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In order to explore the operation performance, kinetic characteristics and bacterial community of the short-cut nitrification and denitrification (SND) system, the SND system with pre-cultured short cut nitrification and denitrification sludge was established and operated under different ferrous ion (Fe (II)) conditions. Experimental results showed that the average NH 4 + -N removal efficiency (ARE) of SND system was 97.3% on Day 5 and maintained a high level of 94.9% ± 1.3% for a long operation period. When the influent Fe(II) concentration increased from 2.3 to 7.3 mg L -1 , the sedimentation performance, sludge concentration and organic matter removal performance were improved. However, higher Fe(II) of 12.3 mg L -1 decreased the removal of nitrogen and COD Cr with the relative abundance (RA) of Proteobacteria and Bacteroidetes decreased to 30.28% and 19.41%, respectively. Proteobacteria, Bacteroidetes and Firmicutes were the dominant phyla in SND system. Higher Fe(II) level of 12.3 mg L -1 increase the RA of denitrifying genus Trichococcus (33.93%), and the denitrifying genus Thauera and Tolumonas dominant at Fe(II) level of no more than 7.3 mg L -1 ., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

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 Fe 2+ 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/Fe 2+ , VUV/Fe 2+ 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 Fe 2+ , i.e., VUV irradiation could effectively split water and largely accelerate the Fe 3+ /Fe 2+ 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/Fe 2+ and VUV/Fe 2+ processes, while • OH, O 2 •- , and 1 O 2 were involved in the VUV process. The operating parameters, such as Fe 2+ 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/Fe 2+ process were also evaluated., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

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 A 2 O 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Development of microalgal-bacterial granular sludge (MBGS) from saline-adapted microalgae is a promising approach for efficient mariculture wastewater treatment, whereas the elusive mechanisms governing granulation have impeded its widespread adoption. In this study, spherical and regular MBGS were successfully developed from mixed culture of pure Spirulina platensis and Chlorella sp. GY-H4 at 10 mg/L Fe 2+ concentration. The addition of Fe 2+ was proven to induce the formation of Fe-precipitates which served as nucleation sites for microbial attachment and granulation initiation. Additionally, Fe 2+ increased the prevalence of exopolysaccharide-producing cyanobacteria, i.e. Synechocystis and Leptolyngbya, facilitating microbial cell adhesion. Furthermore, it stimulated the secretion of extracellular proteins (particularly tryptophan and aromatic proteins), which acted as structural backbone for the development of spherical granule form microalgal flocs. Lastly, it fostered the accumulation of exogenous heterotrophic functional genera, resulting in the efficient removal of DOC (98 %), PO 4 3- -P (98 %) and NH 4 + -N (87 %). Nevertheless, inadequate Fe 2+ hindered microalgal floc transformation into granules, excessive Fe 2+ expanded the anaerobic zone within the granules, almost halved protein content in the TB-EPS, and inhibited the functional genes expression, ultimately leading to an irregular granular morphology and diminished nutrient removal. This research provides valuable insights into the mechanisms by which Fe 2+ promotes the granulation of salt-tolerant microalgae, offering guidance for the establishment and stable operation of MBGS systems in mariculture wastewater treatment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

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 Fe 2+ 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 Fe 2+ 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% Fe 2+ 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 Fe 2+ 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 Fe 2+ 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., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest related to the publication of this manuscript., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In this study, the performance and mechanism of the integrated sulfidated nanosized zero-valent iron and ferrous ions (S-nZVI/Fe 2+ ) system for oxygen activation to remove emerging contaminants (ECs) were comprehensively explored. The S-nZVI/Fe 2+ 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/Fe 2+ systems. Moreover, remarkable EC mineralization efficiency and benign detoxification capacity were also demonstrated in the S-nZVI/Fe 2+ system. We revealed that dosing Fe 2+ promoted the corrosion of S-nZVI by maintaining an acidic solution pH, which was conducive to O 2 activation by dissolved Fe 2+ 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/Fe 2+ 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/Fe 2+ 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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Ferrous ion (Fe 2+ ) 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 Fe 2+ transport in cells, and the stability of its structure is related to the Fe 2+ at an appropriate concentration. In this work, a turn-on type Golgi-targeting fluorescent chemosensor Gol-Cou-Fe 2+ was rationally designed for sensitive and selective detection of Fe 2+ . Gol-Cou-Fe 2+ showed excellent capacity of detecting exogenous and endogenous Fe 2+ in HUVEC and HepG2 cells. It was used to capture the up-regulated Fe 2+ 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 Fe 2+ or addition of nitric oxide (NO) would restore the fluorescence intensity of Gol-Cou-Fe 2+ and the expression of GM130 in HUVEC. Thus, development of chemosensor Gol-Cou-Fe 2+ provides a new window for tracking Golgi Fe 2+ and elucidating Golgi stress-related diseases., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Ferroptosis and oxytosis are iron- and oxidative stress-dependent cell death pathways strongly implicated in neurodegenerative diseases, cancers, and metabolic disorders. Therefore, specific inhibitors may have broad clinical applications. We previously reported that 3-[4-(dimethylamino)benzyl]-2-oxindole (GIF-0726-r) and derivatives protected the mouse hippocampal cell line HT22 against oxytosis/ferroptosis by suppressing reactive oxygen species (ROS) accumulation. In this study, we evaluated the biological activities of GIF-0726-r derivatives with modifications at the oxindole skeleton and other positions. The addition of a methyl, nitro, or bromo group to C-5 of the oxindole skeleton enhanced antiferroptotic efficacy on HT22 cells during membrane cystine-glutamate antiporter inhibition and ensued intracellular glutathione depletion. In contrast, the substitution of the dimethylamino group on the side chain phenyl ring with a methyl, nitro, or amine group dramatically suppressed antiferroptotic activity regardless of other modifications. Compounds with antiferroptotic activity also directly scavenged ROS and decreased free ferrous ions in both HT22 cells and cell-free reactions while those compounds without antiferroptotic activity had little effect on either ROS or ferrous-ion concentration. Unlike oxindole compounds, which we have previously reported, the antiferroptotic compounds had little effect on the nuclear factor erythroid-2-related factor 2-antioxidant response element pathway. Oxindole GIF-0726-r derivatives with a 4-(dimethylamino)benzyl moiety at C-3 and some types of bulky group at C-5 (whether electron-donating or electron-withdrawing) can suppress ferroptosis, warranting safety and efficacy evaluations in animal models of disease.

