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1. Spectral emissivities and temperatures of burning iron as single particles or groups of particles

   https://doi.org/10.1016/j.fuel.2024.132537  

   Yao, Yuan; Chang, Di; Panahi, Aidin; Levendis, Yiannis A (November 2024, Fuel)

   Nimmo, Bill (Ed.)

   This manuscript reports on the combustion of powdered iron, for the purpose of utilizing it as an environmentally friendly circular energy carrier. The conducted research investigated the spectral emissivity and temperature of iron particles, burned either individually or in groups. Combustion experiments were conducted under high heating rates in an externally-heated drop tube furnace. The pressure was atmospheric and the axial temperature was nearly-constant at ~1350 K. The oxidizer gas contained 15-100% oxygen in nitrogen diluent. Iron particles were sieve-classified in the 44-53 µm range. Results showed that, depending on the oxygen concentration, and consequently the particle temperature, the average spectral emissivities of single burning particles varied between 0.18 and 0.46, in the 600-1000 nm wavelength range. Corresponding temperatures of single particles varied between 2300 K and 2800 K, increasing with increasing oxygen concentration in the gas. In the case of groups of iron particles burning in air at different particle number densities, average spectral emissivities were found to be in the range of 0.42-0.45, with the upper value associated with denser particle clouds. Corresponding peak temperatures of particle burning in groups were found to be in the range of 2160 K to 2100 K, with the lower value attributed to denser particle clouds. 

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2. Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts

   https://doi.org/10.1039/c9na00472f  

   de Alwis, Chathura; Leftwich, Timothy R.; Mukherjee, Pinaki; Denofre, Alex; Perrine, Kathryn A. (December 2019, Nanoscale Advances)

   Iron oxide nanomaterials participate in redox processes that give them ideal properties for their use as earth-abundant catalysts. Fabricating nanocatalysts for such applications requires detailed knowledge of the deposition and growth. We report the spontaneous deposition of iron oxide nanoparticles on HOPG in defect areas and on step edges from a metal precursor solution. To study the nucleation and growth of iron oxide nanoparticles, tailored defects were created on the surface of HOPG using various ion sources that serve as the target sites for iron oxide nucleation. After solution deposition and annealing, the iron oxide nanoparticles were found to nucleate and coalesce at 400 °C. AFM revealed that the particles on the sp 3 carbon sites enabled the nanoparticles to aggregate into larger particles. The iron oxide nanoparticles were characterized as having an Fe 3+ oxidation state and two different oxygen species, Fe–O and Fe–OH/Fe–OOH, as determined by XPS. STEM imaging and EDS mapping confirmed that the majority of the nanoparticles grown were converted to hematite after annealing at 400 °C. A mechanism of spontaneous and selective deposition on the HOPG surface and transformation of the iron oxide nanoparticles is proposed. These results suggest a simple method for growing nanoparticles as a model catalyst. 

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3. Confinement Effects in Dynamics of Ionic Liquids with Polymer‐Grafted Nanoparticles

   https://doi.org/10.1002/cphc.202200219  

   Liu, Siqi; Li, Ruhao; Tyagi, Madhusudan; Akcora, Pinar (June 2022, ChemPhysChem)

   Ionic liquid mixed with poly(methyl methacrylate)-grafted nanoparticle aggregates at low particle concentrations was shown to exhibit different dynamics and ionic conductivity than that of pure ionic liquid in our previous studies. In this work, we report on the quasi-elastic neutron scattering results on ionic liquid containing polymer-grafted nanoparticles at the higher particle concentration. The diffusivity of imidazolium (HMIM + ) cations of 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (HMIM-TFSI) in the presence of poly(methyl methacrylate)-grafted iron oxide nanoparticles and the ionic conductivity of solutions were discussed through the confinement. Analysis of the elastic incoherent structure factor suggested the confinement radius decreased with the addition of grafted particles in HMIM-TFSI/solvent mixture, indicating the confinement that is induced by the high concentration of grafted particles, shrinks the HMIM-TFSI restricted volume. We further conjecture that this enhanced diffusivity occurs as a result of the local ordering of cations within aggregates of poly(methyl methacrylate)-grafted particles. 

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4. Reductive transformations of dichloroacetamide safeners: effects of agrochemical co-formulants and iron oxide + manganese oxide binary-mineral systems

   https://doi.org/10.1039/D0EM00331J  

   Ricko, Allison N.; Psoras, Andrew W.; Sivey, John D. (October 2020, Environmental Science: Processes & Impacts)

   null (Ed.)

