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A chemical composition analysis of the leachate in the process of producing alumina from fly ash using the acid method was conducted.Aluminum and iron were found to be the main elements in the leachate, with an aluminum concentration of 263.5 g/L (calculated as aluminum chloride) and a total iron concentration of 4.4 g/L (calculated as FeO), where the Fe2+ concentration was 2.17 g/L (calculated as FeO). A kinetic study on the oxidation of ferrous ions by air, oxygen-enriched gas, and ozone was carried out. Kinetic equations for the oxidation of ferrous ions by these 3 gaseous oxidants were obtained, and the oxidation rates were compared. The oxidation rate by ozone was found to be 1.7 times that of oxygen-enriched gas and 1.9 times that of air. [ABSTRACT FROM AUTHOR]

Tyrosine kinase inhibitors of epidermal growth factor receptor (EGFR-TKIs), such as osimertinib, show great success in non-small-cell lung cancer patients with EGFR mutated tumors. However, almost all patients develop resistance to EGFR-TKIs owing to secondary EGFR mutations. Although genetic and irreversible resistance mechanisms have been proposed, little is known about non-genetic and reversible resistance mechanisms. From this perspective, a recent study revealed that acute drug exposure generates drug-tolerant persister cells (DTPs) as a form of non-genetic resistance. However, the biological characteristics of DTPs remain unclear. As lipid peroxidation is related to cancer progression and drug resistance, we focused on ferroptosis, namely programmed cell death induced by the accumulation of lipid peroxides, in DTPs. We examined the biological characteristics of ferroptosis in osimertinib-mediated DTPs derived from PC9 lung adenocarcinoma cells. Unlike PC9 cells, established PC9 DTPs were highly sensitive to the ferroptosis inducer RSL3. Accordingly, PC9 DTPs had increased levels of lipid reactive oxygen species and ferrous ion accumulation. Moreover, RSL3-mediated cell death in PC9 DTPs was completely rescued by treatment with the iron chelator deferoxamine. These results suggest that PC9 DTPs showed increased intracellular ferrous ion accumulation and were susceptible to ferroptosis. • Osimertinib-tolerant cells are vulnerable to ferroptosis inducer RSL3. • Lipid ROS and ferrous ion are elevated in osimertinib-tolerant cells. • RSL3 treatment blocked the emergence of osimertinib-tolerant cells. • DFO diminished RSL3-mediated cell death in osimertinib-tolerant cells. [ABSTRACT FROM AUTHOR]

The ferrous ion・activated sodium persulfate technique is used for the removal of formaldehyde in wood processing wastewater, the main controlling factors were determined by single-factor experiments as sodium persulfate concentration, ferrous ion concentration and temperature ・ The response surface methodology yielded the optimal conditions for formaldehyde removal by ferrous activated sodium persulfate as follows: sodium persulfate* formaldehyde (molar ratio) 35： 1, ferrous ions* formaldehyde (molar ratio) 5・ 5* 1, pH 4 and 60 °C rection 30 min・ Under the optimal conditions, the formaldehyde removal rate was 96. 88%. [ABSTRACT FROM AUTHOR]

Fe3+strongly interferes the determination of Fe2+ by spectrophotometric method during the Fenton process. This study evaluated a modified spectrophotometric method for the determination of Fe2+ at the presence of Fe3+ during the Fenton process. Based on the traditional o-phenanthroline method, the modified method used a masking agent, namely F–, to form complex with Fe3+ to eliminate its interference. The optimal dosage of F– was dependent on the concentration of Fe3+ and the best molar ratio of F–:Fe3+ was 20:1. The optimal solution pH was found out to be around 3.0 for the modified method to get reliable results. The selected seven metal ions had negligible influence on the determination of Fe2+ by the modified method. The upper limit for the molar ratio of Fe3+:Fe2+ in the solution was 20:1 (95%), above which relatively high error could be reached. The average recovery rate of iron ion was determined to be 98.9%, which suggests that the modified o-phenanthroline method is ideal for the study of iron ion changing during the Fenton process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe(II) enhanced the selective adsorption strength and stability of CA. • The synergistic mechanism of Fe(II) and CA was revealed. • Selective flotation separation of scheelite and cassiterite using Fe(II)/CA was realized. • Synergistic and selective adsorption model of Fe(II) and CA was established. • Fe(II) promoted the selective adsorption of CA on cassiterite surface. Citric acid (CA) exhibits weak inhibitory on some oxidized gangue minerals owing to its relatively few hydrophilic polar groups (OH and COOH). This study investigate the synergistic mechanism of ferrous ions (Fe2+) to enhance both the selective adsorption capacity and stability of CA. The separation of scheelite and cassiterite through a flotation process was successfully achieved using a Fe2+/CA mixed depressant. Micro-flotation test results revealed that with the addition of Fe2+/CA, 84.60 % of scheelite and 23.64 % of cassiterite were recovered in the foam concentrate, with grades of 66.26 % and 17.73 %, respectively. Fe2+/CA had a strong depressing effect on cassiterite, resulting in a 69.30 % decrease in its recovery and a 20.33 % decrease in its grade. This indicates the effective separation of scheelite from cassiterite. Fe2+/CA exhibited a high adsorption affinity for the cassiterite surface, which mainly comprised L3–, Fe2+, and FeOH+ components. Additionally, the FeOH+ complex, formed from the pre-reaction between Fe2+ and CA, exhibited significant chemical adsorption at the Sn active sites, thereby depressing cassiterite. The high-intensity adsorption peaks at cracks and the significant increase in the normalized intensity of FeOH+ on the cassiterite surface indicated that the FeOH+ complex had stronger adsorption on cassiterite and selectively depressed cassiterite. This enhanced both the selective adsorption capacity and stability of CA on the cassiterite surface. The Fe2+/CA mixed depressant achieved efficient flotation separation of scheelite and cassiterite. [ABSTRACT FROM AUTHOR]

The widespread existence of antibiotics in the environment has attracted growing concerns regarding the potential adverse effects on aquatic organisms, ecosystems, and human health even at low concentrations. Extensive efforts have been devoted to developing new methods for effective elimination of antibiotics from wastewater. Herein, a novel process of Fe2+ catalytically enhanced vacuum ultraviolet (VUV) irradiation was proposed as a promising approach for the removal of antibiotic trimethoprim (TMP) in water. Compared with UVC photolysis, VUV photolysis, and UVC/Fe2+, VUV/Fe2+ could increase the pseudo-first-order reaction rate constant of TMP removal by 6.6–38.4 times and the mineralization rate by 36.5%–59.9%. The excellent performance might originate from the synergistic effect of VUV and Fe2+, i.e., VUV irradiation could effectively split water and largely accelerate the Fe3+/Fe2+ cycle to generate more reactive oxygen species (ROS). EPR results indicated that •OH and O 2 •- were identified as the main ROS in the UVC/Fe2+ and VUV/Fe2+ processes, while •OH, O 2 •-, and 1O 2 were involved in the VUV process. The operating parameters, such as Fe2+ dosage and initial TMP contents, were evaluated and optimized. Up to 8 aromatic intermediates derived from hydroxylation, demethylation, carbonylation, and methylene group cleavage were identified by UPLC-QTOF-MS/MS technique, the possible pathways of TMP degradation were proposed. Finally, the acute and chronic toxicity of intermediates formed during TMP degradation in the VUV/Fe2+ process were also evaluated. [Display omitted] • VUV/Fe2+ process enhanced TMP removal with lower EE/O compared with VUV or UVC/Fe2+. • Synergistic effect of VUV irradiation and Fe2+ significantly promoted TMP degradation. • •OH and O 2 •- were proved to be the dominant ROS in the VUV/Fe2+ process. • Mechanism and possible pathway of TMP degradation were proposed. • The variation of acute toxicity during TMP degradation was evaluated. [ABSTRACT FROM AUTHOR]

A new spiropyran-based fluorescent probe was developed for dual detection of Fe2+ ion and pH. Addition of Fe2+ and Ag+ to the probe solution enhanced the fluorescence intensity by 6 and 5 fold, respectively. Addition of Fe3+, Hg2+ and Ni2+ caused slight increase in the fluorescence intensity of the probe. While addition of other common metal ions did not bring about substantial change of the fluorescence. Thus the probe can be used for fluorescence turn-on detection of Fe2+ ion in ethanol/water (9:1) medium. The detection limit of the probe for Fe2+ is 0.77 µM. The suitable pH range for the probe to detect Fe2+ was pH 3 − 9. Other metal ions including Li+, Na+, K+, Ag+, Cu2+, Zn2+, Co2+, Ni2+, Mn2+, Sr2+, Hg2+, Ca2+, Mg2+, Al3+, Cr3+, and Fe3+ did not cause marked interference with Fe2+ recognition. The color of the probe solution was yellow at pH 1 − 2 and colorless at other pH values. The fluorescence intensity of the probe was low at pH 1 − 12 and increased significantly when the pH was 13 and 14, indicating that the probe can be used as a colorimetric and fluorescent probe for sensing extremely acidic or extremely alkaline conditions through different channels. [ABSTRACT FROM AUTHOR]