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 Fe 2+ 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 Fe 2+ but the density functional theory computation demonstrates that resveratrol can form stable monodentate complexes with the alkene moiety and the electron-rich A ring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

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., Competing Interests: Declaration of competing interest All authors have no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

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 (Fe 2+ ) were used to achieve the metal coordination-induced gelation. This as-prepared Fe 2+ -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, Fe 2+ 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 Fe 2+ /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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The availability of dissolved silicon (DSi) exerts an important control on phytoplankton communities in freshwater environments: DSi limitation can shift species dominance to non-siliceous algae and increase the likelihood of harmful algal blooms. The availability of DSi in the water column in turn depends on the dissolution kinetics of amorphous silica (ASi), including diatoms frustules and phytoliths. Here, batch dissolution experiments conducted with diatom frustules from three diatom species and synthetic Aerosil OX 50 confirmed the previously reported non-linear dependence of ASi dissolution rate on the degree of undersaturation of the aqueous solution. At least two first-order dissolution rate constants are therefore required to describe the dissolution kinetics at high (typically, ≥0.55) and low (typically, <0.55) degrees of undersaturation. Our results further showed aqueous ferrous ion (Fe 2+ ), which is ubiquitous in anoxic waters, strongly inhibited ASi dissolution. The inhibition is attributed to the preferential binding of Fe 2+ to Q 2 groups (i.e., surface silicate groups bonded to the silica lattice via two bridging oxygen) which stabilizes the silica surface. However, further increasing the aqueous Fe 2+ concentration likely catalyzes the detachment of Q 3 groups (i.e., silicate groups bonded to the silica lattice via three bridging oxygen) from the surface. Overall, our study illustrates the manyfold effects the aqueous solution composition, notably the inhibition effect of Fe 2+ under anoxic conditions, has on ASi dissolution. The results help to explain the controversial redox dependence of DSi internal loading from sediments, which is vital to quantitatively understanding silicon (Si) cycling in freshwater systems., Competing Interests: Declaration of competing interest The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Crown Copyright © 2022. Published by Elsevier B.V. All rights reserved.)

Fe(II)-activated potassium periodate (KIO 4 ) oxidation was used to improve the dewaterability of waste-activated sludge for the first time. Compared with those of raw sludge, the capillary suction time (CST), specific resistance filtration (SRF), and water content of filter cake (W C ) of sludge treated using the Fe(II)/KIO 4 process under the optimal conditions (i.e., the initial pH = 6.8, KIO 4 dose = 1.4 mmol/g volatile suspended solids, Fe(II)/KIO 4 molar ratio = 1.2) decreased by 64.34%, 84.13%, and 6.69%, respectively. For conditioned sludge flocs, the Zeta potential and particle size were increased, and hydrophilic proteins in extracellular polymeric substances (EPS) were partly degraded, accompanied by the transformation of tightly bound EPS into soluble EPS and the conversion of dense sludge flocs into loose and porous ones. During Fe(II)/KIO 4 oxidation, Fe(IV) and the accompanying • OH were determined as the predominant reactive species and the underlying mechanism of sludge EPS degradation was proposed. This work provides a prospective method for conditioning the sludge dewaterability.

To improve the performance and solve the restrictions of UV/chlorine process (e.g., the narrow pH application range and high disinfection by-products (DBPs) formation), a Fe 2+ assisted advanced oxidation process with electrochemically generated chlorine (UV/E-Cl/Fe 2+ ) was proposed for carbamazepine (CBZ) degradation, which eliminated CBZ (5 mg/L) within 4 min under the optimal conditions. Compared with UV/electro-generated chlorine (UV/E-Cl) and anodic oxidation-chlorination/Fe 2+ (AO-Cl/Fe 2+ ) processes, the apparent first-order kinetics constant in UV/E-Cl/Fe 2+ increased by 2.56 and 3.18 times respectively, and the energy consumption was lower (1.15 kWh/m 3 -log). Simultaneously, the pH application range could be expanded to 9, and DBPs formed in this process were 17.1% less than those in UV/E-Cl. Through quenching tests, electron paramagnetic resonance (EPR) experiments, measurement of • OH concentration, quantification of methyl phenyl sulfoxide (PMSO) and benzosulfone (PMSO 2 ) and processes comparison, possible CBZ degradation pathways and mechanism of UV/E-Cl/Fe 2+ were proposed, in which Fe(IV) played the dominant role in the early stage, while the production of radicals (i.e., • OH and Cl • ) was enhanced with the increase of chlorine generation, accelerating the CBZ removal. Furthermore, this process demonstrated wide application prospect in treating various contaminants and real wastewaters. In conclusion, this study offers an effective and energy-efficient method for organic pollutants degradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The mechanisms of Fe 2+ on nitrogen and phosphorus removal and functional bacterial competition in anammox systems was investigated. Under 0.12 mM Fe 2+ , the performance of nitrogen and phosphorus removal increased by 10.08 % and 151.91 %, respectively, compared with the control stage. Phosphorus removal was achieved through extracellular polymeric substance (EPS) induced biomineralization to form Fe-P minerals, and functional group COC in EPS played a critical role. T-EPSs was the major nucleation site due to it maintaining the supersaturated state (saturation index > 0) of Fe-P minerals for a long time. Population succession showed that Fe 2+ weakened the competition between heterotrophic denitrifier (Denitrasoma) and anammox microbe (Candidatus Brocadia) for space and substrates, which was favorable for the enrichment of anammox biomass. Moreover, the variation in gene abundance (such as Hao, Cyt c, and Nir) indicated that Fe 2+ improved electron behaviors (generation, transport, and consumption) during the nitrogen metabolism of anammox systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The inhibition of hydrogen peroxide (H 2 O 2 ) on the cysteine-mediated aggregation of gold nanoparticles (AuNPs) has great potential to rapidly visualize H 2 O 2 and disease-associated biomarkers. However, associated applications have been rigid due to the low cysteine-oxidation efficiency or the insufficient interference-resistance of previous catalysts. Here, we proposed a novel AuNPs colorimetric method termed Fe 2+ -catalyzed H 2 O 2 -preventing aggregation of AuNPs by oxidizing Cysteine (FeHOAuC) for the visible and rapid detection of H 2 O 2 with high specificity. Formed Fe 2+ -cysteine composites in the beginning, Fe 2+ accelerates the oxidation of cysteine by H 2 O 2 with an intramolecular electron-transferring model, and the generated cysteine oxides (including cysteic acid or cystine, dependent on the ratio of cysteine to H 2 O 2 molecules) lose the pro-aggregation effect on AuNPs. Notably, FeHOAuC can quantify 2-30 μM of H 2 O 2 within 5 min, and the monitoring process works well with tolerance to the impact of dissolved oxygen. The FeHOAuC paired with lactate oxidase was successfully used for measuring lactic acids in real sweat samples with a practicable detection window (2-60 μM) and a low variable coefficient (<10%). In summary, FeHOAuC is a feasible platform for rapid and convenient detection of H 2 O 2 and oxidase-specific substrates., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This study was conducted to evaluate the performance of anammox reaction on the addition of iron. Iron was added in the form of FeSO 4 starting with 2 mg/L (phase I), 5 mg/L (phase II), 8 mg/L (phase III), 10 mg/L (phase IV), 30 mg/L (phase V) and 50 mg/L (phase VI) on the addition of Fe (II) in anammox reactor. The efficiency of ammonia removal increased up to 90% with 5 mg/L of Fe (II) addition as compared to 77% when no Fe (II) was added. As the iron dosing was increased from 10 to 30 mg/L, ammonia removal declined sharply, which recovered slowly at steady-state condition. However, on the addition of 30 and 50 mg/L of Fe (II), the efficiency declined to 55% and 44%, respectively and did not recover. At 5 mg/L Fe (II) the nitrite removal was nearly 80% which declined to 44% at 50 mg/L. This was attributed to low pH values which hindered anammox activity. The mass balance study of nitrogen in the anammox process revealed that gas production was highest at 5 mg/L of Fe (II) conforming that 5 mg/L of Fe (II) is the optimum dose of iron for enhancing anammox reaction.

