Effect Of Iron Species Research Articles

Effects of Iron Species of the Iron-Based Corn Stalk Biochar on the Adsorption of Salicylic Acid from Aqueous Solutions

Effects of Iron Species of the Iron-Based Corn Stalk Biochar on the Adsorption of Salicylic Acid from Aqueous Solutions

Improvement of Biohydrogen and Usable Chemical Products from Glycerol by Co-Culture of Enterobacter spH1 and Citrobacter freundii H3 Using Different Supports as Surface Immobilization

Glycerol is a by-product of biodiesel production in a yield of about 10% (w/w). The present study aims to improve the dark fermentation of glycerol by surface immobilization of microorganisms on supports. Four different supports were used—maghemite (Fe2O3), activated carbon (AC), silica gel (SiO2), and alumina (γ-Al2O3)—on which a newly isolated co-culture of Enterobacter spH1 and Citrobacter freundii, H3, was immobilized. The effect of iron species on dark fermentation was also studied by impregnation on AC and SiO2. The fermentative metabolites were mainly ethanol, 1,3-propanediol, lactate, H2 and CO2. The production rate (Rmax,i) and product yield (Yi) were elucidated by modeling using the Gompertz equation for the batch dark fermentation kinetics (maximum product formation (Pmax,i): (i) For each of the supports, H2 production (mmol/L) and yield (mol H2/mol glycerol consumed) increased in the following order: FC < γ-Al2O3 < Fe2O3 < SiO2 < Fe/SiO2 < AC < Fe/AC. (ii) Ethanol production (mmol/L) increased in the following order: FC < Fe2O3 < γ-Al2O3 < SiO2 < Fe/SiO2 < Fe/AC < AC, and yield (mol EtOH/mol glycerol consumed) increased in the following order: FC < Fe2O3 < Fe/AC < Fe/SiO2 < SiO2 < AC < γ-Al2O3. (iii) 1,3-propanediol production (mmol/L) and yield (mol 1,3PDO/mol glycerol consumed) increased in the following order: γ-Al2O3 < SiO2 < Fe/SiO2 < AC < Fe2O3 < Fe/AC < FC. (iv) Lactate production(mmol/L) and yield (mol Lactate/mol glycerol consumed) increased in the following order: γ-Al2O3 < SiO2 < AC < Fe/SiO2 < Fe/AC < Fe2O3 < FC. The study shows that in all cases, glycerol conversion was higher when the support assisted culture was used. It is noted that glycerol conversion and H2 production were dependent on the specific surface area of the support. H2 production clearly increased with the Fe2O3, Al2O3, SiO2 and AC supports. H2 production on the iron-impregnated AC and SiO2 supports was higher than on the corresponding bare supports. These results indicate that the support enhances the productivity of H2, perhaps because of specific surface area attachment, biofilm formation of the microorganisms and activation of the hydrogenase enzyme by iron species.

Effect of Iron Species in Mesoporous Fe-N/C Catalysts with Different Shapes on Activity Towards Oxygen Reduction Reaction

Effect of Iron Species in Mesoporous Fe-N/C Catalysts with Different Shapes on Activity Towards Oxygen Reduction Reaction

Hydroxyl radical formation upon dark oxidation of reduced iron minerals: Effects of iron species and environmental factors

Dark formation of hydroxyl radical upon oxidation of reduced iron minerals plays an important role in the degradation and transformation of organic and inorganic pollutants. Herein, we compared the hydroxyl radical formation from various reduced iron minerals at different redox conditions. OH production was generally observed from the oxidation of reduced iron minerals, following the order: mackinawite (FeS) > reduced nontronite (iron-bearing smectite clay) > pyrite (FeS2) > siderite (FeCO3). Structural Fe2+ and dissolved O2 play critical roles in OH production from reduced iron minerals. OH production increases with decreasing pH, and Cl− has little effect on this process. More importantly, dissolved organic matter significantly enhances OH production, especially under O2 purging, highlighting the importance of this process in ambient environments. This sunlight-independent pathway in which OH forms during oxidation of reduced iron minerals is helpful for understanding the degradation and transformation of various inorganic and organic pollutants in the redox-fluctuation environments.

EDDS as complexing agent for enhancing solar advanced oxidation processes in natural water: Effect of iron species and different oxidants.

