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In the copper (Cu) hydrometallurgical process, the extractant, and impurity ions in the leaching process would inevitably enter the electrolyte in the electrodeposition with the process cycle. And with the recycling of electrolyte, the impurities would continue to accumulate. When the accumulation of impurities exceeds a certain limit, it could have a large negative impact on the deposited Cu. In this paper, the effects of the ferrous ion (Fe2+) and the commonly used extractant Lix984 (5-nonylsalicylaldehyde oxime and 2-hydroxy-5-nonylacetophenone oxime 1:1 mixture) on the morphology, current efficiency (CE) and energy consumption of Cu cathodes were investigated. In addition, the electrochemical mechanisms were investigated using electrochemical methods such as cyclic voltammetry (CV), linear scanning voltammetry (LSV), Tafel linear fitting and chronopotentiometry (CP). When the Fe2+ concentration was 2.0 g/L, the CE decreased sharply to 93.63%, which was 6.21% lower than normal. And the Lix984 at 50 mg/L reduced the CE from 5.88% to 93.99%. The energy consumption increased by up to 89 kWh/ (t Cu). Electrochemical studies showed that high concentrations of Fe2+ and/or Lix984 in the electrolyte significantly inhibited Cu deposition by increasing the overpotential, decreasing the deposition rate, and covering the electrode surface, resulting in larger Cu coating roughness and larger grain size. Therefore, the concentration of Fe2+ and organic impurities in the electrolyte should be appropriately controlled before proceeding to Cu electrodeposition to obtain a favorable quality Cu cathode. [ABSTRACT FROM AUTHOR]

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]

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 NH4+–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 CODCr 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. [ABSTRACT FROM AUTHOR]

Excessive cadmium (Cd) in rice, caused by Cd pollution of farmlands, poses a serious threat to human health. In this study, a pot experiment was conducted to investigate the effects of two doses of CaCO3 (Ca1: 2 g kg-1, Ca2: 10g kg-1), two types of Fe(II) (EDTA-Fe(II) and FeSO4; 0.14 g Fe kg-1), and their combined application on the uptake and accumulation of Cd in rice plants grown in Cd-contaminated acidic soil. The results revealed that FeSO4 significantly increased rice grain biomass, whereas the other treatments had no significant effects. Further, the addition of EDTA-Fe(II) or FeSO4 significantly enhanced iron plaque formation on the root surface and increased the Fe content in the rice plants and porewater. Compared to the control, CaCO3 addition weakened the formation of iron plaque and reduced the Fe concentration in the porewater and root tissue, stems and leaves, whereas the Fe concentration in brown rice and the husks remained unaffected. Combined application of CaCO3 and Fe(II) significantly promoted the formation of iron plaque and increased the Fe concentration in brown rice. However, the Cd concentration in the iron plaque was reduced by CaCO3 addition but increased by Fe(II) treatment. Notably, all treatments reduced the Cd concentration in all rice plant tissues. The application of Ca1, Ca2, EDTA-Fe(II), FeSO4, Ca1+EDTA-Fe(II), Ca1+FeSO4, Ca2+EDTA-Fe(II) and Ca2+FeSO4 significantly reduced the Cd concentration in brown rice by 69%, 63%, 51%, 60%, 46%, 39%, 38%, and 29%, respectively. These results indicate that the application of CaCO3, EDTA-Fe(II)/FeSO4, or their combination can effectively reduce Cd accumulation and translocation in rice plants. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recovery of valuable metals from used portable batteries is gaining widespread importance owing to the conservation of natural sources and possible environmental pollution from these batteries. In this paper, zinc (Zn) and manganese (Mn) recovery from waste zinc–carbon (Zn–C) batteries was investigated. For this purpose, two-stage leaching experiments were conducted in the laboratory. In the first stage, only sulfuric acid (H2SO4) solution was used, and in the second stage, ferrous ion (Fe2+) was added to the H2SO4 solution as a reducing agent. The burnt and wet sieved battery powder was obtained from manually disassembled waste Zn–C batteries. Particle size fraction of -75 + 53 µm battery powder contained 23.75% Zn and 48.47% Mn. Leaching experiments performed with a solid-to-liquid ratio of 4 g/L showed that Zn and Mn were leached with a recovery of 100% and 58.55%, respectively, using 400 rpm stirring speed, 0.25 M H2SO4 solution, and 70 °C temperature. Reductive leaching experiments showed that all of the Mn was recovered in 0.25 M H2SO4 solution using 3.6 × 10–2 M Fe2+ as a reducing agent at 60 °C temperature. [ABSTRACT FROM AUTHOR]

