrole in situ during actuation in a variety of electrolytes. As part of this study, we demonstrate that the electroactive response in dilute 1-butyl-3-methylimidazolium hexafluorophosphate can be changed from cation- to anion-dominated by adjusting the applied potential waveform. We observe that when conservative electrochemical conditions are applied in order to avoid dual ion movement or significant transfer of neutral solvent, the stiffness is determined by level of counterion swelling. The elastic modulus decreases during the net influx of ions into the bulk polymer and increases as these ions are expelled, regardless of whether the electroactive response is cation- or anion-dominated or whether there is a neutral solvent present in the electrolyte. This effect is quite significant, and we have observed up to a 3× increase in elastic modulus upon actuation in neat 1-butyl-3-methylimidazolium hexafluorophosphate.     

Heuristic and probabilistic wind power availability estimation procedures: Improved tools for technology and site selection

The paper describes two investigative procedures to estimate wind power from measured wind velocities. Wind velocity data are manipulated to visualize the site potential by investigating the probable wind power availability and its capacity to meet a targeted demand. The first procedure is an availability procedure that looks at the wind characteristics and its probable energy capturing profile. This profile of wind enables the probable maximum operating wind velocity profile for a selected wind turbine design to be predicted. The structured procedures allow for a consequent adjustment, sorting and grouping of the measured wind velocity data taken at different time intervals and hub heights. The second procedure is the adequacy procedure that investigates the probable degree of availability and the application consequences. Both procedures are programmed using MathCAD symbolic mathematical software. The math tool is used to generate a visual interpolation of the data as well as numerical results from extensive data sets that exceed the capacity of conventional spreadsheet tools. Two sites located in Southern Ontario, Canada are investigated using the procedures. Successful implementation of the procedures supports informed decision making where a hill site is shown to have much higher wind potential than that measured at the local airport. The process is suitable for a wide spectrum of users who are considering the energy potential for either a grid-tied or off-grid wind energy system.