In this study, peracetic acid (PAA) activated by Fe(II) was proposed to remove diclofenac (DCF) in polluted water. It was found that Fe(II)/PAA system could effectively remove DCF at neutral condition, which has a significant advantage over classical Fenton process. According to the result of scavenging experiment, both hydroxyl radical and peroxy radical were considered to be responsible for the degradation of DCF. The influence of several operational parameters including initial pH, Fe(II) dosage, PAA concentration and common water matrix on DCF removal were investigated. 80% DCF was removed at mild condition (pH 6-7) within 60 s, and its removal rate could be enhanced with the increase in Fe(II) dosage and PAA concentration. Presence of H C O 3 - and natural organic matter (NOM) was proved to have a significantly negative impact on DCF degradation. Four probable degradation pathways of DCF were proposed based on the detected reaction products, including hydroxylation, C-N bond cleavage, decarboxylation and dehydrogenation.

Folates are required for the de novo biosynthesis of purines, thymine, methionine, glycine, and pantothenic acid, key metabolites that bacterial cells cannot survive without. Sulfonamides, which inhibit bacterial folate biosynthesis and are generally considered as bacteriostats, have been extensively used as broad-spectrum antimicrobials for decades. Here we show that, deleting relA in Escherichia coli and other bacterial species converted sulfamethoxazole from a bacteriostat into a bactericide. Not as previously assumed, the bactericidal effect of SMX was not caused by thymine deficiency. When E. coli ∆ relA was treated with SMX, reactive oxygen species and ferrous ion accumulated inside the bacterial cells, which caused extensive DNA double-strand breaks without the involvement of incomplete base excision repair. In addition, sulfamethoxazole showed bactericidal effect against E. coli O157 ∆ relA in mice, suggesting the possibility of designing new potentiators for sulfonamides targeting RelA. Thus, our study uncovered the previously unknown bactericidal effects of sulfonamides, which advances our understanding of their mechanisms of action, and will facilitate the designing of new potentiators for them., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Si, Gu, Wen, Wang, Fleming, Li, Xu, Bi and Deng.)

In this study, we determined the mechanisms and kinetics of the degradations of ibuprofen (IBP) and sulfamethoxazole (SMX), and identified the active species contributions in ferrous ion (Fe(II))/free chlorine (FC) system. Reactive chlorine species (RCS) were the major contributor to the degradations of IBP (73.0%) and SMX (59.3%), respectively, at pH 3. Due to the low reaction rates between Fe(IV) and target pollutants (k Fe(IV), IBP = (1.5 ± 0.03) × 10 3 M -1 s -1 and k Fe(IV), SMX = (4.8 ± 0.2) × 10 3 M -1 s -1 ) and the low [Fe(IV)] ss ((5.0 ± 0.6) × 10 -8 M), Fe(IV) was not the main contributor and only contributed 0.17% and 0.86% to the degradation of IBP and SMX, respectively, at pH 3. The degradations of pharmaceuticals were facilitated by acidic conditions. Chloride (Cl - ) accelerated the degradation of SMX and had a weak effect on the degradation of IBP. Natural organic matter limited the degradation of IBP and SMX. Overall, we demonstrated that multiple active oxidants (Fe(IV) and RCS) are produced by Fe(II)/FC and elucidated the mechanism of active oxidants degradation of pollutants., Competing Interests: Declaration of competing interest All of our authors declare no conflict of interest for this manuscript., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe 2+ ) aggravates it. The underlying mechanism remains unveiled. In this study, Fe 2+ was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe 2+ -mediated aroma deterioration. By enhancing the degradation of catechins, Fe 2+ dramatically increased the production of hydrogen peroxide (H 2 O 2 ). Fe 2+ and H 2 O 2 together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe 2+ enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe 2+ induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.

