1,720,972 research outputs found
Characterizing toluene adsorption onto carbon nanotubes for environmental applications
No full textTwo different types of carbon nanotubes (CNTs), multi-walled and single-walled carbon nanotubes (MWCNTs and SWCNTs, respectively), have been characterized as new potential sorbents for contaminant removal from aqueous phase and can be used through different technological implementations. The performance of the materials has been evaluated in comparison with the most commonly used carbonaceous material, activated carbon (AC). Adsorption properties were evaluated by kinetic and equilibrium batch tests in aqueous solution at different salinity levels. Toluene was chosen as the reference compound to simulate the water phase dissolved portion of an oil spill. The experimental results have clearly demonstrated faster motion and higher adsorption capacity of MWCNTs and SWCNTs compared with AC. CNTs have shown very high removal efficiency for dissolved toluene, up to 30% and 90% for MWCNTs and SWCNTs, respectively. These results are very promising for the prospective use of CNTs as a potential alternative sorbent for hydrophobic organic compound (HOC) removal in environmental applications. © 2017 Desalination Publications. All rights reserved
Low-cost materials for environmental applications: possible alternatives in groundwater remediations
No full textBiochar from Pine Wood, Rice Husks and Iron-Eupatorium Shrubs for Remediation Applications: Surface Characterization and Experimental Tests for Trichloroethylene Removal
Full text linkNowadays porous materials from organic waste, i.e., Biochar (BC), are receiving increased attention for environmental applications. This study adds information on three BCs that have undergone a number of studies in recent years. A Biochar from pine wood, one from rice husk and one from Eupatorium shrubs enriched with Iron, labelled as PWBC, RHBC and EuFeBC respectively, are evaluated for Trichloroethylene (TCE) removal from aqueous solution. Physical-chemical description is performed by SEM-EDS and BET analysis. The decrease of TCE over time follows a pseudo-second order kinetics with increased removal by the PWBC. Freundlich and Langmuir models well fit equilibrium test data. The optimized values of the maximum adsorbed amount, qmax (mg g−1), follows this order 109.41 PWBC > 30.35 EuFeBC > 21.00 RHBC. Fixed-bed columns are also carried out. Best performance is again achieved by PWBC, which operates for a higher number of pore volume, followed by EuFeBC and RHBC. Continuous testing confirms batch studies and makes it possible to evaluate the workability of materials in configurations closer to reality. Results are promising for potential environmental application. In particular, the characterization of several classes of contaminants opens the doors to possible uses in mixed contamination case
Degradazione degli isomeri dell’esaclorocicloesano in suoli altamente contaminati mediante Ferro Zero-Valente
No full textRimozione degli isomeri dell’esaclorocicloesano in suoli reali altamente contaminati ad opera di un solvente ecocompatibile, acetato di etile
No full textCan Biochar be used as an alternative low-cost/cost effective sorbent for groundwater remediation?
No full textContaminated sites by mixture of contaminants are diffused worldwide: DNAPLs, VOCs or heavy metals are commonly revealed in the aquifer. Groundwater’s remediation technologies need to be more effective at lowering concentration imposed by local legislation, more sustainable and cost-effective. The “Pump&Treat” remains the most chosen technology combined with ex situ treatment, like adsorption onto sorbent materials, such as Activated Carbon. New strategies are interested in low-cost carbonaceous materials, like solid waste obtained by thermal treatment of agricultural waste. In this context lots of research are studying capacity of “biochar” (BC) in immobilizing different class of compounds from contaminated solutions. Some works report the BC’s efficiency in immobilizing nutritional compounds for plants and microorganisms and its eco-friendly being. These aspects are interesting for an innovative in situ technology, where the BC could be injected directly into the aquifer for selective contaminants immobilization and for supporting natural attenuation carried out by microorganisms. Furthermore, in the majority of papers, laboratory-made BCs were used. In this study (i) pine wood BC, obtained in a gasification unit in Germany, a (ii) rice husk BC, from a pyrolysis small-scale farmers unit in Indonesia, and a (iii) BC (from Eupatorium sp. shrubs) modified during the pyrolysis process adding oxide-hydroxides of Iron, were used. SEM and X-ray analysis, meso-, micro-porosity analysis and determination of the surface area (BET) confirm the morphological difference between these BCs, due to the different feedstock and process conditions (presence/absence of O2; temperature; residence time). Adsorption tests with contaminated solutions by Trichloroethylene and Lead (Pb2+) are carried out to investigate the behaviour and the efficiency in contaminants removal by batch and column reactors. Kinetic tests in batch reactors are performed to verify the equilibrium time required to write the isotherm curve. Experimental data are fitted with Langmuir and Freundlich model in order to obtain the optimized parameters that allows to compare the materials. To simulate real groundwater conditions, fixed-bed reactors are realized in plexiglass columns packed with a mixture of sand and reactive material and the breakthrough curves are drawn. The early results are very encouraging: at the equilibrium concentration of 5 mg L-1 of TCE the amount of adsorption, with Langmuir modeling, is 20 mg g-1 (i); 4 mg g-1 (ii) and 5 mg g-1 (iii) (tests onto a commercial Activated Carbon report 40 mg g-1); on the other hand at 20 mg L-1 of Pb(II) we obtained 5,5 mg g-1 and 23 mg g-1 for (i) and (ii) respectively (texts onto material (iii) are ongoing). These results are confirmed by the column tests and batch experiments with Toluene contaminated solutions are underway. Moreover, a fluidized-bed reactor (turbulence in the reactive zone) is going to be set up, in order to avoid problems linked to the column experiments (such as dead zone or preferential routs of the solutions) and other adsorption tests, combined with microorganisms’ activity, will be designed
Characterizing biochar as alternative sorbent for oil spill remediation
Full text linkBiochar (BC) was characterized as a new carbonaceous material for the adsorption of toluene from water. The tested BC was produced from pine wood gasification, and its sorption ability was compared with that of more common carbonaceous materials such as activated carbon (AC). Both materials were characterized in terms of textural features and sorption abilities by kinetic and equilibrium tests. AC and BC showed high toluene removal from water. Kinetic tests demonstrated that BC is characterized by faster toluene removal than AC is. Textural features demonstrated that the porosity of AC is double that of BC. Nevertheless, equilibrium tests demonstrated that the sorption ability of BC is comparable with that of AC, so the materials' porosity is not the only parameter that drives toluene adsorption. The specific adsorption ability (mg sorbed m-2 of surface) of the BC is higher than that of AC: toluene is more highly sorbed onto the biochar surface. Biochar is furthermore obtained from biomaterial thermally treated for making energy; this also makes the use of BC economically and environmentally convenient compared with AC, which, as a manufactured material, must be obtained in selected conditions for this type of application. © 2017 The Author(s)
Zero-valent Iron based Permeable Reactive Barrier simulating leaching processes from soil heavily contaminated by hexachlorocyclohexane
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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