Oxyhydroxide Research Articles

Sulfidation of Iron - Based Nanomaterial as Catalyst for Water Splitting Using Hydrothermal

Consumption of fossil fuels causes greenhouse effect and global warming, hence the need for renewable energy sources that are environmentally friendly. Hydrogen is one of the abundant elements on earth. Hydrogen refers to a clean and renewable energy source, hydrogen can be a good choice to reduce greenhouse gas emissions. One way to produce hydrogen is by electrochemical water splitting. This study aims to determine the characterization of iron-based nanomaterials (iron sulfide - iron hydroxide) as a water splitting catalyst in general. Iron sulfide synthesis was carried out using hydrothermal sulfidation method for 6 hours at 80 oC with nickel foam as substrate. Synthesis of iron sulfide varying the concentration of sodium sulfide nonahydrate (0.0125 M, 0.025 M, 0.05 M and 0.1 M) produced brownish yellow to blackish grey colored samples. Characterization results using XRD showed that iron sulfide peaks were detected at higher concentrations of sodium sulfide nonahydrate. Based on the results of analyzing iron hydroxide using SEM, it is known that the sample is in the form of nano walls and on iron sulfide, it is known that the sample is in the form of nanoscale particles. Based on electrochemical measurement results, iron hydroxide can be a good catalyst for hydrogen evolution reaction (HER) compared with commercial Pt/C. The overpotential of iron hydroxide is smaller than Pt/C, which is only 15 mV at a current density 10 mA/cm2 and iron sulfide can be a good catalyst for oxygen evolution reaction (OER) with electrocatalytic measurement results close to commercial RuO2. This is indicated by the small overpotential (260 mV at current densisty 10 mA/cm2 and small tafel slope (51 mV/dec).

Cobalt based bimetallic catalysts for heterogeneous electro-Fenton adapting to vary pH for HEDP and MIT degradation

ABSTRACT Most of the materials studied as catalysts in the electro-Fenton system are variants of iron oxide or iron hydroxide. However, iron-based catalysts often exhibit weak catalytic capabilities under neutral and alkaline conditions. In this work, we synthesized three cobalt based bimetallic oxides, Co2CuOx, Co2AlOx, and Co2NiOx, using hydrothermal method and evaluated them as catalysts for the heterogeneous electro-Fenton system to remove 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and Methylisothiazolinone [2-methyl-4-isothiazolin-3-one] (MIT). Co2NiOx has the highest catalytic degradation activity for HEDP, and Co2CuOx has the best catalytic degradation effect for MIT. Based on characterization results of the catalysts, the reasons for the differences in the pollutant removal efficiency were analysed, and the optimal pH for the three cobalt based oxides to remove HEDP and MIT was investigated. The results showed that the optimal pH values of the three cobalt based bimetallic oxides are not only influenced by the second metal type, but also by the properties of pollutants. Therefore, suitable cobalt based catalysts can be selected based on the different properties of pollutants, or the composition of cobalt based catalysts can be adjusted to meet the different pH requirements of target wastewater. The three cobalt based bimetallic oxides exhibited good degradation of HEDP and MIT under neutral conditions, which to some extent solved the problem of narrow pH range in the practical application of the electro-Fenton process.

Enhancing the oxygen evolution reaction activity of Iron (oxy)hydroxide by increasing reactive sites with morphology modulation

