Investigating the Temporal Effects of Metal-Based Coagulants to Remove Mercury from Solution in the Presence of Dissolved Organic Matter

Abstract

The presence of mercury (Hg), particularly methylmercury (MeHg), is a concern for both human and ecological health as MeHg is a neurotoxin and can bioaccumulate to lethal levels in upper trophic level organisms. Recent research has demonstrated that coagulation with metal-based salts can effectively remove both inorganic mercury (IHg) and MeHg from solution through association with dissolved organic matter (DOM) and subsequent flocculation and precipitation. In this study, we sought to further examine interactions between Hg and DOM and the resulting organo-metallic precipitate (floc) to assess if (1) newly added IHg could be removed to the same extent as ambient IHg or whether the association between IHg and DOM requires time, and (2) once formed, if the floc has the capacity to remove additional Hg from solution. Agricultural drainage water samples containing ambient concentrations of both DOM and IHg were spiked with a traceable amount of isotopically enriched IHg and dosed with ferric sulfate after 0, 1, 5, and 30 days. Both ambient and newly added IHg were removed within hours, with 69-79 % removed. To a separate sample set, isotopically enriched IHg was added to solution after floc had formed. Under those conditions, 81-95 % of newly added Hg was removed even at Hg concentrations 1000-fold higher than ambient levels. Results of this study indicate coagulation with ferric sulfate effectively removes both ambient and newly added IHg entering a system and suggests rapid association between IHg and DOM. This work also provides new information regarding the ability of floc to remove additional Hg from solution even after it has formed.

Puffed Rice Carbon with Coupled Sulfur and Metal Iron for High-Efficiency Mercury Removal in Aqueous Solution

“…Therefore, highly effective decontamination of the toxic mercury from aqueous media has been a greatly challenging task for water researchers since decades ago . Up to now, traditional methods for removing Hg­(II) from water have included chemical precipitation, membrane filtration, ion exchange, biosorption, and carbon adsorption. , Among these traditional methods, carbon adsorption is one of the most promising strategies for both industrial application and environmental remediation owing to the low cost, high surface area, and hydrophilic features of carbon adsorbents. ,, However, carbon adsorbents still suffer from the unsatisfactory adsorption capacities, the weak chemical bonding with Hg­(II), and the intractable ineffectivity at low Hg­(II) concentration. Hence, it is necessary to develop a handy and efficient modification technique to significantly improve the adsorption performance of carbon adsorbents.…”

“…2 Therefore, highly effective decontamination of the toxic mercury from aqueous media has been a greatly challenging task for water researchers since decades ago. 3 Up to now, traditional methods for removing Hg(II) from water have included chemical precipitation, 4 membrane filtration, 5 ion exchange, 6 biosorption, 7 and carbon adsorption. 8,9 Among these traditional methods, carbon adsorption is one of the most promising strategies for both industrial application and environmental remediation owing to the low cost, high surface area, and hydrophilic features of carbon adsorbents.…”

Reviews and syntheses: Iron: A driver of nitrogen bioavailability in soils?

“…Additionally, Fe oxide reactivity is altered by the presence of OM coatings on mineral surfaces (Gao et al, 2018;Kleber et al, 2007;Poggenburg et al, 2018) and the type of coverage (monolayer vs. multilayer coverage). For instance, adsorbed organics can inhibit the development of crystals (Boland et al, 2014;Henneberry et al, 2016), halt the reductive dissolution by surface passivation, reduce the amount of binding sites available for sorption (Kaiser and Zech, 2000a), or limit Fe(II) oxidation under oxic conditions (Daugherty et al, 2017).…”

Reviews and syntheses: Iron – a driver of nitrogen bioavailability in soils?

“…While Fe(III) promotes N stabilization within mineral associations, Fe(III) mobilization, when it is reduced to Fe(II), can release N into solution. Fe reactivity is also driven by the amount and sign of surface charge, surface topography, particle size, crystallinity (Petridis et al, 2014;Li et al, 2015a), and the presence and type of organic matter (OM) coverage (Kaiser and Zech, 2000a;Kleber et al, 2007;Boland et al, 2014;Henneberry et al, 2016;Daugherty et al, 2017;Gao et al, 2018;Poggenburg et al, 2018). Second to this, soil N exists predominantly in organic forms (ON), mostly as proteins and peptides and, to a lesser extent, as amino-sugars and nucleic acids (Schulten and Schnitzer, 1997;Knicker, 2011).…”