Thermal processes for lead removal from the funnel glass of CRT monitors

Abstract

The disposal of CRT monitors increases each year, generating millions of tons of waste containing various types of materials. The glass present in CRT tubes displayed about 20%-25% of lead oxide. If improperly disposed of, this glass can be leached directly in nature or may cause environmental contamination, especially with lead. Because of this leaching possibility, this waste is classified as Class I solid waste, according to the NBR 10004. Thermal processing of these glass tubes was seen as an alternative to remove lead from the glass matrix. Parameters such as reaction time, percentage of reducing agent, the reaction temperature, and atmospheric environment of the system were analyzed in this work. It was concluded that it is possible to remove the lead from the glass matrix by thermal processing. The removal of 92% of the lead from the glass was obtained at 800°C, a vacuum of 1.3 kPa, with 5% carbon as a reducing agent, and 18 hours of thermal processing.

An Innovative Method for the Extraction of Metal from Waste Cathode Ray Tubes through a Mechanochemical Process Using 2-[Bis(carboxymethyl)amino]acetic Acid Chelating Reagent

“…Okada also explored the removal of lead from CRT funnel glass via a reducing and oxidizing atmosphere; the process includes the melting of the funnel glass under a reducing atmosphere and then generation of metallic lead separated and collected through acid leaching . A similar method studied by Viet et al involved the removal of lead from the funnel glass, and the rate of removal of lead was ∼92% under the following conditions: 5% carbon as a reducing agent, 800 °C, vacuum of 1.3 kPa, and thermal processing for 18 h …”

“…24 Okada also explored the removal of lead from CRT funnel glass via a reducing and oxidizing atmosphere; the process includes the melting of the funnel glass under a reducing atmosphere and then generation of metallic lead separated and collected through acid leaching. 27 A similar method studied by Viet et al involved the removal of lead from the funnel glass, and the rate of removal of lead was ∼92% under the following conditions: 5% carbon as a reducing agent, 800 °C, vacuum of 1.3 kPa, and thermal processing for 18 h. 28 Apart from these technologies, the mechanical activation of minerals represents an important development in several solid processing technologies, such as extractive metallurgy, activation by ball milling in pyrometallurgy, and an enhanced leaching process for several oxide minerals in hydrometallurgy. 29 The application of the mechanochemical technique to various e-waste recycling process has been reported.…”

Lead hazard evaluation for cathode ray tube monitors in Brazil

“…Lead is also toxic for other animal cells and plants (Menad, 1999).This statement encourages researches that aim to remove the lead from the waste CRT. Veit et al (2015) studied various thermal parameters to extract the lead from the funnel glass; their optimum result removed 92% of the lead. Okada (2015) extracted lead from the glass of CRT by using hydrochloric acid and by melting the glass under different oxidizing conditions.…”

“…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 (2015), that optimized the conditions for removing lead from CRT monitors ( Table 2). The possible redox reactions are as follows (Veit, et al, 2015): …”

Chemical–Electrochemical Process Concept for Lead Recovery from Waste Cathode Ray Tube Glass

“…Unfortunately, the amount of waste material that can be recycled in the above mentioned technologies is limited due to the fact that waste CRT glass is used without preliminary separation of harmful components, involving higher environmental risks, operation and maintenance costs [ 25 , 26 ]. In order to overcome this drawback, associated with waste CRT glass recycling, there have been attempts to remove the hazardous components like lead employing different hydrometallurgical and pyrometallurgical processes [ 27 , 28 , 29 ]. These processes present some major disadvantages like insufficient lead removal efficiency and polluting byproducts, which can be more harmful than the treated waste material [ 30 ].…”