The effect of a thiol-containing organic molecule on molybdenum adsorption onto pyrite

Freund, Carla; Wishard, Anthony; Brenner, Ryan K.; Sobel, Marisa; Mizelle, Jack; Kim, Alex; Meyer, D.; Morford, Jennifer L.

doi:10.1016/j.gca.2015.11.015

Cited by 30 publications

(24 citation statements)

References 80 publications

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“…Among the potential mechanisms responsible for Mo burial under sulfidic conditions, the Fe pathway has been favored mostly because of the experimental work done with Fe (Bostick et al., ; Freund et al., ; Helz et al., , ) that identified the reactions involved when Mo co‐precipitates with Fe sulfide and from observations that dissolved Mo concentrations in euxinic lake settings become constant below depths where sulfidic waters become saturated with iron monosulfide (Helz et al., ). However, Mo also precipitates with dead/lysed cells and with Fe‐contaminated humic acids in sulfidic solution (Helz et al., ), and the constant, nonzero dissolved Mo profile may also arise from the presence of Mo on non‐sinking organic material (e.g., colloidal, and small particulate organic matter, e.g., <0.2 μm).…”

Section: Resultsmentioning

confidence: 99%

“…In the Fe pathway, thiomolybdates can be reduced in the presence of zero‐valent sulfur to create Mo‐polysulfide species (Vorlicek, Kahn, Kasuya, & Helz, ) that are, for example, adsorbed or co‐precipitated with FeS 2 , FeS (Bostick et al., ; Freund et al., ; Helz, Vorlicek, & Kahn, ; Xu, Christodoulatos, & Braida, ), and clay minerals (i.e., illite and Fe‐contaminated kaolinite and montmorillonite) (Bertine, ; Helz et al., ; Vorlicek & Helz, ). Some of these minerals may even be imbedded in an organic matrix in a coupled Fe‐organic matter pathway (Dahl, Chappaz et al., ; Freund et al., ).…”

Section: Introductionmentioning

confidence: 99%

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Evidence of molybdenum association with particulate organic matter under sulfidic conditions

et al. 2016

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The geochemical behavior of molybdenum (Mo) in the oceans is closely linked to the presence of sulfide species in anoxic environments, where Fe availability may play a key role in the Mo scavenging. Here, we show that Mo(VI) is reduced in the presence of particulate organic matter (represented by sulfate-reducing bacteria). Molybdenum was immobilized at the surface of both living cells and dead/lysed cells, but not in cell-free control experiments. Experiments were carried out at four different Mo concentrations (0.1 to 2 mm) to yield cell-associated Mo precipitates with little or no Fe, consisting of mainly Mo(IV)-sulfide compounds with molecular structures similar to Mo enzymes and to those found in natural euxinic sediments. Therefore, we propose that Mo removal in natural sulfidic waters can proceed via a non-Fe-assisted pathway that requires particulate organic matter (dead or living sulfate-reducing bacteria). This pathway has implications for global marine Mo cycling and the current use of Mo-based proxies for paleo-environmental investigations.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evidence of molybdenum association with particulate organic matter under sulfidic conditions

et al. 2016

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“…Doushantuo Formation samples imply that Mo species structurally similar to intermediate thiomolybdates can undergo long-term burial and preservation, potentially in association with Fe phases as suggested by sample HN12 (Table 6) and by previous workers (Helz et al, 1996;Helz et al, 2004). Importantly, our model does not preclude other mechanisms of Mo fixation in highly sulfidic environments, where MoS 4 2formation is favored and adsorption to Fe-S mineral phases (e.g., pyrite) may occur (Bostick et al, 2003;Chappaz et al, 2014;Freund et al, 2016;Helz et al, 2011). Additionally, thiolation of organic matter at low ([H 2 S (aq) ]) or in the presence of polysulfides, followed by complexation to Mo, could provide another pathway by which Mo is sequestered in sediments during early diagenesis.…”

