Effect Of Ferric Ions Research Articles

Effects of Ferric Ions on Cellulose Nanocrystalline-Based Chiral Nematic Film and Its Applications.

Chiral nematic materials have been attracting attention in fields of advanced functional applications due to their unique iridescent colors and tunable helical structure. A precisely decreased pitch is of importance for construction and applications of chiral nematic materials; however, it remains a huge challenge. Herein, cellulose nanocrystal (CNC) is selected as a constructed matrix for chiral nematic films, and ferric chloride (FeCl3) is used as a modification agent. We investigate the effects of the ferric ion loads on the helical structure and optical characteristics of iridescent film. Subsequently, the influence of ferric ions on the assembly process of CNC liquid crystal and the regulation of the structure color of self-assembled monolayers are discussed. Therefore, the CNC/FeCl3 chiral nematic films showed a blueshifted structural color from orange to blue, which highlights a simple route to achieve the regulation of decreased pitch. Further, we have applied this CNC/FeCl3 chiral nematic film for benzene gas detection. The sensing performance shows that the CNC/FeCl3 chiral nematic film reacts to benzene gas, which can be merged into the nematic layer of the CNC and trigger the iron ions chelated on the CNC, consequently arousing the redshift of the reflected wavelength and the effective colorimetric transition. This CNC/FeCl3 chiral nematic film is anticipated to boost a new gas sensing mechanism for faster and more effective in-situ qualitative investigations.

Effects of Bath Composition and Current Density on the Electrodeposition Behavior of Fe–Ni Invar Alloy

Fe–Ni invar alloy (Fe 64–Ni 36 wt%) has a very low coefficient of thermal expansion (CTE) than any other metals. For this reason, it has been used as fine metal mask (FMM) in RGB patterning of OLED manufacture process. However, as the resolution of OLED display is getting higher, the thickness of FMM is getting thinner and then the conventional extruded invar sheet cannot be used directly. The electrodeposition of invar can be the alternative for fabrication of thin FMM. In this study, the Fe–Ni alloy were electrodeposited varying bath compositions and current density. Also, the effects of ferric ion (Fe3+), produced during electrodeposition on inert anode, on the behavior of deposition were investigated. Finally, the Fe–Ni alloy with 36–40 wt% Ni were obtained at 50 mA/cm2 in 0.30 M Fe2+ bath. The back side and front side composition of the deposits were analyzed to evaluate the composition uniformity of the Fe–Ni alloys. Generally, the Fe content of back side of the deposits were higher than that of front side.Graphical

Effect of ferric ions on surface sulfidization of hemimorphite and implications for xanthate adsorption

• Addition of Fe 3+ weakened the surface activity of hemimorphite. • The sulfidization of hemimorphite was depressed in the presence of Fe 3+ . • Adsorption of xanthate on hemimorphite surfaces was hindered by Fe 3+ . The existence of ferric ions (Fe 3+ ) in the pulp solution will severely affect the surface properties and flotation performance of targeted minerals, so its specific effect on the interaction of flotation reagents with the mineral surface must be understood. In this work, the effect of Fe 3+ on the surface sulfidization of hemimorphite was investigated, and the interaction mechanism of Fe 3+ with the hemimorphite surface was clarified. The results of time-of-flight secondary-ion mass spectrometry and X-ray photoelectron spectroscopy indicated that the addition of Fe 3+ before sulfidization generated Fe–OOH species and hindered the formation of active sulfide species on hemimorphite particles. Infrared spectroscopy and contact-angle measurements showed that the addition of Fe 3+ was detrimental to the adsorption of xanthate species on hemimorphite particles, prohibiting the formation of hydrophobic hemimorphite surfaces in the Fe 3+ –sulfidization–xanthate system. Thus, the presence of Fe 3+ in the pulp of hemimorphite was not conducive to the formation of the desired sulfidization products and stable adsorption layers of xanthate on its surface, resulting in unsatisfactory floatability of zinc oxide minerals containing hemimorphite.

