Academic literature on the topic 'Sulfur remediation'

With the strengthening of human activities, more and more sulfur had entered soil system. The sulfur pollution of soil had threaten environment and human health. This paper reviews the status, sources and danger of sulfur pollution soils, and the physical-chemical remediation and bioremediation technology are also discussed. In addition, the future study on remediation technology for sulfur pollution soils was prospected.

Sulfide is a toxic pollutant in the farming environment. Microbial removal of sulfide always faces various biochemical challenges, and the application of enzymes for agricultural environmental remediation has promising prospects. In this study, a strain of Cellulosimicrobium sp. was isolated: numbered strain L1. Strain L1 can transform S2−, extracellular enzymes play a major role in this process. Next, the extracellular enzyme was purified, and the molecular weight of the purified sulfur convertase was about 70 kDa. The sulfur convertase is an oxidase with thermal and storage stability, and the inhibitor and organic solvent have little effect on its activity. In livestock wastewater, the sulfur convertase can completely remove S2−. In summary, this study developed a sulfur convertase and provides a basis for the application in environmental remediation.

Thiocyanate (SCN–) forms in the reaction between cyanide (CN–) and reduced sulfur species, e.g. in gold ore processing and coal-coking wastewater streams, where it is present at millimolar (mM) concentrations1. Thiocyanate is also present naturally at nM to µM concentrations in uncontaminated aquatic environments2. Although less toxic than its precursor CN–, SCN– can harm plants and animals at higher concentrations3, and thus needs to be removed from wastewater streams prior to disposal or reuse. Fortunately, SCN– can be biodegraded by microorganisms as a supply of reduced sulfur and nitrogen for energy sources, in addition to nutrients for growth4. Research into how we can best harness the ability of microbes to degrade SCN– may offer newer, more cost-effective and environmentally sustainable treatment solutions5. By studying biodegradation pathways of SCN– in laboratory and field treatment bioreactor systems, we can also gain fundamental insights into connections across the natural biogeochemical cycles of carbon, sulfur and nitrogen6.

Recent studies on the use of controlled sulfur amendment to improve the reactivity and selectivity of zerovalent iron (ZVI) in reductive dechlorination reactions have generated renewed interest in ZVI-based remediation materials.

Arsenic and other heavy metal contaminants in water are a significant global health threat. In this study, low-cost, sulfur-free, sustainable, water-insoluble materials with heavy metal remediation properties were produced from renewable resources such as starch, xylan, citric acid, and chitosan. Synthesized starch citrate-chitosan (SCC) foam and xylan citrate-chitosan (XCC) foam were flexible, porous, and elastic. The foams’ arsenic uptake in water was significantly greater than five different commercial metal remediating agents. The mercury and lead uptakes with the synthesized foams were similar to the performance of a commercial sulfur-based product, SorbaTech 450 (ST450). However, the cadmium and selenium uptakes were comparatively lower. The complexation of arsenic with oxygen and nitrogen of the SCC foam was shown with time-of-flight secondary ion mass spectrometry (TOF-SIMS). The XCC foam was also shown to adsorb potassium iodide (KI) at a similar rate to sodium chloride. This may be used to remediate water contaminated with radioactive materials, such as iodine 131.

Sulfur has an affinity for Hg. By polymerising and crosslinking elemental sulfur with dienes, it can be formed into a stable polymer. A salt template method to create porosity in these polymers is reported, and shown to improve the Hg capture.

Inverse vulcanization is a process in which highly abundant and low-cost elemental sulfur is copolymerized with an unsaturated organic molecule such as a polyene. This process has provided a variety of useful materials with high sulfur content—typically 50% or greater in sulfur by mass. These materials have garnered increasing interest in research as sorbents for mercury, due to the high affinity of sulfur for mercury. In this review, the features of mercury sorbents made by inverse vulcanization are presented. Additionally, case studies are provided to illustrate the variety of polymer architectures accessible with this chemistry, the versatility of these materials in mercury remediation, and prospects for industrial use.1 Introduction2 Sulfur Polymers by Inverse Vulcanization3 Sulfur Polymers as Mercury Sorbents4 Increasing Surface Area to Improve Mercury Uptake5 Crosslinker Considerations6 Sorption of Different Forms of Mercury7 Life-Cycle Management8 Conclusions and Outlook

