Examining regeneration technologies for etching solutions: a critical analysis of the characteristics and potentials

Globally, more than one billion cubic meters of waste etchants from printed circuit board industry have been generated annually with an increase of 15-18%. Nowadays, the approach of adding extra chemicals has been utilized to treat a large number of waste etchants, which could obtain low-pure products, but seriously pollute the environment. Furthermore, the processing enterprise cannot gain so much value that is affecting sustainable development. In the previous studies, the regeneration technologies of etching solution have not been studied comprehensively and systematically, so it is of extreme necessity to examine and choose the suitable technology towards a closed-loop supply chain. The results showed that previous etching solution (e.g. ammonium persulfate, sulfur/chromic acid, sulfuric acid/hydrogen peroxide, sodium chloride, ferric chloride) caused severe pollution without proper disposal, but most of the current etchants (e.g. cupric chloride, alkaline etching solution) can be renewable after substantially recycling heavy metals from the etchants. Regarding the latest emerging solution, the used oxidant such as chlorine is regarded as the major risk sources even if it has extraordinary etching ability. The current etching solutions could meet the goal of sustainable development of resources and the environment. For the copper chloride etching solutions that are now widely applied, there are various regeneration approaches, but only two are more favorable than the others. Among all the regeneration technologies, the electrolytic process and membrane technology not only get more pure products, but the residue solution can be renewable. Finally, we employed the analytic hierarchy process to compare the regeneration techniques and found that the electrolytic method and membrane technology are superior to other methods in the economic and environmental performance. The two methods can replace the chemical precipitation, which will sustain the printed circuit board industry.