Degradation of atrazine in water by Bi2MoO6 and visible light activated Fe3+/peroxymonosulfate coupling system

In this study, the effects of ferric ion (Fe3+) on the degradation of atrazine (ATZ) in Bi2MoO6/peroxymonosulfate (PMS) system under visible light irradiation was investigated. With the addition of Fe3+, ATZ in the visible light/Bi2MoO6/PMS system degraded rapidly after 20 min treatment (removal rate > 99%). The enhancement of ATZ removal can be attributed to the role of Fe3+. As an electron transfer mediator, Fe3+ not only inhibits the recombination of photo-charges and prolongs the life of photogenerated carriers, but also promotes the activation of PMS by accelerating the electron transfer from Bi2MoO6 to PMS. The generation of •OH and SO4•− in the system was determined via electron paramagnetic resonance (EPR) technology and quenching experiments. Furthermore, the characterization of Bi2MoO6 before and after reaction, influence of the reaction parameters (i.e., catalyst and PMS dosages, Fe3+ and ATZ concentration, initial pH), influence of inorganic anions and humic acid, and the recyclability of catalyst in the vis/Bi2MoO6/PMS/Fe3+ system was also investigated. Additionally, the existence of Fe3+ also exhibits a wide selectivity for the degradation of different pollutants and high treatment efficiency. In general, the vis/Bi2MoO6/PMS/Fe3+ system demonstrated the potential as an efficient, economical, and environment-friendly water treatment process.

Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion.

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.

Elimination of Ferric Ion Effect on Separation between Kyanite and Quartz Using Citric Acid as Regulator

Ferric ions produced during grinding influence the flotation separation between kyanite and quartz adversely. In this study, citric acid was used as a regulator to eliminate the effect of ferric ions on the separation of kyanite from quartz with sodium oleate (NaOL) as a collector. The microflotation test results indicated that the quartz was selectively activated by FeCl3 and maintained significant quartz recovery. However, the citric acid could selectively eliminate the effect of ferric ions on the quartz and minimally influenced the kyanite. Contact angle tests demonstrated that FeCl3 significantly increased the interaction between NaOL and quartz, resulting in the high hydrophobicity of quartz, and the addition of citric acid made the quartz surface hydrophilic again but slightly influenced the kyanite. Fourier-transform infrared spectroscopy showed that FeCl3 facilitated NaOL adsorption onto the quartz surface, and the addition of citric acid eliminated the activation of FeCl3 on the quartz, resulting in the nonadsorption of NaOL onto the quartz surface. However, the FeCl3 and citric acid exhibited a negligible effect on NaOL adsorption onto the kyanite surface. X-ray photoelectron spectroscopy analysis indicated that the citric acid eliminated FeCl3 activation on the quartz.

DFT study and electrochemical investigation of Fe3+ion interaction on chalcopyrite (0 0 1)-S and M (M = Cu, Fe) surfaces: A thermodynamic insights

Ferric sulfate is a common oxidant of chalcopyrite leaching in an acidic medium, and the oxidation of chalcopyrite in the presence of ferric (Fe3+) ion increases copper extraction. In this work, the effect of ferric ion on chalcopyrite leaching is investigated by electrochemical analysis (cyclic voltammetry and linear sweep voltammetry methods) and density functional theory study. According to the cyclic voltammetry data, the presence of ferric ion showed the positive effect on the anodic and cathodic reactions to reduce the non-faraday region. Moreover, the Tafel plots revealed that the inactive region was removed by the presence of ferric ion with increasing corrosion current density. The reaction free energy value, resulting in the density of corrosion current, was related to the coulombic reaction of electroactive species (Fe3+ ion) with the surface. Subsequently, Fe3+ ion interaction with the (001)-S and (001)-M surfaces (M = Fe and Cu) of chalcopyrite was studied by using the density functional theory calculations. The computational data indicated that the Fe3+ ion interaction on chalcopyrite surfaces was favorable. In order, the presence of sulfur atoms decreased the coordination of the surface cations lead to more reactivity of surfaces. Thermodynamic data from computational and electrochemical studies showed that the interaction of Fe3+ ion with surfaces of chalcopyrite is a spontaneous reaction. The value of free energy for the ferric ion interaction in the presence of pyrite was obtained −17/8 kJ/nonindicated positive effect of pyrite on the reaction with increasing the reduction rate of Fe3+ ion.

