1,721,261 research outputs found
Part 1: EIA and landforms
No full textA landform can be considered as a geomorphologic asset. It can be regarded as such not only on the basis of scenic, social, economic and cultural value, but also on the basis of other criteria related to the more general scientific concept of an asset. The methods for recognizing and evaluating geomorphologic assets on a scientific basis can be subdivided into two phases: 1) geomorphologic survey and mapping, and 2) selection from the geomorphologic maps of those landforms that may be considered as assets. Here, evaluations of geomorphologic assets in three different areas are presented. -from Author
Past and present of electrochemical treatment of organic pollutants
No full textOxidative electrochemical technologies offer an alternative solution to many environmental problems in the process industry, because electrons provide a versatile, efficient, cost-effective, easily automatable, and clean reagent. In electro-oxidation, organic pollutants can be removed by different methods:
(i) Direct electrolysis: the pollutants (R) are oxidized after adsorption on the anode surface without the involvement of any substance other than electrons:
Rads → Pads + ze-
(ii) Oxidation via intermediates of oxygen evolution: organic compounds are oxidised near the anode surface (M) at high potentials in the region of water discharge due to the participation of intermediates of oxygen evolution:
M + H2O → M(•OH) + H+ + e-
R + M(•OH) → M + CO2 + H2O
Anodes with high oxygen evolution overpotential, such as SnO2, PbO2 or boron-doped diamond (BDD) are ideal electrodes for the complete oxidation of organics to CO2 in wastewater treatment.
(iii) Indirect electrolysis mediated by oxidizing agents generated anodically: organic pollutants are removed through the mediation of some electroactive species generated at the anode surface, which act as intermediaries for electrons shuttling between the electrode and the organic compounds. The main oxidizing chemicals electrogenerated anodically are active chlorine and persulfates, that are produced by the oxidation of chloride and sulphates ions commonly present in wastewaters:
2Cl- → Cl2 + 2e-
2SO42- → S2O82- + 2H+ + 2e-
(iv) Electro-Fenton processes: the pollutants are removed by the •OH produced in the bulk of the solution using the electrogenerated Fenton's reagent where H2O2 is supplied in situ from the two-electron reduction of O2 on cathodes such as gas diffusion electrodes (GDE), reticulated vitreous carbon (RVC) or graphite-felt, and Fe2+ is continually regenerated from Fe3+ reduction:
Fe2+ + H2O2 → Fe3+ + OH- + •OH
O2 + 2H+ + 2e- → H2O2
Fe3+ + e- → Fe2+
(v) Coupled anodic and cathodic Processes: using an undivided cell, the contaminants are treated by H2O2 generated on the cathode and oxidizing agents or •OH generated at the anode.
Process selection depends on the nature of the electrode material, experimental conditions, and electrolyte composition. This lecture focuses on recent progress in the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants
Electro-Fenton, solar photoelectro-Fenton and UVA photoelectro-Fenton: Degradation of Erythrosine B dye solution
No full textThe treatment of Erythrosine B, selected as a model compound, has been comparatively studied by electrochemical advanced oxidation processes (EAOPs) such as electro-Fenton, UVA photoelectro-Fenton and solar photoelectro-Fenton at constant current density. Experiments are performed in a one-compartment cell with a BDD anode, and a commercial carbon felt cathode at pH = 3, treating a volume of 0.3 L in each test. The irradiation plays a crucial role in the increasing of hydroxyl radical production and in the recover of iron catalyst. A faster colour and COD removal degradation are achieved under the light application. UVA photoelectro-Fenton and solar photoelectro-Fenton processes allow degrading COD entirely in 90 min, while a conventional electro-Fenton does not reach 90% COD removal after 2 h. Energy consumptions are a substantial factor in process selection. Photo electro-Fenton with a UVA-100 W lamp has one of the best removal performance, but it becomes not suitable for application due to high energy demand, up to 515.6 kWh m−3, and the UVA system requires the main fraction of this energy. Possible alternatives are proposed to contain costs: the first is the reduction of UVA lamp power to 25 W, maintaining a high-performance removal with an Ec decreasing to 187.9 kWh m−3. Nevertheless, the lowest and competitive energy demands is obtained working with a solar photoelectro-Fenton system, where energy consumption are only related to the electrochemical process (20.9 kWh m−3), and removal is complete
