Oxyhydroxide Research Articles

Ag engineered NiFe-LDH/NiFe2O4 Mott-Schottky heterojunction electrocatalyst for highly efficient oxygen evolution and urea oxidation reactions

Efficient and durable electrocatalysts with sufficient active sites and high intrinsic activity are essential for advancing energy-saving hydrogen production technology. In this study, a Mott-Schottky heterojunction electrocatalyst with Ag nanoparticles in-situ grown on NiFe layered double hydroxides (NiFe-LDH)/NiFe2O4 nanosheets (Ag@NiFe-LDH/NiFe2O4) were designed and successfully synthesized through a hydrothermal process and subsequent spontaneous redox reaction. The in-situ growth of metallic Ag on semiconducting NiFe-LDH/NiFe2O4 triggers a strong electron interaction across the Mott-Schottky interface, leading to a significant increase in both the intrinsic catalytic activity and the electrochemical active surface area of the heterojunction electrocatalyst. As a result, the Ag@NiFe-LDH/NiFe2O4 demonstrates impressive oxygen evolution reaction (OER) performance in alkaline KOH solution, achieving a low overpotential of 249 mV at 100 mA cm−2 and a Tafel slope of 42.79 mV dec−1. When the self-supported Ag@NiFe-LDH/NiFe2O4 is coupled with the Pt/C electrocatalyst, the alkaline electrolyzer reaches a current density of 10 mA cm−2 at a cell voltage of only 1.460 V. Furthermore, X-ray photoelectron spectroscopy and in-situ Raman analysis reveal that the Ni(Fe)OOH is the possible active phase for OER in the catalyst. In addition, when employed for UOR catalysis, the Ag@NiFe-LDH/NiFe2O4 also displays intriguing activity with an ultralow potential of 1.389 V at 50 mA cm−2. This work may shed light on the rational design of multiple-phase heterogeneous electrocatalysts and demonstrate the significance of interface engineering in enhancing catalytic performance.

Organic matter preservation through complexation with iron minerals in two basins of a dimictic boreal lake with contrasting deep water redox regimes

The biogeochemical cycles of iron and organic carbon (OC) are closely interconnected in terrestrial and aquatic systems. In ocean waters, the concentration of reactive Fe is tightly controlled by soluble organic ligands. In soils, Fe stabilizes OC by forming aggregates that shield OC from degradation. In lake sediments however, the role of Fe in the preservation of OC has not been explored as extensively yet. We investigated Fe-OC interactions in sediment collected from Lake Tantaré, in which two basins are characterized by contrasting redox conditions. These contrasting redox conditions provide an opportunity to assess their importance in the formation of stable Fe-OC complexes. On average, 30.1 ± 6.4 % of total OC was liberated upon reductively dissolving reactive iron. The Fe-associated and the non-Fe-associated OC pools were characterized at the elemental (OC, TN), isotopic (δ13C, δ15N) and functional group (FTIR) levels. Large differences in OC:Fe and TN:Fe ratios between the two basins were found which were not linked to OM chemical composition but rather to differences in reactive iron concentrations stemming from the higher abundance of iron sulfides in the anoxic basin. Nevertheless, since the affinity of OM for iron sulfides is lower than that for iron hydroxides, using OC:Fe and TN:Fe ratios as a diagnostic tool for the type of OM-Fe interactions should be done with care in anoxic environment. Same caution should be considered for oxic sediments due to the variation of the proportion of iron hydroxides associated with OM from sample to sample.

Pharmacological models of liver iron overload

Iron deposits in tissues (hemosiderosis) accompany various diseases of the liver and pancreas. Overload of the liver with iron occurs due to (1) a diet with excess saturated fats, which provoke inflammation of the liver, (2) slowdown and stagnation of blood flow in the area of the portal vein (physical inactivity, obesity, alcoholism, etc), (3) uncontrolled and long-term use of iron supplements (primarily based on inorganic forms - sulfates, oxides, hydroxides of iron, etc.), (4) hereditary diseases (hemochromatosis). Patients with liver overload with iron require not only correction of diet and lifestyle (including physical activity), but also special therapy using effective and safe drugs. To study the effect of excess iron on the body and search for the most appropriate therapy for hemosiderosis, special models of liver overload with iron have been developed in pharmacology. The degree of iron overload and the rate of hemosiderosis formation in models can be slowed down by the addition of micronutrients with hepatoprotective properties (vitamins A, C) and accelerated by the addition of saturated fat and/or fructose to the diet.