Effect of Ferric Ions on Sulfidization Flotation of Oxidize Digenite Fine Particles and Their Significance

Digenite fine particles are easily oxidized and ferric ions (Fe3+) commonly exist in the flotation pulp of digenite. This study investigated the effect of Fe3+ on the sulfidization flotation of oxidized digenite fine particles using sodium butyl xanthate (SBX) as a collector. The results of microflotation experiments show that the flotation rate and recovery of oxidized digenite fine particles can be improved by adding Na2S and SBX, whereas the existence of large amounts of Fe3+ is not beneficial for the sulfidization flotation of digenite. The results of Fe3+ adsorption, zeta potential, and contact angle measurements indicate that Fe3+ can be adsorbed on the digenite surface mainly in the form of Fe(OH)3, which hinders the adsorption of SBX and significantly reduces the surface hydrophobicity of digenite. X-ray photoelectron spectroscopy analysis further suggests that the poor surface hydrophobicity of digenite in the presence of Fe3+ is due to the production of large amounts of hydrophilic iron and copper oxides/hydroxides on the surface. Furthermore, optical microscopy analysis shows that these hydrophilic species effectively disperse digenite fine particles in the pulp, which eventually leads to the poor floatability of digenite. Therefore, it is necessary to reduce the amount of Fe3+ present in the pulp and adsorbed on digenite surface before sulfidization to realize effective separation of oxidized digenite fine particles and iron sulfide minerals.

Effects of ferric ion on the photo-treatment of nonionic surfactant Brij35 washing waste containing 2,2′,4,4′-tetrabromodiphenyl ether

The effects of ferric iron on the photo-treatment of simulated BDE-47 (2,2′,4,4′- tetrabromodiphenyl ether)-Brij35 (Polyoxyethylene lauryl ether) washing waste were studied to evaluate the influences of ferric iron on BDE-47 removal and Brij35 recovery. The results show that Fe3+ accelerated BDE-47 degradation at lower concentrations (<0.5 mM) but attenuated it at higher concentrations (0.5–5 mM) and that Brij35 loss was increased with increasing Fe3+. These results likely are caused by changes in the rate of •OH production due to the ferric ion, association of Fe3+ and electron transfer from Brij35, and light attenuation at high concentration. The BDE-47 and Brij35 had different degradation rates at different pH values and at different dissolved oxygen concentrations. The BDE-47 products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The results indicated that BDE-47 transformed into mainly lower-brominated products, a few bromodibenzofurans, some rearrangement products, and some hydroxylated polybrominated diphenyl ethers. A series of Brij35 oxidization products were detected by ultra-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS), including hydroxylation products, carboxylation products, and some hydrophilic chain-breaking products. Brij35 was mainly oxidized by Fe3+ and/or reactive oxygen species (ROS) with the final products of CO2 and H2O. The iron ions apparently cycled from ferric to ferrous ions in the micelles such that the Fe3+-Brij35 complex dominated the main redox reaction, leading to both BDE-47 and Brij35 degradation. It appears that in any applied soil washing system, the ferric ions in the washing waste need to be removed because of the adverse effects on BDE-47 removal and eluate reuse.