Co-fermentation of sewage sludge and algae was performed for enhancing the hydrogen production, and the effect of Fe2+ on co-fermentation process was examined. Results showed that both co-fermentation process and Fe2+ addition promoted hydrogen production. Highest hydrogen production of 28 mL/100 mL (14.8 mL H 2 /g VS added) was obtained from the co-fermentation group with 600 mg/L Fe2+ addition, which was 2.15 times, 2.00 times and 1.87 times of mono-fermentation of sludge, mono-fermentation of algae, and the co-fermentation group without Fe2+ addition. Both volatile solids and protein degradation were stimulated by co-fermentation process. Microbial analysis showed that co-fermentation groups with Fe2+ addition enriched Clostridium sensu stricto 13, Clostridium tertium and Terrisporobacter , which were positively correlated with cumulative hydrogen production. This study suggested that the co-fermentation of sludge and algae in the presence of Fe2+ could significantly improve the hydrogen production by stimulating the hydrogen-producing metabolism. Image 1 • Co-fermentation of sewage sludge and algae was performed for H 2 production. • Fe2+ addition promoted the substrate utilization and H 2 production. • H 2 production was positively related with soluble organics and Fe2+ in substrate. • Fe2+ addition enriched Clostridium sp. which was favorable for H 2 production. [ABSTRACT FROM AUTHOR]

The performance of trichloroethylene (TCE) degradation by sodium percarbonate (SPC) activated with Fe(II) in the presence of 3.0 g/L sodium dodecyl sulfate (SDS) as well as the role of SDS in the SPC/Fe(II) system was investigated since SDS is a common surfactant used in groundwater remediation for improving TCE dissolution to the aqueous phase. The results showed that though the introduction of SDS could inhibit the TCE degradation, the inhibiting effect was less with the increasing SDS dose. In the presence of SDS, TCE could be completely removed with the SPC/Fe(II)/TCE molar ratio of 40/80/1. Experiments with free radical probe compounds and radical scavengers elucidated that TCE was mainly oxidized by both HO· and O2-·. A weakly acidic environment was more favorable to TCE degradation. Nevertheless, HCO3- at a high concentration had a strongly inhibitive effect on the TCE degradation but the influence of Cl− was negligible. Finally, the excellent TCE degradation achieved in actual groundwater demonstrated that Fe(II) activated SPC technique was applicable in the remediation of TCE contaminated groundwater in the presence of SDS. Practitioner points: The effects of SDS were evaluatedSPC/Fe(II)/SDS system applied to remediate TCEThe mechanism of HO· and O2-· generation had been investigatedCl− and HCO3- affected TCE degradation at different levelsThe performance of TCE removal in actual groundwater had been studied [ABSTRACT FROM AUTHOR]

At first, C-dots/manganese oxide nanocomposite was synthesized chemically. The presence of Mn3O4 nanostructures and C-dots in the synthesized nanocomposite was confirmed by using of XRD, EDS, FTIR and TEM. The proposed method for synthesis is easy and cheap. The Mn3O4/C-dots nanocomposite shows oxidase-like activity, which is higher than oxidase-like activity of Mn3O4 nanoparticles. In this manner, detection of ferrous ion was possible by using of a competitive reaction between 3,3′,5,5′-tetramethylbenzidine and Fe2+ ion in the presence of the synthesized nanocomposite. So, a sensitive and selective colorimetric sensor for determination of Fe2+ ion was introduced. The linear range and detection limit for determination of Fe2+ ion were obtained as 0.03–0.83 μM and 0.03 μM, respectively. [ABSTRACT FROM AUTHOR]

• Fe(Ⅱ) added to OAR achieved 32.0% sludge reduction and improved nitrate removal rate. • Fe(Ⅱ) addition promoted the electron transfer between endogenous organics and nitrogen species. • Extracellular polymeric substances significantly changed with Fe(Ⅱ) participation. • Fe(Ⅱ) caused the variation in microbial composition and the regulation of gene functions. The creation of large amounts of excess sludge and residual nitrogen are critical issues in wastewater biotreatment. This study introduced Fe(II) into an oligotrophic anaerobic reactor (OAR Fe) that was implemented to modify an anoxic-oxic process to motivate in-situ sludge reduction and enhance denitrification under an effective electron shuttle among organic matter, nitrogen, and Fe. The addition of 15 mg L−1 Fe(II) resulted in a sludge reduction efficiency reached 32.0% with a decreased effluent nitrate concentration of 33.3%. This was mostly attributed to the electron transfer from Fe(II) to organic matters and nitrogen species in OAR Fe. The participation of Fe(II) led to the upregulation of Geothrix and Terrimonas , which caused active organic matter hydrolysis and cell lysis to stimulate the release of extracellular polymeric substances (EPS) and substance transfer between each layer of EPS. The higher utilization of released bioavailable dissolved organic matter improved endogenous denitrification, which can be combined with iron autotrophic denitrification to realize multiple electron donor-based nitrogen removal pathways, resulting in an increased nitrate removal rate of 58.2% in the absence of external carbon sources. These functional bacteria associated with the transformation of nitrogen and carbon and cycling between ferrous and ferric ions were enriched in OAR Fe , which contributed to efficient electron transport occurred both inside and outside the cell and increased 2,3,5-triphenyltetrazolium chloride electronic transport system activity by 46.9%. This contributed to the potential operational costs of chemical addition and sludge disposal of Fe-AO being 1.9 times lower than those of conventional A2O processes. These results imply that the addition of ferrous ions to an oligotrophic anaerobic zone for wastewater treatment has the potential for low-cost pollution control. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, hydrogel beads [SPI/HP-Fe (II)] were prepared by cross-linking soybean isolate protein (SPI) and hawthorn pectin (HP) with ferrous ions as a backbone, and the effects of ultrasound and Fe2+ concentration on the mechanical properties and the degree of cross-linking of internal molecules were investigated. The results of textural properties and water-holding capacity showed that moderate ultrasonic power and Fe2+ concentration significantly improved the stability and water-holding capacity of the hydrogel beads and enhanced the intermolecular interactions in the system. Scanning electron microscopy (SEM) confirmed that the hydrogel beads with 60% ultrasonic power and 8% Fe2+ concentration had a denser network. X-ray photoelectron spectroscopy (XPS) and atomic absorption experiments demonstrated that ferrous ions were successfully loaded into the hydrogel beads with an encapsulation efficiency of 82.5%. In addition, in vitro, simulated digestion experiments were performed to understand how the encapsulated Fe2+ is released from the hydrogel beads, absorbed, and utilized in the gastrointestinal environment. The success of the experiments demonstrated that the hydrogel beads were able to withstand harsh environments, ensuring the bioactivity of Fe2+ and improving its bioavailability. In conclusion, a novel and efficient ferrous ion delivery system was developed using SPI and HP, demonstrating the potential application of SPI/HP-Fe (II) hydrogel beads as an iron supplement to overcome the inefficiency of intake of conventional iron supplements. • Fe2+ cross-linked SPI/HP hydrogel beads had excellent properties. • Ultrasonic power could promote the interaction between molecules in the system. • Fe2+ could be encapsulated in hydrogel and its utilization efficiency was improved. [ABSTRACT FROM AUTHOR]

Emulsion explosives (EE) are one of a typical industrial explosive that is widely used in engineering and mining applications due to its high detonation performance and ideal safety characteristics. However, since an EE is a multicomponent mixture with an oil-in-water structure, the presence of some substances or impurities can reduce the safety of the EE and cause accidents. We investigated the influence of ferrous ion on the thermal behavior and stability of EE during production and storage. The thermogravimetry–differential scanning calorimetry and water solubility method were selected for the assessment of thermal behavior and stability of the EE. According to kinetic parameters, the apparent activation energy (Ea) of the EE and the EE with ferrous ion additives was determined. The results indicated that ferrous ion could decrease the thermal decomposition temperature and Ea of EE. Moreover, the degree of crystallization of ammonium nitrate increases as storage time and ferrous ion content increases. It is of important significance to reduce the hazards of the EE and to improve both safety and stability during production and storage. [ABSTRACT FROM AUTHOR]

