1,720,963 research outputs found
Analysis report on photovoltaic waste as source of valuable materials. Overview on the current material recovery approaches
Full text linkEnd-of-life photovoltaic (EoL PV) modules are hazardous waste belonging to the category of WEEE. They contain environmentally toxic substances, poorly biodegradable materials but also valuable materials. The recovery of these last is the main goal of PV-waste treatments having the materials separation as initial stage conditioning the process. In order to facilitate the recovery and produce released fractions that are suitable for the recovery of glass, Si, Ag, Cu, Sn, Pb, and Al, the mechanical technics applied in the management of all WEEE without differentiation by type, are the most commonly used. However, a new and appropriate management strategy is required to create more profitable roads leading to the industrialization of environmentally and economically sustainable processes. The exponential increase in the volume of PV-waste imposes key challenges in the more efficient management of EoL PV modules. This paper aims to expand knowledge on critical point in the PV-waste management processes and provides information on types and trends for their treatment. It aims to help to formulate diversified management strategies and plans, shedding light on the usefulness of the adoption of a hybrid approach to optimize the recovery rate and recovered materials purity level to send to recycling
Photovoltaic waste as source of valuable materials: A new recovery mechanical approach
No full textEnd-of-life photovoltaic modules are hazardous waste belonging to the category of waste from electrical and electronic equipment. They contain environmentally hazardous substances, poorly biodegradable materials but also valuable materials. The recovery of these last is the main goal of PV-waste treatments. In order to facilitate the recovery and produce released fractions that are suitable for the recycling of glass, Silicon, Silver, Copper, Lead and Aluminium, the mechanical technics applied in the management of all e-waste without differentiation by type, are the most commonly used. However, a new and appropriate management strategy is required to maximize the recovery efficiency and improve the quality of recovered materials. This paper aims to identify and overcome the critical points in the PV-waste management mechanical processes and provides information on more efficient routes for their treatment. It aims to shed some light on the usefulness of adopting a specific and dedicated approach, to optimize the recovery rate and recovered materials purity level to send to recycling. A new mechanical process of separation and recovery of materials is proposed and compared with a typical conventional e-waste treatment process. The developed process makes improvements in the materials separation step, initial stage conditioning the process, making it more efficient than the conventional one
Photocatalytic degradation of atenolol in aqueous suspension of new recyclable catalysts based on titanium dioxide
No full textPhotocatalytic degradation of atenolol in aqueous suspensions using specifically synthetized mesoporous based TiO2 materials as photocatalysts under UVC (254 nm) irradiation was investigated. A batch reactor and a UV lamp 16 W power were used to test the ATL removal with several initial concentrations of ATL (4.5 - 30 mg/L) and four synthetized TiO2 photocatalysts, characterized by different BET surface areas and average pore sizes. Moreover, the effect of solution pH (4.8 - 9.0) and of the oxygen presence were investigated. The performances of the synthetized photocatalysts were compared with commercial Degussa P25. The atenolol degradation was studied using different concentration of catalyst (50 and 1000 mg/L) showing a maximum removal efficiency of 65%. Although the new catalysts showed a lower efficiency when compared to commercial P25, they can be easily recovered from water being in the form of micro-aggregate, and then reused without remarkable changes. The experimental data were fitted using a pseudo first order kinetic model. © 2017 Elsevier Ltd. All rights reserved
UV treatment for the removal of bromate formed during ozonation of groundwater. Influence of the oxidation process on the removal efficiency
No full textThe presence of bromide ions in waters treated with ozone can lead to bromate ions and brominated compounds formation, potentially carcinogenic. This poses a need to remove the bromates through other treatment, as UV. In this work the effects of the water composition, and the corresponding variation due to oxidation, on the UV efficiency for the reduction of bromate to bromide ions in groundwater (GW) were investigated. For this purpose an experimental apparatus was specifically designed and experimental tests with ozone and with a UV lamp 6 W were performed. The experimental results show that the reduction of the bromates to bromides by UV is max 41% in GW, depending on ozone dose and initial bromate concentration. The experimental data were fitted with a first order model and the kinetic constant determined. The effects of the ozone and UV treatment on others groundwater components, as TOC and inorganic nitrogen, were taken into account and the corresponding influence on the bromate removal efficiency was evaluated. To this aim, comparative tests with UV in purified water (PW) (reagent grade) and GW spiked with controlled amount of bromates were performed. It was verified that the removal efficiency of bromate by UV increases with increasing of ammonia concentration, but decreases with increasing of TOC and when intermediate bromide species, produced by ozonation, are presents. © 2016 Elsevier Ltd. All rights reserved
Silicon photovoltaic modules at end-of-life: Removal of polymeric layers and separation of materials
