The recovery of copper and tin from waste tin stripping solution: Part I. Thermodynamic analysis

Stripping solutions containing suspended tin and dissolved copper and iron, are a by-product of printed circuit board manufacture. The recovery of these metals for reuse has economic and environmental benefits. By focusing on this waste stream, a systematic method to determine the process of metal recovery has been developed. Initially the thermodynamics of the system were examined. E–pH diagrams were constructed to ascertain whether metals would be in the solid or liquid phase depending on the ionic concentrations, pH and system potential. Simulations using MINEQL+ were also performed to account for ionic strength. The validity of this thermodynamic study was tested by determining the precipitation pH of the metal solutions. The study showed that the dissolved copper and suspended tin oxide could be separated by filtration if the pH was maintained between −0.4 and 2.4. The dissolved copper could then be removed by electrodeposition, leaving iron in solution.