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Microbiologically influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) in offshore industries, such as the oil and gas pipelines, due to the high concentrations of sulfate in the seawater. SRM act upon the metal by the reactiveness of hydrogen sulfide (HS-), and by withdrawal of the available electrons (Fe --> Fe2+ + 2e-; E° = -0.47 V) in electrical contact with the metal (EMIC). However, methanogenic archaea can also cause MIC. Because they do not produce HS-, withdrawal of electrons may be their main corrosive mechanism; however, mechanistic details and kinetics of the overall process are poorly understood.
To investigate the corrosion potential of methanogens, we studied the EMIC methanogenic strains isolated from marine sediments (Methanobacterium-affiliated strain IM1) and crude oil tanks (Methanococcus maripaludis Mic1c10), in an in-house developed flow-through cell to simulate a fluctuating environment. A co-culture of M. maripaludis and D. alaskensis was also established to study the effect of syntrophic growth on metal corrosion that may occur in industrial pipelines. Results indicate that the rates of iron corrosion due to coupled methanogenesis (up to 0.4 mm/yr) are higher to that caused by the marine SRM Desulfovibrio alaskensis (0.15 mm/yr). Surface analyses of the metal showed severe pitting with high methane production. Genomic analysis of the EMIC methanogen M. maripaludis Mic1c10 will provide an insight on the mechanisms of MIC. Such knowledge and deeper understanding also from an electrokinetic point of view may not only provide further models in microbial electrophysiology, but also contribute to mitigation strategies in MIC.zeige weniger
Microbiologically influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) in offshore industries, such as the oil and gas pipelines, due to the high concentrations of sulfate in the seawater. SRM act upon the metal by the reactiveness of hydrogen sulfide (HS-), and by withdrawal of the available electrons (Fe --> Fe2+ + 2e-; E° = -0.47 V) in electrical contact with the metal (EMIC). However, methanogenic archaea can also cause MIC. Because they do not produce HS-, withdrawal of electrons may be their main corrosive mechanism; however, mechanistic details and kinetics of the overall process are poorly understood.
To investigate the corrosion potential of methanogens, we studied the EMIC methanogenic strains isolated from marine sediments (Methanobacterium-affiliated strain IM1) and crude oil tanks (Methanococcus maripaludis Mic1c10), in an in-house developed flow-through cell to simulate a fluctuating environment. A co-culture of M. maripaludis and D. alaskensis was also established to study the effect of syntrophic growth on metal corrosion that may occur in industrial pipelines. Results indicate that the rates of iron corrosion due to coupled methanogenesis (up to 0.4 mm/yr) are higher to that caused by the marine SRM Desulfovibrio alaskensis (0.15 mm/yr). Surface analyses of the metal showed severe pitting with high methane production. Genomic analysis of the EMIC methanogen M. maripaludis Mic1c10 will provide an insight on the mechanisms of MIC. Such knowledge and deeper understanding also from an electrokinetic point of view may not only provide further models in microbial electrophysiology, but also contribute to mitigation strategies in MIC.
Since the early 19th century microorganisms were studied on their capabilities of causing microbiologically influenced corrosion (MIC) of metals. The most studied ones are sulfate-reducing bacteria (SRB), but others can corrode metals as well, e.g. acid-producing bacteria or methanogenic archaea (MA). However, these studies were mostly focused on metals related to the petroleum industry but metals for other industries, e.g. dentistry, are also susceptible to corrosion. The inert Titanium (Ti) is often used as an implant material, but it is a base metal. The formation of a passivating oxide layer allows Ti to be corrosion resistant at normal conditions.
Nonetheless, scanning electron microscope images on dental implants from patients with acute peri-implantitis showed clear signs of corrosion. Currently, the corrosion mechanism of dental implants is unknown, but many indications suggest that oral microorganisms, including MA (Methanobrevibacter oralis) and SRB (Desulfomicrobium orale), could be involved.
To determine if MA or SRB can corrode Ti (pure Ti or Ti-6Al-4V alloy), corrosion rate, methane and sulfide concentrations were analyzed. Electrical potential measurements using in-house developed electrochemical cells indicated a potential change on Ti in the presence of a corrosive MA strain compared to an abiotic control.
Microbial composition comparison will be analyzed using samples from dental pockets of 150 infected patients by considering the quality of the implant and 50 healthy people by means of amplicon sequencing. Enrichments and isolation of pure cultures from the dentals samples are also examined for their corrosion behavior. Overall, this is the first study investigating the susceptibility of dental implant material to corrosion using human related MA.