The aim of the work was a comprehensive study of the soils (pH, EC, SOC, NT, ST), surface waters (pH, EC, Ca2+ Mg2+, Na+, NO3−, SO42−, Cl−, HCO3−), and reactions of trees and herbaceous plants in the restored forest ecosystem of a former sulfur mine. Common birch and Scots pine growth reaction, vitality (according to IUFRO standards- International Union of Forest Research Organizations), nutrient supply (Na, K, P, Ca, Mg, K), and Calamagrostis epigejos (L.) Roth chemical composition (Na, K, P, Ca, Mg, K) were assayed. The chemistry dynamics (pH, EC, DOC, NT, Ca, Mg, and S at the beginning and end of the experiment) of soil leaching and the sulfur load leached from the sulfur-contaminated soil substrates were evaluated. The remediation effects of birch and pine litter were assayed in an experiment under controlled conditions. It was found that reclamation was effective in the majority of the post-mining site; however, hotspots with sulfur contamination reaching even 45,000 mg kg−1, pH < 2.0 and electrical conductivity (EC) of 6500 µS cm−1 were reported. Surface waters typically displayed elevated concentrations of sulfate ions (average 935.13 mg L−1), calcium ions (up to 434 mg L−1), and high EC (average 1797 µS cm−1), which was related both to sulfur contamination and the sludge lime that was used in neutralization. Calamagrostis epigejos was found to be a species that adapted well to the conditions of elevated soil salinity and sulfur concentration. It was observed that the application of organic matter had a significant beneficial impact on the chemistry of soil solutions, but did not show a remediation effect by increased sulfur leaching in a short-term study.

Immobilization and detoxification of chromium in the vadose zone is made possible by the existence of an effective reductant, SO2, that exists in a gaseous form at room temperature. Experimental studies were designed to characterize stoichiometry and kinetics of chromium reduction both in aqueous solutions at pH values near neutrality and in soil. First, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in water. The stoichiometric ratio of S(IV) removed to Cr(VI) removed ranged between 1.6 and 1.8. The overall reaction is believed to be the result of a linear combination of two reactions in which dithionate is an intermediate and sulfate is the stable oxidized product. The reaction was also rapid, with the half-time of about 45 minutes at pH 6 and about 16 hours at pH 7. A two-step kinetic model was developed to describe changes in concentrations of Cr(VI), S(IV), and S(V). Nonlinear regression was applied to obtain the kinetic parameters. The rate of reaction was assumed to be second-order with respect to [Cr(VI)] and first-order with respect to [S(IV)], and [S(V)]. The values for the rate coefficient for the first reaction (k1) were found to be 4.5 (?10%), 0.25 (?9.4%) (mM-2h-1) at pH 6 and 7, respectively. The values of the rate coefficient for the second reaction (k2) were 25 (?29%), 1.1 (? 30%) (mM-2h-1) at pH 6 and 7, respectively. The reaction rate decreased as pH increased. Experiments showed that the rate at pH 7 was lower than that at pH 6 by one order of magnitude. Second, batch experiments and elemental analyses were conducted to characterize the stoichiometry and kinetics of Cr(VI) reduction in soil. The stoichiometric ratio of S(IV) removed to Cr(VI) removed was almost 2, which is slightly higher than that for the reaction in water. This higher value may be due to S(IV) oxidation by soil-derived Fe(III). The reaction was rapid, with the half-time less than 2 minutes, which is faster than in water. The rate coefficients, k1 and k2, were 22 (?41%) and 13 (?77%) (M-2h-1), respectively.

Mercury and arsenic are widespread contaminants in aqueous environments throughout the world. The elements arise from multiple sources including mercury from coal-fired power plants and wells placed in natural geological deposits of arseniccontaining minerals. Both elements have significant negative health impacts on humans as they are cumulative toxins that bind to the sulfhydryl groups in proteins, disrupting many biological functions. There are currently no effective, economical techniques for removing either mercury or arsenic from aqueous sources. This thesis will demonstrate a superior removal method for both elements by formation of covalent bonds with the sulfur atoms in N,N’-Bis(2-mercaptoethyl)isophthalamide (commonly called “B9”). That B9 can precipitate both elements from water is unusual since aqueous mercury exists primarily as a metal(II) dication while aqueous arsenic exists as As(III) and As(V) oxyanions.

