Case Study: Leaded Glass Separation

Most glass we encounter daily does not contain lead. However, older TVs and computers with CRT displays as well as crystal housewares can contain up to 40% lead oxide. It’s encouraging that we’ve moved away from producing leaded glass; however, there is still a significant amount in the economy that needs to be collected and properly disposed of.

• When glass is collected in bulk, it can be easy to confuse leaded glass with unleaded glass. 
• When it’s time to recycle the glass, leaded and unleaded glass particles need to be processed separately for health and safety reasons.
• Because we’re trying to separate leaded glass for safe disposal, traditional glass sorting methods can be too expensive.

• Because leaded glass has a density of three and unleaded glass has a density below 2.8, Sepro was able to develop a dense media process to separate the two types of glass. 
• Initial heavy liquid tests indicated that a density cut point between 2.85 and 2.90 would provide the best results.
• Sepro’s Condor Dense Media Separator was used for the pilot scale testwork. Approximately two-tonnes of crushed glass split into -10mm/+2mm and -2mm/+1mm size fractions was used for the pilot testwork.

• Despite crushing some particles were not fully liberated and contained a mixture of leaded and unleaded glass (as seen in the photo). These unliberated particles proved difficult to separate because of their intermediate density.
• Despite these challenges, the separation was over 70% efficient which was considered successful given the amount of unliberated particles.