Effect of Fe3+ as an electron-transfer mediator on WO3-induced activation of peroxymonosulfate under visible light

The effect of ferric ions (Fe3+) on the degradation of organic pollutants through the photocatalytic activation of peroxymonosulfate (PMS) was investigated. In the presence of Fe3+, the degradation of 4-chlorophenol (4-CP) was significantly enhanced in the PMS/tungsten oxide (WO3) system under visible light irradiation. The enhanced degradation efficiency by Fe3+ is primarily ascribed to the role of Fe3+ as an electron-transfer mediator, as it induces a cascadal electron transfer from WO3 to Fe3+ to PMS. The production of the sulfate radical (SO4−) and its significant contribution to the degradation of 4-CP in the Fe3+/PMS/WO3 system were verified via electron paramagnetic resonance (EPR) spectroscopy and degradation experiments using radical scavengers (methanol and tert-butyl alcohol), respectively. The addition of Fe3+ to the PMS/WO3 system also significantly increased the degradation rate of other organic pollutants, such as phenol, 2,4-dimethylphenol, bisphenol A, sulfamethoxazole, sulfanilamide, and propranolol. The degradation efficiency of the Fe3+/PMS/WO3 system was largely maintained in multiple degradation cycles by the regular addition of PMS only. In addition, the Fe3+/PMS/WO3 system exhibited a higher degradation efficiency than the conventional cobaltous ion (Co2+)/PMS system at equal transition metal ion concentrations. The addition of Fe3+ for the purpose of enhancing the degradation efficiency is not restricted to the PMS activation system. This method can be applied to the activation of other oxyanions, such as peroxydisulfate (S2O82−) and bromate (BrO3−), for wastewater treatment.

Effect of ferric ions on the anaerobic bio-dissolution of jarosites by Acidithiobacillus ferrooxidans

Large amounts of jarosites are produced during zinc hydrometallurgy and bioleaching, as well as in acid sulfate soils and acid mine drainage environments. As such, understanding the behavior of jarosite dissolution is important for analyzing the iron cycle process and promoting the control and treatment of jarosites. In general, soluble ferric ions and jarosites coexist in acid environments; however, the relationship between soluble ferric ions and jarosites under anaerobic reductive conditions is still not well understood. In this study, the effect of adding Fe3+ on the promotion of the bio-dissolution of jarosites using Acidithiobacillus ferrooxidans is investigated. With the addition of 12 mM Fe3+, the efficiency and maximum rate of jarosite bio-dissolution were found to reach 84.1% and 2.66 mmol/(L·d), respectively. The addition of Fe3+ at concentrations higher than 12 mM did not further improve the jarosite bio-dissolution. These results indicate that the mechanisms underlying these improvements include: (i) the reduction of the zeta potential due to the compression of the diffusion layer of the electric double layer by Fe3+; (ii) bacteria growth enhancement and the stabilization of the pH of cultures via the reduction of soluble Fe3+. Based on these observations, this study serves to promote the development of jarosite bio-dissolution using Acidithiobacillus ferrooxidans and challenges the idea that soluble Fe3+ suppresses the bio-dissolution reaction of solid Fe3+ substances such as jarosite when soluble ferric ions and jarosite coexist.

Photo-Fenton process at natural conditions of pH, iron, ions, and humic acids for degradation of diuron and amoxicillin.

Effect of ferric ions at concentrations typically found in natural waters (0.05 to 1.06mgL-1) and low H2O2 concentrations (between 0.5 and 17.9mgL-1) on simulated sunlight-induced (300Wm-2) photo-Fenton degradation at initial neutral pH (7.0) of amoxicillin and diuron in Milli-Q water was studied using an rotatable central composite experimental design 22 with a central and two axial points. H2O2 concentration was the parameter playing the key role on the degradation of both pollutants. Despite that initial pH was 7.0 in Milli-Q water, this latter decreased rapidly in the first minutes, reaching values of 3.5 and 5.0 for diuron and amoxicillin respectively after 15min of simulated sunlight irradiation. In contrast, in presence of bicarbonate/carbonate (HCO3-/CO3=), fluoride (F-), and humic acids (HAs) at concentrations found often in surface and well waters with ferric ion and H2O2 concentrations of 0.3 and 9.7 and 15.2mgL-1 respectively, both pollutants exhibited a strong degradation keeping the circumneutral pH. Amoxicillin and diuron degradation byproducts found by HPLC/MS were compatible with HO• and/or CO3-• radical attack. Several photo-induced processes such as photo-Fenton (by dissolved ferric-HA complexes), heterogeneous photocatalysis (by colloidal iron), UV-B H2O2 photolysis, irradiated-dissolved organic matter, and their reactions with pollutants would be the main oxidative route responsible of degradations. These findings demonstrated that it could be possible using iron concentrations often found in natural waters to oxidize via photo-Fenton processes among other events, organic pollutants at natural pH conditions.