A continuous stirred tank reactor (CSTR) was utilized in this study to enrich and cultivate anaerobic ammonia oxidation process (ANAMMOX) granular sludge by gradually decreasing its pH, and to investigate the effects of different concentrations of ferrous ions (Fe2+) on the activity of ANAMMOX granular sludge cultivated under biased acidic conditions. The final nitrogen removal of ANAMMOX deteriorated at pH 6.30–6.50 after 220 days of continuous operation, but the nitrogen removal of ANAMMOX was favorable at pH 6.50–7.00. This indicates that a slightly acidic environment (pH = 6.50–7.00) promotes the activity of ANAMMOX, but the pH should not be too low (pH = 6.30–6.50). In the reactor, Candidatus Kuenenia was consistently the dominant ANAMMOX genus and its abundance declined from 11.70% on day 1 to 10.44% on day 220. As Fe2+ concentrations were increased (10, 20, 30 mg/L) in ANAMMOX granular sludge cultured in an acidic environment, the nitrogen removal effects gradually increased. In addition, with the increase in Fe2+ concentrations, the total nitrogen removal load (NRL) in the reactor was increased from 1.16 kg/(m3/d) to 1.42 kg/(m3/d). Increases in Fe2+ concentration did not result in inhibition of ANAMMOX, which may be attributed to the morphology of sludge and the shape of the reactor. As a result of the present study, new insights were gained into the physiological characteristics of ANAMMOX in an acidic environment over the long term, and how Fe2+ affects its ability to remove nitrogen from the environment. [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]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, the process of ferrous ion activating persulfate (PS) was assigned to degrade bisphonel A (BPA) in aqueous solution. The factors affecting the activation of PS by ferrous iron and the degradation rate of BPA have been systematically studied. It was found that the amount of the catalyst ferrous ion, the concentration of the oxidant BPA, the concentration of the substrate BPA, the initial pH value and the initial reaction temperature have important influences on the degradation of BPA in Fe2+/PS system. The best conditions for this experiment was determined as: [FeSO4]0=0.1 g/L, [PS]0=0.4mM, and pH0=5.0. Increasing the concentration of the substrate BPA led to the reduction of the removal rate of BPA. The increase in temperature utilized the progress of catalytic reaction and the degradation of BPA, and the degradation of BPA could reach 96.7% at 70 °C. [ABSTRACT FROM AUTHOR]

In order to investigate the anti-scaling and anti-corrosion characteristics of an electrostatic anti-fouling system in the application process, the influence of an electrostatic field (EF) on the structure and dynamics of hydrated Ca2+ and hydrated Fe2+ in a mixed aqueous system was studied through the calculation and analysis of the radial distribution function (RDF), self-diffusion coefficients, viscosity, and hydrogen bond structure by using molecular dynamics simulation. The study results show that the EF can decrease the radius of the first water shell of hydrated Ca2+ but increase that of Fe2+, which will reduce the possibility of forming calcite. The EF can make water molecules and Fe2+ more active, which can hinder iron release and thus decrease iron corrosion products. In addition, the EF can enhance the hydrogen structure of water molecules in the aqueous solution. [ABSTRACT FROM AUTHOR]

