In 2020, Word Health Organization alerted governments worldwide, classifying the prevalence of antimicrobial resistance in freshwater bodies as a significant public health threat of the century. The Ganga River in India is one such large water body categorized as one of the most polluted freshwater bodies globally. Recent research found antimicrobial contamination in River Ganga because of the combination of bacteria and antibiotic residuals entering the freshwater in the form of poorly treated domestic and industrial effluents. In recent years, Ferrate(VI) has proven to be an effective disinfectant and oxidizing agent capable of treating bacteria such as Escherichia coli, Fecal Coliform, and the antibiotics that make the bacteria antibiotic-resistant. The Ganga River pollution data from the year 2020 and the chemical reaction kinetics between Ferrate(VI) and the antibiotics causing antimicrobial resistance are studied to establish Ferrate(VI) as a potent chemical for treating antimicrobial resistance in River Ganga.

Ferrate(VI) for treating antimicrobial resistance in the waters of lower Ganga River

Metal-organic frameworks (MOFs) are porous crystalline materials, which can capture, transport, and release guest molecules. The nature, quality, and quantity of the associated absorption depend on pore size and volume, surface area, solvent, and in particular the host-guest intermolecular interactions. Various methods for the analysis of intermolecular interactions have been described in the literature and were applied to study e.g. chemical reactivity, catalysis, biomolecular interactions, or organic electronics. However, the application of such methods to host-guest interactions in MOFs is still scarce. For this reason, we computed periodic and finite wavefunctions for well-chosen MOF-guest systems and tested these tools. This includes the interaction energy, its decomposition with different energy decomposition schemes, investigation of the electron density with Bader’s quantum theory of atoms in molecules, the non-covalent interaction index, or the density overlap regions indicator. This analysis contributes to the understanding of host-guest interactions, with the ultimate goal of rationally designing MOFs for targeted applications.

Strength and nature of host-guest interactions in metal-organic frameworks from a quantum chemical perspective

This work describes a metal-free synthetic approach for arylation of phenols and alkanols with aryl iodidesvia the intermediacy of unsymmetrical diaryliodonium salts. Specifically, the aryl iodide is oxidized and trimethoxybenzene installed as a “dummy” aryl ligand on the iodine(III) leaving group on the aryl electrophile. The modification of the leaving and C-O coupling occur in a single pot streamlining the synthesis and facilitating novel chemoselectivity and providing access highly substituted ethers.

C-O coupling mediated by iodine(III) via in situ formation of diaryliodonium salts

This paper deals with research activities concerning the design of polyethylene nets (PE) supported by Sachim S.r.l, Putignano (Italy), a manufacturing company of anti-insect screens and windbreak barriers made from HDPE (high density PE) monofilament. PE were coated with a polyvinylpyrrolidone (PVP)-ethylene glycol dimethyl acrylate (EGDMA) hydrogel layer (HG) in the range of 5-15 % w/w by means of a Fenton-type radical based process induced by cumene hydroperoxide (CHP) and Fe(II) salt. 13C CP/MAS solid-state NMR spectroscopy identified the hydrogel. The surface analysis by ATR FT-IR spectra of the final PE@HG versus the PE, PVP and EGDMA reference profiles shows the hydrogel cross-linked PVP coating layer that endows PE@HG of adsorption capability of insecticides like etofenprox, λ-cyhalothrin and deltamethrin and of inorganic compounds like FeSO4, FeCl3, FeO, Fe2O3, CaCl2 and CaCO3. Figure 1 reports some data about the PE@HG adsorption capability towards etofenprox (EFP) and the iron oxides (IO) reduced to iron in blast furnace. “Biorete 3350” (50 mesh) and its PE@HG of two different HG percentage were exhaustively soaked in an EFP water solution and after draining away were plunged under stirring in ethanol for 24 hrs. As the ratio between released EFP and retained EFP can be assumed at equilibrium, the EFP concentration quantified by UV analysis allowed to calculate the minimum EFP amount (mg) loaded on 1g of net, as reported in Table 1. The trend demonstrates the loading effectiveness of PE@HG respect to PE and suggests that a reduced HG layer is enough to capture a good amount of EFP. Preliminary results on “Biorete 3350” (50 mesh) and “Biorete 3325” (25 mesh) functionalised by roll-to-roll coating technology showed that the HG percentage was 1-3% for 5-10 minutes activation time. The four 25 cm2 pieces in Figure 1 put in contact with 15 g of IO powder for 1 hr absorbed small IO amount. The difference between PE and PE@HG is evident and although this experiment is rough and preliminary, it suggests that PE@HG may be developed to capture IO from air near industrial sites like blast furnace.

