Recycling of mirror waste

Due to the Pb contents of some mirrors, mirror wastes have to be disposed off as hazardous wastes even though it would be interesting to recover silver and glass, the main components of mirror. This paper presents a two-steps process that leads to the recovery of 96% of the glass and more than 90% of the silver. The final residue that is thrown away represents 4% of the initial mirror weight. It is constituted of glass fines, varnish, lead sulphate and other metallic compounds. The first step of the process consists in the leaching of coarse mirror fragments with a sulphuric acid solution. This treatment is carried out in a rotating drum with a very low dilution ratio. During this step, 90% of the silver is solubilized, lead precipitates as PbSO4 and varnish stay within the residue. The glass is then recovered by a wet screening and the final solution is separated from the residue by a classical filtration. The second step of the process concerns the recovery of silver from this final solution. This can be easily realised by chloride precipitation or electrodeposition on a three-dimensional electrode.