An iron metal-organic framework-based electrochemical sensor for identification of Bisphenol-A in groundwater samples

Bisphenol A (BPA) is an endocrine disruptor that leaches into food and is significantly employed in food and beverage storage, and source water cycles. To ensure an outstanding and sustainable biosphere while safeguarding human health and well-being, BPA detection is essential, necessitating an efficient detection methodology. Here, we describe an easy-to-use, inexpensive, and overly sensitive electrochemical detector that uses Fe-MOF nanotextures for identifying BPA in groundwater. This sensing electrode device combines the excellent guest interaction potential of organic ligands with the substantial surface area of metal. Using various analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and powder X-ray diffraction (XRD), the structural and physicochemical behaviors of the as-synthesized material were evaluated. Electrochemical BPA detection was enabled by a diffusion-controlled oxidation procedure with a comparable number of both protons and electrons. With a 0.1 μM detection limit, the sensor displayed a linear sensitivity of around 0.1 μM and 15 μM. Additionally, the sensors demonstrated an outstanding recovery with actual water samples as well as a repeatable and steady performance over the course of a month exhibiting minimal interference from typical inorganic and organic species. Due to its notable sensitivity, inexpensive cost, robust selectivity, excellent repeatability, and reuse ability, the electroanalytical possibilities of the Fe-MOF-modified GCE suggest that the device can be implemented into real-world applications in its primed condition.

Smart Design of ZnFe and ZnFe@Fe Nanoparticles for MRI-Tracked Magnetic Hyperthermia Therapy: Challenging Classical Theories of Nanoparticles Growth and Nanomagnetism

Iron Oxide Nanoparticles (IONPs) hold the potential to exert significant influence on fighting cancer through their theranostics capabilities as contrast agents (CAs) for magnetic resonance imaging (MRI) and as mediators for magnetic hyperthermia (MH). In addition, these capabilities can be improved by doping IONPs with other elements. In this work, the synthesis and characterization of single-core and alloy ZnFe novel magnetic nanoparticles (MNPs), with improved magnetic properties and more efficient magnetic-to-heat conversion, are reported. Remarkably, the results challenge classical nucleation and growth theories, which cannot fully predict the final size/shape of these nanoparticles and, consequently, their magnetic properties, implying the need for further studies to better understand the nanomagnetism phenomenon. On the other hand, leveraging the enhanced properties of these new NPs, successful tumor therapy by MH is achieved following their intravenous administration and tumor accumulation via the enhanced permeability and retention (EPR) effect. Notably, these results are obtained using a single low dose of MNPs and a single exposure to clinically suitable alternating magnetic fields (AMF). Therefore, as far as the authors are aware, for the first time, the successful application of intravenously administered MNPs for MRI-tracked MH tumor therapy in passively targeted tumor xenografts using clinically suitable conditions is demonstrated.

Iron oxide/hydroxide-nitrogen doped graphene-like visible-light active photocatalytic layers for antibiotics removal from wastewater

Hybrid layers consisting of Fe oxide, Fe hydroxide, and nitrogen doped graphene-like platelets have been synthesized by an eco-friendly laser-based method for photocatalytic applications. The complex composite layers show high photodecomposition efficiency towards degradation of antibiotic molecules under visible light irradiation. The photodecomposition efficiency was investigated as a function of relative concentrations of base materials, Fe oxide nanoparticles and graphene oxide platelets used for the preparation of target dispersions submitted to laser irradiation. Although reference pure Fe oxide/Fe hydroxide layers have high absorption in the visible spectral region, their photodecomposition efficiency is negligible under the same irradiation conditions. The high photocatalytic decomposition efficiency of the nanohybrid layer, up to 80% of the initial antibiotic molecules was assigned to synergistic effects between the constituent materials, efficient separation of the electron-hole pairs generated by visible light irradiation on the surface of Fe oxide and Fe hydroxide nanoparticles, in the presence of conducting graphene-like platelets. Nitrogen doped graphene-like platelets contribute also to the generation of electron-hole pairs under visible light irradiation, as demonstrated by the photocatalytic activity of pure, reference nitrogen doped graphene-like layers. The results also showed that adsorption processes do not contribute significantly to the removal of antibiotic molecules from the test solutions. The decrease of the antibiotic concentration under visible light irradiation was assigned primarily to photocatalytic decomposition mechanisms.