Nonprecious transition metal (oxy)hydroxides play a vital role in accelerating the kinetics of sluggish oxygen evolution reaction (OER). The fast electron transfer from the electrocatalyst material surface to the electrode is key to obtaining improved OER activity in terms of improved reaction kinetics and reduced overpotential. Therefore, it is highly desirable to design electrocatalysts with efficient electron transport properties. Here, an approach of modulation of the morphology of Iron (oxy)hydroxide through the incorporation of Cr is used to obtain high electrocatalytic activity. The incorporation of Cr resulted in the modified morphology of Iron (oxy)hydroxide with the formation of a porous pit-like structure which offers large reactive sites to effectively adsorb the reactants and allow an efficient electron transfer pathway from electrocatalyst to circuit through Ni foam electrode. A 50 % Cr incorporated electrocatalyst (Fe5.0Cr5.0 (oxy)hydroxide) exhibits excellent OER activity with an overpotential of 237 mV and 297 mV at current densities of 10 and 100 mA cm─2, respectively owing to fast electron transport from electrocatalyst to substrate due to formation of porous pit-like structure. Furthermore, Fe5.0Cr5.0 electrocatalyst shows high durability of over 100 h at 10 mA cm─2. The enhanced OER activity is attributed to the effect of Cr incorporation and morphology modulation which helps to modulate the electronic structure as well as electrocatalytic active sites of Fe (oxy)hydroxide. The systematic incorporation and modulation of morphology pave the way for designing future electrocatalysts for various electrochemical activities.

Effects of calcined oyster shell powder composited with iron salt on the simultaneous removal of phosphorus and arsenic during algal bloom control process

Calcined oyster shell powder (COS) has the potential to serve as an efficient coagulant aid in water treatment for iron salt (IS) due to its potentially high aid capacity in alkalinity recovery and the simultaneous removal effects on algae, arsenic, phosphorus, and organic substances. However, little information is available on the specific effects and environmental impacts of COS composited with IS in coagulation for algal bloom removal. Hence, the COS was used as a coagulant aid to investigate the simultaneous removal effects on phosphorus and arsenic as well as the water environment changes during the bloom control of Microcystis aeruginosa using ferric chloride as a coagulant impacted by different hydraulic disturbances. Results showed that compared to the single IS coagulation with a pH value of about 3.1, the pH value significantly increased and stabilized at 7.5 from the 3rd day with the COS as the coagulant aid condition. Meanwhile, the removal rates of arsenic and phosphorus also improved by 14.4 % and 50.6 %, respectively, within 12 h, achieving near complete removal with little re-release risk, demonstrating excellent alkalinity adjustment and persistently simultaneous removal effects on phosphorus and arsenic. Furthermore, the coagulation aid of COS effectively inhibited the release of fulvic acid-like substances from algal cells on the 7th day. Meanwhile, it promoted the secretion of humic acid-like substances and microcystins production, as well as the release of fluorescent substances under hydraulic disturbance conditions. From the structural information presented by X-ray photoelectron spectroscopy (XPS), the precipitates mainly consisted of proteins and lipids derived from algal cells, calcium carbonate, ferric hydroxide, and trace amounts of arsenite, further confirming their precipitated mechanism of algal cell combined through COS and IS. The results provide scientific support for the practical application of COS in algal blooms and its subsequent environmental risk control.

ASTER data processing and fusion for alteration minerals and silicification detection: Implications for cupriferous mineralization exploration in the western Anti-Atlas, Morocco

Alteration minerals and silicification are typically associated with a variety of ore mineralizations and could be detected using multispectral remote sensing sensors as indicators for mineral exploration. In this investigation, the Visible Near-Infra-Red (VNIR), Short-Wave Infra-Red (SWIR), and Thermal Infra-Red (TIR) bands of the ASTER satellite sensor derived layers were fused to detect alteration minerals and silicification in east the Kerdous inlier for cupriferous mineralization exploration. Several image processing techniques were executed in the present investigation, namely, Band Ratio (BR), Selective Principal Component Analysis (SPCA) and Constrained Energy Minimization (CEM) techniques. Initially, the BR and SPCA processing results revealed several alteration zones, including argillic, phyllic, dolomitization and silicification as well as iron oxides and hydroxides. Then, these zones were mapped at sub-pixel level using the CEM technique. Pyrophyllite, kaolinite, dolomite, illite, muscovite, montmorillonite, topaz and hematite were revealed displaying a significant distribution in relation with the eastern Amlen region lithological units and previously detected mineral potential zones using HyMap imaging spectroscopy. Mainly, a close spatial association between iron oxides and hydroxide minerals, argillic, and phyllic alteration was detected, as well as a strong silicification was detected around doleritic dykes unit in Jbel Lkest area. A weighted overlay approach was used in the integration of hydrothermal alteration minerals and silicification, which allowed the elaboration of a new mineral alteration map of study area with five alteration intensities. ASTER and the various employed processing techniques allowed a practical and cost effective mapping of alteration features, which corroborates well with field survey and X-ray diffraction analysis. Therefore, ASTER data and the employed processing techniques offers a practical approach for mineral prospection in comparable settings.

