Rio de Janeiro: ABNT (NBR ) (In Portuguese) 7. Brazilian Association of extract from solid residues. Rio de Janeiro: ABNT (NBR ). Brazilian Association of Technical Norms, in ABNT NBR Procedure for obtention leaching extract of solid wastes (Rio de Janeiro, ), p. 16 8. ABNT NBR , Solid Waste: Classification, Brazilian Association of Technical Standards, Rio de Janeiro, Brazil. ABNT NBR , Leaching of.
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Porto Alegre, RS, Brazil. Cathode ray tube CRT monitors are electronic equipment mainly made of glass, polymers and metals.
These devices became obsolete because of emerging technologies such as LCD, LED and plasma; thus generating a huge stockpile of e-waste worldwide. The standard NBR procedure was performed for 7 different monitors. The results show all samples are hazardous according to local environmental law NBR due to lead leaching. Moreover, six optimum thermal lead removal procedures were performed and the NBR procedure was repeated. Three out of six parameters were capable of satisfactorily removing the lead and turning the post-procedure waste lead-leaching safe.
Electrical and Electronic Equipment EEE is – but is not limited to – equipment which is dependent on electric currents or electromagnetic fields in order to work properly. Waste of electric and electronic equipment WEEE includes not only the equipment itself, but also all the components, subassemblies and consumables which are part of the product at the time of discarding European Union, WEEE contains a significant number of precious metals, many of which are being recovered through different studies: Improper WEEE handling and recycling may lead to health problems as these equipment contain harmful substances such as toxic metals and flame retardants Lecler et al.
Despite having proper landfills for the disposal of CRT monitors, most of them end up in improper landfills or in no landfill at all Oliveira, The CRT used in television and computer screens represents one of the main sources of e-waste as flat screens have replaced them over the last ten years Lecler et al.
The glass has three components: The panel component is the heaviest part and it contains elements such as barium, strontium, and yttrium. The other two components usually contain lead in their composition; the total amount of lead in a CRT may reach 3 kg Lecler et al.
The lead content varies according to the manufacturer, but the average concentrations have been published in several works Table 1.
According to Menadthe lead in the CRTs is responsible for the radiation shielding and for stabilizing the glass. As stated by Okada 01005, a material containing lead may scatter and result in oral intake of the dispersed lead by humans, which ultimately results in health problems. Lead is also toxic for other animal cells and plants Menad, abnr This statement encourages researches that aim to remove the lead from the waste CRT.
Okada extracted lead from the glass of CRT by using hydrochloric acid and by abnf the glass under different oxidizing abntt. It is clear that recycling waste of CRT is important not only for mitigating environmental issues, but also for maximizing the value of the waste Zhang et al. As reported in several international publications, waste of CRT monitors represents an environmental threat and yet it has not been classified under Brazilian law. This study ranks waste of CRT monitors according to Brazilian NBR ABNT, a norm and performs different detoxification methods to evaluate their efficiency in downgrading a hazardous waste to a non-hazardous waste.
ABNT – Associação Brasileira de Normas Técnicas
Cathode ray tube monitors were collected for these experiments; their manufacturing year varied from to The monitors were manually dismantled using tools such as pliers, screwdriver, electric saw, saw, hammer, vise.
To ensure personal safety of the operators, the following personal protective equipment PPE were worn: The monitors were weighed and their zbnt were separated and sorted into four categories: In order to open the vacuum sealed tubes, the monitors were placed behind a wooden shield and the metallic threads were removed using a set of pliers. The parts dismantled from the CRT monitors are shown in Fig. The CRTs were split into three, according to the previous delimitation Fig.
Neck, funnel and panel parts Fig 3. In order to make sure the monitor samples used in this work had similar lead distribution to the ones from previous studies Table 1the three milled glass parts were analyzed by X-ray fluorescence XRF using an Axios Advanced PANalytical, Almelo, Netherlands. The obtained results encouraged a study regarding the hazard potential of CRT monitors. Seven CRTs monitors were submitted to the Brazilian standard leaching 100005 to evaluate their hazard potential.