No full textAn eco-friendly process to recover valuable materials deriving from silicon based photovoltaic panels at end-of-life has been proposed. In particular, in this paper a new two-step process to separate and recover glass, Si and metals has been investigated and discussed. A preliminary mechanical treatment to remove fluorinated polymers allows to exclude dangerous emissions of hydrofluoric acid and fluorinated compounds coming out from conventional heat treatments. A subsequent thermal treatment allows the complete removal of the residual polymers and the separation of valuable materials. The influence of treatment time, temperature and atmosphere, during the polymers degradation has been evaluated and the by-products have been examined. The process efficiency has been assessed by determining the quantity and quality of the recovered materials. The results have shown that the combination of the two mechanical/thermal processes allows energy efficiency and environmental sustainability with respect to conventional recovery treatments. The optimal operating conditions for the thermal treatment have turned out 500 °C for 1 h in oxidizing atmosphere. The quality of the recovered materials has been determined by analysing the residual carbon content after the thermal treatment. The gaseous products of the polymeric degradation have been characterized by gas chromatography-mass spectrometry (GC–MS) analysis
End-of-life of silicon PV panels: A sustainable materials recovery process
No full textIn this paper, the management of end-of-life PV modules based on an advanced eco-sustainable process has been presented and discussed. The thermal removal of the polymeric compounds contained in c-Si PV modules has been investigated to separate and recover Si, Ag, Cu, Al and glass. A two-step thermal process has been employed. In the first step, the rear polymeric layer has been removed without emissions of dangerous fluorinated substances. In the second step, the remaining polymers have been completely removed with low volatile organic compounds (VOCs) emissions. The polymers degradation has been studied at combustion equivalent ratios Φ varying from 0.5 to 2 and at 500 °C. The materials recovery has been evaluated from an environmental point of view and optimized by considering the energy cost, through the identification of the best operating conditions, in terms of temperature, time, atmosphere and gas flow. One hour of heat treatment and a slightly oxidizing atmosphere have been enabled to separate and recover the different materials of the module. The elemental compositions of the PV sample and the residue condensed organic products have been determined. The gaseous degradation products have been characterized by gas chromatographic analysis (GC). © 201
New PV encapsulants: assessment of change in optical and thermal properties and chemical degradation after UV aging
No full textThis work aims to investigate the change in chemical and physical properties of different polymeric materials, potentially usable for photovoltaic modules encapsulation, caused by UV aging. Three classes of polymeric materials have been examined: ethylene-vinyl-acetate (EVA), thermoplastic polyolefins (TPO) and polyolefin elastomers (POE). EVA is currently the most used encapsulant in the photovoltaic field; TPO and POE are new materials, alternative to EVA, which can allow to overcome some of the reliability problems of photovoltaic modules linked to the degradation of EVA properties. Of each of these three material classes, different commercially available encapsulating polymer films, with different chemical formulations, have been examined. Stressful environmental conditions have been simulated in a climatic chamber and the associated changes in optical, thermal and chemical properties of the different encapsulants have been analysed and compared before and after UV aging. The link between the chemical structure, formulation and degradation of the encapsulants with their lifetime under simulated conditions of UV stress has been investigated by the assessment of the changes in thermal stability, optical transmittance, crystallinity, yellowness index and chemical degradation. This study helps to better understand the causes of the module performance reduction due to the degradation of the encapsulant material and is a guide for the selection of encapsulant films with improved characteristics, for the manufacture of more durable PV modules
Thermal treatment of waste photovoltaic module for recovery and recycling: Experimental assessment of the presence of metals in the gas emissions and in the ashes
No full textThe rapid expansion of the photovoltaic (PV) module market in the last years will determine in the near future a remarkable growth of corresponding waste. Then, the hazardous materials contained in the modules, such as Cd, Pb and Cr, could be released in the environment if the waste panels will not be handled adequately. Recycling processes of silicon crystalline panels, finalized to separate PV cells from the glass, involve the removal of the EVA (Ethylene Vinyl Acetate) layer through different methods, as the thermal treatment. During this treatment, some hazardous components can be released due to thermal degradation process. In this paper the metals released in the gas emissions and in the ashes due to the thermal treatment of modules were evaluated. For this purpose, three samples of crystalline panels were heated in furnace up to 600°C and the complete degradation of the EVA was obtained. A mass balance between the sample and its components, before and after treatment, was performed in order to assess the weight loss percentage. Finally, after thermal treatment a qualitative analysis on the separated PV cell surface was performed by SEM-EDS (Scanning Electron Microscope equipped with Energy Dispersive Spectrometer). © 2015 Elsevier Ltd
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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