Modification of Mackinawite with L-Cysteine: Synthesis, Characterization, and Implications to Mercury Immobilization in Sediment

Chaves, Marcia R. M.; Valsaraj, Kalliat T.; DeLaune, Ronald D.; Gambrell, Robert P.; Büchler, Pedro Maurício

doi:10.5772/15041

Cited by 8 publications

(11 citation statements)

References 31 publications

(26 reference statements)

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“…In our earlier study, we observed that L-cysteine improved the mackinawite oxidation stability by 55% over unmodified mackinawite (Chaves et al, 2011). However, the effect of the modification on mercury-uptake capacity of mackinawite was not determined.…”

Section: Introductionmentioning

confidence: 87%

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Mercury Uptake by Modified Mackinawite

Chaves

Valsaraj

Gambrell

et al. 2012

Soil and Sediment Contamination: An International Journal

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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.

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Section: Introductionmentioning

confidence: 87%

“…The characterization of the solids before Hg sorption was previously described by Chaves et al (2011). The solids after mercury sorption were analyzed by X-ray powder diffraction (XRPD) using a Bruker/Siemens D5000 automated powder X-ray diffractometer with CuKα.…”

Section: Methodsmentioning

confidence: 99%

Mercury Uptake by Modified Mackinawite

Chaves

Valsaraj

Gambrell

et al. 2012

Soil and Sediment Contamination: An International Journal

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“…These protonations and deprotonations are quantitatively important, as disordered mackinawite has a high surface area of about 350 m 2 g À1 , with a total reactive-site density of 4.0 sites nm À2 (Wolthers et al, 2005). The E h of freshly precipitated mackinawite at pH 7.5 is $-300mV (Chaves et al, 2011). Given these properties, it is plausible that the reduction potential of disordered mackinawite could fall under alkaline conditions to the point that it could reduce CO 2 to CO (E 0 0 = -520mV), HCOOH (E 0 0 = -430mV), or formaldehyde (HCOOH + 2H + + 2e À 4 HCHO + H 2 O, E 0 0 = -580mV).…”

Section: Electron Bifurcation and Ion Gradientsmentioning

confidence: 99%

The Origin of Membrane Bioenergetics

Lane

Martin

2012

Cell

329

349

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Harnessing energy as ion gradients across membranes is as universal as the genetic code. We leverage new insights into anaerobe metabolism to propose geochemical origins that account for the ubiquity of chemiosmotic coupling, and Na(+)/H(+) transporters in particular. Natural proton gradients acting across thin FeS walls within alkaline hydrothermal vents could drive carbon assimilation, leading to the emergence of protocells within vent pores. Protocell membranes that were initially leaky would eventually become less permeable, forcing cells dependent on natural H(+) gradients to pump Na(+) ions. Our hypothesis accounts for the Na(+)/H(+) promiscuity of bioenergetic proteins, as well as the deep divergence between bacteria and archaea.

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“…Second, if lipid membranes or simple protocells line the thin inorganic barriers (which have hydrophobic surfaces [75][76][77]), then the steepness of the proton gradient would depend on several factors: (i) the proton permeability of the wall itself; (ii) the flow rates through neighbouring pores (potentially some distance away); and (iii) the proton permeability of the lipid membrane lining the pore. It is feasible that the main barrier to proton flux -responsible for steepening natural pH gradients -is not the inorganic walls themselves but the lipid membranes lining and insulating them (Figure 1).…”

Section: Proton Flux Across Lipid Membranes and Through Protein Machinesmentioning

confidence: 99%

Proton gradients at the origin of life

Lane

2017

BioEssays

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Chemiosmotic coupling - the harnessing of electrochemical ion gradients across membranes to drive metabolism - is as universally conserved as the genetic code. As argued previously in these pages, such deep conservation suggests that ion gradients arose early in evolution, and might have played a role in the origin of life. Alkaline hydrothermal vents harbour pH gradients of similar polarity and magnitude to those employed by modern cells, one of many properties that make them attractive models for life's origin. Their congruence with the physiology of anaerobic autotrophs that use the acetyl CoA pathway to fix CO gives the alkaline vent model broad appeal to biologists. Recently, however, a paper by Baz Jackson criticized the hypothesis, concluding that natural pH gradients were unlikely to have played any role in the origin of life. Unfortunately, Jackson mainly criticized his own interpretations of the theory, not what the literature says. This counterpoint is intended to set the record straight.

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Modification of Mackinawite with L-Cysteine: Synthesis, Characterization, and Implications to Mercury Immobilization in Sediment

Cited by 8 publications

References 31 publications

Mercury Uptake by Modified Mackinawite

Mercury Uptake by Modified Mackinawite

The Origin of Membrane Bioenergetics

Proton gradients at the origin of life

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