The NBR displays a list of known hazardous materials and their characteristics and can be related to the Code of Federal Regulations title 40, subtitle of the United States 40 C. Wastes that are not characterized in the NBR should be classified according to their leaching potential, which is evaluated using the NBR The procedures presented aabnt NBR simulate the leaching that may occur to a non-sheltered waste; a flowchart of the norm is presented in Fig.
Adapted from ABNT b.
The next step in this study was the removal of lead from the CRT by thermal processes. The chosen glass component for abnnt procedure was the funnel glass because it presented high lead concentration.
A tube furnace structure was assembled to control the process Fig. The funnel glasses from different CRT were all mixed together. Samples A, B, D and F were put into the furnace with carbon graphite Samples C and E were placed in the furnace with no reducing agent. The pressure inside the tube for samples E and F was set at 1. The samples were placed inside alumina crucibles, which were then placed inside the furnace. The choice of the parameters used in the procedure was based on the work of Veit et al.
The possible redox reactions are as follows Veit et al. The next step was intended to evaluate whether the lead removal had been able to convert the CRT from a hazardous waste to a non-hazardous waste according to the Brazilian regulation. The solutions obtained from the procedures were analyzed by atomic absorption spectroscopy and the results were compared to the limits shown in NBR The XRF results from CRT parts confirmed that lead is present in the funnel and in the neck while the panel is lead free, as shown in Table 4.
It also shows that, apart from the concentration of lead, barium, zirconium and strontium in panelthe three glass parts have similar composition. It should be noted that XRF determines the atoms present in the sample and not the compounds. However, given that the sample was glass, the XRF equipment assumes the atoms are in their most oxidized state – resulting in the chemical compounds shown in Table 4.
The panel glass did not present any leached lead, which is logical, since no lead was found in the previous XRF Table 4.
The big variance among the samples is probably related to the year the monitors were manufactured. BeforeCRT did not use high voltage in the electron gun, and thus, did not need as much lead in the glass for shielding Webster, The results from the AAS obtained from the samples that had undergone the thermal process are displayed in Table 6.
Thus, the lead removal conditions were not effective to downgrade the hazardousness of the waste.
On the other hand, samples D, E and F are below the standard. Sample F displayed the best results as it was able to reduce the lead in the glass to a minimum in comparison to the other 5 samples. The lead concentration in the leached solution demonstrates that CRT monitors are a hazardous waste to the environment and are classified as Class I – Dangerous Waste according to NBR The lead removal evaluation showed that parameters abnf samples D, E and F can remove the lead from CRT monitors to an environmentally safe level.
Best results were observed in sample F that was processed with the following parameters: Future studies should evaluate the hazardousness potential of other elements such as barium and strontium.
Extraction and concentration of silver from waste crystalline silicon photovoltaic modules, Waste Management, 57,On line at: Revista Escola de Minas, 68 3 This is an open-access article distributed 100005 the terms of the Creative Commons Attribution License. Services on Demand Journal. Environmental Engineering Lead hazard evaluation for cathode ray tube monitors in Brazil. Abstract Cathode ray tube CRT monitors are electronic equipment mainly made of glass, polymers and metals.
Cathode ray tube monitors The Abng used in television and computer screens represents one of the main sources of e-waste as flat screens have replaced them over the last ten years Lecler et al.
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Recycling CRTs As stated by Okadaa material containing lead may scatter and result in oral intake of the dispersed lead by humans, which ultimately results in health problems.
Lead Hazard Evaluation Seven CRTs monitors were submitted to the Brazilian standard leaching procedure to evaluate their hazard potential.
Lead Removal and Abnr The results from the AAS obtained from the samples that had undergone the thermal process are displayed in Table 6. Ahnt A 5.
June 10, ; Revised: September 26, ; Accepted: How to cite this article.