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1. Enhancing sludge methanogenesis with changed micro-environment of anaerobic microorganisms by Fenton iron mud.

Author

Wu M, Yang ZH, Jiang TB, Zhang WW, Wang ZW, and Hou QX

Subjects
Anaerobiosis, Methane metabolism, Bacteria metabolism, Bioreactors, Sewage microbiology, Iron metabolism
Abstract

Conductive materials have been demonstrated to enhance sludge methanogenesis, but few researches have concentrated on the interaction among conductive materials, microorganisms and their immediate living environment. In this study, Fenton iron mud with a high abundance of Fe(III) was recycled and applied in anaerobic reactors to promote anaerobic digestion (AD) process. The results show that the primary content of extracellular polymeric substances (EPS) such as polysaccharides and proteins increased significantly, possibly promoting microbial aggregation. Furthermore, with the increment of redox mediators including humic substances in EPS and Fe(III) introduced by Fenton iron mud, the direct interspecies electron transfer (DIET) between methanogens and interacting bacteria could be accelerated, which enhanced the rate of methanogenesis in anaerobic digestion (35.21 ± 4.53% increase compared to the control). The further analysis of the anaerobic microbial community confirmed the fact that Fenton iron mud enriched functional microorganisms, such as the abundance of CO 2 -reducing (e.g. Chloroflexi) and Fe(III)-reducing bacteria (e.g., Tepidimicrobium), thereby expediting the electron transfer reaction in the AD process via microbial DIET and dissimilatory iron reduction (DIR). This work will make it possible for using the recycled hazardous material - Fenton iron mud to improve the performance of anaerobic granular sludge during methanogenesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper, (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Published
2023
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2. Synergistic effects in iron-copper bimetal doped mesoporous γ-Al 2 O 3 for Fenton-like oxidation of 4-chlorophenol: Structure, composition, electrochemical behaviors and catalytic performance.

Author

Huang Z, Chen Z, Chen Y, and Hu Y

Subjects
Catalysis, Electrochemistry, Oxidation-Reduction, Aluminum Oxide chemistry, Chlorophenols chemistry, Copper chemistry, Hydrogen Peroxide chemistry, Iron chemistry
Abstract

Iron-copper bimetal supported on mesoporous γ-Al 2 O 3 with different Fe/Cu ratios was prepared via a modified evaporation-induced self-assembly method and employed to degrade 4-chlorophenol (4-CP) in a Fenton-like process. The X-ray photoelectron spectroscopy, X-ray diffraction spectrum and UV-vis diffuse reflectance spectroscopy results confirmed the co-doping of Fe 2+ /Fe 3+ and Cu + /Cu 2+ into the lattice of γ-Al 2 O 3 through the bonds of AlOFe and AlOCu. With the iron and copper co-doped in γ-Al 2 O 3 , three-fold oxygen vacancies (V 0 ) could be achieved compared with that of non-metal catalysts, which was favorable for the reduction of iron and copper species. The 1Fe3Cu-γ-Al 2 O 3 with a Fe/Cu mass ratio of 1:3 exhibited the highest activity on Fenton-like degradation of 4-CP due to the synergistic effects of Fe and Cu by facilitating the electron transfer in the recycles of Cu + /Cu 2+ and Fe 2+ /Fe 3+ based on the results of X-ray photoelectron spectroscopy, cyclic voltammetry and electro paramagnetic resonance analysis. The utilization efficiency of H 2 O 2 was as high as 86.0% when 4-CP almost disappeared (i.e., 99.7 percent of 0.78 mM 4-CP) at 240 min and pH 7.0, additionally, their dechlorination and TOC removal efficiencies were 92.0% and 81.6%, respectively. The catalyst also displayed a good performance after 5th cycles. Furthermore, a possible mechanism for activation of OH on the catalyst surface was also proposed., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Published
2018
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3. Synthesis, characterization, and debromination reactivity of cellulose-stabilized Pd/Fe nanoparticles for 2,2',4,4'-tretrabromodiphenyl ether.