Ortho- to para-hydrogen catalytic conversion kinetics

Hydrogen is a widely considered energy storage option. Hydrogen liquefaction allows for a substantial increase in volumetric energy density; the required conversion of ortho-hydrogen (o-H2) to para-hydrogen (p-H2) is however one of several challenges. This conversion requires a catalyst for sufficiently rapid kinetics, however available conversion data is sparse. To this end, a high throughput ortho-hydrogen (o-H2) to para-hydrogen (p-H2) conversion apparatus is detailed. This enables measurements at a controlled temperature of 77 K via the use of in-situ Raman Spectroscopy for quantitative determination of the ortho-para composition. Conversion kinetic data were acquired for a hydrous ferric oxide catalyst. These data were in reasonable agreement with limited existing literature, thus providing some validation for the use of conversion kinetic models, derived from such data, in hydrogen liquefaction design. Kinetic data was acquired using hydrogen provided via electrolysis; the effect of impurity (H2O) carry-over on conversion kinetics is considered.

Selective Removal of Chlorophyll and Isolation of Lutein from Plant Extracts Using Magnetic Solid Phase Extraction with Iron Oxide Nanoparticles.

In recent years, there has been a growing interest in plant pigments as readily available nutraceuticals. Photosynthetic pigments, specifically chlorophylls and carotenoids, renowned for their non-toxic antioxidant properties, are increasingly finding applications beyond their health-promoting attributes. Consequently, there is an ongoing need for cost-effective methods of isolation. This study employs a co-precipitation method to synthesize magnetic iron oxide nanoparticles. Scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) confirms that an aqueous environment and oxidizing conditions yield nanosized iron oxide with particle sizes ranging from 80 to 140 nm. X-ray photoelectron spectroscopy (XPS) spectra indicate the presence of hydrous iron oxide FeO(OH) on the surface of the nanosized iron oxide. The Brunauer-Emmett-Teller (BET) surface area of obtained nanomaterial was 151.4 m2 g-1, with total pore volumes of pores 0.25 cm3 g-1 STP. The material, designated as iron oxide nanoparticles (IONPs), serves as an adsorbent for magnetic solid phase extraction (MSPE) and isolation of photosynthetic pigments (chlorophyll a, lutein) from extracts of higher green plants (Mentha piperita L., Urtica dioica L.). Sorption of chlorophyll a onto the nanoparticles is confirmed using UV-vis spectroscopy, Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS), and high-performance liquid chromatography (HPLC). Selective sorption of chlorophyll a requires a minimum of 3 g of IONPs per 12 mg of chlorophyll a, with acetone as the solvent, and is dependent on a storage time of 48 h. Extended contact time of IONPs with the acetone extract, i.e., 72 h, ensures the elimination of remaining components except lutein, with a spectral purity of 98%, recovered with over 90% efficiency. The mechanism of chlorophyll removal using IONPs relies on the interaction of the pigment's carbonyl (C=O) groups with the adsorbent surface hydroxyl (-OH) groups. Based on molecular dynamics (MD) simulations, it has been proven that the selective adsorption of pigments is also influenced by more favorable dispersion interactions between acetone and chlorophyll in comparison with other solutes. An aqueous environment significantly promotes the removal of pigments; however, it results in a complete loss of selectivity.

Adsorption of Toxic Metals Using Hydrous Ferric Oxide Nanoparticles Embedded in Hybrid Ion-Exchange Resins.

