Removal of lead from cathode ray tube funnel glass by chloride volatilization

Cathode ray tube funnel glass is an environmentally problematic relict of old television sets. In particular, landfilling of this material is strongly discouraged because of its high lead content. However, recovery of this toxic lead could prevent its release into the environment and allow its reuse. In this research, lead was separated from the glass matrix by a chloride volatilization process. Melting of the funnel glass together with CaCl₂ resulted in the volatilization of 80 % of lead at 1,000 °C. The use of NaCl as a chlorination agent yielded less volatile lead, while poly(vinyl chloride) and gaseous HCl proved to be ineffective chlorination agents. The differences in the chlorination agent efficiencies could be attributed to differences in the corresponding formation of silicates. Energy-dispersive X-ray spectroscopy showed that diffusion plays an important role in the volatilization of PbCl₂.

Keywords
Recycling; Sodium chloride; Calcium chloride; Polyvinyl chloride; Thermodynamics; Diffusion