Analysis of key patents of the regeneration of acidic cupric chloride etchant waste and tin stripping waste

Spent acidic cupric chloride etchant waste and tin stripping waste from printed circuit board (PCB) industry are classified as hazardous wastes. They contain significant amounts of metals and acid. Usually, spent cupric chloride and tin stripping solutions are shipped off-site for reclamation. At the moment, a large proportion of acidic cupric chloride etchant waste and tin stripping waste are treated by neutralization, resulting in metal-bearing sludge that often ends up in special landfills. This wastes valuable natural resources, which could otherwise be recycled. This paper presents a review of some patented methods developed for the regeneration of acidic cupric chloride etchant waste and tin stripping waste. These methods are based on electrowinning, cementation, solvent extraction, precipitation and membrane technology. The advantages and disadvantages of these developed processes are summarized. It can be seen that there is still a need to develop more efficient and economical processes for the regeneration of acidic cupric chloride etchant waste and tin stripping waste.