Treating Copper from CMP Waste Using Photocatalysis

In this investigation particulate titanium dioxide was suspended on glass beads to remove copper (II) concentrate from a chemical mechanical polishing waste stream in the semiconductor manufacturing process. The copper (II) ions were reduced to copper (I) by photodeposition through a process which involved illuminating titanium dioxide at a wavelength of less than 365 nm in an oxygen starved environment. The copper was separated from the titanium dioxide by oxidation in a reverse process. The reverse process was performed by turning the light source off and introducing oxygen into the system returning the copper to Cu (II). This reverse process oxidized the copper (I) ions to copper (II) ions for recovery.