117,521 research outputs found
A comparison between different advanced oxidation processes for the remediation of PCP contaminated wastewaters
No full textIn this paper a comparison between different advanced oxidation processes (AOP), for the remediation of a wastewater contaminated with 100 mg/l of pentachlorophenol (PCP), is proposed. The AOP chosen were: Fenton or Fentonlike reactions in which the soluble iron catalyst salt was added as Fe(II) or Fe(III) or a mixture of Fe(II) and Fe(III), and ozonation. In the latter case the effects of the presence of a solid iron oxide (hematite) were also evaluated. For the Fenton’s reactions, the investigated parameters were: pH (from pH=1.5 to pH=5), reaction time, H2O2/PCP ratio (from 5/1 to 20/1), Fe/H2O2 ratio (from 0 to 2/1) and the effect of a H2O2 stabilizer: KH2PO4. The highest TOC removal (75%) was reached, using stabilized H2O2 and Fe(II), when H2O2/PCP=5/1 and Fe/H2O2=1/1; in this case, dechlorination was 96% and KH2PO4 increased H2O2 lifetime significantly. Fe(III) or the mixture of Fe(II) and Fe(III), proved to be more efficient than Fe(II) when H2O2/PCP<15/1 and Fe/H2O2<1/1. For ozonation the effects of pH and of the ratio between airflow and the solution’s volume, were investigated. The highest efficiencies (TOC removal=35%, Cl- release=80%) were reached when O3=0.24 mg/l at pH=11; however diminishing the volume of treated solution, 47% TOC removal and stoichiometric Cl- release were observed. The addition of hematite resulted in a slight increase of TOC removal and Cl- release. By comparing the experimental results, among the tested AOP systems, Fenton’s reaction proved to be the most effective for PCP remediation
Use of EAF dust as heterogeneous catalyst in Fenton oxidation of PCP contaminated wastewaters
No full textIn this study, chemical oxidation tests using H(2)O(2) were performed on a solution contaminated with 100 mg l(-1) of pentachlorophenol (PCP). The effectiveness of electric arc furnace dust and hematite as heterogeneous catalysts was evaluated. Reactions were conducted at pH 2 for 24 h. Either H(2)O(2) stabilized with KH(2)PO(4) or un-stabilized H(2)O(2) was used. Total organic carbon (T.O.C.) removal and chloride release from PCP molecule were monitored. Results showed that the maximum removal yields for electric arc furnace (EAF) dust (49.2% T.O.C., 56.7% CI) were achieved when H(2)O(2):PCP ratio was 10: 1 and Fe:H(2)O(2) = 1:5 for unstabilized H(2)O(2) and when H(2)O(2):PCP = 10:1 and Fe:H(2)O(2) = 1:1 for stabilized H(2)O(2) (48% T.O.C., 60.6% CI). The maximum yield using hematite (45.2% T.O.C., 55.2% CI) was obtained when H(2)O(2):PCP ratio was 10:1 and Fe:H(2)O(2) was 1:2. When EAF dust was used and Fe:H(2)O(2) > 1:5, CI release was higher than the one expected from T.O.C. removal. (c) 2006 Elsevier B.V. All rights reserved
Effects of Lithium Niobate Polarization on Cell Adhesion and Morphology
No full textUnderstanding how the interfacial effects influence cell adhesion and morphology is of fundamental interest for controlling function, growth, and movement of cells in vitro and in vivo. In particular, the influence of surface charges is well-known but still controversial, especially when new functional materials and methods are introduced. Here, the influence of the spontaneous polarization of ferroelectric lithium niobate (LN) on the adhesion properties of fibroblast cells is investigated. The spontaneous polarization of LN has one of the largest known magnitudes at room temperature (similar to 78 mu C/cm(2)), and its orientation can be patterned easily by an external voltage, this motivating highly the investigation of its interaction with cells. Immunofluorescence and migration assays show strong evidence that the surface polarity regulates the adhesion functions, with enhanced spreading of the cytoskeleton on the negative face. The results suggest the potential of LN as a platform for investigating the role of charges on cellular processes, thus favoring new strategies in fabricating those biocompatible constructs used for tissue engineering. In fact, the orientation of the high-magnitude polarization can be patterned easily and, in combination with piezoelectric, pyroelectric, and photorefractive properties, may open the route to more sophisticated charge templates for modulating the cell response
Determination of sea water salinity by ultraviolet spectroscopic measurements