Author

Huang G, Wang M, Hu Y, Lv S, and Li C

Subjects
Environmental Restoration and Remediation methods, Hypromellose Derivatives chemistry, Metal Nanoparticles ultrastructure, Microscopy, Electron, Scanning, Molecular Structure, Molecular Weight, Particle Size, Photoelectron Spectroscopy, Polyelectrolytes, Polymers chemistry, Spectroscopy, Fourier Transform Infrared, X-Ray Diffraction, Bromine chemistry, Cellulose chemistry, Halogenated Diphenyl Ethers chemistry, Iron chemistry, Metal Nanoparticles chemistry, Palladium chemistry
Abstract

In this study, two kinds of cellulose derivatives (polyanionic cellulose (PAC) and hydroxypropylmethyl cellulose (HPMC)) were selected as stabilizers of Pd/Fe nanoparticles (NPs) to investigate their influences on the debromination performances of 2,2',4,4'-tretrabromodiphenyl ether (BDE47). Field emission scanning electron microscope (FE-SEM) images revealed that the cellulose-stabilized Pd/Fe NPs were smaller and more uniform than the bare-Pd/Fe NPs. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) results suggested that cellulose coatings found on Pd/Fe NPs surfaces featured some antioxidation abilities, which followed the order of HPMC < PAC. Sedimentation tests demonstrated that the stabilizing power of PAC for Pd/Fe NPs was higher than that of HPMC. Fourier transfer infrared spectrometer (FTIR) results indicated that PAC molecules were bound to the Pd/Fe NPs surfaces by polar covalent bonds and hydrogen bonds, while HPMC molecules interacted with the nanoparticles by hydrogen bonds. Batch debromination test for BDE47 demonstrated that the catalytic debromination rate with cellulose-stabilized Pd/Fe NPs was higher than that with bare-Pd/Fe NPs during reaction period of 15 min. Overall, this study indicated that both celluloses are beneficial to forming smaller, more regular, stable and antioxidative Pd/Fe NPs, leading to higher debromination reactivity for BDE47 compared with the bare-Pd/Fe NPs. Therefore Pd/Fe NPs can be utilized as a promising remediation technology for the contaminated groundwater and soils.

Published
2017
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4. Treatment of Ni-EDTA containing wastewater by electrocoagulation using iron scraps packed-bed anode.

Author

Ye X, Zhang J, Zhang Y, Lv Y, Dou R, Wen S, Li L, Chen Y, and Hu Y

Subjects
Coordination Complexes analysis, Electrochemical Techniques, Electrodes, Ferric Compounds analysis, Ferrosoferric Oxide analysis, Industrial Waste analysis, Temperature, Edetic Acid analysis, Iron chemistry, Nickel analysis, Wastewater analysis, Water Pollutants, Chemical analysis, Water Purification methods
Abstract

The unique electrocoagulator proposed in this study is highly efficient at removing Ni-EDTA, providing a potential remediation option for wastewater containing lower concentrations of Ni-EDTA (Ni ≤ 10 mg L -1 ). In the electrocoagulation (EC) system, cylindrical graphite was used as a cathode, and a packed-bed formed from iron scraps was used as an anode. The results showed that the removal of Ni-EDTA increased with the application of current and favoured acidic conditions. We also found that the iron scrap packed-bed anode was superior in its treatment ability and specific energy consumption (SECS) compared with the iron rod anode. In addition, the packed density and temperature had a large influence on the energy consumption (ECS). Over 94.3% of Ni and 95.8% of TOC were removed when conducting the EC treatment at an applied current of 0.5 A, initial pH of 3, air-purged rate 0.2 L min -1 , anode packed density of 400 kg m -3 temperature of 313 K and time of 30 min. SEM analysis of the iron scraps indicated that the specific area of the anode increased after the EC. The XRD analysis of flocs produced during EC revealed that hematite (α-Fe 2 O 3 ) and magnetite (Fe 3 O 4 ) were the main by-products under aerobic and anoxic conditions, respectively. A kinetic study demonstrated that the removal of Ni-EDTA followed a first-order model with the current parameters. Moreover, the removal efficiency of real wastewater was essentially consistent with that of synthetic wastewater., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Published
2016
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5. Influences of pH and substrate supply on the ratio of iron to sulfate reduction

Author

Theodore M. Flynn, Kathleen M. Crank, Qusheng Jin, Kenneth M. Kemner, Matthew F. Kirk, AnneMarie Lower, Maxim I. Boyanov, Ben R. Haller, Janet M. Paper, and Theodore Flynn