Enhanced Sewage Sludge Disintegration and Hydrogen Production by Ionizing Radiation Pretreatment in the Presence of Fe2+

The effect of ferrous ion (Fe2+) on sludge disintegration by ionizing radiation and subsequent hydrogen production was studied. Sludge was pretreated with 20 kGy ionizing radiation at three pH leve...

Long-term stability of the Fe(III)–As(V) coprecipitates: Effects of neutralization mode and the addition of Fe(II) on arsenic retention

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.

Interaction Mechanism of Ferric Ions with Celestite Surface and Implications for Flotation Recovery

In practical celestite flotation, iron contamination is commonly found on celestite surfaces. The effect of ferric ions on celestite flotation was assessed by a combination of ion release experiments, DFT calculation, X-ray photoelectron spectroscopy (XPS) analysis, adsorption isotherm study, and flotation experiments in this work. The ion release experiments showed that the associated limonite released ferric ions to solution. According to DFT calculation and surface complexation theory, we found that ≡SrOH0 and ≡SO4H0 are primary functional groups on celestite surface in aqueous environments. The XPS analysis and adsorption isotherm study revealed that ferric ions mainly adsorbed on celestite surface by complexing with two oxygen atoms of surface ≡SrOH0 groups to form ≡Sr–O–Fe–OH precipitates. Flotation results showed that ferric ions strongly depressed celestite flotation. Combined with the change in surface properties determined by XPS, it can be concluded that the adsorption of ferric ions on celestite surface decreased adsorption sites for the collector, and hence, led to depression on celestite flotation.

The effect of Fe3+ contamination in feed water on proton exchange membrane electrolyzer performance

Abstract The effect of ferric ions on cell performance of proton exchange membrane water electrolyzer (PEM WE) was studied by injecting Fe2 (SO4)3 solution into DI water to prepare different Fe3+ concentrations contamination (1, 10, 100 parts per million (ppm, molar ratio)). Results showed that there was clear cell performance decay with increasing Fe3+ concentrations, and the cell stopped running at 100 ppm Fe3+ concentration in feed water. With increasing temperature, the cell performance increased for a short period. With low Fe3+ concentrations, cell performance decreased with increasing current density, but with 10 ppm Fe3+ concentration and higher current density of 2 A/cm2, cell performance was enhanced. Therefore, both temperature and current density can make positive contributions to improve cell performance under the condition of contaminated feed water.

Scanning Electrochemical Microscopy for the Electroless Deposition of Gold on Natural Pyrite: Effect of Ferric Ions

AbstractThe local electroless deposition of gold on pyrite is studied by scanning electrochemical microscopy (SECM). The SECM and additional SEM experiments provide kinetic and mechanistic insights on the local galvanic replacement of pyrite by gold. We evidence that individual gold nanoparticles or full coverage of gold on the pyrite surface can be obtained by controlling either the deposition time or the flux of gold ions electrogenerated at the ultramicroelectrode. We also studied the influence of ferric ions, known to be implied on gold etching and pyrite corrosion and therefore, on the overall process of gold deposition on pyrite. We then demonstrate that the presence of ferric ions significantly modifies i) the thermodynamic of the gold electrodissolution, ii) the process of adsorption of auric ions on pyrite in the first instants, iii) the number of nucleation sites on the pyrite surface and, iv) the structure of the deposited gold layer.