Fine-tuning nanoflower-like Fe/Co hybrids with high content oxyhydroxide accelerating oxygen evolution kinetics

Iron hydroxide (FeOOH) is a potential active component in iron-based electrocatalysts for water electrolysis. However, its catalytic performance is constrained by its slow oxygen evolution reaction (OER) kinetics. Herein, we synthesized a nanoflower-like FeCo-hydro(oxy)oxides composite with tunable Fe/Co ratios (Fex-Coy) on nickel foam (NF) via a one-step electrodeposition technique. This method allows for precise control over the morphology and composition of the hybrid nanoflowers. The optimized Fe9-Co1 discloses favorable OER performance with a low overpotential of 222 mV at 50 mA cm−2 and demonstrates good stability exceeding 60 h at 10 mA cm−2. Further, an assembled Fe9-Co1(+)||Pt/C(−) dual-electrode configuration achieves a low cell voltage of 1.73 V at the current density of 100 mA cm−2 for water splitting, with long-term stability for 70 h and minimal degradation. Studies indicate that the distinctive nanoflower morphology of Fe9-Co1 enhances active site exposure, while both FeOOH and reconstructed CoOOH serve as catalytic centers, contributing to the observed OER performance. This work introduces a facile approach for synthesizing OER electrocatalysts, underscoring the role of the high-valence state of Fe/Co as active sites in the OER process.

Applying Red Mud in Cadmium Contamination Remediation: A Scoping Review.

Red mud is an industrial solid waste rarely utilized and often disposed of in landfills, resulting in resource waste and environmental pollution. However, due to its high pH and abundance of iron and aluminum oxides and hydroxides, red mud has excellent adsorption properties which can effectively remove heavy metals through ion exchange, adsorption, and precipitation. Therefore, red mud is a valuable resource rather than a waste byproduct. In recent years, red mud has been increasingly studied for its potential in wastewater treatment and soil improvement. Red mud can effectively reduce the migration and impact of heavy metals in soils and water bodies. This paper reviews the research results from using red mud to mitigate cadmium pollution in water bodies and soils, discusses the environmental risks of red mud, and proposes key research directions for the future management of red mud in cadmium-contaminated environments.

Control of phosphorus release from sediment by the combined use of Elodea nuttallii, hydrous ferric oxide, zeolite and calcite: Efficiency, mechanism and response of bacterial communities

The effectiveness of Elodea nuttallii combined with a mixture of hydrous ferric oxide, zeolite and calcite (HZC) to reduce the internal loading of phosphorus (P) from sediment and its mechanism were studied, and the effect of Elodea nuttallii combined with HZC on the composition and function of the microbial communities in the surface sediment was also investigated. The results showed that the combination utilization of Elodea nuttallii and HZC can decrease the risk of phosphorus liberation from sediment to the overlying water, and the controlling efficiency of Elodea nuttallii combined with HZC was higher than that of Elodea nuttallii or HZC alone. The passivation of labile P measured by diffusive gradient in thin film device and mobile P played a crucial role in the control of internal P loading from sediment by the combined Elodea nuttallii + HZC treatment. HZC capping had a promoting effect on the growth of Elodea nuttallii. This was beneficial to the absorption of phosphorus from sediment by Elodea nuttallii. The combined application of Elodea nuttallii and HZC not only had a certain negative effect on the diversity of bacteria in the surface sediment, but also changed the microbial compositions of the surface sediment at the levels of phylum and genus. However, the microbial communities in the surface sediment still can perform good ecological function. The above results suggest that the combined application of Elodea nuttallii and HZC has a high potential in the management of internal P loading from sediment.