   The toxic effects of herbicides are often incompletely selective and can harm crops. Safeners are “inert” ingredients commonly added to herbicide formulations to protect crops from herbicide-induced injury. Dichloroacetamide safeners have been previously shown to undergo reductive dechlorination in anaerobic abiotic systems containing an iron (hydr)oxide mineral (goethite or hematite) amended with Fe( ii ). Manganese oxides ( e.g. , birnessite) are important redox-active species that frequently co-occur with iron (hydr)oxides, yet studies examining the effects of more than one mineral on transformations of environmental contaminants are rare. Herein, we investigate the reactivity of dichloroacetamide safeners benoxacor, furilazole, and dichlormid in binary-mineral, anaerobic systems containing Fe( ii )-amended hematite and birnessite. As the molar ratio of Fe( ii )-to-Mn( iv ) oxide increased, the transformation rate of benoxacor and furilazole increased. The safener dichlormid did not transform appreciably over the sampling period (6 hours). The concentration of pH buffer ([MOPS] = 10–50 mM), ionic strength ([NaCl] = 10–200 mM), and order of solute addition ( e.g. , safener followed by Fe( ii ) or vice versa ) do not appreciably affect transformation rates of the examined dichloroacetamide safeners in Fe( ii ) + hematite slurries. The presence of agrochemical co-formulants, including the herbicide S -metolachlor and three surfactants, in solutions containing Cr(H 2 O) 6 2+ (as a model homogeneous reductant) also did not substantially influence rates of safener transformation. This study is among the first to examine laboratory systems of intermediate complexity ( e.g. , systems containing mixtures of agrochemical co-formulants or mineral phases) when assessing the environmental fate of emerging contaminants such as dichloroacetamide safeners. 

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5. Discovery and potential ramifications of reduced iron-bearing nanoparticles—magnetite, wüstite, and zero-valent iron—in wildland–urban interface fire ashes

   https://doi.org/10.1039/d2en00439a  

   Baalousha, Mohammed; Desmau, Morgane; Singerling, Sheryl A.; Webster, Jackson P.; Matiasek, Sandrine J.; Stern, Michelle A.; Alpers, Charles N. (November 2022, Environmental Science: Nano)

   The increase in fires at the wildland–urban interface has raised concerns about the potential environmental impact of ash remaining after burning. Here, we examined the concentrations and speciation of iron-bearing nanoparticles in wildland–urban interface ash. Total iron concentrations in ash varied between 4 and 66 mg g −1 . Synchrotron X-ray absorption near-edge structure (XANES) spectroscopy of bulk ash samples was used to quantify the relative abundance of major Fe phases, which were corroborated by transmission electron microscopy measurements. Maghemite (γ-(Fe 3+ ) 2 O 3 ) and magnetite (γ-Fe 2+ (Fe 3+ ) 2 O 4 ) were detected in most ashes and accounted for 0–90 and 0–81% of the spectral weight, respectively. Ferrihydrite (amorphous Fe( iii )–hydroxide, (Fe 3+ ) 5 HO 8 ·4H 2 O), goethite (α-Fe 3+ OOH), and hematite (α-Fe 3+ 2 O 3 ) were identified less frequently in ashes than maghemite and magnetite and accounted for 0–65, 0–54, and 0–50% of spectral weight, respectively. Other iron phases identified in ashes include wüstite (Fe 2+ O), zerovalent iron, FeS, FeCl 2 , FeCl 3 , FeSO 4 , Fe 2 (SO 4 ) 3 , and Fe(NO 3 ) 3 . Our findings demonstrate the impact of fires at the wildland–urban interface on iron speciation; that is, fires can convert iron oxides ( e.g. , maghemite, hematite, and goethite) to reduced iron phases such as magnetite, wüstite, and zerovalent iron. Magnetite concentrations ( e.g. , up to 25 mg g −1 ) decreased from black to gray to white ashes. Based on transmission electron microscopy (TEM) analyses, most of the magnetite nanoparticles were less than 500 nm in size, although larger particles were identified. Magnetite nanoparticles have been linked to neurodegenerative diseases as well as climate change. This study provides important information for understanding the potential environmental impacts of fires at the wildland–urban interface, which are currently poorly understood. 

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