No full textA method for the determination of seawater salinity by ultraviolet (UV) spectroscopy is proposed. The effects of single salt concentrations and of salinity on UV absorption in the 190-250-nm range were investigated. These studies revealed that the absorption spectrum of a solution with a given salinity is due mainly, in order, to KBr>MgCl2>NaCl. The influence of the temperature and salt concentration on UV spectra was studied by using synthetic seawater samples with the salinities ranging from 1 to 50 parts per thousand (parts per thousand). Results showed that, in the absence of interferences, the most sensitive and reliable conditions for measuring the salinity are at 212 nm and al temperatures in the range of 25-30°C. Under these conditions this method shows quite linear calibration curves and allows us to perform salinity determinations in seawater solutions at concentrations as low as 4 parts per thousand. Moreover, it requires no sample pretreatment and offers a precision of 0.20 parts per thousand. The proposed method is very simple and rapid for laboratory and on-board analysis. Finally, the interference of organic matter, nitrite, and, nitrate species with the salinity determinations was investigated. These studies show that organic matter does not interfere at concentrations of carbon lower than 1 mg/L and at 210 nm. Interferences due to NOx- species can be ignored if these species are dissolved in solution at concentrations lower than approximate to 0.2 mg/L and the analyses are carried out at wavelengths lower than 212 nm
Distributed measurement of birefringence in uncoupled multicore fibers
No full textWe report the results of the first distributed measurement of local birefringence performed on a nominally-uncoupled four-core fiber. The data show correlation between the intrinsic birefringence of the individual cores. (c) 2021 The Author(s
Effect of acidification and modified Fenton treatment on a contaminated harbour sediment
No full textThis study presents the results of laboratory experimental oxidation treatments conducted on marine sediments highly polluted with hydrocarbons. The purpose of the study was to compare the effect of a modified Fenton treatment conducted with acidified stabilised H2O2 with one of simple acidification with H2SO4 used as control to evaluate the potential of heavy metal mobilisation. The H2O2 initial concentration was 0.62M and KH2PO4=1.15g center dot L-1. To evaluate changes in the solid and liquid phase, chemical oxygen demand (COD), thermogravimetric analysis (TGA) and differential thermal analysis (DTA) under O2 atmosphere analyses were performed on the solid, while total organic carbon (TOC), COD, pH and Eh were measured on the liquid. Evaluation of the heavy metal mobilisation was performed using sequential extraction procedures. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the carbon and to lower the COD of the sediment. In addition, the treated sediment showed easier-to handle characteristics, reduced caking and lower aggregation capacity. However some mobilisation of Cu occurred while the concentration of Fe lowered
Simple and Rapid Bioink Jet Printing for Multiscale Cell Adhesion Islands
No full textA simple and rapid process for multiscale printing of bioinks with dot widths ranging from hundreds of microns down to 0.5 mu m is presented. The process makes use of spontaneous surface charges generated pyroelectrically that are able to draw little daughter droplets directly from the free meniscus of a mother drop through jetting ("p-jet"), thus avoiding time-consuming and expensive fabrication of microstructured nozzles. Multiscale can be easily achieved by modulating the parameters of the p-jet process. Here, it is shown that the p-jet allows us to print well-defined adhesion islands where NIH-3T3 fibroblasts are constrained to live into cluster configurations ranging from 20 down to single cell level. The proposed fabrication approach can be useful for high-throughput studies on cell adhesion, cytoskeleton organization, and stem cell differentiation
Graphene and carbon black nano-composite polymer absorbers for a pyro-electric solar energy harvesting device based on LiNbO3 crystals
No full textA novel scheme for solar energy harvesting based on the pyro-electric effect has been demonstrated. The proposed harvester is based on an optical system focusing solar radiation onto a ferroelectric crystal (i.e. lithium niobate). The face exposed to the heating source is coated with a nanocomposite material (i.e. carbon black and graphene particles) that greatly improves the adsorption of solar radiation. The solar energy focused onto the crystal through a simple optical system allows one to induce a thermal gradient able to generate electric charges. Experiments have been carried out indoor as well as outdoor (in Pozzuoli, Naples, Italy, on December). Results show that two configurations appear to be preferable: (a) pyro-electric element with carbon black-based coating and a Fresnel lens (surface of about 100 cm(2)); (b) pyro-electric element with graphene-based coating and a Fresnel lens (surface of about 600 cm(2)). In both experimental arrangements the maximum temperature variation reached locally onto the lithium niobate substrate is relatively high with peaks greater than 250 degrees C. The maximum electrical power peak is of about 90 mu W and about 50 mu W for (a) and (b) respectively. The results of this first investigation are encouraging for further development of more efficient harvesting devices. (C) 2014 Elsevier Ltd. All rights reserved
Efficiency equalization of up- and down-conversion four-wave mixing in a semiconductor optical amplifier using two pumps with orthogonal polarization
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