Treatment of copper from Cu CMP waste streams using polyethyleneimine

Commercially available Cu CMP waste treatment processes involve: 1) pretreatment chemistry using oxidizers to break down complexed copper resulting in precipitation of copper in the form of copper hydroxide; 2) microfiltration of both slurry particles and copper hydroxide; and 3) ion exchange to remove Cu²⁺ ions. Ion exchange resins used to remove Cu²⁺ ions are limited to only removing cations and also have a low efficiency in binding Cu²⁺ ions. The treatment strategy to be evaluated here only requires using two processes to remove the copper from Cu CMP waste-filtration to remove the particles followed by chelation. This paper focuses on the chelation step. The chelator of interest is polyethyleneimine (PEI) bound to agarose beads. PEI removes both Cu²⁺ ions and Cu-complexes. The particles from slurry in the actual Cu CMP waste were removed by filtration before the experiment. The results show that PEI has a higher binding capacity for Cu²⁺ ions than ion exchange resins. Its performance and reproducibility did not change after multiple regenerations. Furthermore, PEI has the ability to bind Cu-complexes through electrostatic attraction. Although the bonds aren't strong, the result is more overall copper removal from the waste stream. The copper component of the Cu CMP waste was concentrated 12 fold using this system.