Use of electrodialysis to produce and recycle on-site raw materials for waste printed circuit board recycling process. I. HBr and KOH electrosynthesys

The technological progress and consumerism trend stimulate electric and electronic equipment replacing, inducing the generation of huge amounts of wastes, many of them containing dangerous (but valuable) waste printed circuit boards (WPCBs). A promising technology for their recycling is based on the electrochemically regenerable Br-/Br2 leaching system, for which the raw materials can be produced and recycled by electrochemical ways. In this context, the present work presents our research concerning the feasibility to produce by electrodialysis, on-site, HBr and KOH, which are required for the electro-hydrometallurgical recovery of metals from WPCBs. For this purpose, a four-compartment filter-press electrochemical reactor, divided by two cation and one anion exchange membranes, was used. The obtained results demonstrate that the proposed process can produce, at a current density of 4 kA/m2, target solutions with concentrations over the required value (of 0.5 M), with average current efficiencies over 73% and 82%, and average specific energy consumptions around 40 and 25 kWh/kg for HBr and KOH, respectively. Moreover, several preliminary measurements performed simultaneously with the electrodialysis tests revealed that, by acquiring rigorous temperature data, the concentrations of the target solutions can be easily and rapidly evaluated and monitored on-line using simple electrochemical sensors for pH and conductivity, but more accurate and exhaustive calibration data is required.