Zhensha Huang, Zaishan Wei, Xiaoliang Xiao
Oct 7, 2019
Citations
1
Influential Citations
23
Citations
Journal
Environmental science & technology
Abstract
Bioconversion of elemental mercury (Hg0) into immobile, non-toxic and less bioavailable species is of vital environmental significance. Here, we investigated bioconversion of Hg0 in a sulfate-reducing membrane biofilm reactor (MBfR). MBfR achieved effective Hg0 removal by sulfate bio-reduction.16 S rDNA sequencing and metagenomic sequencing revealed that diverse groups of mercury-oxidizing/sulfate-reducing bacteria (Desulfobulbus, Desulfuromonas, Desulfomicrobium and etc.) utilized Hg0 as initial electron donor and sulfate as terminal electron acceptor to form the overall redox, these microorganisms could couple mercury bio-oxidation to sulfate bio-reduction. Analysis on mercury speciation in biofilm by sequential extraction processes (SEPs) and inductively coupled mass spectrometry (ICP-MS) and mercury temperature programmed desorption (Hg-TPD) showed that mercury sulfide (HgS) and humic acid bound mercury (HA-Hg) were two major products of Hg0 bio-oxidation. With HgS and HA-Hg comprehensively characterized by X-ray diffraction (XRD), excitation-emission matrix spectra (EEM), scanning electron microscopy-energy disperse spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR), it was proposed that biologically oxidized mercury (Hg2+) further reacted with biogenic sulfides to form cubically crystallized metacinnbar (β-HgS) extracellular particles. Hg2+ was also complexed with functional groups -SH, -OH, -NH- and -COO- in humic acids from extracellular polymeric substances (EPS) to form HA-Hg. HA-Hg may further react with biogenic sulfides to form HgS. Bioconversion of Hg0 into HgS was therefore achieved and can be a feasible biotechnique for flue gas demercuration.