Solid polymer electrolyte as an alternative approach for the electrochemical removal of herbicide from groundwater
No full textGroundwater represents one of the primary freshwater sources, but their pollution is rapidly increasing, and the development of tailored processes is mandatory. In this scenario, electrochemical advanced oxidation processes (EAOPs) represent a promising alternative to face this issue. Their application to groundwater is limited by low electrical conductivity, which directly affects cell voltage and then operating costs. In this paper, three different approaches to overcome this constrain are compared using a BDD anode and a Ti/RuO2 cathode. The first is the addition of a supporting electrolyte as sodium sulfate (Na2SO4); despite its efficacy to increase conductivity, some new problems are introduced in water source management and treatment plant for the electrolyte removal. An alternative approach is the reduction of gap-electrode from 5 mm up to some microns, equivalent to the thickness of a plastic mesh, used to avoid electrodes short-circuit. The third innovative method proposed here is the substitution of insulated mesh with an ionic conductor layer, a solid polymer electrolyte (SPE), like Nafion®117 sandwiched between the electrodes. This modification allows increasing electrochemical performance such as herbicide and COD removal, preserving energy consumptions. Moreover, SPE does not show any performance deterioration in the first 30 h of utilisation. The results suggest that the usage of SPE can be a promising approach for the treatment of groundwater
Electrochemical oxidation of organic pollutants in low conductive solutions
No full textThis mini-review supplies current opinion about the most recent works, which have been carried out toward the electrochemical treatment of organic compounds spike in low conductive solution. In particular, the first section is focused on the use of a solid polymer electrolyte in order to allow current flux with a low cell voltage even in a solution without supporting electrolyte. Meanwhile, the second section describes the microfluidic cells that are characterized by very small distances between electrodes (tens or few hundreds μm) that reduce the ohmic resistances and increase the mass transport of the pollutants to electrodes’ surfaces
Le Dolomiti dichiarate dall’UNESCO patrimonio mondiale dell’Umanità
No full textIl giorno 30 giugno 2009, durante la 33a sessione del World
Heritage Committee (22-30 giugno 2009 Sevilla, Spagna), le
Dolomiti sono state proclamate patrimonio dell’Umanità e
iscritte nella lista dei beni naturali per i criteri settimo (estetico
e paesaggistico) e ottavo (geologico e geomorfologico).
Si è così concluso nel migliore dei modi il lungo iter della candidatura ufficialmente iniziato nel 2005, ma che riprendeva
delle istanze provenienti dalle associazioni ambientaliste
nazionali e locali già perseguite fin dalla prima metà degli
anni novanta. Nell'articolo vengono discusse le motivazioni e i criteri di questo importante riconosciment
Geomorphology and environmental impact assessment: a methodologic approach
No full textTwo different paths to define geomorphologic environmental impact assessment are outlined. The first considers the relationships between a project and landforms or raw materials, the second the relationships between a project and geomorphologic processes. The term "impact' (I) refers to the relationships among a project, landforms and geomorphologic raw materials, and can be expressed as: I = Ga × F × Ha where: Ga=geomorphologic asset, F=fragility, Ha=human activity related to a project. The term risk (R) refers to the relationships between a project and geomorphologic processes, and covers the expected numbers of lives lost and persons injured, damage to property and the disruption of economic activity by a natural phenomenon. Risk can be expressed as: R=E × V × H, where: E=element at risk, V=vulnerability (ie the degree of loss that a set of elements at risk might suffer if a natural phenomenon of given magnitude recurs at given intervals), H=natural hazard (ie a potentially damaging phenomenon, often expressed as the probability of occurrence in a given area within a specific period). There are four methods of assessing hazards: direct measurements; mechanical models and calculations; overlaying thematic maps of potential causal factors; the statistical approach to effects, including recurrence. -from Author
Micropropagation of Lavandin (Lavandula officinalis Chaix x Lavandula latifolia Villard cv. Grosso
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