Biostabilization of cadmium-containing flue gas by sulfate reducing membrane biofilm reactor

Abstract

Flue gas cadmium may endanger human health and ecological environment due to its persistent, toxic and bioaccumulating. A sulfate reducing membrane biofilm reactor (MBfR) for removal of cadmium-containing flue gas was investigated. Cadmium removal efficiency was up to 95.1%. Desulfovibrio was the dominant genus. Desulfovibrio, Desulfomicrobium, Pseudodesulfovibrio were the core cadmium-resistance-sulfate-reducing genus. Cadmium resistance proteins (transcriptional regulatory protein, efflux protein, binding protein and heavy-metal associated domain protein) and sulfate-reducing enzymes (Sat, AprA, AprB, DsrA, DsrB) involved in the regulation of cadmium stress and dissimilar sulfate reduction. The biofilm was characterized by FTIR, XPS, XRD, EEM, and SEM-EDS. XPS and XRD spectra indicate the formation of a cadmium sulfide (CdS) from flue gas cadmium conversion. Humic acid complex arsenic (HA-Cd) and CdS coprecipitation were formed in MBfR system. Cadmium-containing flue gas was bio-stabilized in the form of CdS and HA-Cd via complexation of humic acids in extracellular polymeric substances (EPS), biosorption and biodeposition. These results show that the sulfate-reducing membrane biofilm reactor is achievable and open new possibilities for applying the MBfR to removal of cadmium-containing flue gas.