Innovative polyethylene nets for agricultural and environmental applications

Ever-growing piles of highly recalcitrant plastic waste are threatening the environment because of both poor degradability and the discharge of greenhouse gases through all stages of conventional plastic production. A sustainable technology that can replace traditional fossil-based plastics is transforming carbon-neutral feedstocks into biodegradable plastics via the bio-inspired process. Bio-based plastics, polyhydroxyalkanoates (PHAs), can be synthesized by different organisms such as bacteria, archaea, and yeasts. However, the process is not as simple as it looks and the carbon sources attribute to 50% of bioplastics production cost. In this vein, our goal is to valorize abundant food waste stream resources such as orange peels. Though the key barriers for building a successful bioplastic synthesis process from orange peels are 1) the necessity of pretreatment to generate sugars as nutrient sources and 2) the limonene extraction step. Limonene, classifies as a cyclic monoterpene, has an inhibitory effect on bioplastic production rate and microbial growth. Reactive oxygen species offer a novel method to degrade orange peels and eliminate the limonene extraction step. From this perspective, we studied the orange peels treatment and limonene oxidation by superoxide radical anion in an aqueous medium. The effects of this radical on the sugar yield, bacteria viability, limonene removal, cell dry weight, and polyhydroxybutyrate (PHB) production rate and its properties were studied. The results demonstrate the potential of oxidized orange peels as a nutrient source for biotechnology processes and reflect the complete oxidation of limonene and high cell viability. The process led to 90% sugar extraction after 15 minutes of reaction, 90-95% cell viability even with 5% oxidized orange peels loading, high cell dry weight, and PHB with a molecular weight of 100 kDa from batch fermentation flask. This study validates the feasibility of the implementation of the oxidation method for high sugar recovery and limonene degradation for efficient bioplastic production from orange peels waste.

Converting orange peels wastes to degradable bioplastics

Oils derived through decomposition and conversion of biomass have potential to help offset our dependence on fossil-based fuels. Bio-oils are produced using different approaches including hydrothermal liquefaction and fast pyrolysis. These biomass-derived oils are a complex mixture of organic compounds ranging from small (1 to 10 carbon atoms) to large (tens of carbon atoms). In addition to size variability, these compounds can have varying functional groups including carboxylic acids, ketones, aldehydes, phenols, etc. Some of these functional groups can be particularly corrosive to materials used for transportation, production, and storage of bio-oils. Characterization and quantification of corrosive impurities in bio-oils is important for compatibility of materials in bio-oil environments. Our preliminary bio-oil characterization and analysis of corrosive impurities will be presented in this talk. Compatibility studies of alloys in bio-oil environments will also be presented.

Characterization of corrosive species and compatibility of alloys in bio-oils

Molten chloride salts (including MgCl2, KCl, NaCl, and ZnCl2) are being considered for heat transfer media for renewable (solar) and nuclear power generators, as a fuel for nuclear reactors, and as a thermal energy storage media. Impurities, such as oxygen, hydroxides, moisture, and sulfur, are known to negatively influence the corrosion of materials in contact with the salt (e.g., structural metals). Commercially available chloride salts come with a range of impurities. Before using the chloride salts at high temperature, it is desirable to remove the impurities to increase the performance of the salt and reduce corrosion. In this study, we tested the use of thionyl chloride vaporized into a stream of argon to react with oxygenated impurities in a mixture of MgCl2-KCl-NaCl, removing them as HCl and SO2. The reagent was bubbled through the salt when both above and below the melting point. The reaction was followed using thermocouple data from the salt and by Fourier Transform Infrared (FTIR) spectroscopy on the exhaust of the reactor. The reaction kinetics were followed by comparing the peaks from SO2 product to SOCl2 reagent in the FTIR spectra. The purity of the salt was assessed at the end of the purification process by X-ray diffraction and inductively coupled plasma analysis. While the process was effective at removing the oxygen content of the mixture, ternary compounds were formed in the process, including KNiCl3 and KMgCl3. The nickel in KNiCl3 came from reaction between the salt and the nickel vessel. Thus, these experiments suggest that improvements to the process need to be made before using SOCl2 vapors for the purification of chloride salts.

Process for chloride salt purification including removal of oxygen, oxygenated compounds, and hydroxides by reaction with thionyl chloride vapors

The current method for preparing particles for nuclear safeguards particle analysis involves dissolving particles in a polymer thin film that is neutron-irradiated to enable fission track location, then removing these particles for electron microscopy and thermal ionization mass spectrometry. The overall process involves a great deal of intensive, manual particle handling and is more time consuming than desired. A collaborative effort between Lawrence Berkeley National Lab (LBNL), Pacific Northwest National Lab (PNNL), and Brookhaven National Lab (BNL) seeks to remedy several of these issues by using a suite of x-ray techniques to perform this analysis without removing those particles from the polymer thin films. Recent experiments performed at the Advanced Light Source (ALS) at LBNL in both the tender x-ray and hard x-ray regimes have made progress towards these objectives. The first effort has focused on evaluating and developing tender x-ray micro-XRF techniques at ALS Beamline 10.3.2 utilizing a specialized sample chamber and specifically improving the XRF capability for lighter elements. The second has exploited the unique optical characteristics of Beamline. 8.3.2 to develop new methodologies for rapid particle location through full-field x-ray microscopy.

