Tellurite Reduction and Extracellular Recovery of\nTellurium Nanorods Using Bioelectrochemical Reactors

Tellurium\nis a critical mineral for the foreseeable future due\nto its scarcity and importance in future energy technology. A biocathode\nof a bioelectrochemical reactor (BEC) was used for the first time\nto extracellularly reduce TeO<sub>3</sub><sup>2–</sup> in simulated\nwastewater to elemental Te<sup>0</sup> nanorods, which could potentially\nbe recovered. Scanning transmission electron microscopy revealed that\nonly 2% of the cells on the biocathode contained intracellular Te<sup>0</sup> nanorods. In contrast, in the conventional bioreactor, 40%\nof the cells contained intracellular Te<sup>0</sup> nanorods. Raman\nspectroscopy determined that the Te<sup>0</sup> nanorods were trigonal\nand amorphous Te<sup>0</sup>. Microbial community analysis showed\nthe dominance of <i>Pseudomonas</i>, <i>Stenotrophomonas</i>, and <i>Azospira</i> phylotypes in the cathode chamber,\ndespite being <8% in the inoculum. They were all putative TeO<sub>3</sub><sup>2–</sup> reducers due to their known ability to\nreduce tellurite and transfer extracellular electrons. The TeO<sub>3</sub><sup>2–</sup> removal efficiency in the BEC reactor\nreached 97% when the influent TeO<sub>3</sub><sup>2–</sup> was\n5 mg of Te/L. The reactor operating conditions, including the flow\nrate, the external resistor, and the cation exchange membrane, were\noptimized. This work demonstrates the potential of BEC reactors for\nthe continuous and green synthesis of Te<sup>0</sup> nanorods.