Rate-limiting factors for indirect two-step biodismantling for printed circuit board recycling

Dismantling of printed circuit boards is a promising pretreatment step for the processing of electronic waste. It allows the separation and subsequent sorting of the different electronic components (ECs) and eases the downstream processes by enriching ECs and the elements contained in them. Biodismantling is a novel process using iron-oxidizing microorganisms to generate an oxidative ferric iron-rich solution to dissolve solder joints, thus releasing ECs. This study evaluates the influence of pH and iron concentration that proved to be rate-limiting factors of the dismantling reaction. Since microbial iron oxidation and dismantling may be performed in separate reactors, it also investigates the effect of sonication on dismantling and thus allows to optimize parameters for industrial applications. At pH 1.2 and 500 mM ferric iron, dismantling times were down to 10 h, but the addition of ultrasound treatment improved dismantling rates even further, reaching complete dismantling within 1.9 h.