Es wurde eine Arsenkontamination von Boden und Grundwasser im Bereich einer Zellstofffabrik untersucht, die auf Ablagerungen von Eisenoxidschlacken (Rückstände aus der Pyritröstung) mit hohem Gehalt an verschiedenen Spurenelementen zurückzuführen ist. Der Standort ist dadurch gekennzeichnet, dass über viele Jahre Lösungen aus der Celluloseproduktion („Sulfitablauge“) versickerten. Hierdurch gelangten größere Mengen an Sulfat und organischen Stoffen in den Untergrund. Infolgedessen weist das Grundwasser einen stark reduzierten, sulfidischen Chemismus auf. Ein Großteil der Spurenelemente wurde aus der Schlacke im Oberboden in den darunter liegenden wassergesättigten Bereich transportiert und dort in Form von sulfidischen Niederschlägen festgelegt. Eine Ausnahme bildet Arsen, das unter den spezifischen Milieubedingungen im Schadenzentrum lösliche schwefelhaltige Verbindungen bildet (max. 4 mg As/L). Diese Arsen-Schwefel-Spezies wurden erstmals mit einer neu entwickelten IC-ICP/MS- Methode in einem Grundwasser nachgewiesen. Die Grundwasser- und Bodenuntersuchungen sowie begleitende hydrogeologische Messungen ergaben, dass die Arsen-Schwefel-Spezies innerhalb einer Fließstrecke von 30-80 m im Abstrom des Schadenzentrums vollständig immobilisiert werden. Bei der Festlegung von Arsen spielt die biologische Sulfatreduktion, die durch versickerte Sulfitablauge ermöglicht wurde, eine entscheidende Rolle. Anhand dieser Erkenntnisse wurde im Jahr 2000 ein natural attenuation-Konzept zur Sicherung des Standortes ausgearbeitet. Nach Auswertung der Ergebnisse der Standortuntersuchungen aus den Jahren 1999-2005 sowie einer Literaturrecherche zur Arsen-Schwefel-Chemie wurden die Struktur und das Verhalten der unbekannten Arsen-Schwefel-Spezies sowie die Vorgänge bei der Festlegung von Arsen im Boden genauer untersucht. Das wesentlichste Ergebnis der Arbeiten ist, dass in sulfidischen Systemen, z.B. in Grundwässern unter Sulfat reduzierenden Bedingungen, Thioarsenate gebildet werden. In Lehrbüchern und Fachpublikationen aus den vergangenen Jahrzehnten wurde bislang ausschließlich die Existenz von Thioarseniten vermutet. Ursache für die Bildung von Thioarsenaten ist eine hohe Affinität zwischen Arsen und Schwefel, die eine Oxidation von As(III) durch Anlagerung eines Schwefelatoms an dessen freiem Elektronenpaar „erzwingt“. In sulfidhaltigen Lösungen wird hierzu ein Teil des As(III) zu elementarem Arsen reduziert. Das zunächst gebildete Monothioarsenat wird weiter zu den schwefelhaltigeren Thioarsenaten sulfidiert. In sulfidischen Grundwässern bestimmen deshalb die Anionen von Oxomonothioarsenat, Oxodithioarsenat, Oxotrithioarsenat und Tetrathioarsenat das Verhalten von Arsen. Wesentlich für das Verständnis der Arsen-Schwefel-Chemie ist auch die Instabilität der As-SH-Gruppen, die entsprechend dem Dissoziationsverhalten der jeweiligen Arsen-Schwefel-Spezies gebildet werden. Dies erfolgt bei pH-Werten im Bereich von ca. 7-8,5, wobei die monomeren Anionen unter Abspaltung von Schwefelwasserstoff kondensieren. Infolgedessen muss in Grundwässern auch mit polymeren Thioarsenaten gerechnet werden. In saurer Lösung zerfallen die Thioarsenate in arsenige Säure und Schwefel bzw. fallen als Arsenpentasulfid aus. Arsen wird in sulfidischen Aquiferen als Sulfid (z.B. As4S4), als Arsenpyrit (FeAsS) oder durch Einbau von Arsen als Schwefelsubstituent in das Kristallgitter von Mackinawite bzw. Pyrit (FeS, FeS2) festgelegt. Die ermittelten Prozesse können ggf. zur Sanierung bzw. Sicherung von Standorten mit arsenhaltigen Rückständen im Boden bzw. von arsenbelasteten Grundwässern eingesetzt werden. Dabei ist auch von Bedeutung, dass Thioarsenate nach derzeitigem Kenntnisstand relativ gering toxisch sind. Im Umgang mit Thioarsenaten, z.B. auch bei der Analyse von Arsen in sulfidischen Proben, ist jedoch deren Umwandlung in arsenige Säure bei einer pH-Absenkung und auch bei Sauerstoffzutritt zu berücksichtigen. Die biologische Sulfatreduktion spielt eine wesentlich größere Rolle für die Mobilität von Arsen in Grundwässern als bisher angenommen. Im Hinblick auf die weltweit große gesundheitliche Relevanz von Arsen im Trinkwasser und auf mögliche Sanierungsverfahren sollten die Umsetzungen von Arsen unter Sulfat reduzierenden Bedingungen eingehender untersucht werden
The motivation for the thesis was a project at an industrial site conducted in 1999 to define a remediation concept for soil and groundwater contaminated with arsenic. The contamination resulted from the deposition of residuals from pyrite burning (iron oxides containing different trace elements) in the upper soil many years ago. Because of long-term pollution with process waters rich in organic substances and sulfate, the aquifer is strongly reduced (sulfidic). Most of the arsenic was transferred out of the contaminated soil into the saturated zone in a depth of 7-10 m. There it is partly immobilized as sulfide precipitations, but part of it is solved in the groundwater in form of arsenic-sulfur-complexes (up to 4 ppm). These complexes were detected for the first time in a groundwater by means of an improved IC-ICP-MS method. It was also found that approx. 80 m downstream of the contaminated spot the concentrations of arsenic in soil and groundwater were not increased. On this basis a natural attenuation concept was proposed in 2000. The data from the investigated site was evaluated and specific laboratory tests were carried out in order to identify the unknown arsenic species as well as the processes which lead to their immobilization in the aquifer. The key role of the soluble arsenic-sulfur complexes for the mobility and toxicity of arsenic in sulfate-reducing environments is commonly accepted. In the past, thioarsenites were assumed to be the existing species in sulfidic systems. In this study, however, thioarsenates were identified in solutions spiked with in arsenite and hydrogen sulfide as well as in the contaminated groundwater. The unexpected finding of an oxidation of arsenite to thioarsenates in strongly reducing systems can be explained by the high affinity between As(III) and sulfur. In sulfide containing solutions without any oxidant, arsenite therefore undergoes disproportionation to thioarsenates and elemental arsenic. This was already found out in the 19th century, but has been neglected in publications from the last decades. According to the results of this study the anions of oxomonothioarsenate, oxodithioarsenate, oxotrithioarsenate und tetrathioarsenate are the dominating arsenic species in sulfidic waters. The partitioning of the four species is governed mainly by the sulfide concentration. Beside the high affinity between arsenic and sulfur, the instability of the As-SH group is essential to understand the reactions in the arsenic-sulfur system. As soon as the arsenic-sulfur complexes form As-SH groups (according to their dissociation characteristics) they condensate in separating hydrogen sulfide. Thioarsenates form polymers in the pH range of approx. 7-8.5. Therefore beside the mentioned monomers, thioarsenate polymers can also be important in natural environments. In more acidic solutions they decay into arsenite and sulfur or precipitate as arsenic-pentasulfide. When analyzing arsenic in sulfide containing solutions, it has always to be taken into account that thioarsenates are highly sensitive to oxygen and pH. Therefore, e.g. arsenic speciation by means of HG-AAS is not suitable for sulfidic waters and can wrongly indicate a mixture of arsenite and arsenate. It has previously been supposed that the mobility as well as the toxicity of arsenic increase if the redox state decreases. For sulfidic waters the opposite is probably the case owing to the formation of thioarsenates. The toxicity of arsenite is due to the high reactivity of the As(III) towards sulfohydroxyl groups in proteins. Without a free electron pair and sulfur already incorporated, thioarsenates should be less toxic compared to arsenite. Arsenic can be mobilized out of contaminated soils in form of thioarsenates via infiltration of sulfide solutions or by input of sulfate and biodegradable organic matter. In the presence of iron, thioarsenates can be fixated in sulfidic aquifers as a minor substitute in mackinawite and biogenic pyrite or as arsenic pyrite. Bacterial sulfate reduction is a crucial factor for the mobilization and immobilization of arsenic in reduced aquifers. Considering the negative health impacts of arsenic for millions of people worldwide, as well as the implementation of the mentioned remediation strategies the arsenic-sulfur chemistry deserves closer attention