Novel use of the electrocatalytic oxidation process with Fe-DSA dual anode configuration for leachate treatment: Significance of in situ ferrate generation

The leachate produced by waste transfer stations (WTSs) contains substantial amounts of refractory organic matter and ammonia, necessitating on-site treatment. In this study, a novel electrocatalytic oxidation (ECO) process with Fe-DSA dual anode configuration was established for leachate pretreatment. In this configuration, chloride in the leachate was converted to active chlorine by the DSA anode, while ferric hydroxide (Fe(OH)3) was produced from Fe anode. As a result, Fe (VI) was in situ formed through the reactions between active chlorine and Fe(OH)3. Simultaneous and efficient removal of COD and NH4+-N in the ECO process with Fe-DSA dual anode configuration was achieved, significantly improving leachate biodegradability compared with the Fe–Fe and DSA-DSA dual anode configurations. The transformation characteristics of organic compounds in the ECO process were investigated through the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) analysis. The ECO process with Fe-DSA dual anode configuration promoted the removal and transformation of lignins/carboxylic rich alicyclic molecules (CRAM)-like and tannins compounds with biologically refractory properties, as well as S-containing compounds with biological toxicity. Further X-ray photoelectron spectroscopy (XPS) analysis revealed that iron oxides, amorphous Fe-(oxy) hydroxide, and amorphous Fe(OH)3 produced by Fe (VI) decomposition in the ECO process with Fe-DSA dual anode configuration enhanced removal performance through coagulation. In addition, the contribution of different active species to organic matter removal in the ECO process was quantified by quenching experiments. High-valent iron oxidation dominated the ECO process with Fe-DSA dual anode configuration, while active chlorine oxidation, •OH oxidation and coagulation synergistically contributed to organic matter removal.

Transformative Dynamics: Self-Assembly of Iron Oxide Hydroxide Nanorods into Iron Oxide Microcubes for Enhanced Perfluoroalkyl Substance Remediation.

We report the controlled synthesis of iron oxide microcubes (IOMCs) through the self-assembly arrays of ferric oxide hydroxide nanorods (NRs). The formation of IOMCs involves a complex interplay of nucleation, self-assembly, and growth mechanisms influenced by time, thermal treatment, and surfactant dynamics. The self-assembly of vertically aligned NRs into IOMCs is controlled by dynamic magnetism properties and capping agents like cetyltrimethylammonium bromide (CTAB), whose concentration and temperature modulation dictate growth kinetics and structural uniformity. These controlled structural growths were obtained via a hydrothermal process at 120 °C at various intervals of 8, 16, 24, and 32 h in the presence of CTAB as the capping agent. In this hydrothermal method, the formation of vertically oriented NR arrays was observed without the presence of ligands, binders, harsh drying techniques, and solvent evaporation. The formation of the self-assembly of NRs to IOMCs is obtained with an increase in saturated magnetization to attain the most stable state. The synthesized IOMCs have a uniform size, quasi-shape, and excellent dispersion. Due to its excellent magnetic and catalytic properties, IOMCs were employed to remove the various emerging pollutants known as per- and polyfluorinated substances (PFAS). Various microscopic and spectroscopic techniques were employed for the characterization and interaction studies of IOMCs with various PFAS. The interaction between IOMCs and perfluoroalkyl substances (PFAS) was investigated, revealing strong adsorption tendencies facilitated by electrostatic interactions, as evidenced by UV-vis and FT-IR spectroscopic studies. Furthermore, the higher magnetic and positive surface charge of IOMCs is responsible for an effective remediation eliminating any secondary pollution with ease of recovery after the sorption interaction studies, thereby making it practically worthwhile.

Coprecipitation of Fe/Cr Hydroxides at Organic-Water Interfaces: Functional Group Richness and (De)protonation Control Amounts and Compositions of Coprecipitates.