This work presented an easy synthesis method for water‐soluble, green and fluorescent silver nanoclusters with poly (methacrylic acid) (AgNCs@PMAA) and preliminarily explored their ability to detect Fe2+ by measuring their fluorescence quenching. The acquired AgNCs@PMAA showed steady, selective, and highly sensitive detection of Fe2+. The Fe2+ detection limit for AgNCs@PMAA was 3 μM, and a linear relationship was observed at 5–150 μΜ ion concentration. AgNCs@PMAA had no biological toxicity and could be used for in vivo imaging and detection of iron ions. This fluorescence detection method based on novel nanomaterials exhibits future application in biolabeling, biosensing, and other purposes. [ABSTRACT FROM AUTHOR]

Electrically resistive CaF 2 -based slags are extensively used in many metallurgical processes such as electroslag remelting (ESR). Chemical and electrochemical reactions as well as transport of ions in the molten slag (electrolyte) are critical phenomena for those processes. In this paper, an electrochemical system including two parallel, planar electrodes and a completely dissociated electrolyte operating under a DC voltage is modeled. The transport of ions by electro-migration and diffusion is modeled by solving the Poisson–Nernst–Planck (PNP) equations using the Finite Volume Method (FVM). The non-linear Butler–Volmer equations are implemented to describe the boundary condition for the reacting ions at the electrode–electrolyte interface. Firstly, we study a binary symmetrical electrolyte, which was previously addressed by Bazant et al. (2005), to verify the numerical model. Secondly, we employed the model to investigate our target CaF 2 –FeO system. The electrolyte is consisted of reacting (Fe2+) and non-reacting (Ca+2, O2−, F−) ions. Spatial distributions of concentrations of ions, charge density, and electric potential across the electrolyte at steady state are analyzed. It is found that the Faradaic reaction of the ferrous ion (Fe2+) has negligible impact on the electric potential field at very low current density (<1 A m−2). The strong impact of electric double layer (EDL) capacitance on the system behavior is addressed throughout our analysis. Furthermore, a linear relationship among activation (surface) overpotential and current density (<1600 A m−2) is observed. The simulation results helps to explain some phenomena observed in the ESR process. The higher melt rate for an anodic ESR electrode than a cathodic one is linked to the interfacial potential drop. It is found that the anodic potential drop near the anode is larger than the cathodic voltage drop near the cathode. The results are tested against an experiment. [ABSTRACT FROM AUTHOR]

• A μPAD with two layers was developed to monitor Cu2+, Fe2+ and free chlorine simultaneously. • The detection limits of μPAD for single analyte were less or equal to each Chinese Drinking Water Standard concentration. • The μPAD exhibited good applicability for real use in different kinds of drinking water. Cu2+, Fe2+ and free chlorine are three important analytes in drinking water. Firstly, the μPAD for single analyte was easily fabricated. Detection limits for Cu2+, Fe2+ and free chlorine were 0.1 mg L−1, 0.1 mg L−1 and 0.2 mg L−1, respectively, less or equal to each Chinese Drinking Water Standard concentration and lower than those of most commercially available testing strips. Another μPAD with two layers was then developed to monitor and report the safety level of these three analytes in drinking water simultaneously. Moreover, the μPADs for Fe2+ and free chlorine provided more distinguishable colors to users with naked eyes. The as-fabricated μPAD not only demonstrated excellent anti-interference capability, production reproducibility, but also exhibited good applicability for real use in different kinds of drinking water. [ABSTRACT FROM AUTHOR]

Inspired by the melanin and marine mussel binders, the super-adhesion polydopamine (PDA) plays a unique role in the surface modification of materials. In this work, dopamine was coated on silk fabric in a short time by rapid oxidative polymerization, and Fe2+ was wrapped by using the reactive groups on the surface of polydopamine (PDA) as a secondary platform. The hydrophobic, flame retardant and UV resistant properties of the treated fabric were investigated. The surface morphology, crystal form, composition and carbon residue morphology of the treated silk fabric were analyzed. The PDA coating and Fe2+ mineralization wrap changed the morphological structure of the silk fabric, giving the fabric superhydrophobicity, flame retardancy and UV shielding ability. In particular, the wrapped Fe2+ mineralization formed micro-nano particles and a rough structure on the surface of silk fibers, endowing silk fabric with superhydrophobicity. The PDA coating also increased the carbonization property of the fabric during combustion. Furthermore, the formation of metal salts by combustion of mineralized materials was helpful to prevent heat and gas sources, thus making silk fabric have good flame retardancy, showing potential applications as multifunctional advanced textiles. • Polydopamine is coated on the fabric by rapid oxidative polymerization. • Environmentally friendly flame retardant was successfully finished onto the fabric. • Finished fabric has multi-functional: superhydrophobic, flame retardant, UV resistant. • Flame retardant properties of the finished fabric have excellent stability. • Provides new idea for the preparation of multifunctional textiles. [ABSTRACT FROM AUTHOR]

• Sonication remarkably affects ilmenite flotation performance. • Sonication increased chemical adsorption of oleate ions on ilmenite surface. • Flotation recovery is improved via significant conversion of Fe2+ to Fe3+. • Possibility of improved selective flotation of ilmenite from gangue minerals. Herein we investigate the flotation and possible adsorption mechanism on the surface of ilmenite and the changes in the surface composition of ilmenite before and after ultrasonic pre-treatment through flotation tests, Fourier-transform infrared (FTIR) spectroscopy, zeta potential measurement, X-ray photoelectron spectroscopy (XPS), and microcalorimetry. The flotation results reveal that, under optimum conditions, sonication has a remarkable effect on the flotation of ilmenite. The maximum flotation recoveries of raw and ultrasonically treated ilmenite in the pH range 4–5 are 43.17 and 89.54%, respectively. The zeta potential of the pre-treated ilmenite shifted toward negative values, thus shifting the iso-electric point from pH 6.2 to pH ∼4.2. The FTIR spectra and zeta potential values indicate that the ultrasonic pre-treatment helped enhance the chemical adsorption of oleate ions on the surface of ilmenite. The results of microcalorimetry analysis suggest that the adsorption heat released (−Q ads) from ultrasonically treated ilmenite is more than that released from raw ilmenite. The XPS analysis confirmed that the relative content of Fe3+ increased from 36.87 to 61.84% following the ultrasonic pre-treatment for 5 min in the pH range 4–5. After the treatment, Fe2+ ions on the ilmenite surface are abundantly oxidised to Fe3+ ions. The significant conversion of Fe2+ to Fe3+ helped improve the flotation recovery of ilmenite over a wide pH range. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new N-oxide based and turn on fluorescent probe for Fe2+ was developed. • The probe possessed a high selectivity for Fe2+ among various biologically relevant species and fast rapid response. • Monitoring Fe2+ with TPM fluorescence imaging for the first time. Abstract Iron is an essential element for human body, involved in important biochemical processes in the body, especially in biological oxidation. Misregulation of iron levels in the cell is concerned with serious diseases. Here, a novel two photon and turn on NIR-fluorescent probe based ICT for detection of Fe2+ is first reported. The probe exhibited brilliant selectivity and excellent sensitivity (DL = 4.5 μM), rapid response (15 min) and "naked-eye colorimetric sensor" for monitoring of Fe2+. More importantly, the probe was successfully applied to real-time monitor Fe2+ in living cell through two-photon microscopy fluorescence imaging with excitation 680 nm. [ABSTRACT FROM AUTHOR]