The main purpose of this pilot plant study was to compare degradation of five microcontaminants (MCs) (antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L) by solar photo-Fenton mediated by EDDS and solar/Fe:EDDS/S2O82-. The effects of the Fe:EDDS ratio (1:1 and 1:2), initial iron species (Fe(II) or Fe(III) at 0.1 mM) and oxidizing agent (S2O82- or H2O2 at 0.25-1.5 mM) were evaluated. The higher the S2O82- concentration, the faster MC degradation was, with S2O82- consumption always below 0.6 mM and similar degradation rates with Fe(II) and Fe(III). Under the best conditions (Fe 0.1 mM, Fe:EDDS 1:1, S2O82- 1 mM) antipyrine, carbamazepine, caffeine, ciprofloxacin and sulfamethoxazole at 100 μg/L where 90% eliminated applying a solar energy of 2 kJ/L (13 min at 30 W/m2 solar radiation <400 nm). Therefore, S2O82- promotes lower consumption of EDDS as Fe:EDDS 1:1 was better than Fe:EDDS 1:2. In photo-Fenton-like processes at circumneutral pH, EDDS with S2O82- is an alternative to H2O2 as an oxidizing agent.

Low levels of iron enhance UV/H2O2 efficiency at neutral pH

While the presence of iron is generally not seen as favorable for UV-based treatment systems due to lamp fouling and decreased UV transmittance, we show that low levels of iron can lead to improvements in the abatement of chemicals in the UV-hydrogen peroxide advanced oxidation process. The oxidation potential of an iron-assisted UV/H2O2 (UV254 + H2O2 + iron) process was evaluated at neutral pH using iron levels below USEPA secondary drinking water standards (<0.3 mg/L). Para-chlorobenzoic acid (pCBA) was used as a hydroxyl radical (HO) probe to quantify HO steady state concentrations. Compounds degraded by different mechanisms including, carbamazepine (CBZ, HO oxidation) and N-nitrosodimethylamine (NDMA, direct photolysis), were used to investigate the effect of iron on compound degradation for UV/H2O2 systems. The effects of iron species (Fe2+ and Fe3+), iron concentration (0–0.3 mg/L), H2O2 concentration (0–10 mg/L) and background water matrix (low-carbon tap (LCT) and well water) on HO production and compound removal were examined. Iron-assisted UV/H2O2 efficiency was most influenced by the target chemical and the water matrix. Added iron to UV/H2O2 was shown to increase the steady-state HO concentration by approximately 25% in all well water scenarios. While CBZ removal was unchanged by iron addition, 0.3 mg/L iron improved NDMA removal rates in both LCT and well water matrices by 15.1% and 4.6% respectively. Furthermore, the combination of UV/Fe without H2O2 was also shown to enhance NDMA removal when compared to UV photolysis alone indicating the presence of degradation pathways other than HO oxidation.

Nitrogen‐Doped Ordered Mesoporous Carbon with Different Morphologies for the Oxygen Reduction Reaction: Effect of Iron Species and Synergy of Textural Properties

AbstractNitrogen‐doped ordered mesoporous carbons (N‐OMCs) with different morphologies are prepared as oxygen reduction reaction (ORR) catalysts through pyrolysis of iron phthalocyanine‐infiltrated SBA‐15 silica with different mesochannel lengths. Excellent ORR activity with a nearly four‐electron transfer process is observed in both alkaline and acidic media. In particular, the difference in half‐wave potential for ORR relative to commercial Pt/C catalyst is only 50 mV negative in acidic medium, whereas it is 50 mV more positive in alkaline medium. Interestingly, it is found that although the use of iron is necessary for the preparation of highly active nitrogen‐doped ORR carbon catalysts, its presence is not necessary for N‐OMC to be active in the ORR in either alkaline or acidic media. In addition, the ORR activity increases gradually with decreasing mesopore channel length, with maximum activity in N‐OMC with short channels, demonstrating the high synergistic influence of structural morphology on ORR in heteroatom‐doped carbon.

Effect of Iron Species and Calcium Hydroxide on High-Sulfur Petroleum Coke CO2 Gasification

The effect of iron species on petroleum coke CO2 gasification was studied in the present work. The effects of the temperature (1173–1673 K), the catalyst types, catalyst loading (ranging from 0 to 5 wt %), and composition during the gasification of petroleum coke CO2 were discussed. The catalytic gasification residue of petroleum coke was identified by X-ray diffraction (XRD). The XRD result shows that the iron species exist as Fe3C at the initial stage of gasification. Then, most Fe3C is transformed into reduced iron Fe0; subsequently, some of these species are oxidized to FeO, Fe2O3, and Fe3O4, while some of which quickly reacted with S in petroleum coke to form stable FeS, leading to catalyst deactivation. The changes during gasification are discussed in terms of the oxygen-transfer mechanism. It is clearly demonstrated that there exists a significant synergistic effect between calcium hydroxide and iron species during petroleum coke gasification. The random pore model is suitable to describe catalytic...