Acid mine drainage (AMD) is a major environmental problem caused by the release of acidic, toxic, and sulfate-rich water from mining sites. This study aimed to develop novel adsorbents for the removal of chromium (Cr(VI)), cadmium (Cd(II)), and lead (Pb(II)) from simulated and actual AMD using hybrid ion-exchange resins embedded with hydrous ferric oxide (HFO). Two types of resins were synthesized: anionic exchange resin (HAIX-HFO) for Cr(VI) removal and cationic exchange resin (HCIX-HFO) for Cd(II) and Pb(II) removal. The resins were characterized using scanning electron microscopy and Raman spectroscopy, which confirmed the presence of HFO particles. Batch adsorption experiments were conducted under acidic and sulfate-enhanced conditions to evaluate the adsorption capacity and kinetics of the resins. It was found that both resins exhibited high adsorption efficiencies and fast adsorption rates for their respective metal ions. To explore the potential adsorption on actual AMD, HCIX-HFO demonstrated significant removal of some metal ions. The saturated HCIX-HFO resin was regenerated using NaCl, and a high amount of the adsorbed Cd(II) and Pb(II) was recovered. This study demonstrates that HFO-embedded hybrid ion-exchange resins are promising adsorbents for treating AMD contaminated with heavy metals.

Elastic anomalies across the P21mn→Pnnm structural phase transition in δ-(Al,Fe)OOH

Abstract Hydrogen may be recycled into the Earth's lower mantle by subduction and stabilized in solid solutions between phase H (MgSiO4H2), δ-AlOOH, ε-FeOOH, and SiO2 post-stishovite. In high-pressure oxyhydroxide phases, hydrogen is incorporated following the typical (OHO) sequence, adopting the asymmetric configuration O-H···O that evolves into a symmetric disordered state upon compression. Moreover these iron-/aluminum-bearing oxyhydroxides [δ-(Al,Fe)OOH] present a structural phase transition from P21nm to Pnnm as pressure increases. Here, the single-crystal elasticity of the P21nm phase of δ-(Al0.97,Fe0.03)OOH has been experimentally measured across the P21nm→Pnnm transition up to 7.94(2) GPa by simultaneous single-crystal X-ray diffraction (XRD) and Brillouin spectroscopy at high pressures. The transition appears to be continuous, and it can be described with a second, fourth and six order terms Landau potential. Our results reveal an enhanced unit-cell volume compressibility, which is linked to an increase of the b- and a-axes linear compressibility in the P21nm phase of δ-(Al0.97,Fe0.03)OOH prior to the transition. In addition, we observed the presence of elastic softening in the P21nm phase that mostly impacts the elastic stiffness coefficients c12, c22 and c23. The observed elastic anomalies cause a significant change in the pressure dependence of the adiabatic bulk modulus (KS). These results provide a better understanding of the relation between elasticity, P21mn→Pnnm structural phase transition and hydrogen dynamics in δ-(Al0.97,Fe0.03)OOH, which may be applied to other O-H···O-bearing materials.

Detoxification of chromium slag using corn stalk for the hierarchical preparation of ultrafine aluminum hydroxide and iron hydroxide

The harmless treatment and resource utilization of chromite ore processing residue (COPR), a consequential byproduct of chromate production, carry profound significance. In this study, corn stalk, an agricultural waste, was used to generate reducing substances through high-temperature and vacuum treatments and was successfully used to detoxify COPR. The acid leaching method combined with multi-step purification was employed to extract iron and aluminum, two crucial metallic elements, from COPR. The successful preparation of iron hydroxide and ultrafine aluminum hydroxide (ATH) was achieved. The prepared ATH has an average particle size of 8.124 μm, with a highly uniform distribution, enabling it to be a promising environmentally friendly inorganic flame retardant. This study not only effectively addresses the issue of pollution caused by COPR but also presents a novel approach to utilizing industrial and agricultural wastes, thereby promoting the maximization of resource utilization.

Boosting oxygen evolution in seawater media at large current density via boron-doped (Ni,Fe)OOH grown on Ni3N nanosheets

Exploiting highly efficient oxygen-evolving electrocatalysts is crucial for hydrogen production through seawater electrolysis. Here, a hierarchical structure of boron-doped (Ni,Fe)OOH grown on Ni3N nanosheets supported on nickel foam [denoted as B-(Ni,Fe)OOH/Ni3N/NF] is fabricated. Benefiting from the formation of abundant active sites and the reduced free energy barrier of the rate-determining step caused by B doping, the obtained B-(Ni,Fe)OOH/Ni3N/NF exhibits extraordinary electrocatalytic activity for oxygen evolution reaction, requiring overpotentials of only 283 mV and 309 mV to achieve a current density of 1000 mA cm−2 in alkaline pure water and seawater media, respectively, as well as superior stability. When driven by a commercial Si solar cell, the electrolyzer using B-(Ni,Fe)OOH/Ni3N/NF as the anode and a previously reported Ru/(Fe,Ni)(OH)2/NF as the cathode can achieve a high current of over 1000 mA in alkaline seawater media. This shows the great potential in applying a photovoltaic-driven electrolyzer toward large-scale hydrogen production in seawater electrolysis.

