Selenate and thiosulfate reduction using methanol as electron donor

2019 ◽  
pp. 42-60
Author(s):  
Tejaswini Eregowda
Keyword(s):  
Electron Donor ◽  
Thiosulfate Reduction

scholarly journals Syngas as Electron Donor for Sulfate and Thiosulfate Reducing Haloalkaliphilic Microorganisms in a Gas-Lift Bioreactor

2020 ◽  
Vol 8 (9) ◽  
pp. 1451
Author(s):  
Caroline M. Plugge ◽  
João A. B. Sousa ◽  
Stephan Christel ◽  
Mark Dopson ◽  
Martijn F. M. Bijmans ◽  
...  
Keyword(s):  
Electron Donor ◽  
Cost Reduction ◽  
Acetate Production ◽  
Potential Cost ◽  
Gas Streams ◽  
Dominant Process ◽  
Co Addition ◽  
Carbon Dioxide Co2 ◽  
Thiosulfate Reduction ◽  
Gas Lift

Biodesulfurization processes remove toxic and corrosive hydrogen sulfide from gas streams (e.g., natural gas, biogas, or syngas). To improve the efficiency of these processes under haloalkaline conditions, a sulfate and thiosulfate reduction step can be included. The use of H2/CO mixtures (as in syngas) instead of pure H2 was tested to investigate the potential cost reduction of the electron donor required. Syngas is produced in the gas-reforming process and consists mainly of H2, carbon monoxide (CO), and carbon dioxide (CO2). Purification of syngas to obtain pure H2 implies higher costs because of additional post-treatment. Therefore, the use of syngas has merit in the biodesulfurization process. Initially, CO inhibited hydrogen-dependent sulfate reduction. However, after 30 days the biomass was adapted and both H2 and CO were used as electron donors. First, formate was produced, followed by sulfate and thiosulfate reduction, and later in the reactor run acetate and methane were detected. Sulfide production rates with sulfate and thiosulfate after adaptation were comparable with previously described rates with only hydrogen. The addition of CO marginally affected the microbial community in which Tindallia sp. was dominant. Over time, acetate production increased and acetogenesis became the dominant process in the bioreactor. Around 50% of H2/CO was converted to acetate. Acetate supported biomass growth and higher biomass concentrations were reached compared to bioreactors without CO feed. Finally, CO addition resulted in the formation of small, compact microbial aggregates. This suggests that CO or syngas can be used to stimulate aggregation in haloalkaline biodesulfurization systems.

Metal-Free Photoinduced Hydroalkylation Cascade Enabled by an Electron-Donor-Acceptor Complex

2020 ◽  
Author(s):  
José Tiago Menezes Correia ◽  
Gustavo Piva da Silva ◽  
Camila Menezes Kisukuri ◽  
Elias André ◽  
Bruno Pires ◽  
...  
Keyword(s):  
Electron Donor ◽  
Functional Group ◽  
Photoexcited Electron ◽  
One Pot ◽  
Quaternary Centers ◽  
Metal Free ◽  
Acceptor Complex ◽  
Catalyst Free ◽  
Donor Acceptor ◽  
Radical Cascade

A metal- and catalyst-free photoinduced radical cascade hydroalkylation of 1,7-enynes has been disclosed. The process is triggered by a SET event involving a photoexcited electron-donor-aceptor complex between NHPI ester and Hantzsch ester, which decomposes to afford a tertiary radical that is readily trapped by the enyne. <a>The method provides an operationally simple, robust and step-economical approach to the construction of diversely functionalized dihydroquinolinones bearing quaternary-centers. A sequential one-pot hydroalkylation-isomerization approach is also allowed giving access to a family of quinolinones. A wide substrate scope and high functional group tolerance was observed in both approaches</a>.

Three-Phase Electrochemistry of a Highly Lipophilic Neutral Ru-Complex Having a Tridentate Bis(benzimidazolate)pyridine Ligand

2020 ◽  
Author(s):  
Vishwanath R.S ◽  
Masa-aki Haga ◽  
Takumi Watanabe ◽  
Emilia Witkowska Nery ◽  
Martin Jönsson-Niedziolka
Keyword(s):  
Redox Potential ◽  
Organic Phase ◽  
Electron Donor ◽  
Ion Transfer ◽  
Neutral Complex ◽  
Pyridine Ligand ◽  
Electrochemical Testing ◽  
Ru Complex ◽  
Three Phase ◽  
Exceptional Stability