Hemin-Modified Multi-Walled Carbon Nanotube-Incorporated PVDF Membranes: Computational and Experimental Studies on Oil-Water Emulsion Separations

The separation of oil/water emulsions has attracted considerable attention for decades due to the negative environmental impacts brought by wastewater. Among the various membranes investigated for separation, polyvinylidene fluoride (PVDF) membranes have shown significant advantages of ease of fabrication, high selectivity, and fair pore distribution. However, PVDF membranes are hydrophobic and suffer from severe fouling resulting in substantial flux decline. Meanwhile, the incorporation of wettable substrates during fabrication has significantly impacted the membrane performance by lowering the fouling propensity. Herein, we report the fabrication of an iron-containing porphyrin (hemin)-modified multi-walled carbon nanotube incorporated PVDF membrane (HA-MWCNT) to enhance fouling resistance and the effective separation of oil-in-water emulsions. The fabricated membrane was thoroughly investigated using the FTIR, SEM, EDX, AFM, and contact angle (CA) analysis. The HA-MWCNT membrane exhibited a water CA of 62° ± 0.5 and excellent pure water permeance of 300.5 L/m2h at 3.0 bar (400% increment), in contrast to the pristine PVDF, which recorded a CA of 82° ± 0.8 and water permeance of 59.9 L/m2h. The hydrophilic HA-MWCNT membrane further showed an excellent oil rejection of >99% in the transmembrane pressure range of 0.5−2.5 bar and a superb flux recovery ratio (FRR) of 82%. Meanwhile, the classical molecular dynamics (MD) simulations revealed that the HA-MWCNT membrane had greater solvent-accessible pores, which enhanced water permeance while blocking the hydrocarbons. The incorporation of the hemin-modified MWCNT is thus an excellent strategy and could be adopted in the design of advanced membranes for oil/water separation.

Checking the Efficiency of a Magnetic Graphene Oxide–Titania Material for Catalytic and Photocatalytic Ozonation Reactions in Water

An easily recoverable photo-catalyst in solid form has been synthesized and applied in catalytic ozonation in the presence of primidone. Maghemite, graphene oxide and titania (FeGOTi) constituted the solid. Additionally, titania (TiO2) and graphene oxide–titania (GOTi) catalysts were also tested for comparative reasons. The main characteristics of FeGOTi were 144 m2/g of surface area; a 1.29 Raman D and G band intensity ratio; a 26-emu g−1 magnetic moment; maghemite, anatase and brookite main crystalline forms; and a 1.83 eV band gap so the catalyst can absorb up to the visible red region (677 nm). Single ozonation, photolysis, photolytic ozonation (PhOz), catalytic ozonation (CatOz) and photocatalytic ozonation (PhCatOz) were applied to remove primidone. In the presence of ozone, the complete removal of primidone was experienced in less than 15 min. In terms of mineralization, the best catalyst was GOTi in the PhCatOz processes (100% mineralization in 2 h). Meanwhile, the FeGOTi catalyst was the most efficient in CatOz. FeGOTi led, in all cases, to the highest formation of HO radicals and the lowest ozone demand. The reuse of the FeGOTi catalyst led to some loss of mineralization efficacy after four runs, likely due to C deposition, the small lixiviation of graphene oxide and Fe oxidation.