Abstract As obligate anaerobes, anammox bacteria are sensitive to oxygen, which might hinder the maximization of anammox activity. However, there are very few effective strategies to rapidly recover anammox activity after its deterioration under exposure of oxygen. In this study, the activity recovery of anammox bacteria encountering dissolved oxygen (DO) exposure (0.2 and 2.0 mg L−1) were compared by three strategies in short-term experiments, nZVI, Fe(II) dosing, and N 2 purging. nZVI is more effective in recovering anammox activity with a high DO exposure (2 mg L−1), compared to a low DO exposure (0.2 mg L−1). After inhibiting by 2.0 mg L−1 DO, anammox activity recovery (normalized to the control) was ranked in the order of nZVI (5 mg L−1) addition (63 ± 8.2%) > Fe(II) (5 mg L−1) addition (41 ± 8.0%) >N 2 purging (39 ± 4.0%). In contrast to Fe(II) ion additions, the shell structure of nZVI combined with the buffering effect of biomass-extracellular polysaccharide (EPS) prevented the sharp pH variation and excessive dissolved Fe(II)/Fe(III) in solution. Under such circumstances, nZVI addition (5 and 25 mg L−1) increased the intracellular reactive oxygen species (ROS) to a moderate level (<200%), which might be responsible for the better activity recovery of anammox than that of Fe(II) addition and N 2 purging. Specifically, 5 mg L−1 nZVI dosage moderately enhanced the intracellular O 2 − production (∼150% of the control) after scavenging 2.0 mg L−1 DO, and the anammox activity recovered better than that of both 5 and 25 mg L−1 Fe(II) ions additions. However, high dosage nZVI (75 mg L−1) inhibited anammox activity in spite of low or high DO exposure. Our findings elucidate that appropriate amount of nZVI (short-term dosing) can rapidly recover anammox activity when anammox bacteria encountering oxygen exposure accidentally and could be useful in facilitating the robust operation of anammox-based processes. Graphical abstract Image 1 Highlights • Ranking of anammox recovery was nZVI > Fe(II) >N 2 after 2 mg L−1 DO shocks. • Low dose nZVI promotes anammox activity by moderate O 2 − increase and DO depletion. • High dose of nZVI/Fe(II) inhibits anammox activity by severe O 2 − increase. • Free Fe(II)/Fe(III) ions regulate intracellular Fenton reaction and O 2 − level. • Mechanism of intracellular O 2 − production after adding nZVI/Fe(II) was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The concentration of Fe(II)-phen in brackish water was determined by HR-ESI-MS. • Solvent extraction was successful for the removal of salt from sea water. • The sensitivity of Fe species in ESI-MS increased due to the transfer of Fe complexes to the organic phase. • Fe3+/total Fe fraction increased in the order of springs, rivers and brackish water. Generally, methods using nebulizers such as in Electrospray Ionization Mass Spectrometry (ESI-MS) or Induced Coupled Plasma Mass Spectrometry(ICP-MS) for the determination of Fe(II) in seawater are difficult because of the high concentration of salt. In earlier studies, we determined Fe(II) in river water with 1,10-phenanthroline (phen) and measured the complexed species by ESI-MS, but a method to reduce the interference of salts in seawater is lacking. After filtration of water samples with a 0.45 µm membrane on site , the sample was immediately added into a previously prepared solution containing sodium perchlorate (NaClO 4) and phen in nitrobenzene (NB). After shaking for 20 min, Fe(II) was extracted into nitrobenzene (NB) with the perchlorate ions. The NB was introduced to an ESI-MS, using a syringe. The Fe(II)-phen complex and perchlorate ions in NB were more stable than in the aqueous solution. Approximately 99.6 % of Fe(II) was extracted into the organic phase. In our previously presented data, Fe(II) was complexed with 1,10-phenanthroline in aqueous solution, and measured by HR-ESI-MS, a standard addition method was used, and a calibration curve was obtained. In this method, the samples were added to 0.025, 0.05, 0.1 and 0.2 Fe(II)/µmol/L and a calibration curve (R2 = 0.993) of the peak intensity was determined by HR-ESI-MS from the total peak areas of [Fe(phen)₂-NB]2+ m / z 269.5 and [Fe(phen) 3 ]2+ m / z 298.2. In the present study, the concentration of Fe(II) in brackish water containing 1 % salt was determined to be 0.184 ± 0.05 µM, and the total iron concentration was determined by ICP-MS and found to be 0.70 µM. Fe(II)/Fe total was 26 %, the groundwater sample contained Fe(II) 0.146 ± 0.002 µM, Fe total was 0.23 ± 0.02 µM, and Fe(II)/Fe total was 63 %. Groundwater is less sensitive to oxygen and therefore has a higher proportion of Fe(II) to total iron. In brackish water, on the other hand, the proportion of Fe(II) can be higher or lower because it is affected by oxygen supply from the surface and reduction from the bottom sediment. Therefore, the Fe(II) concentration was relatively high, but in brackish water, Fe(II) was low, but Fe total was high. [ABSTRACT FROM AUTHOR]

[Display omitted] • The concentration of Fe(II)-phen in brackish water was determined by HR-ESI-MS. • Solvent extraction was successful for the removal of salt from sea water. • The sensitivity of Fe species in ESI-MS increased due to the transfer of Fe complexes to the organic phase. • Fe3+/total Fe fraction increased in the order of springs, rivers and brackish water. Generally, methods using nebulizers such as in Electrospray Ionization Mass Spectrometry (ESI-MS) or Induced Coupled Plasma Mass Spectrometry(ICP-MS) for the determination of Fe(II) in seawater are difficult because of the high concentration of salt. In earlier studies, we determined Fe(II) in river water with 1,10-phenanthroline (phen) and measured the complexed species by ESI-MS, but a method to reduce the interference of salts in seawater is lacking. After filtration of water samples with a 0.45 µm membrane on site , the sample was immediately added into a previously prepared solution containing sodium perchlorate (NaClO 4) and phen in nitrobenzene (NB). After shaking for 20 min, Fe(II) was extracted into nitrobenzene (NB) with the perchlorate ions. The NB was introduced to an ESI-MS, using a syringe. The Fe(II)-phen complex and perchlorate ions in NB were more stable than in the aqueous solution. Approximately 99.6 % of Fe(II) was extracted into the organic phase. In our previously presented data, Fe(II) was complexed with 1,10-phenanthroline in aqueous solution, and measured by HR-ESI-MS, a standard addition method was used, and a calibration curve was obtained. In this method, the samples were added to 0.025, 0.05, 0.1 and 0.2 Fe(II)/µmol/L and a calibration curve (R2 = 0.993) of the peak intensity was determined by HR-ESI-MS from the total peak areas of [Fe(phen)₂-NB]2+ m / z 269.5 and [Fe(phen) 3 ]2+ m / z 298.2. In the present study, the concentration of Fe(II) in brackish water containing 1 % salt was determined to be 0.184 ± 0.05 µM, and the total iron concentration was determined by ICP-MS and found to be 0.70 µM. Fe(II)/Fe total was 26 %, the groundwater sample contained Fe(II) 0.146 ± 0.002 µM, Fe total was 0.23 ± 0.02 µM, and Fe(II)/Fe total was 63 %. Groundwater is less sensitive to oxygen and therefore has a higher proportion of Fe(II) to total iron. In brackish water, on the other hand, the proportion of Fe(II) can be higher or lower because it is affected by oxygen supply from the surface and reduction from the bottom sediment. Therefore, the Fe(II) concentration was relatively high, but in brackish water, Fe(II) was low, but Fe total was high. [ABSTRACT FROM AUTHOR]

Abstract Thermal decomposition of trimethylamine oxide (TMAO) during the processing and storage of jumbo squid was characterized to find an innovative approach to its safe consumption. A combination of Fe2+ with ascorbic acid (AA) promoted the almost complete degradation of TMAO from 438.89 mg/L to 0.23 mg/L, generating considerable equimolar amounts of dimethylamine (DMA) and formaldehyde (FA). Moreover, the role of “Fe2+ + AA” on the decomposition of TMAO could be significantly altered by varying the pH values. At pH 9, TMAO was degraded through two different pathways to give trimethylamine (TMA) with content of 148 mg/L and DMA of 57 mg/L, while at pH 3, TMAO was mainly transformed into TMA (210 mg/L) but a small amount of DMA (15 mg/L). Water activity (a w ) and water mobility were also found to influence the formation of FA, as it obviously dropped from 136.6 μg/g to 100.6 μg/g when a w was reduced from 0.750 to 0.667 with less free water. Interestingly, during accelerated storage experiment, the quantity of FA increased prior to decreasing. This was attributed to its role in crosslinking the squid muscle fibers to give a stable network structure and significantly altering the microstructures observed by scanning electron microscopy. Highlights • Fe2+ with ascorbic acid effectively promoted trimethylamine oxide degradation. • Degradation pathway of trimethylamine oxide changed at pH 3 to reduce formaldehyde. • Lower water activity with less free water could lessen formaldehyde. • Formaldehyde could be exhausted to some extent as a cross-linker. [ABSTRACT FROM AUTHOR]

This study aimed to increase bacterial growth and 5-aminolevulinic acid (ALA) biosynthesis of Rhodobacter sphaeroides in wastewater treatment through adding ferrous ion (Fe 2 + ). Results demonstrated that Fe 2 + effectively enhanced the biomass production and ALA yield of R. sphaeroides . Moreover, the optimal Fe 2 + dosage was found to be 400 μmol/L, which was associated with the highest biomass of 4015.3 mg/L and maximum ALA yield of 15.9 mg/g-dry cell weight (mg/g-DCW). Mechanism analysis revealed that Fe 2 + vastly improved Adenosine Triphosphate (ATP) production by up-regulating the nif gene expression, and increasing ATP enhanced the biomass and ALA yield by supplying energy for bacterial growth and ALA biosynthesis, respectively. Correlation analysis showed that the ALA and ATP yields had positive relation with nifA and nifU gene expression. In addition, the nifA and nifU gene expression displayed high consistency of co-transcription at the optimal Fe 2 + dosage. [ABSTRACT FROM AUTHOR]