In this work, nanopyrite particles (NP) were synthesized by ball mill method and used as a novel source of Fe 2+ in the electro-activation of ozone and peroxydisulfate (PDS) for ofloxacin (OFX) removal. Fourier transform infrared spectroscopy, X-ray powder diffraction, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy analyzes were performed to characterize the as-made NP. Optimal values of operating parameters in NP/PDS and NP/O 3 processes were obtained. The OFX (10 mgL -1 ) removal efficiency and molar ratio of OFX: oxidant in NP/PDS and NP/O 3 processes were 92%, 0.1:11 and 89%, 0.1:9, respectively. Although the synergistic effect was observed in both systems, it was more significant in the NP/PDS. The results of free radical tracing showed that HO • and SO 4 •- had the more contribution in NP/O 3 and NP/PDS systems for OFX degradation, respectively. In this way, the OFX removal mechanism was the effective release of Fe 2+ from the NP in the electro-activation of O 3 and PDS. Moreover, the effect of electrocoagulation process on OFX removal was negligible. The as-made NP overcame the disadvantages of iron electrode corrosion and iron sludge production in the Fe-based classical electro-activation processes. Overall, the performance of the synthesized NP in the OFX oxidation was very successful in terms of sustainability, Fe 2+ distribution, removal efficiency, energy consumption and PDS or O 3 activation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

A new spiropyran-based fluorescent probe was developed for dual detection of Fe 2+ ion and pH. Addition of Fe 2+ and Ag + to the probe solution enhanced the fluorescence intensity by 6 and 5 fold, respectively. Addition of Fe 3+ , Hg 2+ and Ni 2+ 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 Fe 2+ ion in ethanol/water (9:1) medium. The detection limit of the probe for Fe 2+ is 0.77 µM. The suitable pH range for the probe to detect Fe 2+ was pH 3 - 9. Other metal ions including Li + , Na + , K + , Ag + , Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ , Mn 2+ , Sr 2+ , Hg 2+ , Ca 2+ , Mg 2+ , Al 3+ , Cr 3+ , and Fe 3+ did not cause marked interference with Fe 2+ 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.

Electrocatalytic properties of anode and the electrolyte composition are important parameters influence the degradation efficiency for aniline wastewater. Ti/RuO 2 -SnO 2 and Ti/RuO 2 -IrO 2 have been fabricated using thermal decomposition method and experiments in electrolyte containing 0.05 M Na 2 SO 4 , 0.05 M NaCl and 0.05 M Na 2 SO 4 +0.005 M FeSO 4 at different current density were conducted to study the influence on aniline degradation. Linear sweep voltammetry (LSV) showed that Ti/RuO 2 -SnO 2 had higher oxygen evolution potential and degrade aniline through electrochemical transformation and electrochemical combustion while Ti/RuO 2 -IrO 2 degrade aniline mainly through electrochemical transformation. The study showed that Ti/RuO 2 -SnO 2 had higher electrocatalytic activity towards the degradation of aniline than Ti/RuO 2 -IrO 2 anode in 0.05 M Na 2 SO 4 and in 0.05 M NaCl electrolyte. The maximum TOC removal efficiency for Ti/RuO 2 -SnO 2 was 64.2% at 40 mA cm -2 in Na 2 SO 4 electrolyte while the average MCE was 1.6% and the average EC TOC was 1.51 kWh (g TOC) -1 . On the contrary, the maximum TOC removal efficiency for Ti/RuO 2 -IrO 2 was 63.1% at 40 mA cm -2 in NaCl electrolyte while the average MCE was 1.6% and the average EC TOC was 1.95 kWh (g TOC) -1 . The presence of Fe 2+ in Na 2 SO 4 electrolyte would decrease the TOC removal efficiency except at low current density (20 mA cm -2 ) for Ti/RuO 2 -SnO 2 . These results indicated that Ti/RuO 2 -SnO 2 and Ti/RuO 2 -IrO 2 anode were suitable in Na 2 SO 4 and NaCl electrolyte, respectively, while the presence of Fe 2+ would inhibit aniline degradation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The transformation between hexavalent chromium (Cr 6+ ) and trivalent chromium (Cr 3+ ) has a significant impact on ecosystems, as Cr 6+ has higher levels of toxicity than Cr 3+ . In this regard, a variety of Cr 6+ reduction processes occurring in natural environments have been studied extensively. In this work, we investigate the reductive transformation of Cr 6+ by ferrous ions (Fe 2+ ) in ice at -20 °C, and compare the same process in water at 25 °C. The Fe 2+ -mediated reduction of Cr 6+ occurred much faster in ice than it did in water. The accelerated reduction of Cr 6+ in ice is primarily ascribed to the accumulation of Cr 6+ , Fe 2+ , and protons in the grain boundaries formed during freezing, which constitutes favorable conditions for redox reactions between Cr 6+ and Fe 2+ . This freeze concentration phenomenon was verified using UV-visible spectroscopy with o-cresolsulfonephthalein (as a pH indicator) and confocal Raman spectroscopy. The reductive transformation of Cr 6+ (20 µM) by Fe 2+ in ice proceeded rapidly under various Fe 2+ concentrations (20-140 µM), pH values (2.0-5.0), and freezing temperatures (-10 to -30 °C) with a constant molar ratio of oxidized Fe 2+ to reduced Cr 6+ (3:1). This result implies that the proposed mechanism (i.e., the redox reaction between Cr 6+ and Fe 2+ in ice) can significantly contribute to the natural conversion of Cr 6+ in cold regions. The Fe 2+ -mediated Cr 6+ reduction kinetics in frozen Cr 6+ -contaminated wastewater was similar to that in frozen Cr 6+ solution. This indicates that the variety of substrates typically present in electroplating wastewater have a negligible effect on the redox reaction between Cr 6+ and Fe 2+ in ice; it also proposes that the Fe 2+ /freezing process can be used for the treatment of Cr 6+ -contaminated wastewater., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Plasma medicine is a rapidly expanding new field of interdisciplinary research that combines physics, chemistry, biology, and medicine. Non-thermal atmospheric pressure plasma (NTAPP) has recently been applied to living cells and tissues, and has emerged as a novel technology for medical applications, such as wound healing, blood coagulation, and cancer treatment. NTAPP was found to affect cells indirectly through the treatment of cells with previously prepared medium irradiated by NTAPP, termed plasma-activated medium (PAM). The treatment of culture media with NTAPP results in the generation of a large amount of reactive oxygen species and reactive nitrogen species, and their derived species. We found that PAM triggered a spiral apoptotic cascade in the mitochondrial-nuclear network in A549 cancer cells. This process induced the depletion of total cellular NAD + and elevations in intracellular calcium ion, ultimately leading to cell death. We also detected the production of hydroxyl radical and elevations in intracellular ferrous ions in PAM-treated cells. The elevations observed in ferrous ions may have been due to their release from the intracellular iron store, ferritin. However, difficulties are associated with applying PAM to the clinical phase because culture media cannot be used for medical treatments. The anti-tumor activity of plasma-activated Ringer's solution was significantly stronger than that of PAM. At the end, we herein demonstrated the advantages of the combined application of plasma-activated acetate Ringer's solution and hyperthermia, a heat treatment at 42℃, for A549 cancer cell death and elucidated the underlying mechanisms.