Es wurde eine Arsenkontamination von Boden und Grundwasser im Bereich einer Zellstofffabrik untersucht, die auf Ablagerungen von Eisenoxidschlacken (Rückstände aus der Pyritröstung) mit hohem Gehalt an verschiedenen Spurenelementen zurückzuführen ist. Der Standort ist dadurch gekennzeichnet, dass über viele Jahre Lösungen aus der Celluloseproduktion („Sulfitablauge“) versickerten. Hierdurch gelangten größere Mengen an Sulfat und organischen Stoffen in den Untergrund. Infolgedessen weist das Grundwasser einen stark reduzierten, sulfidischen Chemismus auf. Ein Großteil der Spurenelemente wurde aus der Schlacke im Oberboden in den darunter liegenden wassergesättigten Bereich transportiert und dort in Form von sulfidischen Niederschlägen festgelegt. Eine Ausnahme bildet Arsen, das unter den spezifischen Milieubedingungen im Schadenzentrum lösliche schwefelhaltige Verbindungen bildet (max. 4 mg As/L). Diese Arsen-Schwefel-Spezies wurden erstmals mit einer neu entwickelten IC-ICP/MS- Methode in einem Grundwasser nachgewiesen. Die Grundwasser- und Bodenuntersuchungen sowie begleitende hydrogeologische Messungen ergaben, dass die Arsen-Schwefel-Spezies innerhalb einer Fließstrecke von 30-80 m im Abstrom des Schadenzentrums vollständig immobilisiert werden. Bei der Festlegung von Arsen spielt die biologische Sulfatreduktion, die durch versickerte Sulfitablauge ermöglicht wurde, eine entscheidende Rolle. Anhand dieser Erkenntnisse wurde im Jahr 2000 ein natural attenuation-Konzept zur Sicherung des Standortes ausgearbeitet. Nach Auswertung der Ergebnisse der Standortuntersuchungen aus den Jahren 1999-2005 sowie einer Literaturrecherche zur Arsen-Schwefel-Chemie wurden die Struktur und das Verhalten der unbekannten Arsen-Schwefel-Spezies sowie die Vorgänge bei der Festlegung von Arsen im Boden genauer untersucht. Das wesentlichste Ergebnis der Arbeiten ist, dass in sulfidischen Systemen, z.B. in Grundwässern unter Sulfat reduzierenden Bedingungen, Thioarsenate gebildet werden. In Lehrbüchern und Fachpublikationen aus den vergangenen Jahrzehnten wurde bislang ausschließlich die Existenz von Thioarseniten vermutet. Ursache für die Bildung von Thioarsenaten ist eine hohe Affinität zwischen Arsen und Schwefel, die eine Oxidation von As(III) durch Anlagerung eines Schwefelatoms an dessen freiem Elektronenpaar „erzwingt“. In sulfidhaltigen Lösungen wird hierzu ein Teil des As(III) zu elementarem Arsen reduziert. Das zunächst gebildete Monothioarsenat wird weiter zu den schwefelhaltigeren Thioarsenaten sulfidiert. In sulfidischen Grundwässern bestimmen deshalb die Anionen von Oxomonothioarsenat, Oxodithioarsenat, Oxotrithioarsenat und Tetrathioarsenat das Verhalten von Arsen. Wesentlich für das Verständnis der Arsen-Schwefel-Chemie ist auch die Instabilität der As-SH-Gruppen, die entsprechend dem Dissoziationsverhalten der jeweiligen Arsen-Schwefel-Spezies gebildet werden. Dies erfolgt bei pH-Werten im Bereich von ca. 7-8,5, wobei die monomeren Anionen unter Abspaltung von Schwefelwasserstoff kondensieren. Infolgedessen muss in Grundwässern auch mit polymeren Thioarsenaten gerechnet werden. In saurer Lösung zerfallen die Thioarsenate in arsenige Säure und Schwefel bzw. fallen als Arsenpentasulfid aus. Arsen wird in sulfidischen Aquiferen als Sulfid (z.B. As4S4), als Arsenpyrit (FeAsS) oder durch Einbau von Arsen als Schwefelsubstituent in das Kristallgitter von Mackinawite bzw. Pyrit (FeS, FeS2) festgelegt. Die ermittelten Prozesse können ggf. zur Sanierung bzw. Sicherung von Standorten mit arsenhaltigen Rückständen im Boden bzw. von arsenbelasteten Grundwässern eingesetzt werden. Dabei ist auch von Bedeutung, dass Thioarsenate nach derzeitigem Kenntnisstand relativ gering toxisch sind. Im Umgang mit Thioarsenaten, z.B. auch bei der Analyse von Arsen in sulfidischen Proben, ist jedoch deren Umwandlung in arsenige Säure bei einer pH-Absenkung und auch bei Sauerstoffzutritt zu berücksichtigen. Die biologische Sulfatreduktion spielt eine wesentlich größere Rolle für die Mobilität von Arsen in Grundwässern als bisher angenommen. Im Hinblick auf die weltweit große gesundheitliche Relevanz von Arsen im Trinkwasser und auf mögliche Sanierungsverfahren sollten die Umsetzungen von Arsen unter Sulfat reduzierenden Bedingungen eingehender untersucht werden.