Coprecipitation as a One-Step Se Separation for Determination of Isotope Ratios Completed with Revised Uncertainty Evaluation.

This study introduces a simplified purification method for analyzing 82Se/78Se isotope ratios in diverse natural samples using hydride generation MC-ICP-MS. Unlike the thiol resin method, which is time-consuming and sensitive to the concentrations of reagents used at individual stages, our proposed alternative is quicker, simpler, and robust. The procedure involves coprecipitation of selenium with iron hydroxide and dissolution in hydrochloric acid. Combining hydride generation and a second cleanup stage achieves sufficient purification for Se isotope ratio measurements. The method is efficient, taking 3-4 h after sample decomposition, utilizing common reagents [HCl, Fe(NO3)3, NH4Cl] without evaporation or clean lab conditions. Results on 82Se/78Se isotope ratios in various matrices are presented, comparing them with literature data. All isotopic results have been subjected to a newly proposed state-of-the-art approach to uncertainty estimation dedicated to isotope ratio measurements. The approach is based on applying Monte Carlo simulations with consideration of different samples' results normalized by the expected value. By doing that, we obtained estimated uncertainty for any Se sample with the influence of particular measurements on the final estimation included. We employ a Monte Carlo simulation-based uncertainty estimation approach for isotope ratio measurements, providing estimated uncertainty for each selenium sample.

Effect of corrosion pit distribution of rebar on pore, and crack characteristics in concrete

This research paper delves into the impact of corrosion-induced changes, particularly pit distribution, on pore structures and crack propagation in concrete subjected to galvanostatic accelerated corrosion. Two samples with different pit configurations were investigated—one with larger and spread pits, the other with smaller and localized ones. Various characterizations methods were applied including X-ray Computed Tomography (CT), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDS), and Raman spectroscopy. The 3D CT images reveals dynamic changes in pore volumes, pit expansion, emergence of new pores at cement-aggregate interfaces, and distinctive crack formation patterns. Image analysis accurately quantifies corrosion products, highlighting their dependence on pit presence and characteristic. The sample with larger pit volume experiences exclusive initial formation of iron hydroxides, while small pit volume contains both iron oxides and hydroxides simultaneously. Raman spectroscopy shows the dynamic interplay of iron oxides and hydroxides, marking an evolution from oxides to hydroxides within the cement paste. Crack formation analysis reveals distinct patterns in samples with high pit dispersion, including cracks originating from pores near reinforcing bar pits, larger cracks diffusing corrosion products outward, and zipper cracks emerging from distant interconnected pores. Conversely, low pit content sample exhibits a different crack pattern with varying origins and narrower apertures. The temporal evolution of cracks in this sample appears simultaneous, possibly linked to ongoing corrosion processes. Elemental mapping indicates elevated corrosion product volumes within and around cracks, possibly due to water migration into the concrete matrix. These insights deepen our understanding of concrete deterioration mechanisms, guiding strategies to enhance structural integrity and durability in critical infrastructure.

Study on the removal of methylene blue by submerged Arc generated by titanium and iron electrodes

Methylene blue (MB) solution was treated by the submerged arcs generated by the titanium (Ti) and iron (Fe) electrodes, with a subsequent aging process. The removal ratio of each condition was recorded by the absorbance of the treated solution. The experimental results indicated that the submerged arc with Fe electrodes is more efficient with an efficiency nearly 90% after 3.5 min of treatment. Reversible decolorization was observed in the MB solution treated by the Fe submerged arc. However, the removal ratio in the MB solution treated by the Ti submerged arc continuously increased during both the treating and aging process. Furthermore, the particles eroded from the Ti electrodes were characterized by SEM and XRD, and the titanic oxides including TiO, TiO2 and Ti3O5 were found with different diameters ranging from 1 μm to 20 μm. Moreover, complete decomposition occurred during the treatment by the submerged arc generated by the Ti electrodes. The eroded particles from the Fe electrodes were examined by XRD, and the majority of the composition was iron. Unlike the Ti electrodes, the decolorization process by the submerged arc of Fe electrodes was more likely related to the formation of colorless leuco-MB and the physical adsorption by iron hydroxides. Additionally, the pH and chemical oxygen demand (COD) of the treated solutions were also discussed.