ABSTRACT Formation of oxygen in the caffeine aqueous solutions occurs through self-decomposition reactions of the hydrogen peroxide, used as an oxidant in the photo-Fenton treatment. The total concentration of hydrogen peroxide used in the treatment would be the contribution of the stoichiometric concentration that reacts with the organic matter ([H 2 O 2 ] 0  = 2.0 mM) and the excess of oxidant that decomposes to oxygen, through radical mechanisms, according to a ratio of 0.8164 mmol H 2 O 2  mg -1 O 2 . When operating at concentrations lower than [H 2 O 2 ] 0  = 2.0 mM, oxygen is not released because there is no excess of oxidant. Moreover, it is verified that the ferrous ion catalyst is oxidized to ferric ion and its subsequent regeneration to ferrous ion. Working at concentrations higher than [H 2 O 2 ] 0  = 2.0 mM, oxygen is released in the water, verifying that the catalyst remains as ferric species, which does not regenerate. The reaction time in which oxygen evolution happpens depends on the concentration of catalyst used in the oxidation, verifying that the highest oxygen generation rates are obtained when applying [Fe] 0  = 10.0 mg L -1 . Once generated in the water, the maximum concentration of oxygen begins to decrease as the hydrogen peroxide is consumed, until reaching a constant value. The stages of formation and decrease of oxygen are adjusted to zero-order kinetics, estimating the kinetics constants as a function of the catalyst concentration: k f  = 29.48 [Fe] 0 -1.25 (mg O 2  L -1  min -1 ) and k d  = -0.006 [Fe] 0 2.0  + 0.244 [Fe] 0 -3.69 (mg O 2  L -1  min -1 ).

Extensive use of CuO nanoparticles (CuO-NPs ) inevitably leads to their accumulation in wastewater and toxicity to microorganisms that effectively treat nitrogen pollution. Due to the effects of different mediums, the sources of CuO-NPs-induced toxicity to microorganisms and methods to mitigating the toxicity are still unclear. In this study, CuO-NPs were found to impact the nitrate reduction of Pseudomonas tolaasii Y-11 mainly through the action of NPs themselves while inhibiting the ammonium transformation of strain Y-11 through releasing Cu 2+ . As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO 3 - and NH 4 + decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe 2+ significantly promoted the aggregation of CuO-NPs, reduced the possibility of contact with bacteria, and slowed down the damage of CuO-NPs to strain Y-11. When 0.01 mol/L Fe 2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO 3 - were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH 4 + were 55.95%, 96.71%, 38.11%, 20.71% and 7.43%, respectively. This study provides a method for mitigating the toxicity of CuO-NPs on functional microorganisms., Competing Interests: The authors declare there are no competing interests., (©2020 Yang et al.)

The inhibition of cadmium (Cd) absorption by selenium (Se) in rice may be associated with iron plaque (IP) formation, but the driving mechanisms are still unclear. This study investigated the effects of Se on the growth, oxidative toxicity, radial oxygen loss (ROL), IP formation, and Cd absorption of rice exposed to Cd. The results of this study showed that Cd stress elevated the levels of O 2 - and H 2 O 2 and depressed superoxide dismutase (SOD) and catalase (CAT) activities. The maximum ROL and IP were reduced by 43.3 % and 74.5 %, respectively. However, Se alleviated Cd toxicity by stimulating SOD and CAT activities by scavenging O 2 - and H 2 O 2 and enhancing the ROL profiles. Under culture conditions without Fe 2+ , Se had no impact on the total Cd levels in rice (T Cd ). However, with the addition of Fe 2+ , T Cd was significantly reduced by 23.3 % due to the enhancement of IP formation by Se. These results indicated that Se can reduce Cd accumulation in rice in the presence of Fe 2+ treatments. However, Se just alleviated Cd toxicity in the absence of Fe 2+ treatments. The enhancement of ROL was a potential reason for the elevated IP formation induced by Se., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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 O 2 - · . A weakly acidic environment was more favorable to TCE degradation. Nevertheless, HCO 3 - 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 evaluated SPC/Fe(II)/SDS system applied to remediate TCE The mechanism of HO· and O 2 - · generation had been investigated Cl - and HCO 3 - affected TCE degradation at different levels The performance of TCE removal in actual groundwater had been studied., (© 2020 Water Environment Federation.)

