This research focuses on the microbial recovery of elemental tellurium (Te0) from aqueous streams containing soluble tellurium oxyanions, tellurate (TeVI), and tellurite (TeIV). An anaerobic mixed microbial culture occurring in methanogenic granular sludge was able to biocatalyze the reduction of both Te oxyanions to produce Te0 nanoparticles (NPs) in sulfur-free medium. TeIV reduction was seven times faster than that of TeVI, such that TeIV did not accumulate to a great extent during TeVI reduction. Endogenous substrates in the granular sludge provided the electron equivalents required to reduce Te oxyanions; however, the reduction rates were modestly increased with an exogenous electron donor such as H2. The effect of four redox mediators (anthraquinone-2,6-disulfonate, hydroxocobalamin, riboflavin, and lawsone) was also tested. Riboflavin increased the rate of TeIV reduction eleven-fold and also enhanced the fraction Te recovered as extracellular Te0 NPs from 21% to 64%. Lawsone increased the rate of TeVI reduction five-fold, and the fraction of Te recovered as extracellular material increased from 49% to 83%. The redox mediators and electron donors also impacted the morphologies and localization of Te0 NPs, suggesting that NP production can be tailored for a particular application.
ASJC Scopus subject areas
- Environmental Chemistry