A sustainable way to reuse Cr(VI) into an efficient biological nanometer electrocatalyst by Bacillus megaterium

The remediation of heavy metal is facing the great challenge of failing to achieve valuable transformation. Therefore, the development of a sustainable technology for heavy metal recycling and reuse is essential. The present study proposed a new way to convert Cr(VI) into value-added biological Cr2O3 nanoparticles (bio-Cr(2)O(3 )NPs) with B. megaterium-secreted tryptophan residues proteins (TPN). In this process, Cr(VI) was reduced extracellularly to Cr(III) by B. megaterium without additional reductant and electron donors. This study overcomes the difficulty of separation of NPs and biomass, and realizes the recovery of bio-Cr2O3 NPS from biomass. The conversing efficiency of bio-Cr2O3 NPs reached the highest level (96.56%) at the concentration of 10 ppm Cr (VI). In particular, bio-Cr2O3 NPs exhibited excellent catalytic activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, outperforming chemically synthesized Cr-base catalysts. Three-dimensional matrix fluorescence (EEM), verification of tryptophan reduction and computation chemistry fully confirmed that TPN was responsible for the bio-Cr(2)O(3 )NPs formation. This comprehensive approach to bioremediation, synthesis NPs and recovery, as well as application will open a window for sustainable energy development and heavy metal pollution remediation.

Automated summary

The study proposed a new method to convert Cr(VI) into bio-Cr2O3 nanoparticles using B. megaterium-secreted TPN, achieving a high conversion efficiency of 96.56%. The bio-Cr2O3 NPs exhibited excellent catalytic activity in 1 M KOH, surpassing chemically synthesized Cr-based catalysts. The role of TPN in the formation of bio-Cr(2)O(3)NPs was confirmed through various analyses, opening up possibilities for sustainable energy development and heavy metal pollution remediation.