(642b) Synergistic Cr(VI) Treatment with S. Oneidensis-reduced Metal-Organic Frameworks

Developing effective methods for Cr(VI) removal is a priority for sustainable wastewater treatment solutions. A variety of material and biological schemes have been developed, but they suffer from slow kinetics, low capacities, limited treatment condition ranges, or harsh regeneration schemes. Metal-organic frameworks are a class of highly porous materials that have garnered attention for catalysis, gas storage, and, notably, adsorption. Recently, a synergistic effect of pairing Fe(II) ions with a metal-organic framework was reported to dramatically improve Cr(VI) adsorption. We hypothesized that we could create a self-regenerative system for Cr(VI) adsorption that capitalizes on this synergy by pairing iron-based metal organic frameworks with the electroactive bacterium Shewanella oneidensis MR-1, which is capable of reducing Fe(III) based materials. We first confirm that water stable metal-organic frameworks (MIL-100, FeBTC, and MIL-88A) can serve as growth substrates for S. oneidensis in a similar manner to iron oxides. We then show that bacterially reduced frameworks promote a 10-fold increase in Cr(VI) adsorption (after a single challenge) relative to abiotic controls. Finally, we demonstrate that S. oneidensis growing on MIL-100 can survive multiple challenges of lethal Cr(VI) concentrations and that the metabolic action of this bacteria dramatically improves Cr(VI) adsorption kinetics and capacities by continuously regenerating the metal-organic framework. Overall, our system constitutes a recyclable, living process for Cr(VI) treatment, as well as expands the potential substrates for metal-reducing bacteria to include tunable frameworks.