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On the Reactivity of Nanoparticulate Elemental Sulfur : = Experimentation and Field Observations.

紀錄類型:	書目-語言資料,手稿 : Monograph/item
正題名/作者:	On the Reactivity of Nanoparticulate Elemental Sulfur :/
其他題名:	Experimentation and Field Observations.
作者:	Kafantaris, Fotios Christos.
面頁冊數:	1 online resource (259 pages)
附註:	Source: Dissertation Abstracts International, Volume: 79-04(E), Section: B.
標題:	Geochemistry. -
電子資源:	click for full text (PQDT)
ISBN:	9780355550207

On the Reactivity of Nanoparticulate Elemental Sulfur : = Experimentation and Field Observations.
Kafantaris, Fotios Christos.

On the Reactivity of Nanoparticulate Elemental Sulfur :Experimentation and Field Observations. - 1 online resource (259 pages)

Source: Dissertation Abstracts International, Volume: 79-04(E), Section: B.

Thesis (Ph.D.)--Indiana University - Purdue University Indianapolis, 2017.

Includes bibliographical references

The reaction between elemental sulfur and sulfide is a lynchpin in the biotic and abiotic cycling of sulfur. This dissertation is focused on the reactivity of elemental sulfur nanoparticles (S8weimarn, S 8raffo) among other forms of elemental sulfur (S8aq, S 8aq-surfactant, alpha-S8), and how the variation of their surface area, character and coatings reflect on the analytical, physical-chemical and geochemical processes involving sulfur cycling. A comprehensive electrochemical investigation utilizing mercury-surface electrodes showed that elemental sulfur compounds are represented by three main voltammetric signals, corresponding to potentials at --1.2V, --0.8V, and --0.6V in the absence of organics at circumneutral pH. Dissolved S8aq-surfactant signals can be found from --0.3V up to --1.0V, depending on the surfactant in the system. Variations in current response resulted from differences in electron transfer efficiency among the forms of S8, due to their molecular structural variability. Based on this observation a new reaction pathway between S8 and Hg-surface electrodes is proposed, involving an amalgam-forming intermediate step. The kinetics of the nucleophilic dissolution of S8nano by sulfide, forming polysulfides, were investigated under varying surface area, surface character and presence or absence of surfactant coatings on S8nano. Hydrophobic S8weimarn and hydrophilic S8raffo show kinetic rate laws of rS8weimarn = 10--11.33(e[--700.65/ RT]) (Molar(S8)/second/dm--1) and rS8raffo = 10--4.11 i --0.35 (e[--615.77/RT]) (Molar(S8)/second), respectively. The presence of surfactant molecules can influence the reaction pathways by dissolving S8nano and releasing S8aq-surfactant, evolving the rate-limiting step as a function of the degree of the solubilization of S8nano. The reaction rate of S8biological can be compared with those of S8raffo and S8weimarn in circumneutral pH values and T = 50oC, making the forms of S8nano successful abiotic analogue models of microbially produced S8biological. Field observations and geochemical kinetic modeling in the geothermal features of Yellowstone indicate that the nucleophilic dissolution reaction appears to be a key abiotic pathway for the cycling of sulfur species and the enhancement of elemental sulfur bioavailability. Furthermore, in situ and ex situ voltammetry in the same geothermal waters disclosed chaotic variability in chemical gradients of sulfide (observed over small temporal and spatial scales) which can be considered as an ecological stressor capable of influencing single cell physiology and microbia.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355550207Subjects--Topical Terms:

648291
Geochemistry.
Index Terms--Genre/Form:

554714
Electronic books.

On the Reactivity of Nanoparticulate Elemental Sulfur : = Experimentation and Field Observations.
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502 $a Thesis (Ph.D.)--Indiana University - Purdue University Indianapolis, 2017.
504 $a Includes bibliographical references
520 $a The reaction between elemental sulfur and sulfide is a lynchpin in the biotic and abiotic cycling of sulfur. This dissertation is focused on the reactivity of elemental sulfur nanoparticles (S8weimarn, S 8raffo) among other forms of elemental sulfur (S8aq, S 8aq-surfactant, alpha-S8), and how the variation of their surface area, character and coatings reflect on the analytical, physical-chemical and geochemical processes involving sulfur cycling. A comprehensive electrochemical investigation utilizing mercury-surface electrodes showed that elemental sulfur compounds are represented by three main voltammetric signals, corresponding to potentials at --1.2V, --0.8V, and --0.6V in the absence of organics at circumneutral pH. Dissolved S8aq-surfactant signals can be found from --0.3V up to --1.0V, depending on the surfactant in the system. Variations in current response resulted from differences in electron transfer efficiency among the forms of S8, due to their molecular structural variability. Based on this observation a new reaction pathway between S8 and Hg-surface electrodes is proposed, involving an amalgam-forming intermediate step. The kinetics of the nucleophilic dissolution of S8nano by sulfide, forming polysulfides, were investigated under varying surface area, surface character and presence or absence of surfactant coatings on S8nano. Hydrophobic S8weimarn and hydrophilic S8raffo show kinetic rate laws of rS8weimarn = 10--11.33(e[--700.65/ RT]) (Molar(S8)/second/dm--1) and rS8raffo = 10--4.11 i --0.35 (e[--615.77/RT]) (Molar(S8)/second), respectively. The presence of surfactant molecules can influence the reaction pathways by dissolving S8nano and releasing S8aq-surfactant, evolving the rate-limiting step as a function of the degree of the solubilization of S8nano. The reaction rate of S8biological can be compared with those of S8raffo and S8weimarn in circumneutral pH values and T = 50oC, making the forms of S8nano successful abiotic analogue models of microbially produced S8biological. Field observations and geochemical kinetic modeling in the geothermal features of Yellowstone indicate that the nucleophilic dissolution reaction appears to be a key abiotic pathway for the cycling of sulfur species and the enhancement of elemental sulfur bioavailability. Furthermore, in situ and ex situ voltammetry in the same geothermal waters disclosed chaotic variability in chemical gradients of sulfide (observed over small temporal and spatial scales) which can be considered as an ecological stressor capable of influencing single cell physiology and microbia.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
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