Tender micro-XRF and full-field microscopy for nuclear safeguards particle analysis

Since impurities directly affect degradation of structural materials in molten salt environments, impurity analysis in molten salts is important for the deployment of the next generation molten salt nuclear reactors. Various impurities affect corrosion of structural alloys. Some of the most prevalent trace impurities present in halide salts are water, hydroxides, oxides, HCl, HF and others. Chloride and fluoride salts used for this study were chemically purified using CCl4 chlorination and HF fluorination, respectively. Purity of these salts was assessed through analytical approaches using at least one of the following: titrations, O and H analysis and static corrosion tests. In addition, trace cationic and anionic impurities were characterized and their effect on corrosion of structural alloys will be presented. Analysis of the post-corrosion salt samples was done to quantify the amount of alloy constituent elements leached into the salt, as well as to understand the formation of corrosion products in molten salts.

Analysis of impurities in molten salts

Molten salts have been proposed to be promising candidates as primary and secondary coolants or liquid fuel solvents in MSRs, and heat transfer fluid and thermal energy storage salt for the CSP plants. Structural materials corrosion has been one of the major issues that limited the applications of molten salts. Impurities, such as OH- and H2O can accelerate material corrosion. The fundamental kinetic parameters of these impurities are of importance to understand the corrosion mechanism in the molten salts. In the present work, the electrochemical measurements were conducted in molten MgCl2-KCl-NaCl salts with different concentration of NaOH (0.04-4wt%) at different temperatures (600-800°C). Due to the high temperature and co-existence of OH- and Mg2+, the reaction of Mg (OH)2(l) = MgO(s) + H2O was thermal-favored. Thus, the real concentration of OH- was determined from equilibrium concentration difference of Mg2+ before and after OH- addition with the assistance of ICP-MS analysis. Moreover, the fundamental data of OH- (diffusion coefficient and exchange current density ) were measured accordingly using cyclic voltammetry and potentiodynamic scan, which followed Arrhenius law and were in the reasonable range comparing with values of Fe, Ni or Cr ions in our previous study.

Electrochemical study of OH- in molten MgCl2-NaCl-KCl salts

After a first meeting in Lima in 1996, our group (Non-Crystalline Solids) at the University of Sevilla begun a fruitful scientific collaboration with Jean Marc Greneche. Fe-57 Mössbauer spectroscopy (MS) has been an especially useful tool for studying Fe and Co-based nanocrystalline and multicomponent amorphous alloys, where a variety of environments exists for each atomic species, due to its character of sensitive local probe. Also, MS provides an invaluable complement of X-ray diffraction and magnetic measurements. In this work we will review the main results derived of our collaboration. We proposed a method to describe accurately Mössbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components that were associated to different local environments. The refinement of Mössbauer spectra allowed to compare the kinetics and the local structural rearrangement mechanisms associated with the nanocrystallization process. Also, the combined use of x-ray diffraction and Mössbauer spectrometry allowed to estimate the compositions of both the nanocrystalline grains (Fe,Co,Mn)(Si, Al) and the amorphous residual phase of FINEMET and HITPERM nanocrystalline alloys with several compositions, allowing to establish how the different species partition to the amorphous matrix. These results were corroborated by results from different complementary techniques including x-ray diffraction, electron microscopy and atom probe.  We have also presented a comparative study of the effects of partial substitution of Co for Fe on thermal stability, crystallization and magnetic properties of Co-containing FINEMET and HITPERM alloys series. The difference in metalloid and Nb content between the two alloy series and the presence of Si in the nanocrystals in the case of FINEMET alloys appeared as key parameters with clear effect in Móssbauer spectra. Later on, Mössbauer spectroscopy allowed to characterize the hyperfine structure of the amorphous phase in FeCoSiAlGaPCB multicomponent alloys with different compositions and, also, of the nanocrystalline phase emerging in Cu-containing (Fe, Cr, Mo) (Ga, P, C, B) alloys.  The active cooperation, the opportunity to develop short stays at Jean Marc’s lab and his guidance allowed the development of a productive Mössbauer spectroscopy research line in our group at the University of Sevilla.

Mössbauer studies of Fe and Co-based nanocrystalline and multicomponent amorphous alloys

Coatings exhibiting both self-cleaning and self-healing properties are envisioned for a wide range of applications. Herein we report a simple fabrication approach toward poly(urea-urethane) (PU) coatings having self-healing and self-cleaning properties. The self-cleaning component is a poly(dimethylsiloxane) (PDMS), which is affordable in cost and also has a lower environmental footprint relative to its fluorinated counterpart. The self-healing properties are imparted by dynamic urea bonds of the matrix. The obtained surfaces are evaluated for their anti-smudge properties such as water-, oil- and ink-repellency, as well as optical properties. The self-healing properties of these coatings are evaluated by making scores with a doctor blade and monitoring the healing under different conditions using optical microscopy. The resultant coatings are also investigated for their good mechanical properties. The surface chemical compositions are determined by x-ray photoelectron spectroscopy, while atomic force microscopy is used for microstructural analysis of these coatings.

Self-healing and self-cleaning clear coating

ACS Fall 2021

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