Voltage activation induced MoO42− dissolution to enhance performance of iron doped nickel molybdate for oxygen evolution reaction

Transition metal-based precatalysts are typically voltage-activated before electrochemical testing in the condition of alkaline oxygen evolution reaction. Nevertheless, the impact of voltage on the catalyst and the anion dissolution is frequently disregarded. In this study, Fe-doped NiMoO4 (Fe-NiMoO4) was synthesized as a precursor through a straightforward hydrothermal method, and MoFe-modified Ni (oxygen) hydroxide (MoFe-NiOxHy) was obtained via cyclic voltammetry (CV) activation. The effects of voltage on Fe-NiMoO4 and the dissolved inactive MoO42− ions in the process were examined in relation to OER performance. It has demonstrated that the crystallinity of the catalyst is reduced by voltage, thereby enhancing its electrocatalytic activity. The electron distribution state can be adjusted during the application of voltage, leading to the generation of additional active sites and an acceleration in the reaction rate. Additionally, MoO42− exhibits potential dependence during its dissolution. In the OER process, the dissolution of MoO42− enhances the reconstruction degree of Fe-NiMoO4 into the active substance and expedites the formation of active Ni(Fe)OOH. Hence, the optimized MoFe-NiOxHy exhibited exceptional electrocatalytic performance, with a current density of 100 mA cm−2 achieved at an overpotential of only 256 mV. This discovery contributes to a more comprehensive understanding of alkaline OER performance under the influence of applied voltage and the presence of inactive oxygen ions, offering a promising avenue for the development of efficient electrocatalysts.

Palladium nanoparticles integrated ternary nickel cobalt iron hydroxide as an efficient bifunctional electrocatalyst for direct ethanol fuel cell

The rational design and identification of the underlying role of the support materials to promote the electrocatalytic activity of the active catalyst are the main objectives of the current research. Herein, we synthesized different compositions of ternary nickel cobalt iron transition metal hydroxide (TMH) supported palladium (Pd) nanoparticles (Pd/Hy) to improve the ethanol electrooxidation reaction (EOR) and oxygen reduction reaction (ORR) kinetics of Pd NPs. The TMH supports modified the surface electronic structures of Pd through strong metal support interaction, thereby improving the EOR and ORR reaction kinetics. Herein, we explored potential-dependent electrochemical impedance spectroscopy (EIS) to identify the intermediates species formed during the ORR and EOR process and rationalize the reaction mechanism. The potential-dependent EIS reveals that TMH supports eliminating the adsorption of the poisonous carbonaceous species during the EOR. The synthesized bifunctional Pd/Hy catalyst integrated alkaline direct ethanol fuel cell device exhibits a peak power density of 28.1 mW/cm2, which is a higher performance than that of the Pt/C integrated devices. Finally, Pd/Hy catalyst-integrated passive DEFC was tested, and a portable electronic application was demonstrated.

Regeneration of As(V)-loaded granular activated carbon through electrocoagulation.

