Modeling copper leaching from non-pulverized printed circuit boards at high concentrations of bioregenerated ferric sulfate

• A model has been developed for the kinetics of ferric leaching of copper from non-pulverized PCB. • The leaching rate increases proportionally with the concentration of ferric iron in solution. • The leaching rate is limited by internal mass transfer. • Regeneration of ferric iron in a separate bioreactor allows to work at high solid/liquid ratios. • 99% copper extraction in less than 24 h have been achieved for 10% solid/liquid ratio of non-pulverized PCBs. This work studies the leaching of copper contained in waste printed circuit boards (PCB) with ferric sulfate, with the aim of improving the results found in the literature for an industrial application of the process. For this purpose, temperatures and concentrations of ferric ion higher than those of previous works (up to 60 °C and 40 g/L) are used. Furthermore, ferric sulfate can be continuously regenerated by ferro-oxidizing bacteria immobilized in a bioreactor, avoiding physical contact between waste and microorganisms to optimize independently operation conditions. A kinetic model was developed for the interpretation of the experimental results validated at different conditions. The model was based on a shrinking core model limited by mass transfer inside the PCB where the geometry and structure of the PCB has been considered and an excellent fit of the model to the experimental data was obtained. The connection with the bioreactor for biooxidation of the generated ferrous ion allows maintaining high concentrations of ferric when operating at high solid concentrations (5–10 %). In all the cases studied, more than 99 % of the copper contained in the non-pulverized PCB parts was dissolved in less than 24 h, with an average copper extraction rate of 0.6 g/L·h higher than those found in previous works.