The motivation for the thesis was a project at an industrial site conducted in 1999 to define a remediation concept for soil and groundwater contaminated with arsenic. The contamination resulted from the deposition of residuals from pyrite burning (iron oxides containing different trace elements) in the upper soil many years ago. Because of long-term pollution with process waters rich in organic substances and sulfate, the aquifer is strongly reduced (sulfidic). Most of the arsenic was transferred out of the contaminated soil into the saturated zone in a depth of 7-10 m. There it is partly immobilized as sulfide precipitations, but part of it is solved in the groundwater in form of arsenic-sulfur-complexes (up to 4 ppm). These complexes were detected for the first time in a groundwater by means of an improved IC-ICP-MS method. It was also found that approx. 80 m downstream of the contaminated spot the concentrations of arsenic in soil and groundwater were not increased. On this basis a natural attenuation concept was proposed in 2000. The data from the investigated site was evaluated and specific laboratory tests were carried out in order to identify the unknown arsenic species as well as the processes which lead to their immobilization in the aquifer. The key role of the soluble arsenic-sulfur complexes for the mobility and toxicity of arsenic in sulfate-reducing environments is commonly accepted. In the past, thioarsenites were assumed to be the existing species in sulfidic systems. In this study, however, thioarsenates were identified in solutions spiked with in arsenite and hydrogen sulfide as well as in the contaminated groundwater. The unexpected finding of an oxidation of arsenite to thioarsenates in strongly reducing systems can be explained by the high affinity between As(III) and sulfur. In sulfide containing solutions without any oxidant, arsenite therefore undergoes disproportionation to thioarsenates and elemental arsenic. This was already found out in the 19th century, but has been neglected in publications from the last decades. According to the results of this study the anions of oxomonothioarsenate, oxodithioarsenate, oxotrithioarsenate und tetrathioarsenate are the dominating arsenic species in sulfidic waters. The partitioning of the four species is governed mainly by the sulfide concentration. Beside the high affinity between arsenic and sulfur, the instability of the As-SH group is essential to understand the reactions in the arsenic-sulfur system. As soon as the arsenic-sulfur complexes form As-SH groups (according to their dissociation characteristics) they condensate in separating hydrogen sulfide. Thioarsenates form polymers in the pH range of approx. 7-8.5. Therefore beside the mentioned monomers, thioarsenate polymers can also be important in natural environments. In more acidic solutions they decay into arsenite and sulfur or precipitate as arsenic-pentasulfide. When analyzing arsenic in sulfide containing solutions, it has always to be taken into account that thioarsenates are highly sensitive to oxygen and pH. Therefore, e.g. arsenic speciation by means of HG-AAS is not suitable for sulfidic waters and can wrongly indicate a mixture of arsenite and arsenate. It has previously been supposed that the mobility as well as the toxicity of arsenic increase if the redox state decreases. For sulfidic waters the opposite is probably the case owing to the formation of thioarsenates. The toxicity of arsenite is due to the high reactivity of the As(III) towards sulfohydroxyl groups in proteins. Without a free electron pair and sulfur already incorporated, thioarsenates should be less toxic compared to arsenite. Arsenic can be mobilized out of contaminated soils in form of thioarsenates via infiltration of sulfide solutions or by input of sulfate and biodegradable organic matter. In the presence of iron, thioarsenates can be fixated in sulfidic aquifers as a minor substitute in mackinawite and biogenic pyrite or as arsenic pyrite. Bacterial sulfate reduction is a crucial factor for the mobilization and immobilization of arsenic in reduced aquifers. Considering the negative health impacts of arsenic for millions of people worldwide, as well as the implementation of the mentioned remediation strategies the arsenic-sulfur chemistry deserves closer attention.

