Vitrification of the solid waste obtained from the vacuum crushing of fluorescent lamps: chemical analysis and determination of the chemical stability in water of the vitrified solids

Abstract

This paper deals with the vitrification processing of the wastes of glass and phosphor powder obtained after the vacuum crushing of spent fluorescent lamps. Both materials were characterized by means of scanning electron microscopy and X-ray fluorescence chemical analysis. The vitrification tests were performed at 1,100°C and 20 wt % borax was added to the samples as fluxing aid. Four formulations (batches) of glasses were made, the first one consisted only of spent lamp glass, the second one of spent lamp glass plus borax, the third one was the same as the second, but incorporating 20% weight of spent phosphor powder. The fourth one, a control, was made combining soda-lime glass cullet and borax. All four batches were chemically analyzed by X-ray fluorescence and no Hg was found on them. Rare earth elements were detected in the third batch glass prepared. The chemical stability of all batches was tested by contacting tests of the glasses with distilled water. As indicative of the stability, pH and electrical conductivity of the supernatants was measured. It was found that the more stable glasses were those incorporating only borax and spent lamp glass.