Effects of iron species and inert minerals on coagulation and direct filtration for humic acid removal

The behavior of various iron species (e.g. ferrous, prehydrolyzed(ph)-ferrous ion and ferric ion) as a coagulant and effects of inert mineral on the coagulation process combined with direct microfiltration (MF) membrane process was studied for humic acid (HA) removal. When 0.01 mM to 1 mM of the various iron salts added to remove HA at pH 3 to pH 9, HA removal efficiencies were evaluated. The maximum complexation capacity of ferric and ferrous salt for HA removal was 739.2 mg DOC/L-mM and 472.3 mg DOC/L-mM, respectively. The optimum pH region for HA removal ranges from pH 4.5 to 6.3 as ferric salts are added, pH 3–4 and pH 6–7 are optimum regions for ferrous and ph-ferrous salts, respectively. The optimum pH region of ph-ferrous was broader than that of ferrous salts. The influence of inert mineral particles (e.g. glass, bentonite, and zeolite) on iron salts coagulation with HA was also examined. Results showed that the pH range for HA removal dramatically expanded when the inert particles were added with iron salts even though the inert mineral only adsorbed HA in acidic condition below pH 5. Moreover, added inert particles increased the critical flux by 700 L/m 2-h (TMP 101 kPa), which is seven times higher than that with ferric salt added alone.

The effects of iron species and mineral particles on advanced oxidation processes for the removal of humic acids

Influence of iron species and mineral particles added on the advanced oxidation processes (AOP) for the humic acids (HA) removal was elucidated. It was observed that decomposition rate of hydrogen peroxide increased when the modified ferrous ion (M-Fe, of which main species are pre-hydrolyzed ferrous species as FeOH +) was added. Addition of bentonite in the iron-catalyzed oxidation process adversely affected H 2O 2 degradation. Iron salts, were adsorbed onto the surface of bentonite, suppressed the reaction between iron and H 2O 2. In contrast, adding glass powder slightly increased the H 2O 2 degradation rate. In addition, changes in the molecular and structural characteristics of HA and the hydrophobic and hydrophilic fractions of trihalomethanes (THMs) precursors after the Fenton and photo-Fenton oxidation were evaluated by GPC, NMR spectra and Py-GC/MSD.

Microcalorimetric Investigation of the Toxic Effect of Iron Species on Escherichia coli

ABSTRACTA microcalorimetric technique based on bacterial heat output was explored to evaluate the toxic effect of iron species on Escherichia coli. Power–time curves of the growth metabolism of E. coli and the effect of different iron species on it were studied using the TAM III multichannel microcalorimetric system, isothermal mode, at 37°C. The differences in shape of the power–time curves and the thermodynamic and kinetic characteristics of E. coli growth have been compared. The thermodynamic parameters, that is, growth rate constant (k), inhibitory ratio (I), half-inhibitory concentration (IC50), Pmax, and Qtotal, have been calculated. The experimental results reveal that the sequence of antibiotic activity of the different iron species (three forms) on E. coli growth is Fe3+ (ferric citrate) > Fe2+ (ferrous chloride) > Fe3+ (ferric chloride). These results are important to further studies of the physiology and pharmacology of iron species as antibacterial agents.

Effects of iron species in the photocatalytic degradation of an azo dye in TiO 2 aqueous suspensions

The effects of Fe(III) species on the photocatalytic degradation of azo dye Acid Red 1 (AR1) have been studied in titanium dioxide aqueous suspensions under irradiation in the 315–400 nm range. The initial increase of the photocatalytic degradation rate observed in water suspensions containing Fe(III) aquo ions (10 −5 to 10 −4 M) was attributed to the increased amount of dye adsorbed on the iron(III)-modified semiconductor surface. This was confirmed by the fact that iron species not adsorbed on the semiconductor, such as ferrioxalate complexes and Fe(II) species, had no kinetic effects. The mineralisation kinetic profiles obtained under simultaneous sonication further confirmed the role of AR1 adsorption. The accumulation of hydrogen peroxide during the photocatalytic degradation of the dye was completely suppressed in the presence of all iron species, mainly due to the Fenton reactions consuming H 2O 2 in the aqueous phase, although a decrease in the rate of H 2O 2 formation cannot be excluded, due to the competition between adsorbed Fe(III) species and adsorbed oxygen for photo-promoted conduction band electrons.

X-Ray Photoelectron Spectroscopy of In-Situ Fractured Reaction Bonded Silicon Nitride

AbstractThe grain boundary chemistry of reaction bonded silicon nitride (RBSN) and the effects of iron species and content on this chemistry are investigated using X-ray photoelectron spectroscopy (XPS). Data are reported for semiconductor grade RBSN, Fe-doped semiconductor grade RBSN, and metallurgical grade RBSN specimens. Results indicate that the grain boundaries have an elemental composition of Si, N, O, and C, with important chemical differences depending on the purity of the starting material. In the RBSN made from metallurgical grade silicon, the grain boundaries have a distinct “oxide-like” layer, with a subregion of Si3N4. No distinct oxide layer was observed in the RBSN made from semiconductor-grade silicon, where the O appears to be uniformly incorporated into the Si3N4.