Obtenção e caracterização de espumas vítreas a partir de resíduos de lâmpadas fluorescentes descontaminados de mercúrio

Abstract

Glass foams are heterophasic materials applied in acoustic and thermal insulation, and compared to other materials, are lightweight and sturdy. Glass foams can be prepared from glass packaging, cathode ray tubes and other wastes like fly ashes. Waste fluorescent lamps, classified according the NBR 10.004-04 as hazardous due to the presence of mercury, have potential characteristics for use in the obtainment of glass foams. Decontamination of such residues makes their sending to controlled landfills possible, however it is necessary to development of processes that address the use of these materials in economic interest products, considering environmental issues. Therefore, this work aims to prepare ceramic bodies from glass of fluorescent lamps decontaminated by mercury, with calcium carbonate as a foaming agent, seeking the development and characterization of glass foams. The process variables investigated were: percentage of foaming agent (2, 3, 4 and 8 %), compaction pressure (20, 30 and 40 MPa); burning temperature (700, 750, 800 and 850 °C); heating rate (2.5, 5.0 and 7.5 °C∙min-1) and the glass size (11.0, 29. 0 and 91.0 μm). The following properties were monitored: density, porosity, mechanical strength and thermal conductivity. The results highlighted were the combination of burning temperature and percentage of foaming agent in determining the volumetric expansion, while the variable conformation pressure has unrepresentative influence. The best result obtained for burning temperature was at 800 °C in which the content of 3 % of CaCO3 showed expansion around 600 %. Decreases in glass size and increases in heating rate induced decreases in expansion. The results showed that all glass foams obtained in this study have density (0.187 to 0.282 g∙cm-3) compatible with commercial products. The maximum mechanical strength obtained was 0.75 MPa also compatible with commercial glass foams. The thermal conductivity showed a value of 0.03 W∙m-1 ∙°C1 at 150 °C, which characterizes the glass foams prepared with 3% of CaCO3 as a thermal insulator. Regarding the analysis of the presence of metals, the preparation of glass foams is presented as an alternative to the disposal of fluorescent lamps glasses, with a reduction of 97.8 % in the emission of lead, in comparison to the emission observed in the decontaminate glass.