So far, most studies on microbiologically induced carbonate precipitation for limestone conservation have been performed at temperatures optimal for the activity of the calcinogenic bacteria (i.e., ...20–28 °C). Successful application in practice, however, requires adequate performance in a wide range of environmental conditions. Therefore, the aim of this study was to select microorganisms that are most suited for biodeposition at temperatures relevant for practice. In a first step, ureolytic microorganisms were screened for their growth and ureolytic activity at different temperatures (10, 20, 28, and 37 °C). Large differences in calcinogenic activity could be observed between experiments performed on agar plates and those performed in solution and in limestone. In a second step, the influence of temperature on the performance of the biodeposition treatment with different ureolytic microorganisms was evaluated, both on the consolidative and protective effect of the treatment. In contrast with the experiments on agar plates, the
Sporosarcina psychrophila
strains failed to produce significant amounts of calcium carbonate on limestone in conditions relevant for practice, even at 10 °C. This resulted in a poor performance of the treatment. From experiments performed on limestone prisms, it appeared that the mesophilic
Bacillus sphaericus
produced the highest amount of carbonate in the shortest amount of time at all temperatures tested. As a result, compared to the untreated specimens, the highest consolidative (64 % lower weight loss upon sonication) and protective effect (46 % decreased sorptivity) were observed for the treatments with this species. From this study, it appears that among all ureolytic strains tested,
B. sphaericus
is most suited for biodeposition applications in practice.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
Most research on the hydrogen embrittlement of steel dealt with the interaction of hydrogen with the metal bulk microstructural features, whereas the first contact with hydrogen-containing ...environments occurs at the metal surface. Steel (when un-polarized) is always covered with an oxide layer, varying in composition and thickness. The impact of the oxide layer on the hydrogen transport is, however, not fully understood. This study focused on the effect of controlled pre-formed thermal oxide layers at the exit side on the hydrogen transport through the surface of SEA 1010 steel, considering two distinct thermally produced oxide types as test cases. Results demonstrated that thermal oxides can greatly limit hydrogen diffusion, with bilayers (hematite/magnetite) having a greater effect compared to magnetite layers. Increased oxide thickness resulted also in greater limiting diffusion. The main objective of this manuscript is to provide experimental evidence concerning the effect of oxide layers on the hydrogen transport through steel. Model thermal oxide layers were used to emphasize the importance of considering the surface characteristics when investigating hydrogen transport through metallic components.
Dual-phase low-alloy steels combine a soft ferrite phase with a hard martensite phase to create desirable properties in terms of strength and ductility. Nickel additions to dual-phase low-alloy ...steels can increase the yield strength further and lower the transformation temperatures, allowing for microstructure refining. Determining the correct intercritical annealing temperature as a function of nickel content is paramount, as it defines the microstructure ratio between ferrite and martensite. Likewise, quantifying the influence of nickel on the intercritical temperature and its synergistic effect with the microstructure ratio on mechanical properties is vital to designing dual-phase steels suitable for corrosive oil and gas services as well as hydrogen transport and storage applications. In this work, we used a microstructural design to develop intercritical annealing heat treatments to obtain dual-phase ferritic-martensitic low-alloy steels. The intercritical annealing and tempering temperatures and times were targeted to achieve three different martensite volume fractions as a function of nickel content, with a nominal content varying between 0, 1, and 3-wt% Ni. Mechanical properties were characterized using tensile testing and microhardness measurements. Additionally, the microstructure was studied using scanning electron microscopy coupled with electron backscatter diffraction analysis. Tensile strength increased with increasing martensite ratio and nickel content, with a further grain refinement effect found in the 3-wt% Ni steel. The optimal heat treatment parameters for oil and gas and hydrogen transport applications are discussed.