Degradation of amoxicillin by Fenton and Fenton-integrated hybrid oxidation processes

The present study aims to investigate the degradation of amoxicillin (AMX) using the Fenton process and hybrid Fenton-like processes such as photo-Fenton, solar photo-Fenton, sono-Fenton, and sono-photo-Fenton. The effect of ferrous ions (Fe2+), hydrogen peroxide (H2O2), and pH was evaluated. Complete degradation was achieved within 12 min of reaction time under the optimized conditions of Fe2+- 30 mg/l, H2O2 – 375 mg/l, and pH – 3.0 during Fenton’s process. Efficiency towards degradation of AMX was enhanced when the Fenton’s process was coupled with UV- light illumination, solar light illumination, and UV light-Ultrasound treatment. Complete degradation was observed within 3.5 min and 9 min during the photo-Fenton and solar photo-Fenton process, respectively. The sono-Fenton process takes a longer time to degrade AMX than other processes while sono-photo-Fenton process degrades AMX within 6 min. The reason for a reduced rate of degradation of AMX in the sono-Fenton process may be attributed to the competition of ultrasound and Fenton for H2O2, which ultimately decreases Fenton reagent in the process. The study concluded that the Fenton process coupled with other UV/solar light is more efficient than the stand-alone Fenton process towards degradation of AMX.

The effect of ferrous ions, calcium ions and citric acid on absorption of ciprofloxacin across caco-2 cells: practical and structural approach

Objective: To study the potential influence of selected metal ions on absorption (and hence oral bioavailability of ciprofloxacin (Cipro) in presence and absence of a competing ligand.Significance: The presence of metal ions together with Cipro results in complexes exhibiting a decreased bioavailability. Attempts were made to better understand the mechanism of decreased Cipro bioavailability in the presence of metals such as calcium and ferrous ions, and a small-sized ligand citric acid (CitA).Methods: Effect of complex size or other potential factors was studied using diffusion through synthetic membrane, permeation studies across Caco-2 cells and capillary electrophoresis. A molecular dynamics (MD) simulation study was conducted to find the arrangement and the nature of the interactions between Cipro molecules and ferrous ions.Results: Cipro was shown to form complexes with metals and CitA. The presence of CitA improved permeation of Cipro through the synthetic membrane but this was not as obvious in case of Caco-2 cells. Capillary electrophoresis suggested the existence of large molecular aggregates of Cipro: metal complexes. MD simulations offered clear evidence of large size aggregates in line with the experimental findings. CitA alone significantly improved permeation of Cipro through Caco-2 cells.Conclusions: The size of the formed complexes, rather than the decrease in the solubility of formed complexes, plays a significant role in permeation (absorption) of Cipro. CitA might ameliorate the effect of co-administered metal ions on the bioavailability of Cipro.

Biogas Emission from an Anaerobic Reactor

Anaerobic denitrification is accompanied by biogas emissions, which may orient greenhouse gases or air pollutants. Ferrous iron play an important role in wastewater treatment. However, the effect of ferrous ion on biogas emission and the relationship between microbial community and nitrogen removal performance are not fully understood, especially in up-flow anaerobic sludge blanket (UASB) reactors. Here, the results revealed that nitrogen gas increased rapidly with Fe(II) addition. And ferrous ions enhanced denitrification and COD removal efficiency with more than 60% and 10%, respectively. Moreover, Ferrous ions addition evidently increased Hydrogenophaga, Methylotenera, Zoogloea and Fluviicola during the whole UASB reactor operation progress. The correlation coefficient analysis further confirmed that Fe(II) was positively correlated with the abundances of Hydrogenophaga, Methylotenera and Fluviicola. Based on these results of chemicals transformation kinetics, microbial community and the correlations coefficient analysis, a hypothetical mechanism is proposed: In the UASB system with Fe(II) and NH4+, firstly Paludibacter made a contribution to NH4+ oxidation and generated NO3–, and then Hydrogenophaga, played an important role in NO3– reduction, Zoogloea coupled NO3– reduction to Fe(II) oxidation, Fluviicola combined with Methylotenera conducted NO2– reduction together with Fe(II) oxidation. This study will improve our understanding of ferrous ion’s influence on biogas emission, denitrification process and corresponding microbial community.