Bioprecipitation facilitates the green synthesis of sulfidated nanoscale zero-valent iron particles for highly selective dechlorination of trichloroethene

Compared with nanoscale zero-valent iron particles (nZVI), sulfidated zero-valent iron nanoparticles (S-nZVI) exhibit higher reactivity and selectivity towards the remediation of halogenated organic pollutants such as trichloroethene (TCE). However, traditional methods of preparing S-nZVI are not safe and environmentally friendly to some degree. In this study, we developed a biological precipitation method to prepare S-nZVI, in which sulfate-reducing bacteria (SRB) played an important role for the in situ formation of ferrous disulfide on the surface of nZVI. The results show that the obtained sulfidated nZVI particles (BP-S-nZVI) exhibit excellent performance in TCE degradation, and the first-order rate coefficient (Kobs) and the efficiency of electron utilization were up to (1.66 ± 0.1)× 10-1 h-1 and 85%, respectively. Moreover, zero-valent iron utilization efficiency of BP-S-nZVI reached 95%. Meanwhile, the particles were well characterized and the mechanism for enhanced reactivity was explored. The prominent advantage of this novel method is that the harmful chemical sulfidating agents such as dithionite (S2O42−) and sodium sulfide (Na2S) are not required, making the preparation process more environmental-friendly, green and sustainable.