Heterostructured γ-Fe2O3/FeTiO3 magnetic nanocomposite: An efficient visible-light-driven photocatalyst for the degradation of organic dye

The catalyst recovery is the major concern in commercialization of photocatalysts for the industrial effluent treatment process. To overcome this major issue, Fe₂O₃ based magnetic photocatalytic heterostructure ɣ-Fe₂O₃/FeTiO₃ nanocomposite was synthesized by hydrothermal method. Fe₂O₃ is the cheapest visible active magnetic photocatalytic material, but it has the limitation of fast e^-/h + recombination. Titanium (Ti) was loaded on γ-Fe₂O₃ to overcome this issue. The loaded Ti has grown as FeTiO₃ on the surface of ɣ-Fe₂O₃ nanocrystals and emerged as heterostructure ɣ- Fe₂O₃/FeTiO₃ nanocomposites, which was confirmed by XRD and TEM results. The loading concentration of Ti on γ-Fe₂O₃ was optimized to achieve the maximum photocatalytic efficiency without compromising the magnetic property of γ-Fe₂O₃ to facilitate the magnetic separation. DRS-UV spectra revealed the strong visible light response of γ- Fe₂O₃/FeTiO₃ nanocomposite. The photocatalytic efficiencies of the synthesized materials were evaluated using methylene blue (MB) as a model pollutant under sunlight. The built-in electric field between p-n junction between FeTiO₃ and Fe₂O₃ and type II charge transfer mechanism extended the lifetime of the charge carriers at the heterojunction of γ- Fe₂O₃/FeTiO₃, which was confirmed by PL spectra. The vibrating sample magnetometer (VSM) study revealed the decreasing magnetization, coercivity (Hc), and retentivity (Mr) of γ-Fe₂O₃ with increasing concentration of Ti. 92% of the used-up 20 wt% Ti loaded γ-Fe₂O₃/FeTiO₃ magnetic nanocomposite was recovered from the treated wastewater using an electromagnet. Both magnetic properties and efficiency of the nanocomposite increased up to 20 wt% of Ti loading, beyond that decreased due to the increasing composition of antiferromagnetic FeTiO₃ and the increasing number of defect sites as recombination centers. Hence, 20 wt% loading of Ti was concluded as the optimum to enhance the efficiency and to retain the magnetic properties. This work aims the commercialization of magnetic photocatalytic materials for the industrial effluent treatment.

Uptake of Hg0(g) on TiO2, Al2O3, and Fe2O3 Nanoparticles: Importance in Atmospheric Chemical and Physical Processes

Mineral dust aerosols play an important role in tropospheric chemistry and aerosol-cloud interaction processes. Yet, their interactions with gaseous elemental mercury (Hg⁰_(g)) are not currently well understood. Using a coated-wall flow tube (CWFT) reactor, we measured the uptake of Hg⁰_(g) on some common components of mineral dust aerosols, including TiO₂, Al₂O₃, and Fe₂O₃, and the effects of irradiation (dark, visible and UV-A) and relative humidity (<2% to 60%) on the uptake kinetics. Under UV-A irradiation (320-400 nm) in dry air, we measured uptake coefficients (γ) equal to >1 × 10^-3 and (3 ± 1) × 10^-6 on TiO₂ and Al₂O₃, respectively. Under visible light irradiation (380-700 nm), Hg⁰_(g) uptake was only observed on TiO₂, with γ = (4 ± 3) × 10^-4. Raising the relative humidity inhibited the uptake on both TiO₂ and Al₂O₃, and the uptake coefficient at 60% RH for TiO₂ under UV-A irradiation was lower by ca. 3 orders of magnitude than dry conditions. Furthermore, we observed that water vapor induced the desorption of two distinct fractions from Hg-exposed surfaces via the displacement of weakly, physisorbed Hg and the photocatalyzed reduction of chemisorbed Hg. Based on the uptake coefficients from this report, we estimate that heterogeneous interactions with mineral dust may be significant under conditions with low relative humidity (<30%) and high dust loading masses. We herein discuss the implication of this study on understanding the life cycle analysis of atmospheric mercury in nature.