This study aimed to improve the speed of the electrochemical process by graphene oxide nanoparticle as a current accelerator in Acid Blue 25 removal from aqueous solutions. To do so, the effect of different parameters including pH, dye concentration, sodium persulfate concentration, the ratio of sodium persulfate to iron (II) sulfate concentration, current density, and the distance between electrodes was investigated on dye removal. Under optimal conditions of pH = 5, dye concentration = 200 mg/L, sodium persulfate concentration = 500 mg/L, iron (II) sulfate concentration = 100 mg/L, current density = 16.67 mA/cm2, and electrode distance = 2 cm, 95% of dye was removed after 60 min in the electro-activated persulfate process; while the modified electro-activated persulfate process achieved 95% dye removal after only 40 min under the same conditions. This system was able to remove 90% of dye after 60 min at a higher concentration (300 mg/L). Also, the modified electro-activated persulfate process obtained the removal of 80% of COD, and 54% of TOC after 180 min in the mentioned conditions, for the dye concentration of 300 mg/L. HIGHLIGHTS Geraphene oxide nanoparticles raised the reaction rate by 17% by increasing the conductivity.; The increase in conductivity, decreased the energy consumption by 50%.; More 100 mg/L dye can be removed by the modified system.; The oxidation state reduction made the dye structure simpler with less toxicity.;

Copyright of Nativa is the property of Revista Nativa and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Removal of ferrous ions from waste battery leachate by manganese dioxide oxidation--sodium carbonate precitation process was researched. The effects of manganese dioxide amount, leachate pH, ferrous ions initial mass concentration, stirring speed, reaction time and temperature were examined. The results show that for 500 mL leachate, under the conditions of pH of 1.5, ferrous ions initial mass concentration of 1.3 g/L, reaction temperature of 65 °C, stirring speed of 400 r/min, and manganese dioxide amount of 1.2 times of theory amount, reaction time of 40 min, the ferrous ions oxidation rate is 99.7%. The leaching solution pH is adjusted to 4.0 using sodium carbonate, under 65 °C for 30 min, the ferrous ions removal rate reaches 99.8%. The effect of ferrous ions removal is good. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

This study was conducted to evaluate the performance of anammox reaction on the addition of iron. Iron was added in the form of FeSO4 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. [ABSTRACT FROM AUTHOR]

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. [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]

Abstract p-Anisidine being a component of wastewater generated through dye and pharmaceutical industries is highly toxic and carcinogenic in nature. Therefore, its presence in wastewater requires prior treatment before its disposal from the point of safety of human and aquatic life. Fenton’s oxidation is a type of advanced oxidation processes which is efficient, ecofriendly and reliable, and this was not studied for the removal of p-anisidine from wastewater. In this study, the effect of influent pH, hydrogen peroxide (H2O2) concentration and ferrous ion (Fe2+) concentration on the removal of p-anisidine by Fenton’s reagent was carried out on a laboratory scale. All samples were examined for initial and final concentrations of p-anisidine using UV–Vis spectrophotometry, and also initial and final COD was analyzed. p-Anisidine shows maximum absorbance at 296 nm. At pH 2.5 and [H2O2]/[Fe2+] of 70:1 for the initial p-anisidine concentration of 0.5 mM and for 24 h reaction time, the maximum removal of p-anisidine was found to be 88.95% and maximum COD removal was 76.43%.

• O 2 microbubbles have strong oxidizing ability in H 3 PO 4 solutions due to the generation of ROS. • The main ROS specie generated by O 2 microbubbles in H 3 PO 4 solution was determined to be H 2 O 2 • The generation of H 2 O 2 was via a sequential one-electron reduction of O 2 molecule. • The generation of H 2 O 2 was affected by the temperature and H 3 PO 4 concentration. • The activation energy of Fe2+ oxidation reaction was significantly reduced due to the strong oxidation effects of ROS generated by the microbubbles. Microbubbles have been widely used in advanced oxidation processes due to the generation of reactive oxygen species (ROS). In this study, the oxidation of ferrous ions in phosphoric acid solutions has been examined, focusing on the advanced oxidation activity of oxygen microbubbles. Ultraviolet spectroscopy was used to determine the species and content of ROS. Electron spin-resonance spectroscopy and radical quenching experiments have confirmed the path of ROS generation. It is concluded that the main ROS in the phosphoric acid solution was H 2 O 2 , and the generation of H 2 O 2 was due to sequential single electron reduction of oxygen molecules. The amount of H 2 O 2 generated was determined to be dependent on the temperature and phosphoric acid concentration, and under the optimal conditions (100 ºC and 7 mol/L H 3 PO 4), 4.23 mmol/L H 2 O 2 was produced from microbubbles. The kinetics analysis with respect to the oxidation of ferrous ions suggested significant reduction of reaction activation energy from greater than 56.1kJ/mol to 43.84 kJ/mol due to the oxidation via ROS, demonstrating that microbubble intensification is a facile and effective advanced oxidation method. [Display omitted] [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]