Platinum (Pt) and palladium (Pd) are precious metals considered critical in our society and are needed in a variety of sustainable technologies. Their scarcity urges the increase of recycling from ...secondary waste streams through new and efficient recovery techniques. Adsorption is an established recovery method for liquid streams, where chitosan shows promising results as a low-cost adsorbent, derived from biomass. This biopolymer is able to capture metals, but suffers from a low stability under acidic conditions and poor adsorbing properties. In this study, three new chitosan derivatives were synthesized and employed for Pd( ii ) and Pt( iv ) recovery from acidic solutions. Specific and simple modifications were selected based on their known affinities for these metal ions and taking into account the principles of green chemistry. The prepared derivatives consist of 1,10-phenanthroline-2,9-dicarbaldehyde cross-linked chitosan (Ch-PDC), 2,2′-bipyridine-5,5′-dicarbaldehyde cross-linked chitosan (Ch-BPDC) and glutaraldehyde cross-linked chitosan grafted with 8-hydroxyquinoline-2-carbaldehyde (Ch-GA-HQC). For all derivatives, the adsorption occurred fast and equilibrium reached within 30 min. The Langmuir isotherms revealed a maximum adsorption capacity for Pd( ii ) and Pt( iv ) of respectively 262.6 mg g −1 and 119.5 mg g −1 for Ch-PDC, 154.7 mg g −1 and 98.3 mg g −1 for Ch-BPDC and 340.3 mg g −1 and 203.9 mg g −1 for Ch-GA-HQC. Such adsorption capacities are considerably higher compared to the biosorbents reported in the literature. Excellent physical properties in homo- and heterogeneous systems and high regeneration performances demonstrate that chitosan-based adsorbents are very promising for Pd( ii ) and Pt( iv ) recovery from acidic solutions.
In the current study, ferritic steels containing NbC or NbN precipitates were investigated. The materials were subjected to various heat treatments, giving rise to different precipitate size ...distributions as determined by transmission electron microscopy. Both NbC and NbN precipitates act as hydrogen traps. The steels were hydrogen charged both electrochemically and/or from the gaseous hydrogen source, followed by multiple thermal desorption spectroscopy (TDS) measurements. Electrochemical charging gave rise to a low-temperature peak 323 K to 523 K (50 °C to 250 °C), originating from the hydrogen trapped near grain boundaries, with activation energy ranging between 24 and 33 kJ/mol, and at small NbC (39 to 48 kJ/mol) or NbN precipitates (23 to 24 kJ/mol). Gaseous charging caused a high-temperature TDS peak 723 K to 923 K (450 °C to 650 °C), which was attributed to the presence of incoherent precipitates. The activation energy for NbC precipitates, charged in a hydrogen atmosphere, ranged between 63 and 68 kJ/mol and between 100 and 143 kJ/mol for NbN precipitates.
Hydrogen can degrade the mechanical properties of steel components, which is commonly referred to as "hydrogen embrittlement" (HE). Quantifying the effect of HE on the structural integrity of ...components and structures remains challenging. The authors investigated an X70 pipeline steel through uncharged and hydrogen-charged (notched) tensile tests. This paper presents a combination of experimental results and numerical simulations using a micro-mechanics-inspired damage model. Four specimen geometries and three hydrogen concentrations (including uncharged) were targeted, which allowed for the construction of a fracture locus that depended on the stress triaxiality and hydrogen concentration. The multi-physical finite element model includes hydrogen diffusion and damage on the basis of the complete Gurson model. Hydrogen-Assisted degradation was implemented through an acceleration of the void nucleation process, as supported by experimental observations. The damage parameters were determined through inverse analysis, and the numerical results were in good agreement with the experimental data. The presented model couples micro-mechanical with macro-mechanical results and makes it possible to evaluate the damage evolution during hydrogen-charged mechanical tests. In particular, the well-known ductility loss due to hydrogen was captured well in the form of embrittlement indices for the different geometries and hydrogen concentrations. The limitations of the damage model regarding the stress state are discussed in this paper.