Synthesis of Fe2O3/Mn2O3 Nanocomposites and Impregnated Porous Silicates for Dye Removal: Insights into Treatment Mechanisms

Fe2O3/Mn2O3 nanocomposites and impregnated porous silicates (Fe2O3/Mn2O3@SiO2 [FMS]) were prepared and investigated as catalytic adsorbents. The catalysts were applied for cationic and anionic dye pollutants in the adsorption, Fenton reaction, and photocatalysis processes at a pH of 7. Fe2O3/Mn2O3 nanoparticles (FM-NPs) were prepared using the co-precipitation method and were impregnated in SiO2 by the sol–gel process. The synthesized materials were characterized using various sophisticated techniques. Results indicated that the impregnation of bi-metallic NPs in SiO2 increased the surface area, and the function of the adsorbent also improved. FMS showed a significant adsorption effect, with 79.2% rhodamine B removal within 15 min. Fenton and photocatalyst reaction showed removal rates of 85.3% and 97.9%, respectively, indicating that negatively charged porous silicate attracts cationic pollutants. In the case of the anionic pollutant, Congo red, the adsorption reaction of FMS did not occur, and the removal rate of the photocatalyst reaction was 79%, indicating the repulsive force between the negatively charged silica and the anionic dye. Simultaneously, bi-metal-bonded FM-NPs facilitated the photocatalytic reaction, reducing the recombination of electron-hole pairs. This study provides new insights into the synthesis of FM-NPs and FMS as photocatalytic adsorbents and their photocatalytic mechanisms based on reaction conditions and contaminant characteristics. The developed materials have potential applications for environmental mitigation.

[Ru(tmphen)3]2[Fe(CN)6] and [Ru(phen)3][Fe(CN)5(NO)] complexes and formation of a heterostructured RuO2-Fe2O3 nanocomposite as an efficient alkaline HER and OER electrocatalyst

Water electrolysis is one of the most capable processes for supplying clean fuel. Herein, two novel ionic Ru(II)-Fe(II) complexes, [Ru(tmphen)₃]₂[Fe(CN)₆] and [Ru(phen)₃][Fe(CN)₅(NO)], where tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline and phen = 1,10-phenanthroline, were synthesized and characterized by UV-Vis spectroscopy, elemental analysis, FT-IR, and single-crystal X-ray structural analysis. By thermally decomposing the [Ru(tmphen)₃]₂[Fe(CN)₆] complex at 600 °C for 4 h, a heterostructured RuO₂-Fe₂O₃ nanocomposite was fabricated through a facile one-pot treatment and then characterized by FT-IR, XRD, FT-Raman, UV-Vis (DRS), ICP-OES, FE-SEM, TEM, TGA/DTG, BET, and XPS analyses, which revealed the formation of highly crystalline RuO₂-Fe₂O₃ nanoparticles with an average size of 8-12 nm. The prepared nanocomposite was an efficient heterostructured electrocatalyst for performing water-splitting redox reaction processes, including hydrogen and oxygen evolution reactions (HER and OER) in alkaline solutions. In this regard, RuO₂ and Fe₂O₃ samples were also prepared through thermal decomposition of [Ru(tmphen)₃](NO₃)₂ and K₄[Fe(CN)₆] precursors, respectively, as control experiments to compare their HER and OER electrocatalytic activity with that of the RuO₂-Fe₂O₃ nanocomposite. Specifically, the RuO₂-Fe₂O₃ nanocomposite exhibited significant electrocatalytic performance, generating 10 mA cm^-2 current density at -148 and 292 mV overpotentials, and the Tafel slope results from fitting the LSV curves to the Tafel equation were -43 and 56.08 mV dec^-1 for the HER and OER, respectively. Therefore, the heterostructured RuO₂-Fe₂O₃ nanocomposite can be viewed as a bi-functional electrocatalyst for HER and OER because it exploits the synergistic effects of heterostructures and active sites at its interface.

