Tellurite Reduction and Extracellular Recovery of Tellurium Nanorods Using Bioelectrochemical Reactors

Tellurium is a critical mineral for the foreseeable future due to its scarcity and importance in future energy technology. A biocathode of a bioelectrochemical reactor (BEC) was used for the first time to extracellularly reduce TeO32– in simulated wastewater to elemental Te0 nanorods, which could potentially be recovered. Scanning transmission electron microscopy revealed that only 2% of the cells on the biocathode contained intracellular Te0 nanorods. In contrast, in the conventional bioreactor, 40% of the cells contained intracellular Te0 nanorods. Raman spectroscopy determined that the Te0 nanorods were trigonal and amorphous Te0. Microbial community analysis showed the dominance of Pseudomonas, Stenotrophomonas, and Azospira phylotypes in the cathode chamber, despite being <8% in the inoculum. They were all putative TeO32– reducers due to their known ability to reduce tellurite and transfer extracellular electrons. The TeO32– removal efficiency in the BEC reactor reached 97% when the influent TeO32– was 5 mg of Te/L. The reactor operating conditions, including the flow rate, the external resistor, and the cation exchange membrane, were optimized. This work demonstrates the potential of BEC reactors for the continuous and green synthesis of Te0 nanorods.