Preparation of a novel flavin-adsorbing biocarrier and its accelerating mechanism on anaerobic bioreduction of 3-nitrobenzenesulfonate

To harness the potential of low-concentration, microbially secreted flavins as redox mediators, a novel biocarrier was designed via molecular simulation and synthesized via covalently grafting 2-chloro-4,6-diamino-1,3,5-triazine (CDAT) onto reduced graphene oxide (rGO)-modified polyurethane foam (CDAT-rGO-PUF). CDAT-rGO-PUF exhibited higher adsorption capacity for flavins and more efficiently resisted the interference of inorganic salt and cell lysate compared with rGO-PUF and CDAT-PUF, which was primarily attributed to the formed hydrogen bonding between CDAT and flavins. In Shewanella sp. RQs-106 -mediated reduction system of 3-nitrobenzenesulfonate (3-NBS), the adsorption behavior of CDAT-rGO-PUF accelerated extracellular electron transfer from flavin to rGO and cellular synthesis of flavins, resulting in over 37% increase in the bioreduction rate of 3-NBS compared with those in the presence of rGO-PUF and CDAT-PUF. Repeated usage experiments showed that CDAT-rGO-PUF had good catalytic stability. These findings indicate that the novel biocarrier is of potential application for adsorbing extracellular flavins to enhance the treatment of wastewaters containing nitroaromatic compounds.