Sources and Transformation Mechanisms of Atmospheric Particulate Bound Mercury Revealed by Mercury Stable Isotopes

This study examined the isotopic composition of particulate bound mercury (PBM) in 10 Chinese megacities and explored the associated sources and transformation mechanisms. PBM in these cities was characterized by negative δ²⁰²Hg (mean: -2.00 to -0.78‰), slightly negative to highly positive Δ¹⁹⁹Hg (mean: -0.04 to 0.47‰), and slightly positive Δ²⁰⁰Hg (mean: 0.02 to 0.06‰) values. The positive PBM Δ¹⁹⁹Hg signatures were likely caused by physiochemical reactions in aerosols. The Δ¹⁹⁹Hg/Δ²⁰¹Hg ratio varied from 0.94 to 1.39 in the cities and increased with the increase in the corresponding mean Δ¹⁹⁹Hg_PBM value. We speculate that, in addition to the photoreduction of oxidized Hg, other transformation mechanisms in aerosols (e.g., isotope exchange, complexation, and oxidation, which express nuclear volume effects) also shape the Δ¹⁹⁹Hg_PBM signatures in the present study. These processes are likely enhanced in the presence of strong gas-particle partitioning of gaseous oxidized Hg (GOM) and elevated levels of redox active metals (e.g., Fe), halides, and elemental carbon. Based on Δ²⁰⁰Hg_PBM data presented in this and previous studies, we estimate that large proportions (∼47 ± 22%) of PBM were sourced from the oxidation of gaseous elemental Hg followed by the partitioning of GOM onto aerosols globally, indicating the transformation of Hg(0) to PBM as an important sink of atmospheric Hg(0).

Iron–Gold Nanoflowers: A Promising Tool for Multimodal Imaging and Hyperthermia Therapy

The development of nanoplatforms prepared to perform both multimodal imaging and combined therapies in a single entity is a fast-growing field. These systems are able to improve diagnostic accuracy and therapy success. Multicomponent Nanoparticles (MCNPs), composed of iron oxide and gold, offer new opportunities for Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) diagnosis, as well as combined therapies based on Magnetic Hyperthermia (MH) and Photothermal Therapy (PT). In this work, we describe a new seed-assisted method for the synthesis of Au@Fe Nanoparticles (NPs) with a flower-like structure. For biomedical purposes, Au@Fe NPs were functionalized with a PEGylated ligand, leading to high colloidal stability. Moreover, the as-obtained Au@Fe-PEG NPs exhibited excellent features as both MRI and CT Contrast Agents (CAs), with high r2 relaxivity (60.5 mM−1⋅s−1) and X-ray attenuation properties (8.8 HU mM−1⋅HU). In addition, these nanoflowers presented considerable energy-to-heat conversion under both Alternating Magnetic Fields (AMFs) (∆T ≈ 2.5 °C) and Near-Infrared (NIR) light (∆T ≈ 17 °C). Finally, Au@Fe-PEG NPs exhibited very low cytotoxicity, confirming their potential for theranostics applications.

Vancomycin conjugated iron oxide nanoparticles for magnetic targeting and efficient capture of Gram-positive and Gram-negative bacteria