In modern society, the use of cosmetics has increased extensively; unfortunately, so-called several toxic metal salts are present as the colorant or filler in cosmetics. The ferrous ion (Fe 2+ ) is one of the metal ions used in cosmetics as a colorant. Ferrous ion (Fe 2+ ) is a vital component in live cells. Considering the adverse effect of high doses of ferrous ions in cosmetics and live cells, we developed a turn-on fluorescent probe P Fe( for quantitative estimation of ferrous ion (Fe II ) for quantitative estimation of ferrous ion (Fe 2+ showed a visual color change from colorless to orange in the presence of ferrous ion (Fe 2+ ) in the cosmetics. We observed that UV-absorption increased at 390 nm upon incubation with ferrous ion (Fe Fe( II has provided quantitative information on ferrous ion (Fe ) showed a visual color change from colorless to orange in the presence of ferrous ion (Fe 2+ ) in the cosmetics. We observed that UV-absorption increased at 390 nm upon incubation with ferrous ion (Fe 2+ ion pool via a fluorescence imaging. It is a new addition to the diagnostic inventory for detecting ferrous ion in live cells and cosmetics.Fe( II ) has provided quantitative information on ferrous ion (Fe 2+ ) in various cosmetics, kajol, lip balm, face foundation, mascara, eyeliner, lipliner, face makeup, sindoor, lipstick, nail polish in ppm level through the fluorescence signaling at 460 nm.The probe P Fe( II ) provided information on labile Fe 2+ ion pool via a fluorescence imaging. It is a new addition to the diagnostic inventory for detecting ferrous ion in live cells and cosmetics., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Soil waterlogging is a common problem in some agricultural areas, including regions under soybean ( Glycine max ) cultivation. In waterlogged soils, soil O 2 depletion occurs due to aerobic microorganisms and plants, affecting the metabolic and physiological processes of plants after suffering anoxia in their root tissue. Another harmful factor in this situation is the exponential increase in the availability of iron (Fe) in the soil, which may result in absorption of excess Fe. The present study sought to evaluate the response mechanisms in soybean leaves 'Agroeste 3680' by physiological and biochemical analyses associating them with the development of pods in non-waterlogged and waterlogged soil, combined with one moderate and two toxic levels of Fe. Gas exchange was strongly affected by soil waterlogging. Excess Fe without soil waterlogging reduced photosynthetic pigments, and potentiated this reduction when associated with soil waterlogging. Starch and ureide accumulation in the first newly expanded trifoliate leaves proved to be response mechanisms induced by soil waterlogging and excess Fe, since plants cultivated under soil non-waterlogged soil at 25 mg dm -3 Fe showed lower contents when compared to stressed plants. Thus, starch and ureide accumulation could be considered efficient biomarkers of phytotoxicity caused by soil waterlogging and excess Fe in soybean plants. The reproductive development was abruptly interrupted by the imposition of stresses, leading to a loss of pod dry biomass, which was largely due to the substantial decrease in the net photosynthetic rate, as expressed by area ( A ), the blockage of carbohydrate transport to sink tissues and an increase of malondialdehyde (MDA). The negative effect on reproductive development was more pronounced under waterlogged soil., (© Prof. H.S. Srivastava Foundation for Science and Society 2020.)

The Fe element is essential for human beings, but overdose of Fe leads to unwanted toxicity. However, overwhelming Fe accumulation in tumor cells could arouse strong oxidative stress for cancer therapy. Therefore, the fast and specific accumulation of Fe in tumor cells without systemic toxicity is critical for this purpose. Herein, we report that a carbon nanoparticles-Fe(II) complex (CNSI-Fe) could efficiently load Fe into tumor cells and inhibit tumor growth with low toxicity in H22 tumor-bearing mice. Upon intratumoral injection, CNSI-Fe only induced meaningful Fe increase in the tumor to significantly inhibit tumor growth with competitive efficiency to cis -dichlorodiammineplatinum(II). Fe accumulation stimulated the hydroxyl radical generation and serious oxidative stress in the tumor. Due to the lack of Fe accumulation in other tissues, CNSI-Fe was of low systemic toxicity to tumor-bearing mice. With the clinical success of CNSI for decades, CNSI-Fe might be used for cancer therapy through "off label" use to benefit patients immediately.

Nitroimidazoles are found in pharmaceuticals and personal care products (PPCPs) and, when discharged into the environment, have adverse effects on human health and survival. Advanced oxidation technologies (AOTs) based on persulfate (PS) can rapidly and efficiently degrade organic pollutants via strong oxidizing radicals under activation conditions. This study investigated the degradation of ronidazole (RNZ) by indirect electrolytic generation of PS and its activator, ferrous ion (Fe 2+ ). An electrochemical system was developed, with a high concentration of PS generated at the anode while the activator Fe 2+ was produced at the cathode. It showed that ammonium polyphosphate (APP) could effectively promote the electrolysis of PS. A high current efficiency (88%) at the anode could be obtained after 180 min at a high current density (300 mA cm -2 ). However, Fe 2+ was inhibited at the cathode due to material control. The degradation of RNZ in the Fe 2+ /PS system generated from the electrochemical system was also explored. Increasing PS concentration and Fe 2+ /PS ratio were beneficial to the RNZ degradation. In homogeneous reactions, the degradation efficiency of RNZ could be improved by decreasing the Fe 2+ addition rate through a peristaltic pump. Five intermediates were also detected and the degradation pathways were proposed. These findings provide a new method and mechanism for rapid and efficient degradation of RNZ., (Copyright © 2019. Published by Elsevier Ltd.)