Iron/chromium hydroxide coprecipitation controls the fate and transport of toxic chromium (Cr) in many natural and engineered systems. Organic coatings on soil and engineered surfaces are ubiquitous; however, mechanistic controls of these organic coatings over Fe/Cr hydroxide coprecipitation are poorly understood. Here, Fe/Cr hydroxide coprecipitation was conducted on model organic coatings of humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA). The organics bonded with SiO2 through ligand exchange with carboxyl (-COOH), and the adsorbed amounts and pKa values of -COOH controlled surface charges of coatings. The adsorbed organic films also had different complexation capacities with Fe/Cr ions and Fe/Cr hydroxide particles, resulting in significant differences in both the amount (on HA > SA(-COOH) ≫ BSA(-NH2)) and composition (Cr/Fe molar ratio: on BSA(-NH2) ≫ HA > SA(-COOH)) of heterogeneous precipitates. Negatively charged -COOH attracted more Fe ions and oligomers of hydrolyzed Fe/Cr species and subsequently promoted heterogeneous precipitation of Fe/Cr hydroxide nanoparticles. Organic coatings containing -NH2 were positively charged at acidic pH because of the high pKa value of the functional group, limiting cation adsorption and formation of coprecipitates. Meanwhile, the higher local pH near the -NH2 coatings promoted the formation of Cr(OH)3. This study advances fundamental understanding of heterogeneous Fe/Cr hydroxide coprecipitation on organics, which is essential for successful Cr remediation and removal in both natural and engineered settings, as well as the synthesis of Cr-doped iron (oxy)hydroxides for material applications.

Selection of parenteral iron supplement for iron deficiency anemia: A review

The article reviews medicinal products for the treatment of iron deficiency conditions and iron deficiency anemia, the prevalence of which is about 30% among the world population. Iron deficiency is a significant cause of anemia, which can lead to hospitalization and even death. In case of intolerance or ineffectiveness of oral formulations of iron supplements, if it is necessary to replenish the iron level quickly, trivalent iron formulations for intravenous administration are used. These supplements are iron complexes with an iron hydroxide core surrounded by a carbohydrate shell. Iron formulations for intravenous administration can be divided into drugs of the "old" and "new" generation. One of the most studied and popular representatives of the "new" generation is iron carboxymaltose (ICM). The results of clinical studies showed that ICM better and faster increases hemoglobin concentration and replenishes iron stores in patients compared to the "old" generation formulations and also has a more favorable safety profile. Large doses of ICM can be administered in a short time, saving resources and increasing patient satisfaction. The injection of large doses of iron with a small number of infusions in the case of ICM is more economically beneficial for all departments of medical institutions, as it significantly reduces the total cost of medical care. Intravenous iron plays an essential role in the perioperative treatment of iron deficiency anemia, especially in elective surgery. Currently, there is a reliable evidence base confirming the efficacy and safety of intravenous iron formulations in chronic kidney disease, inflammatory bowel disease, heart failure, gynecological and obstetric diseases, and cancer.

Ortho-parahydrogen catalyst test facility

With the growing interest in hydrogen as one pillar of the future energy economy, the relevance of hydrogen liquefaction for storage and transportation is increasing rapidly. However, the liquefaction process still offers much potential for improvement in terms of cost and efficiency. One problem faced with achieving more cost- and energy-efficient liquefiers is the uncertainty associated with the dimensioning of the ortho-para converters. Literature data on the existing ortho-para catalysts stem mainly from the 1950s and 1960s and are partly inconsistent. Therefore, a new facility for the comprehensive investigation of catalytic ortho-parahydrogen conversion was set up at the Dresden University of Technology (TU Dresden) as part of the government-funded HyCat (“Improvement of the Ortho-Para-Catalysts for Hydrogen Liquefaction”) project. It enables the testing of catalysts in the whole operational range of ortho-para converters in modern large-scale liquefaction plants by allowing the independent variation of temperature, pressure, flow rate, inlet ortho-para ratio, and sample reactor internal geometry. The setup has been tested and validated preliminarily. It can soon be used to produce new high-quality data sets on the performance of the commercial catalyst Ionex (hydrous ferric oxide), for the qualification of alternative catalysts, and for gaining a deeper understanding of the reaction kinetics involved.