Section: Discussionmentioning

confidence: 57%

“…Additionally, thiolation of organic matter at low ([H 2 S (aq) ]) or in the presence of polysulfides, followed by complexation to Mo, could provide another pathway by which Mo is sequestered in sediments during early diagenesis. Abiotic thiol formation has been shown to occur in reducing sediments Mopper, 1987, 1989), and MoS 4 2is capable of simultaneously binding to pyrite and thiols (Freund et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

Wagner

Chappaz

Lyons

2017

Geochimica et Cosmochimica Acta

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Sedimentary molybdenum (Mo) accumulation is a robust proxy for sulfidic conditions in both modern and ancient aquatic systems and has been used to infer changing marine redox chemistry throughout Earth's history. Accurate interpretation of any proxy requires a comprehensive understanding of its biogeochemical cycling, but knowledge gaps remain concerning the geochemical mechanism(s) leading to Mo burial in anoxic sediments. Better characterization of Mo speciation should provide mechanistic insight into sedimentary Mo accumulation, and therefore in this study we investigate Mo speciation from both modern (Castle Lake, USA) and ancient (Doushantuo Formation, China) environments using X-Ray Absorption Near Edge Structure (XANES) spectroscopy. By utilizing a series of laboratory-synthesized oxythiomolybdate complexes-many containing organic ligands-we expand the number of available standards to encompass a greater range of known Mo chemistry and test the linkage between Mo and total organic carbon (TOC). In weakly euxinic systems ([H 2 S (aq) ] < 11 µM), or where sulfide is restricted to pore waters, natural samples are best represented by a linear combination of MoO 3 , MoO x S 4-x 2-(intermediate thiomolybdates), and [MoO x (cat) 4-x ] 2-(cat = catechol, x = 2 or 3). These results suggest a revised model for how Mo accumulates in weakly sulfidic sediments, including a previously unrecognized role for organic matter in early sequestration of Mo and a de-emphasized importance for MoS 4 2-(tetrathiomolybdate).

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“…To date, only the adsorption of molybdates on goethite and gibbsite has been extensively studied [13]. However, in recent years, new, functionalized materials such as magnetic macroporous cross-linked copolymers of glycidyl methacrylate [14] or thiol-containing organic molecule of pyrite [15] have become increasingly popular in the immobilization of molybdates from aqueous solutions. In addition, an evaluation of the adsorption of mono- and polytungstates onto selected soil minerals (gibbsite, birnessite, kaolinite, illite, and montmorillonite) has been described by Sen Tuna [4] and Iwai and Hashimoto [7].…”

Section: Introductionmentioning

confidence: 99%

Sorption of Molybdates and Tungstates on Functionalized Montmorillonites: Structural and Textural Features

et al. 2019

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Montmorillonite—the most popular mineral of the smectite group—has been recognized as a low-cost, easily available mineral sorbent of heavy metals and other organic and inorganic compounds that pollute water. The aim of this work was to determine the sorption mechanism and to identify the reaction products formed on the surface of montmorillonite and organo-montmorillonite after sorption of molybdates (Mo(VI)) and tungstates (W(VI)). Montmorillonites are often modified to generate a negative charge on the surface. The main objective of the study was to investigate and compare the features of Na-montmorillonite (Na-M), montmorillonite modified with dodecyl trimethyl ammonium bromide (DDTMA-M), and montmorillonite modified with didodecyl dimethyl ammonium bromide (DDDDMA-M) before and after sorption experiments. The material obtained after sorption was studied by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The XRD pattern showed the presence of a new crystallic phase in the sample that was observed under an SEM as an accumulation of crystals. The FTIR spectra showed bands related to Mo–O and W–O vibration (840 and 940 cm−1, respectively). The obtained results suggest that molybdenum(VI) and tungsten(VI) ions sorb onto the organo-montmorillonite in the form of alkylammonium molybdates and tungstates.

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The effect of a thiol-containing organic molecule on molybdenum adsorption onto pyrite

Cited by 30 publications

References 80 publications

Evidence of molybdenum association with particulate organic matter under sulfidic conditions

Evidence of molybdenum association with particulate organic matter under sulfidic conditions

Molybdenum speciation and burial pathway in weakly sulfidic environments: Insights from XAFS

Sorption of Molybdates and Tungstates on Functionalized Montmorillonites: Structural and Textural Features

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