Aquaculture wastewater seriously threatens the human health. In this study, non-poisonous iron was added into constructed wetlands to purify aquaculture wastewater and the wastewater treatment performances of CWs were explored under the treatment conditions of different plant species and different dosages of ferrous ions. The optimal treatment conditions were experimentally determined as follows: 20 mg/L ferrous ions in CWs planted with Canna indica after 7-day operation, the removal efficiencies of TN, TP and COD were respectively 95 ± 1.9%, 77 ± 1.2% and 62 ± 2%. The improvements in the pollutant removal performance depended on biological mechanisms of plants and microorganisms. The optimal dosage of iron ions could adjust enzyme activities and functional amino acids. Specific functional bacteria (Paracoccus detected based on nirK genetic information and Hydrogenophaga detected based on pufM genetic information) were cultured and domesticated by iron ions. The functional bacteria promoted nitrogen and phosphorus removals., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The coprecipitation of arsenic with Fe(III) by lime neutralization is widely used in industrial practices to treat arsenic-containing waste waters generated from mineral processing operations. In this work, coprecipitation was conducted directly at pH 8 to simulate the operations in hydrometallurgical practices, which differed from the conventional laboratory operations. Moreover, although ferric is the major species of iron in arsenic-containing waste waters, the coexistence of ferrous ions cannot be ignored. Therefore, the effect of different neutralization modes, as well as the effect of ferrous ions on the removal of arsenic and the stability of the generated arsenic-bearing wastes, was systematically investigated. The result showed that arsenic was still released back into the liquid phase under alkaline conditions even for the samples formed directly at alkaline pH. It was found that the extra addition of Fe(II) may exert negative effect on the stability of the as-formed Fe(II)-Fe(III)-As(V) coprecipitates at pH 7 - 10. The concentration of ferrous ions in the liquid/solid phase decreased with increasing pH for each sample formed at different Fe(II)/Fe(tot). The results indicated that complete oxidation of the ferrous ions before coprecipitation with arsenic should be conducted to achieve optimal stability of the arsenic-bearing wastes for hydrometallurgical practice and waste disposal., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Fat mass and obesity-associated (FTO) protein is a ferrous ion (Fe2+)/2-oxoglutarate (2-OG)-dependent demethylase preferentially catalyzing m6A sites in RNA. The FTO gene is highly expressed in the hypothalamus with fluctuation in response to various nutritional conditions, which is believed to be involved in the control of whole body metabolism. However, the underlying mechanism in response to different nutritional cues remains poorly understood. Here we show that ketogenic diet-derived ketone body β-hydroxybutyrate (BHB) transiently increases FTO expression in both mouse hypothalamus and cultured cells. Interestingly, the FTO protein represses Fto promoter activity, which can be offset by BHB. We then demonstrate that FTO binds to its own gene promoter, and Fe2+, but not 2-OG, impedes this binding and increases FTO expression. The BHB-induced occupancy of the promoter by FTO influences the assembly of the basal transcriptional machinery. Importantly, a loss-of-function FTO mutant (I367F), which induces a lean phenotype in FTOI367F mice, exhibits augmented binding and elevated potency to repress the promoter. Furthermore, FTO fails to bind to its own promoter that promotes FTO expression in the hypothalamus of high-fat diet-induced obese and 48-h fasting mice, suggesting a disruption of the stable expression of this gene. Taken together, this study uncovers a new function of FTO as a Fe2+-sensitive transcriptional repressor dictating its own gene switch to form an auto-regulatory loop that may link with the hypothalamic control of body weight., (© The Author(s) (2018). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.)

Graphdiyne (GDY) is a novel two-dimensional (2D) carbon allotrope with sp-hybridized carbon atoms and hexagonal rings. Because of its unique structure and electronic property, GDY was reported as a promising candidate applied in energy storage, catalysis, biosensing and so on. However, using GDY as a platform to immobilize metal ion or enzyme was still not reported. Here, we presented a GDY-based composite with dual-enzyme activity by immobilizing ferrous ion and glucose oxidase onto GDY sheet. GDY showed great adsorption capacity and maintained the high catalytic activity of ferrous ion. The ferrous ion preferred to adsorb in between the neighboring two C-C triple bonds of GDY with lower adsorption energy (-5.64 eV) if compared to graphene (-1.69 eV). Meanwhile, GDY exhibited the ability of adsorbing glucose oxidase while did not obviously influence the structure and catalytic activity of the enzyme. The as-prepared composite was successfully used in one-step blood glucose detection. This work provides a new insight on ion and enzyme immobilization by 2D material.

The Escherichia coli gene initially named ygaT is located adjacent to lhgO, encoding L-2-hydroxyglutarate oxidase/dehydrogenase, and the gabDTP gene cluster, utilized for γ-aminobutyric acid (GABA) metabolism. Because this gene is transcribed specifically during periods of carbon starvation, it was renamed csiD for carbon starvation induced. The CsiD protein was structurally characterized and shown to possess a double-stranded ß-helix fold, characteristic of a large family of non-heme Fe(II)- and 2-oxoglutarate (2OG)-dependent oxygenases. Consistent with a role in producing the substrate for LhgO, CsiD was shown to be a glutarate L-2-hydroxylase. We review the kinetic and structural properties of glutarate L-2-hydroxylase from E. coli and other species, and we propose a catalytic mechanism for this archetype 2OG-dependent hydroxylase. Glutarate can be derived from l-lysine within the cell, with the gabDT genes exhibiting expanded reactivities beyond those known for GABA metabolism. The complete CsiD-containing pathway provides a means for the cell to obtain energy from the metabolism of l-lysine during periods of carbon starvation. To reflect the role of this protein in the cell, a renaming of csiD to glaH has been proposed., (Copyright © 2019 Elsevier Inc. All rights reserved.)

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 400μmol/L, which was associated with the highest biomass of 4015.3mg/L and maximum ALA yield of 15.9mg/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., (Copyright © 2017. Published by Elsevier B.V.)

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 Δfur mutant decreased significantly compared to the parental strain. Conversely, •O 2 - and H 2 O 2 accumulate in colistin, gentamicin, rifampicin or tigecycline-treated Δfur mutant compared to the parental strain. Ferrous ion (Fe 2+ ) content of Δfur 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 Δfur mutant compared to the WT. Glutathione content of Δfur mutant was significantly depleted compared to parental strain following exposure to the antibiotics. We conclude that decreased capability of Δfur mutant to detoxify reactive oxygen species raised its susceptibility to antibiotics through Fenton chemistry., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

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., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The evolution of sludge filteration dewaterability, floc structure and hydrolytic kinetics with calcium peroxide oxidation pre-treatment was investigated in this study. The effect of sludge characteristics with combined process of ferrous ion and calcium peroxide was deeply analyzed and the result suggested that the sludge dewatering performance was improved first and then worsened after CaO 2 addition. When the dosage was 20 mg·g -1 , sludge reached its optimal dewaterability. At the same time, sludge was effectively dissolved and the floc structure became loose and broken with the increase of organic matters in the supernatant. Moreover, sludge solubilization process followed the pseudo-zero-order kinetic equation well and the reaction rate of sludge with CaO 2 treatment was 15.2 mg·L -1 ·h -1 . In addition, sludge floc lysis was enhanced by the treatment of ferrous ion and calcium peroxide oxidation, whilst sludge dewaterability was improved due to the reconstruction of sludge floc structure by the iron ions produced. This study provided theoretical basis for application of calcium peroxide pre-treatment and its combining technique in sludge treatment.