Degradation of pharmaceuticals and other emerging pollutants employing bi-metal catalysts/magnesium and/or (green) hydrogen in aqueous solution

Contaminations by pharmaceuticals, personal care products, and other emerging pollutants in water resources have become a seriously burgeoning issue of global concern in the first third of the twenty-first century. As societal reliance on pharmaceuticals continues to escalate, the inadvertent introduction of these substances into water reservoirs poses a consequential environmental threat. Therefore, the aim of this study was to investigate reductive degradation, particularly, catalytic hydrogenation regarding model pollutants such as diclofenac (DCF), ibuprofen (IBP), 17α-ethinylestradiol (EE2), or bisphenol-A (BPA), respectively, in aqueous solutions at lab scale. Iron bimetals (zero valent iron, ZVI, and copper, Cu, or nickel, Ni) as well as zero valent magnesium (Mg, ZVM) in combination with rhodium, Rh, or palladium, Pd, as hydrogenation catalysts (HK), were investigated. Studies were executed through various short-term batch experiments, with multiple sample collections, over a total range of 120 min. The results indicated that DCF was attenuated at over 90 % when exposed to Fe-Cu or a Fe-Ni bimetal (applied as a single model pollutant). However, when DCF was part of a mixture alongside with IBP, EE2, and BPA, the attenuation efficacy decreased to 79 % with Fe-Cu and 23 % with Fe-Ni. Conversely, both IBP and BPA exhibit notably low attenuation levels with both bimetals, less than 50 %, both deployed as single substances or in mixtures. No reaction (degradation) products could be identified employing LC-MS, but sometimes a release of the parent pollutant when applying an acetic acid buffer could be noted to a certain extent, suggesting adsorption processes on corrosion products such as iron hydroxide and/or oxides. Surprisingly, Mg in combination with Rh (Rh-HK) or Pd (Pd-HK) showed a significantly rapid decrease in the concentrations of DCF, EE2, and BPA, in part up to approximately 100 %, that is, within a few minutes only in part due to hydrogenation degradation reactions (related reaction products could actually be identified by LC-MS; adsorption processes were not observed here). Moreover, kinetic modeling of the DCF degradation with Mg-Rh-HK was conducted at different temperatures (15 °C, 20 °C, 25 °C, 35 °C) and varied initial concentrations (2.5 mg/L, 5.0 mg/L, 7.5 mg/L, 10.0 mg/L). The outcomes prove that the degradation of DCF at the Rh-HK’s surface followed a modified first-order kinetics, most probably by catalytic hydrodehalogenation and subsequent hydrogenation of the aromatic moieties (molecular hydrogen was provided by the corrosion of Mg). From the determined reaction rate constants at four different temperatures, the activation energy was estimated to be 59.6 kJ/mol by means of the Arrhenius equation what is in good agreement with similar results reported in the literature. This coupled hydrodehalogenation and hydrogenation approach may be upscaled into a new promising technical process for comprehensively removing such pharmaceuticals and similar pollutants in sewage plants in a single step, furthermore, even in combination with adsorption by activated carbon and/or ozonation which have already been established at some sewage plants in Switzerland and Germany recently.

Fast degradation of vinyl chloride by green rust and nitrogen-doped graphene

Carbonaceous materials catalyze reductive dechlorination of chlorinated ethylenes (CEs) by iron(II) materials providing a new approach for the remediation of CE polluted groundwater. While most CEs are reduced via β-elimination, vinyl chloride (VC), the most toxic and recalcitrant CE, degrades by hydrogenolysis. The significance of carbon catalysts for reduction of VC is well documented for iron(0) systems, but hardly investigated with iron(II) materials as reductants. In this study, a layered iron(II)‑iron(III) hydroxide sulfate (green rust) was used as reductant for VC, with an N-doped graphene (NG), prepared by co-pyrolysis of graphene and urea, as catalyst. VC (80 μM) was completely reduced to ethylene within 336 h in the presence of 5 g Fe/L GR and 5 g/L NG pyrolyzed at 950 °C, following pseudo-first-order kinetics with a rate constant of 0.017 h−1. Dosing experiments demonstrated that dechlorination of VC takes place on the NG phase. Monitoring of hydrogen formation, cyclic voltammetry, and quenching experiments demonstrated that atomic hydrogen contributes significantly to the dehalogenation reaction, where NG is critical for formation of atomic hydrogen. CE competition experiments demonstrated the presence of specific VC reduction sites with hydrogenolysis being unaffected by concurrent β-elimination reactions. The system exhibited excellent performance in natural groundwaters and in comparison with iron(0) systems. This study demonstrates that GR + NG is a promising system for remediation of VC contaminated groundwater, and the mechanistic part of the study can be used as a reference for subsequent studies.