As(V)-loaded granular activated carbon was regenerated through electrocoagulation assisted by elution with NaCl. Adsorption of As(V) by activated carbon was highest at pH6, and subsequent desorption in water was highest at pH 11, followed by pH3. Lower initial pH improved arsenic removal during electrocoagulation, NaCl concentration was insignificant, but removal increased with current density. Adding Fe(II) before electrocoagulation led to an improved removal efficiency up to a concentration of 30 mg/L. Regeneration of As(V)-loaded activated carbon increased with current density and time up to a maximum of 85%. An increase in NaCl concentration to 6000 mg/L further improved regeneration to 92%. Regeneration at a lower current density only dropped slightly from 54% to 51% when doubling activated carbon concentration, demonstrating excellent scalability. Repeated adsorption-desorption tests were performed, where 81% and 69% regeneration were obtained after four regenerations with NaCl concentrations of 6000 and 750 mg/L, respectively. NaCl concentration in the tested range did not influence electrocoagulation but improved regeneration through elution. The combination of electrocoagulation and elution facilitated a higher regeneration efficiency, meanwhile removing As(V) from the solution through adsorption on iron hydroxide. PRACTITIONER POINTS: As(V)-loaded activated carbon was regenerated by electrocoagulation with elution. Regeneration increased with regeneration time and current density up to 85%. Addition of 6000 mg/L NaCl further increased regeneration to 93%. Regeneration of 82% was achieved after four regenerations. NaCl did not affect electrocoagulation but improved regeneration through elution.

Study on corrosion characteristics of reinforcing bars in concrete under industrial SO2 environment

Sulfur dioxide (SO2) is the primary pollutant in industrial atmospheres, leading to significant damage to industrial buildings. The corrosion caused by SO2 in concrete, including neutralization and solid phase volume expansion, poses particular concerns. However, there is a lack of research on the electrochemical behaviour and corrosion mechanisms of reinforcing bars embedded in concrete. This study conducted indoor simulations of reinforced concrete specimens exposed to industrial SO2 corrosion utilizing an SO2 testing chamber. The corrosion behavior of the reinforcing bars was monitored through half-cell potential, weak polarization, and electrochemical impedance spectroscopy (EIS). Additionally, the corrosion mechanisms of the reinforcing bars under SO2 exposure were investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and Raman spectra. The results demonstrated a consistent correlation between variations in corrosion potential (Ecorr) and corrosion current density (icorr) of steel rebars in different types of concrete. The corrosion rates of the reinforcing steel in C1 (w/b=0.57), C2 (w/b=0.47), and C3 (w/b=0.37) concrete exceeds 0.1 μA/cm2 after 42, 72, and 90 days of SO2 corrosion, respectively. At this time, the ratio of the depth of neutralization to the thickness of the protective layer is 0.51–0.65. The rust exhibits a layered structure with a presence of S elements adsorbed and deposited on the surface of the rust layer. Moreover, the research has identified the accumulation of S elements within corrosion pits, which can be attributed to localized acidification reactions. The rust products identified include iron hydroxide (FeOOH), and iron oxide (Fe2O3), rozenite (FeSO4·4 H2O). The formation of FeSO4·4 H2O in corrosion pits suggests that significant localized corrosion on the surface of reinforcing bars in concrete under the impact of SO2.

A rapid method to quantify sub-micrometer polystyrene particles in aqueous model systems by TOC analysis

For several laboratory experiments with microplastics, a simple and fast quantification method is advantageous. At the same time, the requirements are often lower compared to microplastic detection from environmental samples. We determined the concentration of non-purgable organic carbon of polystyrene (PS) particles (diameter 0.5, 1, 2, 6 μm) in suspension with known concentrations. Commercially available PS particles were used to test the Total Organic Carbon (TOC) analyzer method for quantifying microplastics in the lower micrometer range under absence of other organic compounds. Addition of iron or aluminum hydroxide to the samples prior to the measurement increased the recovery from 52.9 to 89.7% relative to measurements in the absence of metal hydroxides. With increasing particle size, the recovery in the presence of iron hydroxides decreased from 95.1% at 0.5 μm to 67.1% at 6 μm PS particles and in the presence of aluminum hydroxides from 92.6% at 0.5 μm to 88.9% at 6 μm PS particles. We conclude that metal hydroxides have a catalytic effect on the thermocatalytic oxidation of PS particles and allow a complete conversion to CO2 for a successful quantification of PS particles using a TOC analyzer. Especially for particles larger than 0.5 μm, in the absence of metal hydroxides, the TOC device is not able to fully oxidize the PS particle to CO2 and subsequently detect its concentration. Thus, TOC analysis of PS particles in the presence of metal hydroxides provides a cheap and simple alternative for quantifying microplastic particles in the lower micrometer range for laboratory experiments (e.g. sedimentation studies) where no other organic substances are present.