Ferric uptake regulator (Fur) is important in the regulation of bacterial iron metabolism and uptake of Fe from the environment. We evaluated the contribution of fur to the sensitivity and oxidative response of A. baumannii to antibiotics. Deletion of fur increased the sensitivity of A. baumannii AB5075 to colistin, gentamicin, rifampicin and tigecycline. Furthermore, activities of superoxide dismutase and catalase in Δ fur mutant decreased significantly compared to the parental strain. Conversely, •O 2 − and H 2 O 2 accumulate in colistin, gentamicin, rifampicin or tigecycline-treated Δ fur mutant compared to the parental strain. Ferrous ion (Fe 2+ ) content of Δ fur mutant increased compared to the parental strain. Fe chelator 2,2′-bipyridyl lowered the sensitivity of A. baumannii to the antibiotics. The antibiotics, except tigecycline, raised the NAD+/NADH and ADP/ATP ratio of Δ fur mutant compared to the WT. Glutathione content of Δ fur mutant was significantly depleted compared to parental strain following exposure to the antibiotics. We conclude that decreased capability of Δ fur mutant to detoxify reactive oxygen species raised its susceptibility to antibiotics through Fenton chemistry. [ABSTRACT FROM AUTHOR]

Finding a good sorbent for phosphorus (P) recovery from the aquatic environment is critical for preventing eutrophication and providing P resources. The activated iron system (mainly consisted of zero-valent iron (ZVI), Fe 3 O 4 and Fe 2+ ) has been reported to exhibit a favorable performance towards various contaminants in wastewater, but its effect on P recovery has not been studied systematically. In this study, we used Fe 2+ -nitrate pretreatment reaction to prepare the activated iron system and then applied it to P recovery. Results show that more than 99% P was removed from water in 60 min; co-existing anions (NO 3 − , Cl − and SO 4 2− ) and natural organic matter (NOM) had little effect on P removal. The P removal capacity of activated iron system is very high compared with currently reported sorbents. Externally-supplied Fe 2+ plays an important role on P removal in the system. Regeneration study shows that the activated iron system exhibited stable P recovery ability by using 0.1 M NaOH solution. Various methods were applied to characterize the ZVI and iron corrosion, and results conclude that sorption precipitation, and co-precipitation contribute to P removal. This method will be promising and have an application potential in the field for efficient and cost-effective recovery of P with cheap microscale zero valent iron. [ABSTRACT FROM AUTHOR]

In this study, the performance and mechanism of the integrated sulfidated nanosized zero-valent iron and ferrous ions (S-nZVI/Fe2+) system for oxygen activation to remove emerging contaminants (ECs) were comprehensively explored. The S-nZVI/Fe2+ system exhibited a 2.4–8.2 times of increase in the pseudo-first order kinetic rate constant for the oxidative degradation of various ECs compared to the S-nZVI system under aerobic conditions, whereas negligible removal was observed in both nZVI and nZVI/Fe2+ systems. Moreover, remarkable EC mineralization efficiency and benign detoxification capacity were also demonstrated in the S-nZVI/Fe2+ system. We revealed that dosing Fe2+ promoted the corrosion of S-nZVI by maintaining an acidic solution pH, which was conducive to O 2 activation by dissolved Fe2+ and surface-absorbed Fe(II) to produce •OH. Furthermore, the generation of H* was enhanced for the further reduction of Fe(III) and H 2 O 2 to Fe(II) and •O 2 –, resulting in the improvement of consecutive single-electron O 2 activation for •OH production. Additionally, bisphenol A (BPA) degradation by S-nZVI/Fe2+ was positively correlated with the S-nZVI dosage, with an optimum S/Fe molar ratio of 0.15. The Fenton-like degradation process by S-nZVI/Fe2+ was pH-insensitive, indicating its robust performance over a wide pH range. This study provides valuable insights for the practical implementation of nZVI-based technology in achieving high-efficiency removal of ECs from water. [Display omitted] • Dosing Fe2+ enhanced oxidative degradation of emerging contaminant by S-nZVI. • Remarkable pollutant mineralization and detoxification capacity were obtained. • S-nZVI/Fe2+ boosted consecutive single-electron O 2 activation and •OH production. • Improved Fe(0) corrosion and H* production resulted in enhanced pollutant removal. • The Fenton-like degradation process byS-nZVI/Fe2+ was pH-insensitive. [ABSTRACT FROM AUTHOR]

• The low temperature hematite process with adding neutralizer was proposed for the first time. • The operating temperature of the hematite process was dramatically decreased to 423.15 K, even 393.15 K. • The operating duration of the hematite process was significantly reduced to <100 min, and the iron removal efficiency can reach 99%. • The iron ions in the zinc leaching solution were recycled as resources, and the environmental problem of iron removal residue storage was solved. Here, a clean, low-temperature hematite process using a neutralizer was proposed to remove iron ions from a zinc leaching solution and reutilize iron removal residue. The results showed that the solution acidity played a crucial role in this process. For a ZnSO 4 solution with an Fe2+ concentration of 12–14 g/L and an initial pH > 3.0, the iron ion concentration decreased to 20 mg/L within 95 min when using the low-temperature hematite process with pure ZnO (10–13 g/L) added as a neutralizer in the temperature range of 408.15–423.15 K. The iron removal efficiency reached 99%. Increasing the initial pH of the initial solution significantly improved the iron removal efficiency, and it was necessary to control the pH above 3.0. After ferrous ion mineralization, the residual iron concentration in the solution was inversely proportional to the final pH. The precipitated hematite products contained an Fe content of >55%, with a Zn loss of <1% and S contamination level of <3%. These hematite products can be sold as raw materials for ironmaking to solve the environmental issues associated with the storage of iron removal residue. The results showed that zinc oxide dust could not be used as a neutralizer because it resulted in the loss of valuable metals such as Pb, Ag, and In. Compared with the hematite process (453.15–473.15 K, reaction time of 3.0 h) used by the Iijima Refinery of Akita Zinc Co. in Japan, the ferrous ion mineralization in this study was shortened to <100 min. This significantly increased the treatment capacity of the low-temperature hematite process for zinc leaching solutions. The low-temperature hematite process could be performed at 393.15 K, 408.15 K, and 423.15 K, which can realize energy savings and consumption reduction. [ABSTRACT FROM AUTHOR]

In this paper, a system consisting of acid-washed zero-valent iron (ZVI), ferrous ion (Fe2+), and hydrogen peroxide (H2O2) was employed for the removal of nitrate (NO3-) from water, and the reaction mechanism for this is discussed. The effects of acid-washed ZVI, Fe2+, H2O2, and initial NO3- concentration on nitrate removal were investigated. Acid-washed ZVI before and after reaction with nitrate were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results reveal that the combined system can enhance the corrosion of ZVI and facilitate aqueous nitrate reduction. The products of nitrate reduction are mainly ammonium, with some N2. The ZVI particles after reaction may have a core of ZVI with an oxidation layer mainly consisting of Fe3O4. [ABSTRACT FROM AUTHOR]

The authors report on a chromogenic system based MnO nanosheet and the chomgenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB). The MnO nanosheet can oxidize TMB in acidic environment to form a yellow solution with an absorption peak at 450 nm. The process does not require the presence of an enzyme or HO. However, on addition of ferrous ion to the chromogenic system, the MnO nanosheet is decomposed via the redox reaction that occurs between Fe(II) and MnO. As a result, the intensity of the absorption at 450 nm is reduced. This finding is exploited in a photometric method for determination of Fe(II) that shows high selectivity and a 0.3 μM detection limit (based on the 3σ/slope criterion). Fe(II) can also be detected visually in concentrations down to 100 μM. The method was applied to the determination of Fe(II) in spiked water samples and gave satisfactory recoveries. [ABSTRACT FROM AUTHOR]