Thesis (PhD.(Chemistry)--University of Pretoria, 2008.
On title page: Submitted in partial fulfilment of the requirements for the degree Philosophiae Doctor in Chemistry in the faculty of Natural and Agricultural Sciences of the University of Pretoria. Includes bibliographical references.

Microorganisms play very important role in elemental and mineral chemistry on earth surface. Along with the major biogeochemical cycles such as Carbon, Nitrogen, Sulphur and Phosphorus, which are crucially involved in thermodynamic balances in earth system, microbes are also involved in trace metal cycling. The organic carbon sustaining the indigenous microbial communities critically controls these microbial processes. A large number of the microbial communities are able to form a wide variety minerals, of which many have only biogenic origin and cannot be formed inorganically. Microbes also play a critical role in dissolution of minerals; a process which not only helps in soil formation and the transport of nutrients to higher trophic levels, but can also have many important industrial roles. Thus, in these metabolic activities, microorganisms contribute to the geological phenomenon of the transformation of metals and minerals. This chapter focuses on the role of various microbial metabolic processes that are involved in mineralization and mineral dissolution and the consequences involved with it.

The oxidation studies of a sulfur to a sulfate ion by various oxyhalide oxidants in organic (thiourea, methionine) and inorganic (sulfate, thiophosphate) compounds were carried out in an acidic solution. The optimized result of the oxidation reaction was obtained when a bromate compound (BrO3−) as an oxidant and a 3 M HNO3 solvent. The chemical yield for the oxidation of the organic and inorganic sulfur compounds to a sulfate ion was monitored as 80% for thiophosphate, 87% for methionine, and 100% for thiourea and sulfate within 5% RSD. The oxidation of thiourea required at least 1.6 equivalents of the bromate in an acidic solution. In the case of the oxidation of methionine and thiophosphate, the oxidation yield was above 80% if the bromate was used at 20 times that of the substrates. The chemical yield in the paper sample (WypAll) exceeded 100% because of its background sulfur contents (910 ppm). The sulfate ion was quantitatively measured by using GPC and/or LSC counting of 35S followed by precipitates of BaSO4. The interfering nuclides (14C, 32P) were removed in an acidic condition. The minimum detectable activity (MDA) of 35S was found to be 0.1 Bq/g.

