Effects of NO2 aging on bismuth nanoparticles and bismuth-loaded silica xerogels for iodine capture

The capture of long-lived radioactive iodine (¹²⁹I) from oxidizing off-gasses produced from reprocessing used nuclear fuel is paramount to human health and environmental safety. Bismuth has been investigated as a viable iodine getter but the phase stability of bismuth-based sorbents in an oxidizing environment have not yet been researched. In the current work, bismuth nanoparticle-based sorbents, as free particles (Bi-NPs) and embedded within silica xerogel monoliths made with a porogen (TEO-5), were exposed to I_2(g) before and after aging in 1 v/v% NO₂ at 150 °C. For unaged sorbents, BiI₃ was the dominant phase after iodine capture with 8-30 mass% BiOI present due to native Bi₂O₃ on the surface of the unaged nanoparticles. After 3 h of aging, 82 mass% of the Bi-NPs was converted to Bi₂O₃ with only a small amount of iodine captured as BiOI (18 mass%). After aging TEO-5 for 3 h, iodine was captured as both BiI₃ (26 %) and BiOI (74 %) and no Bi₂O₃ was detected.". Additionally, bismuth lining the micrometer-scale pores in the TEO-5 led to enhanced iodine capture. In a subsequent exposure of the sorbents to NO₂ (secondary aging), all BiI₃ converted to BiOI. Thus, direct capture of iodine as BiOI is desired (over BiI₃) to minimize loss of iodine after capture.

Coordination and thermophysical properties of select trivalent lanthanides in LiCl-KCl

The coordination chemistry of various fission and decay products, such as actinides and lanthanides, are crucial to the commercial deployment of molten salt reactors as they can affect the thermophysical properties. Here, we examined the structure, coordination environment, and physical properties such as the density and the vibrational density of states for three lanthanide species, namely Ce, Eu, and Sm in the LiCl-KCl eutectic system using a combination of quantum mechanics simulations and spectroscopic experiments. Quantum mechanics molecular dynamics (QM-MD) modelling was employed to determine the physical properties of each system resulting in accurate local coordination of each species. Then, the vibrational density of states (DOS) was determined using a two-phase thermodynamic modelling which was then compared to the experimentally obtained Raman spectra of the species in molten LiCl-KCl having the eutectic composition. We find that Ce³⁺, Eu³⁺ and Sm³⁺ all adopt octahedral local coordination environments in the eutectic salt composition in good agreement with experimental results. Ce³⁺ is found to fluctuate between an octahedral six-coordinated and a seven-coordinated structure due to the increased local proximity of Cl in the eutectic salt, resulting in a lower fluidicity/diffusivity than the other trivalent lanthanides studied. The thermophysical properties of the eutectic composition with trivalent lanthanides were not significantly different from the pure eutectic salt composition, but several changes were noted.

High-Temperature Corrosion in Advanced Energy Systems

Our energy demands will be increasing for the near future due to factors such as population growth, improved standards of living, increased automation, and increased mobility. New power generation systems are being designed to meet this growing demand efficiently. These designs are also being influenced by our desire to meet more of our energy needs using sustainable sources. One of the primary goals of these advanced designs is to improve operational efficiency, which is low at ∼35% for thermal power plants. A straightforward method to improve efficiency is by operating the thermal power cycles at higher temperatures of up to 1000°C. Higher temperature operations, in turn, require newer heat transfer fluids such as molten salts, molten metals, or gases. The design criteria for these newer power systems are often limited by the choice of materials that can operate under these harsh environments. All of these demands mean that corrosion scientists need to study, understand, and develop strategies to control corrosion in these newer and harsher environments. This issue of Interface aims to provide an overview of some of these corrosion issues, identify promising materials, and highlight the research needs.

Use of electrospun threads in immobilized cell reactors for continuous ethanol production

Saccharomyces cerevisiae immobilized in electrospun Pluronic F127 dimethacrylate (FDMA) was successfully employed for the production of ethanol in an immobilized cell reactor. Yeast cells were immobilized into fibers formed through the process of electrospinning and cross-linking. The threads had an average diameter of 0.88 μm and were used in continuous-flow immobilized cell reactors. The immobilized cell reactors were able to maintain a high ethanol yield of >90% from day 4 through to the end of the time course at day 14. The reactor was able to achieve a maximum ethanol yield of 94.3%. This study shows that the use of electrospinning is a promising method for continuous ethanol production through immobilized cell-based continuous flow reactors.

Microbial synthesis of metallic molybdenum nanoparticles

The production of nanoparticles through biosynthesis is a reliable, non-toxic, and sustainable alternative to conventional chemical and physical methods of production. While noble metals, such as palladium, gold, and silver, have been formed via bioreduction, biologically-induced reduction of electroactive elements to a metallic state has not been reported previously. Herein, we report the reduction of an electroactive element, molybdenum, via microbial reduction using Clostridium pasteurianum. C. pasteurianum was able to reduce 88% of the added Mo⁶⁺ ions. The bioreduced molybdenum was shown to be metallically bonded in a prototypical crystal structure with an average particle size of 15 nm. C. pasteurianum was previously shown to degrade azo dyes using in situ formed Pd nanoparticles, but this study shows that in situ formed Mo particles also act as catalysts for degradation of azo dyes. C. pasteurianum cultures with the bioformed Mo nanoparticles were able completely degrade 155 μM methyl orange within 6 min, while controls with no Mo took 36 min. This research demonstrates, for the first time, that the bioreduction of active elements and formation of catalytic particles is achievable.

