Measurements of dissolved oxygen in bioleaching reactors by optode application

Abstract

Tank bioleaching of ore promises to give high yields due to the ability to control the leaching process. For that, various parameters like pH, EH and pO2 must be measured regularly. However, the measurement of oxygen is especially difficult to realise since oxygen probes are relatively expensive and possess only a low durability. Through the use of an optode system, we propose an easy and less expensive alternative for oxygen measurements. Furthermore, we demonstrate the optode achieves similar and possibly more accurate readings than the conventional electrode. Since we were able to fix the optode sensor at the lower end of a glass tube, this system is suitable for various reactor designs and hence allows for non-invasive, in-situ oxygen measurements.The proof of concept was demonstrated by cultivating Escherichia coli, Rhodococcus erythropolis, Acidithiobacillus ferrooxidans, and Sulfobacillus thermosulfidooxidans inside 2L bioreactors. Both optode and oxygen electrode showed similar concentration values, which demonstrates the optode is a reliable tool for oxygen measurements during bioreactor cultivation, especially of iron-oxidisers. Subsequent leaching tests, performed with fine grained residue from copper smelting and copper-rich black shale, demonstrated that the optode is resistant to mechanical wear. Therefore, the optode was found to be a suitable alternative to the amperometric oxygen probe.