Study on the removal of fulvic acid in water by potassium ferrate-enhanced iron-manganese co-oxide film and its mechanism.

The previous studies have shown that iron-manganese co-oxide film (MeOx) could simultaneously remove ammonium, manganese ion and bisphenol A. In this study, the removal of fulvic acid (FA) was explored by adding potassium ferrate (K2FeO4) to heighten the catalytic activity of MeOx. After adding about 3.0mg/L potassium ferrate, the elimination efficiency of 7.0mg/L FA by the MeOx increased from 20 to 50%. The effects of temperature and ammonium on the elimination of FA were investigated. Higher temperature (above 22°C) and higher ammonium concentration (above 2.0mg/L) caused a decrease in FA removal. Most of FA combined with the ferric hydroxide colloid produced by K2FeO4 in water to form macromolecular groups, and they were subsequently absorbed and covered on the surface of MeOx. Scanning electron microscope showed that more viscous flocs appeared on the surface of MeOx, and the film thickness became thicker. Electron energy-dispersive spectrometer analysis revealed a notable increased in the C-O element ratio and a significant decreased in the Mn-Fe element ratio on the surface of MeOx. From Fourier transform infrared spectroscopy, the content of transition metal carbonyl compounds increased in the surface of MeOx. XPS analysis confirmed that the presence of Fe3O4, FeO, Mn2O3 and Mn3O4 along with functional group substances of FA attached on the surface of MeOx. The removal mechanism of FA was studied.

First report on binder-free boehmite (AlOOH) based prototype, flexible, high-energy and high-power density solid-state symmetric supercapacitor

Supercapacitor has potential to accomplish the world-wide growing demand for clean and sustainable energy. It has virtue of both the battery and the conventional capacitor. The proper selection of electrode material is one of the deterministic factors for the excellent performance of supercapacitor. This work presents the first report on the boehmite phase of a polymorph of earth abundant and inexpensive aluminum based oxy hydroxide for energy storage application. The binder-free synthesis of AlOOH electrode has been carried out by the simple, user-friendly, and low-cost successive ionic layer adsorption and reaction (SILAR) technique at 300 K. The X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy characterizations are performed for the knowledge of crystal structure, chemical bonds, oxidation states, morphology and elements present in the sample, respectively. The electrochemical activities of electrode as well as fabricated solid-state symmetric device are disclosed by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The maximum specific capacitance of 726.5 F g−1 @ 5 mV s−1 has been achieved for AlOOH electrode with ~67 % cyclic stability for 6500 cycles. The assembled device exhibits an excellent specific capacitance of 314 F g−1 @ 5 mV s−1, energy density of 242 Wh Kg−1 and power density of 4701 W Kg−1 with ~80 % stability up to 6500 cycles. The device has ability to glow red, green, blue and white coloured light emitting diodes (LEDs) for 50, 52, 27 and 21 min respectively. Also, the fabricated device is successful for glowing a panel ‘MNNIT’ made up by 56 red coloured LEDs. These results indicate that this work can be beneficial for fulfilling the energy demand of future generation.

Fenton Reaction in vivo and in vitro. Possibilities and Limitations.

The review considers the problem of hydrogen peroxide decomposition and hydroxyl radical formation in the presence of iron in vivo and in vitro. Analysis of the literature data allows us to conclude that, under physiological conditions, transport of iron, carried out with the help of carrier proteins, minimizes the possibility of appearance of free iron ions in cytoplasm of the cell. Under pathological conditions, when the process of transferring an iron ion from a donor protein to an acceptor protein can be disrupted due to modifications of the carrier proteins, iron ions can enter cytosol. However, at pH values close to neutral, which is typical for cytosol, iron ions are converted into water-insoluble hydroxides. This makes it impossible to decompose hydrogen peroxide according to the mechanism of the classical Fenton reaction. A similar situation is observed in vitro, since buffers with pH close to neutral are used to simulate free radical oxidation. At the same time, iron hydroxides are able to catalyze decomposition of hydrogen peroxide with formation of a hydroxyl radical. Decomposition of hydrogen peroxide with iron hydroxides is called Fenton-like reaction. Studying the features of Fenton-like reaction in biological systems is the subject of future research.