Presence of Li Clusters in Molten LiCl-Li

Molten mixtures of lithium chloride and metallic lithium are of significant interest in various metal oxide reduction processes. These solutions have been reported to exhibit seemingly anomalous physical characteristics that lack a comprehensive explanation. In the current work, the physical chemistry of molten solutions of lithium chloride and metallic lithium, with and without lithium oxide, was investigated using in situ Raman spectroscopy. The Raman spectra obtained from these solutions were in agreement with the previously reported spectrum of the lithium cluster, Li₈. This observation is indicative of a nanofluid type colloidal suspension of Li₈ in a molten salt matrix. It is suggested that the formation and suspension of lithium clusters in lithium chloride is the cause of various phenomena exhibited by these solutions that were previously unexplainable.

Production of renewable aviation fuel range alkanes from algae oil

Jet fuels produced from sources other than petroleum are receiving considerable attention since they offer the potential to diversify energy supplies while mitigating the net environmental impact of aviation.

Ni-Ci oxygen evolution catalyst integrated BiVO4 photoanodes for solar induced water oxidation

Electrodeposition of a Ni-Ci oxygen evolution catalyst onto W-doped BiVO₄ photoanodes enhances the solar water oxidation kinetics and durability.

Photoelectrochemical generation of hydrogen and electricity from hydrazine hydrate using BiVO4 electrodes

Photoelectrochemical production of energy from hydrazine hydrate containing aqueous solutions using a BiMo_0.02V_0.98O₄ photoanode under neutral pH conditions.

Concomitant microbial generation of palladium nanoparticles and hydrogen to immobilize chromate

The catalytic properties of various metal nanoparticles have led to their use in environmental remediation. Our aim is to develop and apply an efficient bioremediation method based on in situ biosynthesis of bio-Pd nanoparticles and hydrogen. C. pasteurianum BC1 was used to reduce Pd(II) ions to form Pd nanoparticles (bio-Pd) that primarily precipitated on the cell wall and in the cytoplasm. C. pasteurianum BC1 cells, loaded with bio-Pd nanoparticle in the presence of glucose, were subsequently used to fermentatively produce hydrogen and to effectively catalyze the removal of soluble Cr(VI) via reductive transformation to insoluble Cr(III) species. Batch and aquifer microcosm experiments using C. pasteurianum BC1 cells loaded with bio-Pd showed efficient reductive Cr(VI) removal, while in control experiments with killed or viable but Pd-free bacterial cultures no reductive Cr(VI) removal was observed. Our results suggest a novel process where the in situ microbial production of hydrogen is directly coupled to the catalytic bio-Pd mediated reduction of chromate. This process offers significant advantages over the current groundwater treatment technologies that rely on introducing preformed catalytic nanoparticles into groundwater treatment zones and the costly addition of molecular hydrogen to above ground pump and treat systems.

Virus removal by biogenic cerium

The rare earth element cerium has been known to exert antifungal and antibacterial properties in the oxidation states +III and +IV. This study reports on an innovative strategy for virus removal in drinking water by the combination of Ce(III) on a bacterial carrier matrix. The biogenic cerium (bio-Ce) was produced by addition of aqueous Ce(III) to actively growing cultures of either freshwater manganese-oxidizing bacteria (MOB) Leptothrix discophora or Pseudomonas putida MnB29. X-ray absorption spectroscopy results indicated that Ce remained in its trivalent state on the bacterial surface. The spectra were consistent with Ce(III) ions associated with the phosphoryl groups of the bacterial cell wall. In disinfection assays using a bacteriophage as model, it was demonstrated that bio-Ce exhibited antiviral properties. A 4.4 log decrease of the phage was observed after 2 h of contact with 50 mg L(-1) bio-Ce. Given the fact that virus removal with 50 mg L(-1) Ce(III) as CeNO(3) was lower, the presence of the bacterial carrier matrix in bio-Ce significantly enhanced virus removal.

Engineering of bio-hybrid materials by electrospinning polymer-microbe fibers

Although microbes have been used in industrial and niche applications for several decades, successful immobilization of microbes while maintaining their usefulness for any desired application has been elusive. Such a functionally bioactive system has distinct advantages over conventional batch and continuous-flow microbial reactor systems that are used in various biotechnological processes. This article describes the use of polyethylene oxide(99)-polypropylene oxide(67)-polyethylene oxide(99) triblock polymer fibers, created via electrospinning, to encapsulate microbes of 3 industrially relevant genera, namely, Pseudomonas, Zymomonas, and Escherichia. The presence of bacteria inside the fibers was confirmed by fluorescence microscopy and SEM. Although the electrospinning process typically uses harsh organic solvents and extreme conditions that generally are harmful to bacteria, we describe techniques that overcome these limitations. The encapsulated microbes were viable for several months, and their metabolic activity was not affected by immobilization; thus they could be used in various applications. Furthermore, we have engineered a microbe-encapsulated cross-linked fibrous polymeric material that is insoluble. Also, the microbe-encapsulated active matrix permits efficient exchange of nutrients and metabolic products between the microorganism and the environment. The present results demonstrate the potential of the electrospinning technique for the encapsulation and immobilization of bacteria in the form of a synthetic biofilm, while retaining their metabolic activity. This study has wide-ranging implications in the engineering and use of novel bio-hybrid materials or biological thin-film catalysts.