Optode-Based Oxygen Measurements in Bioleaching Reactors

Abstract

Tank bioleaching promises high yields due to controllability of the leaching process. For that various parameters like pH, EH and pO2 have to be measured regularly. However, especially the measurement of oxygen is difficult to realise, since oxygen probes are very expensive and posses only a low durability. With optode measurements we propose an easy and less expensive, but still very accurate alternative. Since we were able to fix the optode sensor spot at the lower end of a glass tube, this system is applicable with various reactor designs and hence allows non-invasive in-situ oxygen measurements between each second and every hour.In order to show the principal applicability of this system inside a bioreactor, Escherichia coli was cultivated at a defined oxygen level. Both optode and oxygen probe showed similar concentration values. In the following, a cultivation of Acidithiobacillus ferrooxidans was performed in a 2 L bioreactor with different oxygen levels set by controlling the air flow. Again, both systems showed similar concentrations. This demonstrates the optode to be a reliable tool for oxygen measurements during the cultivation of iron-oxidisers in bioreactors. Furthermore, we performed leaching tests with fine grained residue from copper smelting in order to show the durability of the optode in terms of mechanical wearing and hence a suitable alternative to oxygen probes.