Flow-back and produced waters from shale gas and shale oil fields contain high ammonium, which can be formed by methanogenic degradation of methylamines into methane and ammonium. Methylamines are added to fracturing fluid to prevent clay swelling or can originate from metabolism of the osmolyte triglycinebetaine (GB).
We analyzed field samples from a shale gas reservoir in the Duvernay Formation and from a shale oil reservoir in the Bakken formation in Canada to determine the origin of high ammonium. Fresh waters used to make fracturing fluid, early flow-back waters, and late flow back waters from the shale gas reservoir had increasing salinity of 0.01, 0.58, and 2.66 Meq of NaCl, respectively. Microbial community analyses reflected this fresh water to saline transition with halophilic taxa including Halomonas, Halanaerobium, and Methanohalophilus being increasingly present. Early and late flow-back waters had high ammonium concentrations of 32 and 15 mM, respectively.
Such high concentrations had also been found in the Bakken produced waters.
Enrichment cultures of Bakken produced waters in medium containing mono, di-, or trimethylamine, or triglycinebetaine (GB) converted these substrates into ammonium (up to 20 mM) and methane. The methylotrophic methanogen Methanohalophilus, which uses methylamines for its energy metabolism and uses GB as an osmolyte, was a dominant community member in these enrichments. Halanaerobium was also a dominant community member that metabolizes GB into trimethylamine, which is then metabolized further by Methanohalophilus. However, the micromolar concentrations of GB measured in shale reservoirs make them an unlikely source for the 1,000-fold higher ammonium concentrations in flow-back waters. This ammonium either originates directly from the reservoir or is formed from methylamines, which originate from the reservoir, or are added during the hydraulic fracturing process. These methylamines are then converted into ammonium and methane by halophilic methylotrophic methanogens, such as Methanohalophilus, present in flow-back waters.
Test methods for efficacy assessment of antimicrobial coatings are not modelled on a hospital environment, and instead use high humidity (>90%) high temperature (37 ◦C), and no airflow. Therefore, an inoculum will not dry, resulting in an antimicrobial surface exhibiting prolonged antimicrobial activity, as moisture is critical to activity. Liquids will dry quicker in a hospital ward, resulting in a reduced antimicrobial efficacy compared to the existing test, rendering the test results artificially favourable to the antimicrobial claim of the product. This study aimed to assess how hospital room environmental conditions can affect the drying time of an inoculum, and to use this data to inform test parameters for antimicrobial efficacy testing based on the hospital ward. The drying time of different droplet sizes, in a range of environmental conditions likely found in a hospital ward, were recorded (n = 630), and used to create a model to inform users of the experimental conditions required to provide a drying time similar to what can be expected in the hospital
ward. Drying time data demonstrated significant (p < 0.05) variance when humidity, temperature, and airflow were assessed. A mathematical model was created to select environmental conditions for in vitro antimicrobial efficacy testing. Drying time in different environmental conditions demonstrates that experimental set-ups affect the amount of time an inoculum stays wet, which in turn may affect the efficacy of an antimicrobial surface. This should be an important consideration for hospitals and other potential users, whilst future tests predict efficacy in the intended end-use environment.
Microbially influenced corrosion (MIC) of iron is usually attributed to sulfate-reducing microorganisms (SRM) which act upon the metal by the reactiveness of hydrogen sulfide, and by withdrawal of the available electrons in electrical contact with the metal. Methanogenic archaea can also cause MIC by directly withdrawing electrons from the iron surface for methanogenesis. However, the mechanistic details and kinetics of the overall process are poorly understood. Precipitation of siderite, a by-product of methanogenesis, (4Fe + 5HCO3 + 5H+ 4FeCO3 + CH4 + 3H2O) can lead to an insulating layer on the metal surface and lower the corrosion rate. Still, the extent of FeCO3 precipitation may be significantly influenced by environmental conditions such as pH and advective processes.
Near-ambient pressure XPS makes it possible to characterise samples not compatible to ultra-high vacuum, and enables the study of liquid-solid, gas-liquid and gas-solid interfaces. NAP-XPS meas-urements of biofilms, suspended nanoparticles and metal-organic frameworks were performed with EnviroESCA developed by SPECS.
An interesting application is surface characterisation of biofilms, which are bacterial communities embedded in a self-produced polysaccharide matrix. Various model systems ranging from pure polysaccharides of alginate to biofilms harvested directly from the growth medium have been char-acterised in humid conditions[1].