Drug conjugated iron oxide magnetite (Fe₃O₄) nanoparticles are of great interest in the field of biomedicine. In this study, vancomycin (Van) conjugated magnetite (Fe₃O₄) nanoparticles were envisioned to capture and inhibit the growth of bacteria. Hydrophobic Fe₃O₄ nanoparticles were synthesized by using co-precipitation of ferrous (Fe²⁺) and ferric (Fe³⁺) ions following a surface modification step with oleic acid as stabilizers. Thereafter, a ligand exchange technique was employed to displace oleic acid with hydrophilic dopamine (DOPA) molecules which have a catechol group for anchoring to the iron oxide surface to prepare water dispersible nanoparticles. The surface of the resulting Fe₃O₄/DOPA nanoparticles contains amino (–NH₂) groups that are conjugated with vancomycin via a coupling reaction between the –NH₂ group of dopamine and the –COOH group of vancomycin. The prepared vancomycin conjugated Fe₃O₄/DOPA nanoparticles were named Fe₃O₄/DOPA/Van and exhibited a magnetic response to an external magnetic field due to the presence of magnetite Fe₃O₄ in the core. The Fe₃O₄/DOPA/Van nanoparticles showed bactericidal activity against both Gram positive Bacillus subtilis (B. subtilis) and Streptococcus and Gram-negative bacteria Escherichia coli (E. coli). Maximum inhibition zones of 22 mm, 19 mm and 18 mm were found against B. subtilis, Streptococcus and E. coli respectively. Most importantly, the vancomycin conjugated nanoparticles were effectively bound to the cell wall of the bacteria, promoting bacterial separation and growth inhibition. Therefore, the prepared Fe₃O₄/DOPA/Van nanoparticles can be promising for effective bacterial separation and killing in the dispersion media.

(a) The separation of bacteria by vancomycin conjugated Fe₃O₄/DOPA/Van nanoparticles and (b) H-bonding interactions between the vancomycin molecule and the d-alanyl-d-alanine dipeptide of the bacterial surface.

Facile synthesis of Fe3O4/CuO a core-shell heterostructure for the enhancement of photocatalytic activity under visible light irradiation

A magnetically separable Fe₃O₄/CuO core-shell heterostructure photocatalyst was synthesized by hydrothermal method. The obtained photocatalyst was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and UV-visible diffuse reflectance (UV-DRS). The obtained photocatalyst was used for the degradation of azo dye Direct Red 89 (DR89), under visible light irradiation provided by fluorescent lamp of 100 W in the presence of 7 mL of H₂O₂ (30%); the results of the photocatalytic activity for Fe₃O₄/CuO photocatalyst showed that in the presence of 0.75 g dispersed in 250 mL of 40 mg/L of DR89 dye at pH 6 the dye was completely removed after 240 min. Moreover, the photocatalytic activity of the prepared Fe₃O₄/CuO was enhanced 11 and 9 times compared with the pure Fe₃O₄ or CuO. The effect of initial dye concentrations on the photocatalytic activity was studied in the range of 20-60 mg/L, and the results showed that the catalyst has a good photocatalytic activity of 89% even at high concentration (60 mg/L). Furthermore, the catalyst maintained its activity after 5 cycles, and its paramagnetic property facilitates its recovery. The excellent photodegradation activity of Fe₃O₄/CuO was attributed to the low band gap of the catalyst equal to 1.54 eV and the enhancement of light absorption in visible range of 330-780 nm, but also to a better charge carriers separation, due to the presence of Fe₃O₄ that reduces electron/hole recombination.

A hybrid nanosensor based on novel fluorescent iron oxide nanoparticles for highly selective determination of Hg2+ ions in environmental samples

Novel fluorescent iron oxide nanoparticles were prepared for the determination of Hg²⁺ in real samples. The fluorescence behaviors of the sensor were examined using absorption and fluorescence (steady-state, time-resolved, 3-D, EEM) spectroscopies.

Photoredox Organic Synthesis Employing Heterogeneous Photocatalysts with Emphasis on Halide Perovskite

Lately, heterogeneous semiconductor materials have been explored as an emerging type of efficient photocatalyst for photoredox organic synthesis. Among these semiconductors, lead halide perovskite materials demonstrate unique properties towards excellent charge separation and charge transfer, extremely long charge carrier migration, high efficiency in visible light absorption, and long excited states lifetimes, etc., as proved in ground-breaking solar cell applications, garnering necessary merits for an efficient catalytic system for photoredox organic reactions. Here, the latest progress in heterogeneous semiconductor materials towards this endeavor is examined, with particular emphasis on lead halide perovskite nanocrystals (NCs) in photocatalytic organic synthesis.