Self-forming barrier layer for carbon dioxide corrosion protection of mild steel in NaCl solution containing hydroxychavicol isolated from Piper betle L. leaf

Hydroxychavicol compound was isolated from Piper betle L. leaf and identified via preparative high performance liquid chromatography (Prep-HPLC) and nuclear magnetic resonance (NMR) spectroscopy. Hydroxychavicol compound was demonstrated to be a potential inhibitor for mild steel corrosion in carbon dioxide-containing environments due to the formation of a barrier layer on the steel surface. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the inclusion of hydroxychavicol in the aggressive environment made steel surfaces more homogeneous and smoother with a rough mean square roughness of 7.78 nm, whereas the steel surface was severely corroded in the blank solution. Moreover, X-ray photoelectron spectroscopy (XPS) results showed an enrichment of hydroxychavicol species combined with iron oxides and hydroxides on the mild steel surface. This can lead to the creation of a protective layer on the mild steel surface, thereby enhancing corrosion protection and localized inhibition. The work suggested a novel approach to isolate corrosion inhibitors from natural products, particularly agricultural by-products for mild steel in carbon dioxide and chloride ion environment with high inhibition performance.

Isolation and Electrochemical Analysis of a Facultative Anaerobic Electrogenic Strain Klebsiella sp. SQ-1.

Electricigens decompose organic matter and convert stored chemical energy into electrical energy through extracellular electron transfer. They are significant biocatalysts for microbial fuel cells with practical applications in green energy generation, effluent treatment, and bioremediation. A facultative anaerobic electrogenic strain SQ-1 is isolated from sludge in a biotechnology factory. The strain SQ-1 is a close relative of Klebsiella variicola. Multilayered biofilms form on the surface of a carbon electrode after the isolated bacteria are inoculated into a microbial fuel cell device. This strain produces high current densities of 625 μA cm-2 by using acetate as the carbon source in a three-electrode configuration. The electricity generation performance is also analyzed in a dual-chamber microbial fuel cell. It reaches a maximum power density of 560 mW m-2 when the corresponding output voltage is 0.59 V. The facultative strain SQ-1 utilizes hydrous ferric oxide as an electron acceptor to perform extracellular electricigenic respiration in anaerobic conditions. Since facultative strains possess better properties than anaerobic strains, Klebsiella sp. SQ-1 may be a promising exoelectrogenic strain for applications in microbial electrochemistry.

Materials analysis in three paintings of Thomas Gainsborough (1727–1788) by portable X-ray fluorescence

Three paintings of Thomas Gainsborough (1727–1788), one of the most influential English portrait painters of the late 18th century, from the collection of the Museu de Arte de São Paulo (MASP) - “Francis Rawdon” (1783–1784), “Portrait of Mrs. John Bolton” (1770), and “Drinkstone Park” (1747) - were investigated using portable X-ray fluorescence (pXRF), employing a W tube anode and an XR-100CR detector. These artworks represent the only paintings by Thomas Gainsborough located in the southern hemisphere. Through an analysis of the behavior of X-ray line net areas for all identified elements in various regions of the oil paintings, it was observed that XRF accurately identified the original materials: Lead White, Calcium Carbonate, Calcium Sulfate, Bone Black, Ivory Black, Yellow Iron Oxide, Prussian Blue, Vermillion, Red Iron Oxide, Umber, and Sienna Earth. Additionally, certain regions exhibited the presence of 19th century pigments: Zinc White, Cobalt Blue, and Chrome Yellow, indicating areas that had undergone restoration. The findings presented in this study align closely with results obtained from other investigations into paintings by Thomas Gainsborough.