Here we describe the synthesis and electrochemical testing of a heteroleptic bis(tridentate) ruthenium(II) complex [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> (LR =2,6-bis(1-(2-octyldodecan)benzimidazol-2-yl)pyridine, L = 2,6-bis(benzimidazolate)pyridine). It is a neutral complex which undergoes a quasireversible oxidation and reduction at relatively low potential. The newly synthetized compound was used for studies of ion-transfer at the three-phase junction because of the sensitivity of this method to cation expulsion. The [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> shows exceptional stability during cycling and is sufficiently lipophilic even after oxidation to persist in the organic phase also using very hydrophilic anions such as Cl<sup>−</sup>. Given its low redox potential and strong lipophilicity this compound will be of interest as an electron donor in liquid-liquid electrochemistry.

Three-Phase Electrochemistry of a Highly Lipophilic Neutral Ru-Complex Having a Tridentate Bis(benzimidazolate)pyridine Ligand

2020 ◽  
Author(s):  
Vishwanath R.S ◽  
Masa-aki Haga ◽  
Takumi Watanabe ◽  
Emilia Witkowska Nery ◽  
Martin Jönsson-Niedziolka
Keyword(s):  
Redox Potential ◽  
Organic Phase ◽  
Electron Donor ◽  
Ion Transfer ◽  
Neutral Complex ◽  
Pyridine Ligand ◽  
Electrochemical Testing ◽  
Ru Complex ◽  
Three Phase ◽  
Exceptional Stability

Here we describe the synthesis and electrochemical testing of a heteroleptic bis(tridentate) ruthenium(II) complex [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> (LR =2,6-bis(1-(2-octyldodecan)benzimidazol-2-yl)pyridine, L = 2,6-bis(benzimidazolate)pyridine). It is a neutral complex which undergoes a quasireversible oxidation and reduction at relatively low potential. The newly synthetized compound was used for studies of ion-transfer at the three-phase junction because of the sensitivity of this method to cation expulsion. The [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> shows exceptional stability during cycling and is sufficiently lipophilic even after oxidation to persist in the organic phase also using very hydrophilic anions such as Cl<sup>−</sup>. Given its low redox potential and strong lipophilicity this compound will be of interest as an electron donor in liquid-liquid electrochemistry.

Three-Phase Electrochemistry of a Highly Lipophilic Neutral Ru-Complex Having a Tridentate Bis(benzimidazolate)pyridine Ligand

2020 ◽  
Author(s):  
Vishwanath R.S ◽  
Masa-aki Haga ◽  
Takumi Watanabe ◽  
Emilia Witkowska Nery ◽  
Martin Jönsson-Niedziolka
Keyword(s):  
Redox Potential ◽  
Organic Phase ◽  
Electron Donor ◽  
Ion Transfer ◽  
Neutral Complex ◽  
Pyridine Ligand ◽  
Electrochemical Testing ◽  
Ru Complex ◽  
Three Phase ◽  
Exceptional Stability

Here we describe the synthesis and electrochemical testing of a heteroleptic bis(tridentate) ruthenium(II) complex [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> (LR =2,6-bis(1-(2-octyldodecan)benzimidazol-2-yl)pyridine, L = 2,6-bis(benzimidazolate)pyridine). It is a neutral complex which undergoes a quasireversible oxidation and reduction at relatively low potential. The newly synthetized compound was used for studies of ion-transfer at the three-phase junction because of the sensitivity of this method to cation expulsion. The [Ru<sup>II</sup>(LR)(L)]<sup>0</sup> shows exceptional stability during cycling and is sufficiently lipophilic even after oxidation to persist in the organic phase also using very hydrophilic anions such as Cl<sup>−</sup>. Given its low redox potential and strong lipophilicity this compound will be of interest as an electron donor in liquid-liquid electrochemistry.