NAP-XPS also makes it possible to characterise nanoparticles in solution. Silver nanoparticles in aqueous solution were characterised and the Ag 3d-spectrum compared to spectra obtained of dried nanoparticles in UHV-conditions[2]. The binding energy of the Ag 3d-core level peak was shifted by 0,6 eV towards higher binding energy for suspended nanoparticles compared to the dried sample measured in UHV. This can be assigned to a change in surface potential at the water-nanoparticle interface.
Metal-organic frameworks (MOFs) are suitable materials for gas storage of small molecules due to their nanoporous, crystalline structure. However, instability in humidity remains an issue for many types of MOFs. XPS-measurements of the MOF-structure HKUST-1 were performed in various NAP-conditions to assess the stability of the sample and its interaction with the gas molecules as water, methanol and pyridine.
Environmental sustainability and –stability of Materials concerning the Migration of pollutants
(2018)
MaUS is an acronym for ”Material und Umweltsimulationen“. Plastics are in the focus of environmental politics due to their long-term behaviour and therefore to their persistence. Not only that they appear as visible contaminants in the sea and on the beach, but their unknown behaviour concerning their additives as well as the related transformation products are anxious. Therefore, we wish to establish a certified reference method to provide a method for testing plastics.
Aim of this project is the development of fast motion standard reference methods for testing plastics regarding to their environmental compatibility. To establish these testing methods, we use polystyrene (PS) and polypropylene (PP) with environmental relevant brominated flame retardants, known for their persistent bioaccumulative and toxic (PBT) properties. In case of PS the material contains 1 wt% of 1,2,5,6,9,10-hexabromocyclododecan (HBCD) and in case of PP 0.1 wt% bromodiphenylether (BDE-209), which is known as a substance of very high concern (SVHC). Furthermore, we use polycarbonate (PC), which is still used as material in baby flasks and releases Bisphenol A (BPA), an estrogenic active substance.
As an additional material PTFE is used for its importance as a source for two ubiquitous environmental substances (PFOS and PFOA), whose toxicological effects are still incompletely known.
The focus in this current work is set on the transfer of potential pollutants out of applied materials mentioned above into environmental compartments like water or soil. Here an accelerated aging concept should be developed to shortened time consuming natural processes. For these resulting simulations we use a programmable weathering chamber with dry and wet periods and with high and low temperatures. These programmes run for several weeks and according to a defined sampling schedule we take water samples, run a clean-up procedure by SPE (Molecular imprinted polymers (MiPs) resp. polymer-based cartridges (Waters Oasis HLB)) and analyse them by HPLC-UV resp. LC-MS/MS. Of most interest in case of flame retardants are photocatalytic transformation products. Therefore, we conduct a non-target-screening resp. a suspected target-screening by LC-MS/MS and HRMS.
Synchrotron XPS in the soft-X-ray regime is suitable for the detection of light elements commonly found in biological samples. Various model systems of biofilms have been developed and characterised at synchrotron- and lab-based facilities. By obtaining the chemical composition at various information depths, the vertical distribution of iodine in an artificial biofilm have been determined.
ABSTRACT: A collection of thioimidazolium salts were synthesized and used as a new class of nonvolatile alkylating agents. Their nonvolatility prevents exposure during use or handling and are thus drastically safer than conventional alkylating agents. We discovered that thioimidazolium Iodide salts cannot release volatile compounds in the solid state, but instead only decompose when molten. Since decomposition proceeds via alkyl iodide elimination, SN2 of iodide on the thioimidazolium cation is constrained in the solid state, and instead can occur only upon melting when ions are mobile. By smart design of these alkylators, the melting point and thus the decomposition temperature of these salts can be increased from 106 to 169 °C and release negligible volatile organic compounds prior to melting. Thioimidazolium-bis(trifluoromethanesulfonyl)imide (TFSI) ionic liquids act as a completely nonvolatile and air-stable TFSI-based alkylating agent and can be used for high-throughput Synthesis of TFSI ionic liquids without solvent. Alkyl groups from methyl to dodecyl can be transferred to a nucleophile and the product purified by sublimation of the thione byproduct, which can then be recycled. We also found that thioimidazolium salts with a dodecyl chain are bactericidal, yet can hydrolyze in water to form benign neutral products, and thus wont accumulate in the environment. These results demonstrate that thioimidazolium salts are a designable platform for the pursuit of safer and more environmentally friendly alkylating and antiseptic agents.