Mercury Uptake by Modified Mackinawite

Abstract

This study investigated the mercury uptake capacity of synthetic mackinawite regarding its surface modification with L-cysteine. Mackinawite (FeS) is an excellent material for mercury uptake from anoxic-contaminated sediments. However, one limitation to its use is the low oxidation stability; it is easily transformed when applied to natural sediments. The modification of mackinawite with L-cysteine improves its oxidation stability, making it a promising material to be used in sediment remediation by insitu capping. The results showed that L-cysteine does not affect the mercury-uptake capacity of mackinawite (around 490 mg/g for modified and unmodified mackinawite). The Hg (II) uptake decreased as the solution pH changed from acid to alkaline range, especially in solutions with low Hg (II) concentrations. Sorption curves for Hg (II) on modified mackinawite, as a function of initial concentration of Hg (II) and mackinawite,showed the same pattern as that on unmodified mackinawite, indicating no significant difference in the mercury-sorption mechanism. The solids before and after Hg (II) uptake were analyzed by X-ray powder diffraction (XRPD) by noting the composition of both modified and unmodified mackinawite, and the results were in agreement with the sorption experiments.

Mercury remobilization in Saguenay Fjord (Quebec, Canada) sediments: Insights following a mass-flow event and its capping efficiency

“…Our results are consistent with the hypothesis that chalchophile elements, such as Hg and As, that either form distinct insoluble sulfide minerals, co-precipitate with or adsorb to Fe sulfides (HuertaDiaz and Morse, 1992;Mucci et al, 2003;Wolfenden et al, 2005;Jeong et al, 2007;Liu et al, 2008;Xiong et al, 2009;Chavez et al, 2013) would be immobilized and trapped in the vicinity of the former sediment-water interface following a mass-flow event in the Saguenay Fjord (or any organic-rich marine or estuarine sediment). Nevertheless, a fraction of the Hg(II) released from the buried, contaminated sediments migrated up into the flood deposit where it was scavenged by AVS and particulate organic matter.…”

“…Variable and elevated [THg d ] within the flood layer as well as in the older indigenous sediments reflect the remobilization of mercury following the dissolution of authigenic Fe oxides and the degradation of organic matter from the older, Hg-laden indigenous sediments, remobilization driven by the concentration gradient in the Hg-poor flood sediments and, to a smaller degree, compaction of the high porosity flood deposit (Maurice and Locat, 2000;Tremblay et al, 2003). Given the high affinity of mercury for organic matter and AVS (Bono, 1997;Chavez et al, 2013;Johannesson and Neumann, 2013;this study), this results in a high degree of covariance between [THg d ], [THg s ], C org and AVS throughout the cores.…”

“…Nevertheless, studies carried out with mono-mineralitic phases have demonstrated the strong affinity of Hg for iron monosulfides (Wolfenden et al, 2005;Jeong et al, 2007;Chavez et al, 2013). The amount of mercury associated with pyrite [py-Hg] in sediments recovered from SAG-30, SAG-09 and SAG-05 in 2002, was determined using the method of Lord (1982), the dissolution of the isolated solid in concentrated nitric acid, and CVAFS analysis, but our results are clearly plagued by a procedural artefact as an anomalously large fraction of the total mercury content of the sediments (47-79% of the THg s ) was recovered in the last extraction step.…”

“…In lacustrine and estuarine sediments, remediation of mercurycontaminated sediments usually include dredging (Hosokawa, 1993; Barbosa and de Almaida, 2001;Wang et al, 2004;Randall and Chattopadhyay, 2013), in-situ and ex-situ capping (Jacobs and Förstner, 2001;Eek et al, 2007;Johnson et al, 2010), binding to sorbent materials (Knox et al, 2008;Bower et al, 2008;Gosh et al, 2011;Chavez et al, 2013), (co)-precipitation (Piao and Bishop, 2006), and phytoremediation (Chattopadhyay et al, 2012). When the sediments are to be isolated from the overlying water column, it is critical to have detailed knowledge of the speciation and distribution of mercury in the sediments as well as to continuously monitor their evolution after isolation to detect remobilization of the mercury (Johnson et al, 2010).…”

The Aging Process of Cadmium in Paddy Soils under Intermittent Irrigation with Acid Water: A Short-Term Simulation Experiment

“…(ii) H + is consumed as a result of the reduction in oxides, such as NO 3 − , SO 4 2− and Fe-oxides under reduction conditions [ 41 , 42 ]. Han et al [ 31 ] attributed the decrease in pH to the oxidative dissolution of FeS in soil during the periods of drainage, and the reaction can be described with Equation (1) [ 43 ]. As a whole, the pH remained relatively constant at values between 5.2 and 6.9 throughout the experiments.…”