Diclofenac, a nonsteroidal anti-inflammatory drug, is one of the most commonly detected pharmaceuticals in sewage treatment plant (STP) effluents. In this work, biologically produced manganese oxides ...(BioMnOx) were investigated to remove diclofenac. At neutral pH, the diclofenac oxidation with BioMnOx was 10-fold faster than with chemically produced MnO2. The main advantage of BioMnOx over chemical MnO2 is the ability of the bacteria to reoxidize the formed Mn2+, which inhibits the oxidation of diclofenac. Diclofenac-2,5-iminoquinone was identified as a major transformation product, accounting for 5−10% of the transformed diclofenac. Except for 5-hydroxydiclofenac, which was identified as an intermediate, no other oxidation products were detected. Diclofenac oxidation was proportional to the amount of BioMnOx dosed, and the pseudo first order rate constant k was 6-fold higher when pH was decreased from 6.8 to 6.2. The Mn2+ levels remained below the drinking water limit (0.05 mg L−1), thus indicating the efficient in situ microbiological regeneration of the oxidant. These results combined with previous studies suggest the potential of BioMnOx for STP effluent polishing.
The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the ...association of silver nanoparticles with the bacterial cell surface of
Lactobacillus fermentum (referred to as biogenic silver or bio-Ag
0) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag
0 particles, preventing aggregation during encapsulation. In this study, bio-Ag
0 was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag
0 and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag
+ from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag
0
powder m
−2 in a submerged plate membrane reactor operated at a flux of 3.1 L m
−2 h
−1. Upon startup, the silver concentration in the effluent initially increased to 271 μg L
−1 but after filtration of 31 L m
−2, the concentration approached the drinking water limit ( = 100 μg L
−1). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m
−2 h
−1, showing the potential of this membrane technology for water disinfection on small scale.
► In biogenic silver, silver nanoparticles are attached to a bacterial carrier matrix. ► Bio-Ag
0 was successfully immobilized in PVDF membranes using immersion-precipitation. ► The antiviral activity of this material was demonstrated in a plate membrane reactor. ► The antimicrobial mechanism was most probably related to the slow release of Ag
+ ions. ► The membranes can be applied for treatment of limited volumes of contaminated water.
In the study of the liquid metal embrittlement (LME) of the T91/lead-bismuth eutectic (LBE) system, it is observed that LME occurs in a temperature interval which is similar to the temperature range ...where dynamic strain aging (DSA) is observed. However, the potential correlation between DSA and LME has not yet been satisfactorily investigated. This investigation for the T91/LBE system is exactly the topic of this work. For the evaluation of DSA and LME, slow strain rate tensile tests are conducted in the temperature range between 200 °C and 450 °C with strain rates of 5×10−5 s−1 and 5×10−6 s−1 in reference and a molten oxygen-depleted LBE environment. The resulting tensile properties, as well as the fracture surfaces and lateral surfaces of the failed samples, suggest a correlation between DSA and LME in the T91/LBE system. The maximum mechanical degradation of T91 is observed in the case where the effects of both DSA and LME on material properties are found to be at maximum. However, the observation of DSA was not identified as a prerequisite for LME to take place. Therefore, these results may indicate that DSA partly contributes to the ductility minimum observed in the T91/LBE system. In addition, the results of this work show that changes in the fracture surface and lateral surface are more sensitive features to claim for the potential occurrence of LME than the changes in total elongation.
•Local passivation at metal grain boundaries was studied in situ on copper.•Metallic and passivated surfaces were analysed with scanning tunneling microscopy.•The Cu(I) passive film is found thicker ...at grain boundaries than on grains.•A thicker passive film is formed at random grain boundaries than at coherent twins.•No metal is preferentially consumed by transient dissolution at grain boundaries.
Passivation at grain boundaries was investigated on copper with Electrochemical Scanning Tunneling Microscopy. The depth in intergranular regions was measured and its variation was discussed in terms of dissolution or passive film formation. The Cu(I) passive film is found to be thicker at grain boundaries than on grains but with a similar stoichiometry. A thicker Cu(I) passive film is observed at random grain boundaries than at coherent twins. No metal is preferentially consumed at grain boundaries by transient dissolution during Cu(I) passivation. Comprehensive comparison with Cu(I)/Cu(II) passivation shows that transient dissolution is a revelator of the grain boundary-type dependent behavior.