In a green house pot experiment, the effects of three amendments, sulphur (S), ammonium sulphate ((NH4)2SO4) and ethylenediaminetetracetic acid (EDTA) were tested for phytoextraction of Cd and Zn by rapeseed (Brassica napus L.). Elemental sulphur was applied as 20.00, 60.00, and 120.00 mg.kg−1 soil. EDTA was tested at a dose of 585.00 mg.kg−1 soil, and (NH4)2SO4) at a rate of 0.23 mg.kg−1 soil. All treatments received a base fertilization (Hogland) before sowing. Plants were harvested after 51 days of growth and shoot dry matter and soil samples were analysed for metal contents. All amendments caused a significant increase in Cd and Zn contents in plant shoots of all treatments than control treatment. Further, EDTA was most effective for extraction metals concentrations in shoot biomass but the plants showed significant signs of toxicity and yield were severely depressed. The addition of sulfur favorably influenced plant biomass production. The fertilized ammonium sulfate treatment resulted in the highest phytoextraction of Cd and Zn and the amounts of these metals accumulated in plant shoot exceeded by a factor of 4 and 3 respectively. Finally, Brassica napus could be used for soil remediation keeping its other uses which will make the contaminated site income generating source for the farmers.

Current estimates and glass formulation efforts are conservative vis-à-vis achievable waste loadings. These formulations have been specified to ensure that glasses are homogenous, contain essentially no crystalline phases, are processable in joule-heated, ceramic-lined melters and meet WTP Contract terms. The WTP’s overall mission will require the immobilization of tank waste compositions that are dominated by mixtures of aluminum, chromium, bismuth, iron, phosphorous, zirconium, and sulfur compounds as waste-limiting components. Glass compositions for these waste mixtures have been developed based upon previous experience and current glass property models. DOE has a testing program to develop and characterize HLW glasses with higher waste loadings. This work has demonstrated the feasibility of increases in waste loading from 25 wt% to 33–50 wt% (based on oxide loading) in the glass depending on the waste stream. It is expected these higher waste loading glasses will reduce the HLW canister production requirement by 25% or more.

The current estimates and glass formulation efforts have been conservative in terms of achievable waste loadings. These formulations have been specified to ensure that the glasses are homogenous, contain essentially no crystalline phases, are processable in joule-heated, ceramic-lined melters and meet WTP Contract terms. The WTP’s overall mission will require the immobilization of tank waste compositions that are dominated by mixtures of aluminum (Al), chromium (Cr), bismuth (Bi), iron (Fe), phosphorous (P), zirconium (Zr), and sulfur (S) compounds as waste-limiting components. Glass compositions for these waste mixtures have been developed based upon previous experience and current glass property models. Recently, DOE has initiated a testing program to develop and characterize HLW glasses with higher waste loadings. Results of this work have demonstrated the feasibility of increases in waste loading from about 25 wt% to 33–50 wt% (based on oxide loading) in the glass depending on the waste stream. It is expected that these higher waste loading glasses will reduce the HLW canister production requirement by about 25% or more.

On a global basis, trace-metal pollution is one of the most pervasive environmental problems. It is particularly difficult to prevent or clean up because the metals are toxic in their elemental form and cannot be decomposed. Bioremediation has been shown to be a powerful system for heavy metal pollution clean up and prevention. In this work, we characterized the cadmium (Cd)-resistant bacteria isolated from rice field soil downstream from zinc (Zn) mineralized area which the owners were contaminated at high level of cadmium content in their blood (&gt;10 μgCd/g creatinine). We found that all 24 isolated bacteria tolerated toxic Cd concentrations (2,500 μM). In order to determine whether the Cd toxicity affected the growth of isolated bacteria, we grew the isolated bacterial cells in the absence and presence of toxic concentrations of CdCl2 (500 μM). In the absence of Cd, all isolated bacterial cells grew slightly better than in the presence of toxic concentrations of Cd. In addition, the Cd binding capacity of all isolated bacteria were very high, ranging from 6.38 to 9.38 log[Cd(atom)]/cell when grown in the presence of 500 μM CdCl2. Furthermore, the stability of Cd-bacteria complex of all isolated bacteria was affected by 1mM EDTA. When grown in the presence of 500 μM CdCl2, Cd-resistant isolates S2500-6, -8, -9, -15, -17, -18, -19, and -22 increasingly produced proteins containing cysteine (SH-group) (from 1.3 to 2.2 times) as well as 11 isolates of Cd-resistant bacteria, including S2500-1, -2, -3, -5, -6, -8, -9, -11, -16, -20, and -21, increasingly produced inorganic sulfide (1.5 to 4.7 times). Furthermore, the Sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy studies indicated that Cd-resistant isolated S2500-3 precipitated amounts of cadmium sulfide (CdS), when grown in the presence of 500 μM CdCl2. The results suggested that these Cd-resistant bacteria have potential ability to precipitate a toxic soluble CdCl2 as nontoxic insoluble CdS. Interestingly, Cd-resistant bacteria isolated S2500-3, -8, -9,and -20 increased cadmium tolerance of Thai jasmine rice (Kao Hom Mali 105) when grown in the presence of 200 μM CdCl2. These 4 isolates also decreased cadmium concentration accumulation in Kao Hom Mali 105 plant at 61, 9, 6, and 17%, respectively when grown in the presence of 200 μM CdCl2. They were identified by 16S rDNA sequence analysis and classified as Cupriavidus taiwanensis (isolate S2500-3) and Pseudomonas aeruginosa (isolates S2500-8, -9, and -20).