Electrochemical reactions always occur at the electrode-slag and slag-metal melt interfaces during the electroslag remelting (ESR) process. However, those reactions together with the ion transport phenomenon in the molten slag region are still poorly understood. A numerical model considering both the ion transport and the electrochemical reactions is demanding. For this purpose, a numerical model is proposed. The ion transport is modeled by solving the Poisson-Nernst-Planck (PNP) equations, while the kinetics of the reaction at the slag-metal interface is modeled with the well-known 'Butler-Volmer' formula. Demonstratively, a one- dimensional case is calculated: a DC electric current is applied to a molten multi-ion slag (CaF2-FeO) between the anode and the cathode. The modeling results show that the redox reaction occurs only for the ferrous ion (Fe2+), not for other ions at low current density (<2 kA m−2), which was verified experimentally. We also find that formation of ferric iron (Fe3+) or discharge of calcium at large current density (>5 kA m−2) may not take place, although some researchers have proposed such a hypothesis. Therefore, further research steps are suggested to verify this point so that the model is fully applicable for the industrial ESR process. [ABSTRACT FROM AUTHOR]

Air flooding can be successfully applied in a low-temperature reservoir due to the existence of ferrous ions in formation water. However, few published papers can be found about the mechanism of oxidation of crude oil on condition with Fe2+at a low temperature, by far. Therefore, in order to reveal the mechanism, some static oxidation experiments are carried out at 30°C in this paper. On condition with Fe2+, the rate of oxygen consumption is increased by 2.3 times as that on condition without Fe2+, and the concentration of O2in the air is decreased to 7.5% after oxidation. According to the results of the changes in the compositions of the air and the crude oil, not only can Fe2+accelerate the rate of the oxidation but can also affect the pathway of the oxidation. The experimental results can provide a basis for how to further improve the development effect of air flooding in Ganguyi oilfield and safely make use of air flooding in other low-temperature reservoirs. [ABSTRACT FROM PUBLISHER]

[Display omitted] • Montmorillonites clays modification with 1,10-phenanthroline. • Adsorption of iron(II) on k 10 and MMT-Na is physical. • The iron (II) adsorption on k 10-phen is chemical and on MMT-phen is mixed physical and chemisorption. • All clays are characterized via XRD, IR, TGA, and BET. • The equivalent CEC for all cations on MMT-Na is 80% and reaches 97%. The use of clays for the adsorption of contaminants from water has gained significant attention in recent decades. Clays and their modified forms have been extensively studied for their ability to adsorb both inorganic and organic pollutants. The purpose of this study is to investigate the use of montmorillonite (k 10), local montmorillonite (MMT-Na), and their 1,10-phenanthroline modified forms (k 10-phen and MMT-phen) for the adsorption of iron(II) ions. Adsorption of iron(II) on k 10 and MMT-Na has been observed to be physical; however, adsorption on k 10-phen is chemical. Nevertheless, iron (II) adsorption on MMT-phen combines physical and chemical adsorption. To characterize all these clays, X-ray diffraction (XRD), Infrared spectroscopy (IR), thermogravimetric analysis (TGA), and BET nitrogen adsorption–desorption isotherm were performed. In order to determine the specific surface area of the clays, the BET and methylene blue methods were used, and both ways were quite similar. A cation exchange capacity (CEC) of 39 meq/100 g for k 10 and 85 meq/100 g for MMT-Na is calculated. To optimize the Fe(II) adsorption on clays, pH, clay mass, and contact time were studied. The adsorption isotherms were analyzed using linear and nonlinear Langmuir, Freundlich, Dubinin-Radushkevich, Sips, and Toth isotherms. A study of adsorption kinetics was conducted using linear, nonlinear, and differential pseudo first and second orders. An Elovich model has been applied to the obtained data about chemisorption character. Boyd and Weber& Morris's intraparticle diffusions have also been examined. Upon adsorption of Fe(II) on all clays, the standard free energies were negative, confirming the spontaneous nature of the adsorption process. As a result of the endothermic nature of the adsorption, the enthalpies are positive. In the presence of other cations, k 10-phen and MMT-phen demonstrated the most excellent selectivity in uptaking Fe(II). [ABSTRACT FROM AUTHOR]

[Display omitted] • A Golgi-targeting Fe2+ fluorescent chemosensor Gol-Cou-Fe2+ is rationally developed. • Gol-Cou-Fe2+ shows high sensitivity and selectivity for Fe2+ in aqueous solution. • Gol-Cou-Fe2+ monitors the fluctuation of Golgi Fe2+ under hypoxia in living cells. • Fe2+ overload under monesin-induced Golgi stress and alleviation of overload by NO can be indicated by Gol-Cou-Fe2+. Ferrous ion (Fe2+) is a crucial metal ion in the body and participates in the diseases related to oxidation and reduction. Golgi apparatus is the main subcellular organelle of Fe2+ transport in cells, and the stability of its structure is related to the Fe2+ at an appropriate concentration. In this work, a turn-on type Golgi-targeting fluorescent chemosensor Gol-Cou-Fe2+ was rationally designed for sensitive and selective detection of Fe2+. Gol-Cou-Fe2+ showed excellent capacity of detecting exogenous and endogenous Fe2+ in HUVEC and HepG2 cells. It was used to capture the up-regulated Fe2+ level during the hypoxia. Moreover, the fluorescence of sensor was enhanced over time under Golgi stress combining with the reduce of Golgi matrix protein GM130. However, elimination of Fe2+ or addition of nitric oxide (NO) would restore the fluorescence intensity of Gol-Cou-Fe2+ and the expression of GM130 in HUVEC. Thus, development of chemosensor Gol-Cou-Fe2+ provides a new window for tracking Golgi Fe2+ and elucidating Golgi stress-related diseases. [ABSTRACT FROM AUTHOR]

Nitrate reduction by Fe(II) species was previously known to occur only in Cu2+-catalyzed and alkaline conditions or at high temperatures. In this study, a reactant system consisting of nitrate, iron oxide particles, and Fe(II) (in different forms) was used to study possible reactions between nitrate and Fe(II). At near-neutral pH, nitrate could not be reduced by aqueous Fe(II) species or by FedOHT2 gel. In the presence of magnetite (Fe3O4) particles, however, a significant amount of Fe2+ could be adsorbed onto an Fe3O4 surface at pH = 7.3 and became surface-bound Fe2+(S:B: Fe2+), which could react with nitrate via the reaction: 12 S:B: Fe2+ + NO.3- 13H2O ×4 Fe3O4 +NH4+ t 22H+. The reaction stopped when pH decreased to <6.8. Introducing trace amount of O2 or Fe3tdaqT into the nitrate- Fe2t reactant system was as effective as seeding magnetite particles in triggering the nitrate-Fe(II) reaction, suggesting that lepidocrocite (ƒÁ-FeOOH) is a precursor for initiating the nitrate-Fe(II) reaction. Hematite and Kaolinite particles could also serve as the reactive sites for the nitrate-Fe(II) reaction upon surface transformation by S:B: Fe2t. The observed abiotic nitrate reduction by Fe(II) could be an important link between the nitrogen cycling and the Fe(II)/Fe(III) redox couple in the biosphere or geosphere. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model on Fe(II)-activated persulfate oxidation of atrazine (ATZ) was tested using the rate constants from literature, and the degradation kinetics and mechanism of ATZ degradation in Fe(II)/persulfate (Fe 2+ /PS) system were investigated to verify the model. Some influence factors were taken into consideration in this model, including molar ratio of Fe 2+ and PS, initial ATZ concentration, natural organic matter (NOM) concentration, tertiary butanol (TBA) and methanol (MeOH) concentrations. Corresponding experimental data could be predicted accurately according to this model. Both experimental data and predicted results implied that a molar ratio of Fe 2+ and PS at 1:1, low initial ATZ and NOM concentrations were favorable for ATZ degradation. Besides, the radical species were determined via evaluating the effect of TBA and MeOH, and results confirmed that both sulfate radical (SO 4 − ) and hydroxyl radical (OH ) existed in this system. To investigate the predominant radical in Fe 2+ /PS system, nitrobenzene (NB) was used as a probe compound which only react with OH . According to the degradation efficiency of NB and ATZ in Fe 2+ /PS system, it could be concluded that only small amount of OH were produced and SO 4 − made a major contribution to ATZ degradation in Fe 2+ /PS system. Experimental data, as well as the mathematical model in this study, improved our understanding on the effect of operating parameters for ATZ degradation in Fe(II)-based advanced oxidation processes. [ABSTRACT FROM AUTHOR]