The Effect of Laser Re-Solidification on Microstructure and Photo-Electrochemical Properties of Fe-Decorated TiO2 Nanotubes

Fossil fuels became increasingly unpleasant energy source due to their negative impact on the environment; thus, attractiveness of renewable, and especially solar energy, is growing worldwide. Among others, the research is focused on smart combination of simple compounds towards formation of the photoactive materials. Following that, our work concerns the optimized manipulation of laser light coupled with the iron sputtering to transform titania that is mostly UV-active, as well as exhibiting poor oxygen evolution reaction to the material responding to solar light, and that can be further used in water splitting process. The preparation route of the material was based on anodization providing well organized system of nanotubes, while magnetron sputtering ensures formation of thin iron films. The last step covering pulsed laser treatment of 355 nm wavelength significantly changes the material morphology and structure, inducing partial melting and formation of oxygen vacancies in the elementary cell. Depending on the applied fluence, anatase, rutile, and hematite phases were recognized in the final product. The formation of a re-solidified layer on the surface of the nanotubes, in which thickness depends on the laser fluence, was shown by microstructure studies. Although a drastic decrement of light absorption was recorded especially in UV range, laser-annealed samples have shown activity under visible light even 20 times higher than bare titania. Electrochemical analysis has shown that the improvement of photoresponse originates mainly from over an order of magnitude higher charge carrier density as revealed by Mott-Schottky analysis. The results show that intense laser light can modulate the semiconductor properties significantly and can be considered as a promising tool towards activation of initially inactive material for the visible light harvesting.

Natural Kaolin: Sustainable Technology for the Instantaneous and Energy-Neutral Recycling of Anthropogenic Mercury Emissions

Kaolin, a natural and inexpensive clay mineral, is ubiquitous in soil, dirt, and airborne particles. Amongst four commonly available clay minerals, kaolin, as a result of its layered structure, is the most efficient natural gaseous Hg adsorbent to date (Langmuir maximum adsorption capacity Q_m =574.08 μg g^-1 and Freundlich Q_m =756.49 μg g^-1 ). The Hg uptake proceeds by homogeneous monolayer and heterogeneous processes. Hg physisorption on kaolin occurs in the dark, yet the adsorption rate is enhanced upon irradiation. The effects of several metal complexes, salts, halides and solvents on the Hg uptake were examined. The addition of CuCl₂ particles leads to a significant enhancement of the Hg uptake capacity (>30 times) within second timescales and without irradiation. The physisorption with kaolin is switched to chemisorption upon the addition of CuCl₂ to kaolin. This process is entirely reversible upon the addition of Zn/Sn granules at room temperature without any added energy. However, the investment of a small amount of renewable energy can speed up the process. This technology demonstrates the facile and efficient capture and recycling of elemental Hg⁰ from air. A wide range of metal particles and diverse physicochemical processes, which include the microphysics of nucleation, are herein examined to explore the potential reaction mechanism by using a suite of complementary analytical techniques. These new mechanistic insights open a new era of energy-neutral environmental remediation based on natural soil/airborne particles.