Primary loop resin waste is eluted by sulfuric acid in The Kansai Electic Company Mihama, Takahama and Ohi nuclear power station. Waste solution from this elution process is planned to be solidified by cement. This study bring out a range of chemical composition and crud concentration of waste solution from this elution process, and examine the properties of alumina cement solidification process and solidified material. Test for sulfate ion, borate, lithium, ammonium ion was carried out. Volume reduction ratio of over 0.5 was achieved for 5 to 25wt% of sulfate ion and <5,000ppm of borate. Lithium ion restrained the solidification delay by borate. Also, ammonium ion shows no significant effect. Based on this study, we concluded that the aluminum cement is applicable to all range of composition of waste solution from the resin elution process. This study is a part of committed work of The Kansai electric company.

Since 1979, Uranium enrichment technology has been researched through the gas centrifuge method, at Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency (JAEA). In addition, the Demonstration Plant, that is final stage test facilities, was operating continuously from 1988 to 2001. As a result, a lot of residues accumulated in the plant. Most of this accumulation was found be uranium intermediate fluoride. The basic decommission policy of JAEA is that equipments of gas centrifuge will be decontaminated by sulfuric acid immersion method for clearance and reuse. In our plan, approximately 90% of metals will be cleared and reused, and then the remaining 10% will be disposed of radioactive waste. We propose a combination of sulfuric acid immersion method and the systematic chemical decontamination as an efficient method for decontamination of uranium enrichment facilities. This paper focuses on the method and performance of systematic chemical decontamination using IF7 gas. The following (Figure 1) shows our decommission policy and position of systematic chemical decontamination by IF7 gas for uranium enrichment plant. The IF7 treatment technique belongs to the systematic decontamination technology. It has the high performance decontamination technique for the plant that accumulates the uranium intermediate fluoride, such as UF4, UF5, U2F9, and U4F17, which exist in the uranium enrichment plant through the Gas Centrifuge, called GCF. The one of characteristics of the IF7 treatment, the secondary waste is just an IF5 and little residues. In addition, this IF5 can be reused as materials for making new IF7 gas. The IF7 treatment can also be performed in the room temperature and very low pressure like a 10–45hPa. Furthermore, the IF7 treatment is a simple method using chemical reaction. For this reason, we hardly need to care about secondary reaction with the exception of the reaction with IF7 gas and the uranium intermediate fluoride. This is a very important feature when applying to a large-scale plant. In order to carry out the IF7 treatment, we only set up a few equipments in GCF uranium enrichment plant, which were IF7 feeding equipment and two circulating pumps. IF7 gas cylinders are seated in IF7 feeding equipment. This is the only equipment. Figure 2 shows the IF7 treatment system. We carried out the IF7 treatment for the four cascades in the uranium enrichment Demonstration Plant. The weights of uranium residue in the cascades were approximately 700kgU per cascade prior to the IF7 treatment. In the IF7 treatment, we were able to find the near-optimal processing condition. As a result, we could confirm the IF7 treatment period for one cascade which was 60 days. The main factor to determine the IF7 treatment period is the pressure and the flow rate of reaction product gas (UF6 and IF5 mixture gas) exhausted from the cascade. Although we carried out the IF7 treatment with the maximum value of the flow rate, which our facility has, it is possible to further shorten the IF7 treatment period by setting a higher gas flow rate. Moreover, after the IF7 treatment, we evaluated the uranium recovery rate for cascades and the residues’ uranium weight in the main equipment of GCF. In addition, in the evaluation of the uranium recovery rate, we enable to confirm the uranium recovery rate of all cascades achieved more tan 98%. Furthermore, the average of uranium recovery rate more than 99% in the cascade that has been processed at the end. As a result, radioactive concentration of uranium in the main parts of the GCF fell to 1.0B q/g and below.