This work investigated the degradation of methyl orange by ozone in the presence of ferrous and persulfate ions ( O 3 / Fe 2 + / S 2 O 8 2 − ) in a rotating packed bed. The effects of various operating parameters such as initial pH, rotational speed, gas–liquid ratio, ozone inlet concentration and reaction temperature on the degradation rate of methyl orange were studied with an aim to optimize the operation conditions. Results reveal that the degradation rate increased with an increase in rotational speed, gas–liquid ratio and ozone inlet concentration, and reached a maximum at 25 °C and initial pH 4. Contrast experiments involving ozone and ferrous ions (O 3 /Fe 2+ ) were also carried out, and the results show approximately 10% higher degradation rate and COD removal in the O 3 / Fe 2 + / S 2 O 8 2 − process than in the O 3 /Fe 2+ process. Additionally, the intermediates of the degradation process were analyzed to ascertain the degradation products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different peroxides-based oxidative pathways were compared towards NOR degradation. • The peroxide HSO 5 − performed best in the degradation of NOR under UV-C and Fe2+. • The peroxides yield ●OH and SO 4 ●− under activation by UV-C and Fe2+ activation. • The ●OH and SO 4 ●− scavengers inhibited degradation of NOR. • Degradation products and ecotoxicities of NOR as well as its DPS were estimated. The removal of norfloxacin (NOR), a widely used pharmaceutical and emerging water pollutant, was studied using UV-C and Fe2+ catalyzed peroxides-based oxidative processes (e.g., UV-C/Fe2+/H 2 O 2 , UV-C/Fe2+/S 2 O 8 2− and UV-C/Fe2+/HSO 5 −) and compared with UV-C and UV-C/Fe2+. The UV-C and UV-C/Fe2+ degraded NOR to 38 and 55 %. However, use of peroxides, i.e., H 2 O 2 , S 2 O 8 2−, HSO 5 − with UV-C and UV-C/Fe2+ promoted NOR %degradation to 75, 83, and 90 % using [peroxides] 0 = 50 mg/L, [Fe2+] 0 = 1 mg/L, and [NOR] 0 = 10 mg/L, respectively. The significant impact of peroxides on NOR degradation was due to their decomposition into ●OH and SO 4 ●− which showed high activity towards NOR degradation. The ●OH and SO 4 ●− formation from peroxides decomposition and their contribution in NOR degradation was verified by different scavenger studies. Among the UV-C/Fe2+/peroxides processes, UV-C/Fe2+/HSO 5 − showed better performance. The changing concentrations of peroxides, Fe2+, and NOR affected degradation of NOR. The use of different pH and inorganic anions also influenced NOR degradation. The degradation pathways of NOR were established and analyzed acute as well as chronic toxicities of NOR and its DPs. [ABSTRACT FROM AUTHOR]

Oxidative stress is the central pathomechanism in multiple cell death pathways, including ferroptosis, a form of iron-dependent programmed cell death. Various phytochemicals, which include the inducers of the nuclear factor erythroid-2-related factor 2–antioxidant response element (Nrf2–ARE) transcription pathway, prevent ferroptosis. We recently reported that several compounds, such as the potent Nrf2–ARE inducer curcumin, protect mouse hippocampus-derived HT22 cells against ferroptosis independently of Nrf2–ARE activity. The present study characterized the anti-ferroptotic mechanisms of two additional Nrf2–ARE inducers, quercetin and resveratrol. Both compounds prevented erastin- and RSL3-induced ferroptosis of wild-type HT22 cells, and also blocked the exacerbated erastin- and RSL3-induced ferroptosis of Nrf2-knockdown HT22 cells. In both HT22 cells, quercetin and resveratrol blocked erastin- and RSL3-induced elevation in reactive oxygen species. These results suggest that the Nrf2–ARE pathway does protect against ferroptosis, but quercetin and resveratrol act by reducing oxidative stress independently of Nrf2–ARE induction. Quercetin and resveratrol also reduced Fe2+ concentrations in HT22 cells and in cell-free reactions. Thus, quercetin and resveratrol likely protect against erastin- and RSL3-induced ferroptosis by inhibiting the iron-catalyzed generation of hydroxyl radicals. Unlike quercetin, resveratrol cannot form a chelate structure with Fe2+ but the density functional theory computation demonstrates that resveratrol can form stable monodentate complexes with the alkene moiety and the electron-rich A ring. [Display omitted] • Nrf2 activators quercetin and resveratrol inhibit ferroptosis of HT22 cells. • Anti-ferroptotic effect of quercetin and resveratrol is maintained under Nrf2 knockdown. • Quercetin and resveratrol also inhibit ROS generation and chelate or coordinate ferrous ions. • These anti-ferroptotic effects are mediated primarily by iron chelation or coordination. [ABSTRACT FROM AUTHOR]

Severe skin wound healing is mainly hindered by bacterial infection and uncontrolled inflammatory reaction. As a wound dressing, multifunctional hydrogel is expected to offer the potential possibility for overcoming current barriers in wound therapeutics. Herein, a natural drug molecule (glycyrrhizic acid, GA) and metal ion (Fe2+) were used to achieve the metal coordination-induced gelation. This as-prepared Fe2+-induced GA hydrogel showed excellent injectability, self-healing property, and sustained release behavior at a relatively lower concentration of GA, thereby reducing the high dose-caused cytotoxicity. In addition to acting as an inducer of gelation, Fe2+ promoted the antibacterial performance of hydrogel against Escherichia coli and Staphylococcus aureus through causing lipid peroxidation, membrane damage, and DNA degradation. Moreover, the released GA from hydrogel significantly accelerated cell migration and inhibited the inflammatory reaction by mediation of NF-κB signaling pathway to downregulate levels of important inflammatory cytokines in lipopolysaccharide-stimulated RAW264.7 cells. Using a mouse skin infected model, we revealed that the Fe2+/GA hydrogel applied to the wound resulted in the rapid wound healing. It is believed that the construction of natural drug molecule-derived hydrogel with antibacterial and anti-inflammatory capabilities may shed a new light to serve as a promising dressing for managing the severe skin wounds. [Display omitted] • Fe2+ induced the formation of GA-based hydrogels in low concentration. • Fe2+/GA hydrogels integrated antibacterial activity and anti-inflammatory function. • Fe2+/GA hydrogels provided a promising combination modality for infected wound healing. [ABSTRACT FROM AUTHOR]

The synthesis of a novel spirooxazine (1-benzyl-3,3-dimethylspiro[indoline-2,3′-naphtho [2,1-b] [1,4] oxazine, BSP-SP) was developed as a colorimetric probe for the quantitative analysis of Fe2+ and Pb2+ in water samples. The device is based on a microfluidic paper-based analytical device (μPAD). BSP-SP was characterized by various techniques, e.g. single-crystal X-ray diffraction (SC-XRD) and time-dependent density functional theory (TD-DFT). In addition, the density functional theory (DFT) allowed us to understand better the adsorption of Fe2+ and Pb2+ over other cations adsorption on the BSP-MO structure. The structural isomerization of BSP-SP occurs as an open-form merooxazine (BSP-MO), which acts as a ligand to form Fe2+/BSP-MO and Pb2+/BSP-MO complexes. We observed these complexes under UV irradiation as having a light blue coloration. The μPADs were also proposed as detection platforms to maintain photostability and photochromic efficiency and extend the lifetime of the spirooxazine. Under optimal conditions, the developed μPAD enables rapid and sensitive quantitative analysis of Fe2+ at pH 6 and Pb2+ at pH 11. The limits of detection (LOD) were 0.036 mg L−1 for Fe2+ and 0.152 mg L−1 Pb2+. Overall, the developed sensors, particularly the μPADs, promise the practical analysis of Fe2+ and Pb2+ in water samples. [Display omitted] • Our novel spirooxazine (BSP) was successfully synthesized as colorimetric probe. • BSP-coated μPAD was illustrated to enhance photochromic efficiency. • This method features selectivity toward Fe2+ and Pb2+ determination. [ABSTRACT FROM AUTHOR]

Single-chain nanoparticles can be obtained via single-chain folding assisted by intramolecular crosslinking reversibly or irreversibly. Single-chain folding is also an efficient route to simulate biomacromolecules. In present study, poly( N-hydroxyethylacrylamide-co-4′-(propoxy urethane ethyl acrylate)-2,2′:6′,2″-terpyridine) (P(HEAm-co-EMA-Tpy)) is synthesized via reversible addition fragmentation chain transfer polymerization. Single-chain folding and intramolecular crosslinking of P(HEAm-co-EMA-Tpy) are achieved via metal coordination chemistry. The intramolecular interaction is characterized on ultraviolet/visible spectrophotometer (UV-vis spectroscopy), proton nuclear magnetic resonance (1H NMR), and differential scanning calorimetry (DSC). The supramolecular crosslinking mediated by Fe2+ plays an important role in the intramolecular collapsing of the single-chain and the formation of the nanoparticles. The size and morphology of the nanoparticles can be controlled reversibly via metal coordination chemistry, which can be characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic force microscope (AFM). [ABSTRACT FROM AUTHOR]