The transformation between hexavalent chromium (Cr6+) and trivalent chromium (Cr3+) has a significant impact on ecosystems, as Cr6+ has higher levels of toxicity than Cr3+. In this regard, a variety of Cr6+ reduction processes occurring in natural environments have been studied extensively. In this work, we investigate the reductive transformation of Cr6+ by ferrous ions (Fe2+) in ice at −20 °C, and compare the same process in water at 25 °C. The Fe2+-mediated reduction of Cr6+ occurred much faster in ice than it did in water. The accelerated reduction of Cr6+ in ice is primarily ascribed to the accumulation of Cr6+, Fe2+, and protons in the grain boundaries formed during freezing, which constitutes favorable conditions for redox reactions between Cr6+ and Fe2+. 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 Cr6+ (20 µM) by Fe2+ in ice proceeded rapidly under various Fe2+ concentrations (20–140 µM), pH values (2.0–5.0), and freezing temperatures (–10 to −30 °C) with a constant molar ratio of oxidized Fe2+ to reduced Cr6+ (3:1). This result implies that the proposed mechanism (i.e., the redox reaction between Cr6+ and Fe2+ in ice) can significantly contribute to the natural conversion of Cr6+ in cold regions. The Fe2+-mediated Cr6+ reduction kinetics in frozen Cr6+-contaminated wastewater was similar to that in frozen Cr6+ solution. This indicates that the variety of substrates typically present in electroplating wastewater have a negligible effect on the redox reaction between Cr6+ and Fe2+ in ice; it also proposes that the Fe2+/freezing process can be used for the treatment of Cr6+-contaminated wastewater.

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 Cu2+. As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO3− and NH4+ decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe2+ 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 Fe2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO3- were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH4+ 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.

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]

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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 ([H2O2]0 = 2.0 mM) and the excess of oxidant that decomposes to oxygen, through radical mechanisms, according to a ratio of 0.8164 mmol H2O2 mg−1 O2. When operating at concentrations lower than [H2O2]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 [H2O2]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: kf = 29.48 [Fe]0−1.25 (mg O2 L−1 min−1) and kd = −0.006 [Fe]02.0 + 0.244 [Fe]0–3.69 (mg O2 L−1 min−1). [ABSTRACT FROM AUTHOR]

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 Cu2+. As the content of CuO-NPs increased from 0 to 20 mg/L, the removal efficiency of NO3− and NH4+ decreased from 42.29% and 29.83% to 2.05% and 2.33%, respectively. Exogenous Fe2+ 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 Fe2+ was added to 0, 1, 5, 10 and 20 mg/L CuO-NPs treatment, the removal efficiencies of NO3 - were 69.77%, 88.93%, 80.51%, 36.17% and 2.47%, respectively; the removal efficiencies of NH4+ 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. [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]

Soil waterlogging is a common problem in some agricultural areas, including regions under soybean (Glycine max) cultivation. In waterlogged soils, soil O2 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. [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]