Novel Technology for the Removal of Brilliant Green from Water: Influence of Post-Oxidation, Environmental Conditions, and Capping

Chemical dyes are used in a wide range of anthropogenic activities and are generally not biodegradable. Hence, sustainable recycling processes are needed to avoid their accumulation in the environment. A one-step synthesis of Fe_core-maghemite_shell (Fe-MM) for facile, instantaneous, cost-effective, sustainable, and efficient removal of brilliant green (BG) dye from water has been reported here. The homogenous and monolayer type of adsorption is, to our knowledge, the most efficient, with a maximum uptake capacity of 1000 mg·g^-1, for BG on Fe-MM. This adsorbent was shown to be efficient in occurring in time-scales of seconds and to be readily recyclable (ca. 91%). As iron/iron oxide possesses magnetic behavior, a strong magnet could be used to separate Fe-MM coated with BG. Thus, the recycling process required a minimum amount of energy. Capping Fe-MM by hydrophilic clay minerals further enhanced the BG uptake capacity, by reducing unwanted aggregation. Interestingly, capping the adsorbent by hydrophobic plastic (low-density polyethylene) had a completely inverse effect on clay minerals. BG removal using this method is found to be quite selective among the five common industrial dyes tested in this study. To shed light on the life cycle analysis of the composite in the environment, the influence of selected physicochemical factors (T, pH, hν, O₃, and NO₂) was examined, along with four types of water samples (melted snow, rain, river, and tap water). To evaluate the potential limitations of this technique, because of likely competitive reactions with metal ion contaminants in aquatic systems, additional experiments with 13 metal ions were performed. To decipher the adsorption mechanism, we deployed four reducing agents (NaBH₄, hydrazine, LiAlH₄, and polyphenols in green tea) and NaBH₄, exclusively, favored the generation of an efficient adsorbent via aerial oxidation. The drift of electron density from electron-rich Fe_core to maghemite shells was attributed to be responsible for the electrostatic adsorption of N⁺ in BG toward Fe-MM. This technology is deemed to be environmentally sustainable in environmental remediation, namely, in waste management protocol.

Physicochemical studies of aerosols at Montreal Trudeau Airport: The importance of airborne nanoparticles containing metal contaminants

Airborne particles, specifically nanoparticles, are identified health hazards and a key research domain in air pollution and climate change. We performed a systematic airport study to characterize real-time size and number density distribution, chemical composition and morphology of the aerosols (∼10 nm-10 μm) using complementary cutting-edge and novel techniques, namely optical aerosol analyzers, triple quad ICP-MS/MS and high-resolution STEM imaging. The total number density of aerosols, predominantly composed of nanoparticles, reached a maximum of 2 × 10⁶ cm^-3 and is higher than reported values from any other international airport. We also provide evidence for a wide range of metal in aerosols, and emerging metals in nanoparticles (e.g., Zn and Ni). The geometric mean, median and 99th and 1st percentile values of observed nanoparticle number densities at the apron were 1.0 × 10⁵, 9.0 × 10⁴, 1.2 × 10⁶ and 9.3 × 10³ cm^-3, respectively. These observations were statistically higher than corresponding measurements in downtown Montreal and at major highways during rush hour. This airport is thus a hotspot for nanoparticles containing emerging contaminants. The diurnal trends in concentrations exhibit peaks during flight and rush hours, showing correlations with pollutants such as CO. The HR-TEM-EDS provided evidence for nano-sized particles produced in combustion engines. Implications of our results for air pollution and health are discussed.

Fast, Cost-effective and Energy Efficient Mercury Removal-Recycling Technology

We herein present a novel and sustainable technology for mercury recycling, with the maximum observed uptake capacity. Facile synthesis of the most efficient (~1.9 gg-1) nano-trap, made of montmorillonite-Fe-iron oxides, was performed to instantaneously remove mercury(II) ions from water. Elemental Hg was recovered from the adduct, by employing Fe granules, at ambient conditions. Varied pHs and elevated temperatures further enhanced this already highly efficient recycling process. The reduction of Hg(II) to Hg(I) by the nano trap and Hg(I) to Hg(0) by Fe granules are the main driving forces behind the recycling process. Facile sustainable recycling of the nano-trap and Fe granules require no additional energy. We have further developed a recyclable model for Hg nano-trap, which is inexpensive (<$5 CAD), and can remove mercury in a few seconds. This technology has multiple applications, including in the communities exposed to mercury contamination.