193 research outputs found
Effect of organic matter release from natural cork used on bisphenol a removal from aqueous solution
The paper presents an experimental study aimed at investigating the mechanism responsible for Bisphenol A adsorption on natural cork, and the role played on process kinetics by the organic matter released from the cork. Obtained data show that natural cork has a good affinity toward Bisphenol A, with removal efficiency being as high as 75% in less than 24 h. The adsorption process is characterized by a fast-initial rate which tends to reduce progressively, and follows a pseudo second order model equation. Statistical physics analysis allows for obtaining a molecular description of the adsorption, which is shown to take place through a single anchorage point, perpendicularly to the adsorbent surface. Nuclear magnetic resonance spectroscopy and fluorescence analysis reveal that the colloidal organic matter released from the cork interacts with Bisphenol A; it also plays a relevant role in the slowing down of the adsorption rate, as it competes with cork adsorption sites for Bisphenol A. Organic matter is found to be highly heterogenous, presenting at the same time carbohydrates, aromatic and aliphatic domains. Such moieties interact stably with the contaminant in the solution probably due the establishment of dispersive forces (e.g. π-stacking) which sequestrate Bisphenol A into the inner hydrophobic core of the organic matter three-dimensional structure
Is there a reentrant glass in binary mixtures?
By employing computer simulations for a model binary mixture, we show that a
reentrant glass transition upon adding a second component only occurs if the
ratio of the short-time mobilities between the glass-forming component
and the additive is sufficiently small. For , there is no
reentrant glass, even if the size asymmetry between the two components is
large, in accordance with two-component mode coupling theory. For , on the other hand, the reentrant glass is observed and reproduced only by
an effective one-component mode coupling theory.Comment: 4 pages, 3 figure
Dewatering of excess sludge produced by cas and mbr aerobic treatment plants. effects of biochemical stability and eps composition
This paper investigates the behavior of different sludges from several treatment plants at full and pilot scale configured as Conventional Activated Sludge (CAS) and Membrane Bio Reactor (MBR) plants treating different kinds of wastewaters. The sludges collected were subjected to complete analytical and technological characterization in order to correlate the rheological properties that affect the dewatering behavior to the sludge chemical physical properties. In detail the EPS from the samples collected is extracted and characterized in terms of carbohydrates, proteins, uronic acids and humic acids content. Moreover, once characterized, the sludges were subjected to AD in order to assess their bio-methanation potential and hence their biological stability. The final aim was to find correlations between the WWTP operational parameters (i.e. HRT, SRT, volumetric load coefficient, aeration) that finally affect its chemical composition (i.e. BMP, EPS composition) and the physical behavior of the sludge
Atomic-scale surface demixing in a eutectic liquid BiSn alloy
Resonant x-ray reflectivity of the surface of the liquid phase of the
BiSn eutectic alloy reveals atomic-scale demixing extending over
three near-surface atomic layers. Due to the absence of underlying atomic
lattice which typically defines adsorption in crystalline alloys, studies of
adsorption in liquid alloys provide unique insight on interatomic interactions
at the surface. The observed composition modulation could be accounted for
quantitatively by the Defay-Prigogine and Strohl-King multilayer extensions of
the single-layer Gibbs model, revealing a near-surface domination of the
attractive Bi-Sn interaction over the entropy.Comment: 4 pages (two-column), 3 figures, 1 table; Added a figure, updated
references, discussion; accepted at Phys. Rev. Let
First AGILE Catalog of High Confidence Gamma-Ray Sources
We present the first catalog of high-confidence gamma-ray sources detected by
the AGILE satellite during observations performed from July 9, 2007 to June 30,
2008. Catalogued sources are detected by merging all the available data over
the entire time period. AGILE, launched in April 2007, is an ASI mission
devoted to gamma-ray observations in the 30 MeV - 50 GeV energy range, with
simultaneous X-ray imaging capability in the 18-60 keV band. This catalog is
based on Gamma-Ray Imaging Detector (GRID) data for energies greater than 100
MeV. For the first AGILE catalog we adopted a conservative analysis, with a
high-quality event filter optimized to select gamma-ray events within the
central zone of the instrument Field of View (radius of 40 degrees). This is a
significance-limited (4 sigma) catalog, and it is not a complete flux-limited
sample due to the non-uniform first year AGILE sky coverage. The catalog
includes 47 sources, 21 of which are associated with confirmed or candidate
pulsars, 13 with Blazars (7 FSRQ, 4 BL Lacs, 2 unknown type), 2 with HMXRBs, 2
with SNRs, 1 with a colliding-wind binary system, 8 with unidentified sources.Comment: Revised version, 15 pages, 3 figures, 3 tables. To be published in
Astronomy and Astrophysics. Text improved and clarified. Refined analysis of
complex regions of the Galactic plane yields a new list of high-confidence
sources including 47 sources (compared with the 40 sources appearing in the
first version
Porosity of silica Stöber particles determined by spin-echo small angle neutron scattering.
Stöber silica particles are used in a diverse range of applications. Despite their widespread industrial and scientific uses, information on the internal structure of the particles is non-trivial to obtain and is not often reported. In this work we have used spin-echo small angle neutron scattering (SESANS) in conjunction with ultra small angle X-ray scattering (USAXS) and pycnometry to study an aqueous dispersion of Stöber particles. Our results are in agreement with models which propose that Stöber particles have a porous core, with a significant fraction of the pores inaccessible to solvent. For samples prepared from the same master sample in a range of H2O : D2O ratio solutions we were able to model the SESANS results for the solution series assuming monodisperse, smooth surfaced spheres of radius 83 nm with an internal open pore volume fraction of 32% and a closed pore fraction of 10%. Our results are consistent with USAXS measurements. The protocol developed and discussed here shows that the SESANS technique is a powerful way to investigate particles much larger than those studied using conventional small angle scattering methods
Gamma-ray burst detection with the AGILE mini-calorimeter
The mini-calorimeter (MCAL) instrument on-board the AGILE satellite is a non-imaging gamma-ray scintillation detector sensitive in the 300 keV-100 MeV energy range with a total on-axis geometrical area of 1400 cm(2). Gamma-ray bursts (GRBs) are one of the main scientific targets of the AGILE mission and the MCAL design as an independent self-triggering detector makes it a valuable all-sky monitor for GRBs. Furthermore MCAL is one of the very few operative instruments with microsecond timing capabilities in the MeV range
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