The oxidation of s-triazines (using atrazine (ATZ) as a model compound) by a solar-enhanced Fenton-like process involving persulfate and ferrous ion was studied. A flow-through tubular photoreactor was employed for the experiments. The solar-enhanced oxidative system involving ferrous ion and persulfate (Solar/S 2 O 8 2- /Fe 2+ ) showed the highest ATZ degradation efficiency when compared with other treatments (unactivated S 2 O 8 2- , Solar - sunlight only, S 2 O 8 2- /Fe 2+ , Solar/S 2 radicals were shown to be involved in ATZ oxidation using the radical scavengers methanol and tert-butyl alcohol. Furthermore, iron compounds were shown to act not only as catalysts but also as photo-sensitizers, as the introduction of ferrous ion into the reaction mixture led to an increased absorbance of the solution and expansion of the absorption spectrum into the longer wavelength spectral region.8 2- ). Complete degradation of ATZ and 20% reduction in total organic carbon (TOC) content were observed after 30min of the treatment. The in situ generated • ОН and SO 4 -• radicals were shown to be involved in ATZ oxidation using the radical scavengers methanol and tert-butyl alcohol. Furthermore, iron compounds were shown to act not only as catalysts but also as photo-sensitizers, as the introduction of ferrous ion into the reaction mixture led to an increased absorbance of the solution and expansion of the absorption spectrum into the longer wavelength spectral region., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Iron anode was employed to enhance the degradation of Orange G (OG) by permanganate (EC/KMnO 4 ). Continuously generated Fe 2+ from iron anode facilitated the formation of fresh MnO 2 , which plays a role in catalyzing permanganate oxidation. The EC/KMnO 4 system also showed a better performance to remove OG than Fe 2+ /KMnO 4 , indicating the importance of in situ formed fresh MnO 2 . Besides, the effects of applied current, KMnO 4 dosage, solution pH, and natural organics were evaluated and results demonstrated that high current and oxidant dosage are favorable for OG removal. And the application of iron anode has a promoting effect on the KMnO 4 oxidation over a wide pH range (5.0-9.0), while the Fe 2+ /KMnO 4 process does not. For natural organics, its presence could inhibit OG removal due to its competitive role. And the promoting effect of OG removal by the EC/KMnO 4 process in natural water was confirmed. At last, the EC/KMnO 4 process showed a satisfying performance on the decolorization and mineralization of OG. This study provides a potential technology to enhance permanganate oxidation and broadens the knowledge of azo dye removal.

The potential mechanisms underlying the increase in serum iron concentration in gamma-irradiated mice were studied. The gamma irradiation dose used was 4 Gy, and cobalt-60 ((60)Co) source was used for the irradiation. The dose rate was 0.25 Gy/min. In the serum of irradiated mice, the concentration of ferrous ions decreased, whereas the serum iron concentration increased. The concentration of ferrous ions in irradiated mice returned to normal at 21 day post-exposure. The concentration of reactive oxygen species in irradiated mice increased immediately following irradiation but returned to normal at 7 day post-exposure. Serum iron concentration in gamma-irradiated mice that were pretreated with reduced glutathione was significant lower (p < 0.01) than that in mice exposed to gamma radiation only. However, the serum iron concentration was still higher than that in normal mice (p < 0.01). This change was biphasic, characterized by a maximal decrease phase occurring immediately after gamma irradiation (relative to the irradiated mice) and a recovery plateau observed during the 7th and 21st day post-irradiation, but serum iron recovery was still less than that in the gamma-irradiated mice (4 Gy). In gamma-irradiated mice, ceruloplasmin activity increased and serum copper concentration decreased immediately after irradiation, and both of them were constant during the 7th and 21st day post-irradiation. It was concluded that ferrous ions in irradiated mice were oxidized to ferric ions by ionizing radiation. Free radicals induced by gamma radiation and ceruloplasmin mutually participated in this oxidation process. The ferroxidase effect of ceruloplasmin was achieved by transfer of electrons from ferrous ions to cupric ions.

This work investigated the degradation of methyl orange by ozone in the presence of ferrous and persulfate ions (O3/Fe(2+)/S2O8(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 (O3/Fe(2+)) were also carried out, and the results show approximately 10% higher degradation rate and COD removal in the O3/Fe(2+)/S2O8(2-) process than in the O3/Fe(2+) process. Additionally, the intermediates of the degradation process were analyzed to ascertain the degradation products., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Increased usage and discharge of sunscreens have led to ecological safety crisis, and people are developing the advanced oxidation processes (AOPs) to treat them. The present study aimed to determine the degradation efficiency and mechanism of the sunscreen agent p-aminobenzoic acid (PABA) using the UV/Fe(2+)/persulphate (PS) method. A series of irradiation experiments were conducted to optimise the system conditions and to study the impacts of the natural anion. Free radicals and degradation products were identified in order to clarify the degradation mechanism. Initial PS and Fe(2+) concentrations showed significant impacts on PABA degradation. Natural anions, such as Cl(-), NO3 (-), H2PO4 (-) and HCO3 (-), impeded PABA degradation because of ion (Fe(2+)) capture, radical scavenging or pH effects. Hydroxyl (HO·) and sulphate (SO4 (·-)) radicals were two main radicals observed in the UV/Fe(2+)/PS system; of these, SO4 (·-) showed greater effects on PABA degradation. Over 99 % of the available PABA was completely degraded into carbon dioxide (CO2) and water (H2O) by the UV/Fe(2+)/PS system, and the remaining PABA participated in complex radical reactions. By-products were identified by total ion chromatography and mass spectrometry. Our research provides a treatment process for PABA with high degradation efficiency and environmental safety and introduces a new strategy for sunscreen degradation.

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 H2O2 also decreased presumably by the production of hydroxyl radical (·OH). Reduction in the endogenous H2O2 concentration was recorded to be 38% and 98% in the absence and presence of Fe(2+) respectively in the first day and the H2O2 level remained considerably low until day 7 which then gradually increased slightly. Simultaneous reduction of IBP and endogenous H2O2 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 (NaHCO3) 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., (Copyright © 2015 Elsevier Ltd. All rights reserved.)