Subjects
Goethite, 010504 meteorology & atmospheric sciences, Iron, Inorganic chemistry, iron reduction, anoxic environments, 010502 geochemistry & geophysics, 01 natural sciences, chemistry.chemical_compound, sulfate reduction, Bioreactor, goethite, Sulfate, Groundwater, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, General Environmental Science, biology, Sulfates, Substrate (chemistry), Hydrogen-Ion Concentration, biology.organism_classification, Anoxic waters, Iron reduction, chemistry, visual_art, visual_art.visual_art_medium, General Earth and Planetary Sciences, Water quality, Geobacter, Oxidation-Reduction
Abstract

Iron reduction and sulfate reduction often occur simultaneously in anoxic systems, and where that is the case, the molar ratio between the reactions (i.e., Fe/SO42- reduced) influences their impact on water quality and carbon storage. Previous research has shown that pH and the supply of electron donors and acceptors affect that ratio, but it is unclear how their influences compare and affect one another. This study examines impacts of pH and the supply of acetate, sulfate, and goethite on the ratio of iron to sulfate reduction in semi-continuous sediment bioreactors. We examined which parameter had the greatest impact on that ratio and whether the parameter influences depended on the state of each other. Results show that pH had a greater influence than acetate supply on the ratio of iron to sulfate reduction, and that the impact of acetate supply on the ratio depended on pH. In acidic reactors (pH 6.0 media), the ratio of iron to sulfate reduction decreased from 3:1 to 2:1 as acetate supply increased (0-1 mM). In alkaline reactors (pH 7.5 media), iron and sulfate were reduced in equal proportions, regardless of acetate supply. Secondly, a comparison of experiments with and without sulfate shows that the extent of iron reduction was greater if sulfate reduction was occurring and that the effect was larger in alkaline reactors than acidic reactors. Thus, the influence of sulfate supply on iron reduction extent also depended on pH and suggests that iron reduction grows more dependent on sulfate reduction as pH increases. Our results compare well to trends in groundwater geochemistry and provide further evidence that pH is a major control on iron and sulfate reduction in systems with crystalline (oxyhydr)oxides. pH not only affects the ratio between the reactions but also the influences of other parameters on that ratio.

Published
2021

6. Influence of pH on the balance between methanogenesis and iron reduction

Author

Ben R. Haller, Qusheng Jin, Ganiyat Shodunke, Colleen M. Gura, Maxim I. Boyanov, Matthew F. Kirk, Theodore M. Flynn, Janet M. Paper, and Kyle A. Marquart

Subjects
Goethite, 010504 meteorology & atmospheric sciences, Methanogenesis, Iron, 010502 geochemistry & geophysics, Ferric Compounds, 01 natural sciences, Methane, chemistry.chemical_compound, Bioreactors, medicine, Groundwater, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, General Environmental Science, Minerals, Oxide minerals, Bacteria, biology, Hydrogen-Ion Concentration, biology.organism_classification, Anoxic waters, chemistry, Environmental chemistry, visual_art, visual_art.visual_art_medium, General Earth and Planetary Sciences, Ferric, Clay minerals, Oxidation-Reduction, Iron Compounds, medicine.drug, Geobacter
Abstract

Methanogenesis and iron reduction play major roles in determining global fluxes of greenhouse gases. Despite their importance, environmental factors that influence their interactions are poorly known. Here, we present evidence that pH significantly influences the balance between each reaction in anoxic environments that contain ferric (oxyhydr)oxide minerals. In sediment bioreactors that contained goethite as a source of ferric iron, both iron reduction and methanogenesis occurred but the balance between them varied significantly with pH. Compared to bioreactors receiving acidic media (pH 6), electron donor oxidation was 85% lower for iron reduction and 61% higher for methanogenesis in bioreactors receiving alkaline media (pH 7.5). Thus, methanogenesis displaced iron reduction considerably at alkaline pH. Geochemistry data collected from U.S. aquifers demonstrate that a similar pattern also exists on a broad spatial scale in natural settings. In contrast, in bioreactors that were not augmented with goethite, clay minerals served as the source of ferric iron and the balance between each reaction did not vary significantly with pH. We therefore conclude that pH can regulate the relative contributions of microbial iron reduction and methanogenesis to carbon fluxes from terrestrial environments. We further propose that the availability of ferric (oxyhydr)oxide minerals influences the extent to which the balance between each reaction is sensitive to pH. The results of this study advance our understanding of environmental controls on microbial methane generation and provide a basis for using pH and the occurrence of ferric minerals to refine predictions of greenhouse gas fluxes.

Published
2018