Recovery and immobilization of lead in cathode ray tube funnel glass by a combination of reductive and oxidative melting processes

Abstract

Abstract Reductive melting treatment has been reported to be an effective method to recover lead from funnel glass in used cathode ray tubes, but a small amount of lead, a potential contaminant, remains in the treated glass. This paper applied a combination process of reductive and oxidative melting to the funnel glass to recover and immobilize lead in the glass. The funnel glass was melted in a lab‐scale reactor changing the atmosphere, and the effects of the temperature and the Na 2 CO 3 dosage on the efficiencies of the lead recovery and immobilization were investigated. In the reductive melting, the lead recovery was promoted by increasing the Na 2 CO 3 dosage, however the lead extraction from the glass into water and hydrochloric acid was increased. Although the content of lead in the glass after the reductive melting was low, the lead extraction into water and the acid was larger than 0.01 mg‐Pb/L‐water and 150 mg‐Pb/kg‐glass, respectively (Japanese environmental criteria). The lead extraction was decreased by the oxidative melting with SiO 2 , Al 2 O 3 , MgO, and NaNO 3 . In the proposed method, metallic lead was recovered from the funnel glass with high lead recovery, and the lead remaining in the glass was immobilized to meet the Japanese environmental criteria.