Online UV-Vis spectrophotometer technology as accurate, convenient and fast monitoring method was used to detect instantaneous dye concentration in aqueous medium. Ferrous ion coupling with Persulphate to degrade methylene blue (MB) exhibited a very high degradation rate, and therefore online UV-Vis spectrophotometer showed great advantage in this study. The effects of ferrous ion concentration, sodium Persulphate concentration, pH value and initial MB concentration on MB degradation were investigated. The online spectrophotometer could minimize the systematic error caused by the termination of adding chemicals and manual operation. At room temperature, the optimal condition was acquired with 73.6% MB removal after 100s at neutral medium when initial ferrous dosage and sodium Persulphate were 1.25 mmol/L and 0.2 mmol/L, respectively. Fe2+/S2O8 2- system exhibited a great degradation efficiency in acidic or neutral environment. [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]

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 (Fe2+) aggravates it. The underlying mechanism remains unveiled. In this study, Fe2+ was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe2+-mediated aroma deterioration. By enhancing the degradation of catechins, Fe2+ dramatically increased the production of hydrogen peroxide (H2O2). Fe2+ and H2O2 together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe2+ 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 Fe2+ 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.

Aluminum is a recognized neurotoxin in dialysis encephalopathy and may also be implicated in the etiology of neurodegenerative disease, particularly Alzheimer's disease. Alzheimer's disease is suspected to be associated with oxidative stress, possibly due to the pro-oxidant properties of beta-amyloid present in the senile plaques. The underlying mechanism by which this occurs is not well understood although interactions between amyloid and iron have been proposed. The presence of low molecular weight iron compounds can stimulate free radical production in the brain. This study provides a possible explanation whereby both aluminum and beta-amyloid can potentiate free radical formation by stabilizing iron in its more damaging ferrous (Fe2+) form which can promote the Fenton reaction. The velocity, at which Fe2+ is spontaneously oxidized to Fe3+ at 37 degrees C in 20 mM Bis-Tris buffer at pH 5.8, was significantly slowed in the presence of aluminum salts. A parallel effect of prolongation of stability of soluble ferrous ion, was found in the presence of beta-amyloid fragment (25-35). Ascorbic acid, known to potentiate the pro-oxidant properties of iron, was also capable of markedly stabilizing ferrous ions.

Aluminum is a recognized neurotoxin in dialysis encephalopathy and may also be implicated in the etiology of neurodegenerative disease, particularly Alzheimer's disease. Alzheimer's disease is suspected to be associated with oxidative stress, possibly due to the pro-oxidant properties of beta-amyloid present in the senile plaques. The underlying mechanism by which this occurs is not well understood although interactions between amyloid and iron have been proposed. The presence of low molecular weight iron compounds can stimulate free radical production in the brain. This study provides a possible explanation whereby both aluminum and beta-amyloid can potentiate free radical formation by stabilizing iron in its more damaging ferrous (Fe2+) form which can promote the Fenton reaction. The velocity, at which Fe2+ is spontaneously oxidized to Fe3+ at 37 degrees C in 20 mM Bis-Tris buffer at pH 5.8, was significantly slowed in the presence of aluminum salts. A parallel effect of prolongation of stability of soluble ferrous ion, was found in the presence of beta-amyloid fragment (25-35). Ascorbic acid, known to potentiate the pro-oxidant properties of iron, was also capable of markedly stabilizing ferrous ions.

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]

p-Anisidine being a component of wastewater generated through dye and pharmaceutical industries is highly toxic and carcinogenic in nature. Therefore, its presence in wastewater requires prior treatment before its disposal from the point of safety of human and aquatic life. Fenton's oxidation is a type of advanced oxidation processes which is efficient, ecofriendly and reliable, and this was not studied for the removal of p-anisidine from wastewater. In this study, the effect of influent pH, hydrogen peroxide (H2O2) concentration and ferrous ion (Fe2+) concentration on the removal of p-anisidine by Fenton's reagent was carried out on a laboratory scale. All samples were examined for initial and final concentrations of p-anisidine using UV–Vis spectrophotometry, and also initial and final COD was analyzed. p-Anisidine shows maximum absorbance at 296 nm. At pH 2.5 and [H2O2]/[Fe2+] of 70:1 for the initial p-anisidine concentration of 0.5 mM and for 24 h reaction time, the maximum removal of p-anisidine was found to be 88.95% and maximum COD removal was 76.43%. [ABSTRACT FROM AUTHOR]