Effects of Complexing on the Homogeneous Reduction of Mercuric Salts in Aqueous Solution by Molecular Hydrogen

Korinek, G. J.; Halpern, Jack

doi:10.1139/v56-176

Cited by 8 publications

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References 9 publications

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“…Chloride (Cl − ) is ubiquitous in aquatic and terrestrial environments and is known to form strong aqueous complexes with Hg(II) [80]. The formation of these complexes (e.g., HgCl + , HgCl 2 , HgCl 3 − , and HgCl 4 2− ) can influence the behavior of Hg(II), including inhibition of Hg(II) reduction [44,46,[81][82][83] and sorption on clays, metal oxides, and natural sediments [53,[84][85][86][87]. Previous work has shown that the presence of Cl − in a reducing Fe(II)/(III)-oxide system can prevent complete reduction of Hg(II) to Hg(0) and promote formation of metastable Hg(I) as calomel (Hg 2 Cl 2 ) [46].…”

Section: Effect Of Chloride Concentration On Hg(ii) Reduction By Cbd-mentioning

confidence: 99%

Reduction of Hg(II) by Fe(II)-Bearing Smectite Clay Minerals

et al. 2020

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Aluminosilicate clay minerals are often a major component of soils and sediments and many of these clays contain structural Fe (e.g., smectites and illites). Structural Fe(III) in smectite clays is redox active and can be reduced to Fe(II) by biotic and abiotic processes. Fe(II)-bearing minerals such as magnetite and green rust can reduce Hg(II) to Hg(0); however, the ability of other environmentally relevant Fe(II) phases, such as structural Fe(II) in smectite clays, to reduce Hg(II) is largely undetermined. We conducted experiments examining the potential for reduction of Hg(II) by smectite clay minerals containing 0–25 wt% Fe. Fe(III) in the clays (SYn-1 synthetic mica-montmorillonite, SWy-2 montmorillonite, NAu-1 and NAu-2 nontronite, and a nontronite from Cheney, Washington (CWN)) was reduced to Fe(II) using the citrate-bicarbonate-dithionite method. Experiments were initiated by adding 500 µM Hg(II) to reduced clay suspensions (4 g clay L−1) buffered at pH 7.2 in 20 mM 3-morpholinopropane-1-sulfonic acid (MOPS). The potential for Hg(II) reduction in the presence of chloride (0–10 mM) and at pH 5–9 was examined in the presence of reduced NAu-1. Analysis of the samples by Hg LIII-edge X-ray absorption fine structure (XAFS) spectroscopy indicated little to no reduction of Hg(II) by SYn-1 (0% Fe), while reduction of Hg(II) to Hg(0) was observed in the presence of reduced SWy-2, NAu-1, NAu-2, and CWN (2.8–24.8% Fe). Hg(II) was reduced to Hg(0) by NAu-1 at all pH and chloride concentrations examined. These results suggest that Fe(II)-bearing smectite clays may contribute to Hg(II) reduction in suboxic/anoxic soils and sediments.

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