Efficacy and mechanism of enhanced Sb(V) removal from textile wastewater using ferric flocs in aerobic biological treatment

Antimony contamination from textile industries has been a global environmental concern and the existing treatment technologies could not reduce Sb(V) to meet the discharge standards. To overcome this shortcoming, ferric flocs were introduced to expedite the biological process for enhanced Sb(V) removal in wastewater treatment plant (WWTP). For this purpose, a series of laboratorial-scale sequential batch reactor activated sludge processes (SBRs) were applied for Sb(V) removal with varied reactor conditions and the transformation of Fe and Sb in SBR system was investigated. Results showed a significant improvement in Sb(V) removal and the 20 mg L−1 d−1 iron ions dosage and iron loss rate was found to be only 15.2%. The influent Sb(V) concentration ranging 153–612 μg L−1 was reduced to below 50 μg L−1, and the maximum Sb(V) removal rate of the enhanced system reached about 94.3%. Furthermore, it exhibited high stability of Sb(V) removal in the face of antimonate load, Fe strike and matrix change of wastewater. Sludge total Sb determination and capacity calculation revealed decreasing in Sb adsorption capacity and desorption without fresh Fe dosage. While sludge morphology analysis demonstrated the aging and crystallization of iron hydroxides. These results verify the distinct effects of fresh iron addition and iron aging on Sb(V) removal. High-throughput gene pyrosequencing results showed that the iron addition changed microbial mechanisms and effect Fe oxidized bacterial quantity, indicating Sb(V) immobilization achieved by microbial synergistic iron oxidation. The present study successfully established a simple and efficient method for Sb(V) removal during biological treatment, and the modification of biological process by iron supplement could provide insights for real textile wastewater treatment.

In-Situ Nanoarchitectonics of Fe/Co LDH over Cobalt-Enriched N-Doped Carbon Cookies as Facile Oxygen Redox Electrocatalysts for High-Rate Rechargeable Zinc-Air Batteries.

The reality of long-term rechargeable and high-performance zinc-air batteries relies majorly on cost-effective and eminent bifunctional electrocatalysts, which can perform both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Herein, we demonstrate a new approach for the synthesis of in-situ-grown layered double hydroxide of iron and cobalt over a cobalt nanoparticle-enriched nitrogen-doped carbon frame (CoL 2:1) by a simple coprecipitation reaction with facile scale-up and explore its electrocatalytic ORR and OER activity for an electrically rechargeable zinc-air battery. Consequently, the developed composite displays excellent ORR and OER activity with an ORR half-wave potential of 0.84 V, a limiting current density of 5.85 mA/cm2, and an OER overpotential of 320 mV with exceptional stability. The outstanding bifunctionality index of the catalyst (ΔE = 0.72 V) inspired us to utilize it as a cathode catalyst in an in-house developed prototype zinc-air battery. The battery could easily supply a specific capacity of 804 mAh/g with a maximum peak power density of 161 mW/cm2. The battery exhibits an attractive charge-discharge profile with a lesser voltage gap of 0.76 V at 10 mA/cm2 with durability for a period of 200 h and a voltage efficiency of 97%, which surpassed the corresponding Pt/C + RuO2-based zinc-air battery. Further, a maximum load of 50 mA/cm2 could easily be sustained during cycling, revealing its outstanding stability. A series-connected two CoL 2:1-based zinc-air batteries effortlessly enlighten a pinwheel fan and LED panel simultaneously, revealing its practicality. The high electrical conductivity and greater specific surface area of Co/N-C and its robust attachment with Fe/Co LDH preserves both active sites, thereby resulting in exceptional performance. Our method is capable of being flexible enough to create various bifunctional Co/N-C-based composite electrodes, opening up a feasible pathway to rechargeable zinc-air batteries with maximum energy density.