The Effect of Mixtures of Xenobiotics and Primary Electron Donor on the Anaerobic Biotransformation of High Concentrations of Chlorinated Aliphatics

1992 ◽  
Vol 26 (1-2) ◽  
pp. 117-126 ◽  
Author(s):  
J. B. Hughes ◽  
G. F. Parkin
Keyword(s):  
Electron Donor ◽  
Mixed Effects ◽  
Primary Electron ◽  
Primary Electron Donor ◽  
Loading Rates ◽  
Chlorinated Aliphatics ◽  
Anaerobic Biotransformation ◽  
Transformation Rates ◽  
High Concentrations ◽  
Effect Of Feeding

Results are presented from experiments addressing the anaerobic biotransfoimation of high concentrations of three chlorinated aliphatics, dichloromethane (DCM), chloroform (CF), and 1,1,1-trichloroethane (TCA), when fed alone and in mixtures. Experiments were conducted to address the effect of feeding mixtures of these compounds on the transformation rates of individual components in the mixture, and to assess the effect of acetate loading rates on the extent of transformation of the chlorinated aliphatics. Feeding mixtures of chlorinated aliphatics caused decreased transformation of TCA, increased the transformation of DCM, and had mixed effects on CF transformation. The systems fed higher acetate loading rates demonstrated an increased ability to transform the chlorinated aliphatics.

Abiotic reduction of 2,4-dinitrotoluene in the presence of sulfide minerals under anoxic conditions

1996 ◽  
Vol 34 (10) ◽  
pp. 25-33 ◽  
Author(s):  
Cheng Jiayang ◽  
Makram T. Suidan ◽  
Albert D. Venosa
Keyword(s):  
Electron Donor ◽  
Chemical Reduction ◽  
Sulfide Minerals ◽  
Sulfide Concentration ◽  
Magnesium Ions ◽  
High Concentration ◽  
Anoxic Conditions ◽  
High Affinity ◽  
Iron Nickel ◽  
Abiotic Reduction

Abiotic reduction of 2,4-dinitrotoluene (DNT) in the presence of sulfide minerals has been investigated under anoxic conditions at 35°C. 2,4-DNT was abiotically reduced to 4-amino-2-nitrotoluene (4-A-2-NT) and 2-amino-4-nitrotoluene (2-A-4-NT) in the presence of high concentration of sulfide (0.84 mM). No abiotic reduction of 2,4-DNT was observed in the presence of low sulfide concentration (0.42 mM). The rate and the extent of the abiotic reduction of 2,4-DNT were increased with an increase in sulfide concentration. Sulfide served as an electron donor for the reduction of 2,4-DNT. The 2-nitro group was preferentially reduced, making the 2-A-4-NT:4-A-2-NT ratio in the final products 2:1. The addition of iron, nickel, and cobalt minerals significantly enhanced the abiotic reduction. The FeS, NiS, and CoS solids formed in the serum bottles catalyzed the reduction of 2,4-DNT preferentially to 4-A-2-NT. MnS and CuS solids also catalyzed the reduction of 2,4-DNT to 4-A-2-NT, but did not change the overall reduction of 2,4-DNT. However, the presence of calcium, zinc, and magnesium minerals impeded 2,4-DNT reduction. The calcium, zinc, and magnesium ions have a high affinity to sulfide, inactivating sulfide as an electron donor for the chemical reduction of 2,4-DNT.

Reductive transformation of tetrachloroethylene to ethylene and ethane by an anaerobic filter

1997 ◽  
Vol 36 (6-7) ◽  
pp. 125-132 ◽  
Author(s):  
Toshiya Komatsu ◽  
Jun Shinmyo ◽  
Kiyoshi Momonoi
Keyword(s):  
Electron Donor ◽  
Laboratory Scale ◽  
Groundwater Contaminants ◽  
Reductive Transformation ◽  
Filter System ◽  
Anaerobic Filter ◽  
Anaerobic Microorganisms ◽  
Chlorinated Ethylenes ◽  
Start Up ◽  
Low Concentrations

Tetrachloroethylene (PCE) is one of the most common groundwater contaminants in Japan. PCE can be completely dechlorinated to ethylene (ETY) and ethane (ETA) by anaerobic microorganisms in the presence of a suitable electron donor. This study was conducted to examine the feasibility of using an anaerobic filter for the degradation of PCE in a bioremediation process. Laboratory-scale anaerobic filters were operated at 25°C using ethanol as the electron donor. Rapid start-up of the reactors was achieved by using anaerobic completely PCE-dechlorinating enrichment cultures as the inoculum. During the continuous operating periods, low concentrations (2.8 mg/L) of PCE were almost completely dechlorinated to ETY and ETA at hydraulic retention times of 49-15 hours with 100 mgCOD/L of ethanol. PCE concentrations as high as 80 mg/L was dechlorinated to ETY with a relatively low supply (200 mgCOD/L) of ethanol. Results of this study suggest that the anaerobic filter system is a feasible bioremediation process for the cleanup of groundwater which is contaminated by chlorinated ethylenes.

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