In this study, the removal of ibuprofen (IBP), a pharmaceutical compound, from aqueous media by Money plant ( Epipremnum aureum ) was investigated. The effect of ferrous iron (Fe 2+ ) on enhancing the IBP removal rate was also analyzed. The first-order removal rate constants showed higher values for lower IBP initial concentrations in the range of 0.20–0.28 d −1 for an initial concentration of 125 μg L −1 to 0.03–0.13 d −1 for an initial concentration of 1000 μg L −1 . Introducing ferrous iron to the aqueous media enhanced the first-order removal rate constant up to 6.5 times in a 3 d time period. Along with the removal of IBP from the media, the endogenous concentration of H 2 O 2 also decreased presumably by the production of hydroxyl radical ( OH). Reduction in the endogenous H 2 O 2 concentration was recorded to be 38% and 98% in the absence and presence of Fe 2+ respectively in the first day and the H 2 O 2 level remained considerably low until day 7 which then gradually increased slightly. Simultaneous reduction of IBP and endogenous H 2 O 2 concentration could be due to the reaction of IBP with OH and presumably OH production itself accelerated via Fenton reaction. In addition, presence of sodium bicarbonate (NaHCO 3 ) as OH scavenger in the system showed reduction of first-order removal rate constant from 1.30 d −1 to 0.07 d −1 which could be a possible evidence of biological advanced oxidation process which is believed to play an important role in phytoremediation. [ABSTRACT FROM AUTHOR]

To explore novel high efficiency and low toxicity antitumor agents, a series of dihydroartemisinin-cinnamic acid ester derivatives modified on C-12 and/or C-9 position (s) were synthesized and the in vitro antitumor activities against PC-3, SGC-7901, A549 and MDA-MB-435s cancer cell lines were assessed. The hybrids ( 3–36 ) were prepared by esterification of 9α-hydroxyl-dihydroartemisinin (9α–OH DHA), the biotransformation product of dihydroartemisinin (DHA), and cinnamic acid derivatives. Compound 17 (IC 50 = 0.20 μM) was the most potent anti-proliferative agent against the human lung carcinoma A549 cells, although it displayed low cytotoxicity on normal hepatic L-02 cells. The mechanism of action of compound 17 was further investigated by analysis of cell apoptosis and intracellular ROS generation. The results indicated that both ROS and ferrous ion contributed to the compound 17 -induced cell death. Meanwhile, high intracellular ferrous ion and endogenous oxidative stress in A549 cells made them easier to suffer to compound 17 -induced apoptosis. Our promising findings indicated the compound 17 could stand as drug candidate against lung cancer for further investigation. [ABSTRACT FROM AUTHOR]

Iron ions are monitored in processes such as bio-leaching, bio-oxidation, ferric leaching, passivation control, and others. The role of iron in different hydrometallurgy processes is very important because it affects strongly several industrial ore production, as chalcopyrite cooper extraction. In this work we present an amperometric FIA system that allows rapid quantification and speciation of iron in bio-mining processes. Linearity range, passivation of the working electrode and interferences were studied. We found a useful lineal range from 10 to 1500 mg L −1 for each of the ions, with a detection limit (Fe 2+ and Fe 3+ ) determined at 15 ± 2 mg L −1 . High copper concentrations could interfere with the amperometric readings, though not in the copper/iron relationship encountered in this industry. Real samples, including an acid mine drainage sample, and the monitoring of the bio-oxidation kinetics of iron by Acidithiobacillus ferrooxidans were also quantified. In all cases, our results were compared with a standard colorimetric method that allows iron speciation (1,10-phenanthroline), showing good agreement between both methods. The electrochemical method presented here allows high sample throughput (ca. 45 samples h −1 ), fast analysis (ca. 1 min), and reagent free quantification of total iron, ferric and ferrous ions. [ABSTRACT FROM AUTHOR]

The production of reactive oxidants from nanoparticulate zero-valent iron (nZVI) and ferrous ion (Fe(II)) in the presence of oxygen was greatly enhanced by the addition of tetrapolyphosphate (TPP) as an iron-chelating agent. Compared to other ligands, TPP exhibited superior activity in improving the oxidant yields. The nZVI/TPP/O 2 and the Fe(II)/TPP/O 2 systems showed similar oxidant yields with respect to the iron consumed, indicating that nZVI only serves as a source of Fe(II). The degradation efficacies of selected organic compounds were also similar in the two systems. It appeared that both hydroxyl radical ( OH) and ferryl ion (Fe(IV)) are produced, and OH dominates at acidic pH. However, at pH > 6, little occurrence of hydroxylated oxidation products suggests that Fe(IV) is a dominant oxidant. The degradation rates of selected organic compounds by the Fe(II)/TPP/O 2 system had two optimum points at pH 6 and 9, and these pH-dependent trends are likely attributed to the speciation of Fe(IV) with different reactivities. [ABSTRACT FROM AUTHOR]

Background: In soils and sediments, manganese oxides and oxygen usually participate in the oxidation of ferrous ions. There is limited information concerning the interaction process and mechanisms of ferrous ions and manganese oxides. The influence of air (oxygen) on reaction process and kinetics has been seldom studied. Because redox reactions usually occur in open systems, the participation of air needs to be further investigated. Results: To simulate this process, hexagonal birnessite was prepared and used to oxidize ferrous ions in anoxic and aerobic aqueous systems. The influence of pH, concentration, temperature, and presence of air (oxygen) on the redox rate was studied. The redox reaction of birnessite and ferrous ions was accompanied by the release of Mn2+ and K+ ions, a signiicant decrease in Fe2+ concentration, and the formation of mixed lepidocrocite and goethite during the initial stage. Lepidocrocite did not completely transform into goethite under anoxic condition with pH about 5.5 within 30 days. Fe2+ exhibited much higher catalytic activity than Mn2+ during the transformation from amorphous Fe(III)-hydroxide to lepidocrocite and goethite under anoxic conditions. The release rates of Mn2+ were compared to estimate the redox rates of birnessite and Fe2+ under diferent conditions. Conclusions: Redox rate was found to be controlled by chemical reaction, and increased with increasing Fe2+ concentration, pH, and temperature. The formation of ferric (hydr)oxides precipitate inhibited the further reduction of birnessite. The presence of air accelerated the oxidation of Fe2+ to ferric oxides and facilitated the chemical stability of birnessite, which was not completely reduced and dissolved after 18 days. As for the oxidation of aqueous ferrous ions by oxygen in air, low and high pHs facilitated the formation of goethite and lepidocrocite, respectively. The experimental results illustrated the single and combined efects of manganese oxide and air on the transformation of Fe2+ to ferric oxides. [ABSTRACT FROM AUTHOR]

Background: In soils and sediments, manganese oxides and oxygen usually participate in the oxidation of ferrous ions. There is limited information concerning the interaction process and mechanisms of ferrous ions and manganese oxides. The influence of air (oxygen) on reaction process and kinetics has been seldom studied. Because redox reactions usually occur in open systems, the participation of air needs to be further investigated. Results: To simulate this process, hexagonal birnessite was prepared and used to oxidize ferrous ions in anoxic and aerobic aqueous systems. The influence of pH, concentration, temperature, and presence of air (oxygen) on the redox rate was studied. The redox reaction of birnessite and ferrous ions was accompanied by the release of Mn2+ and K+ ions, a significant decrease in Fe2+ concentration, and the formation of mixed lepidocrocite and goethite during the initial stage. Lepidocrocite did not completely transform into goethite under anoxic condition with pH about 5.5 within 30 days. Fe2+ exhibited much higher catalytic activity than Mn2+ during the transformation from amorphous Fe(III)-hydroxide to lepidocrocite and goethite under anoxic conditions. The release rates of Mn2+ were compared to estimate the redox rates of birnessite and Fe2+ under different conditions. Conclusions: Redox rate was found to be controlled by chemical reaction, and increased with increasing Fe2+ concentration, pH, and temperature. The formation of ferric (hydr)oxides precipitate inhibited the further reduction of birnessite. The presence of air accelerated the oxidation of Fe2+ to ferric oxides and facilitated the chemical stability of birnessite, which was not completely reduced and dissolved after 18 days. As for the oxidation of aqueous ferrous ions by oxygen in air, low and high pHs facilitated the formation of goethite and lepidocrocite, respectively. The experimental results illustrated the single and combined effects of manganese oxide and air on the transformation of Fe2+ to ferric oxides. [ABSTRACT FROM AUTHOR]