Antimonate Controls Manganese(II)-Induced Transformation of Birnessite at a Circumneutral pH

2021 ◽  
Author(s):  
Niloofar Karimian ◽  
Kerstin Hockmann ◽  
Britta Planer-Friedrich ◽  
Scott G. Johnston ◽  
Edward D. Burton
Keyword(s):  
Circumneutral Ph

Sulfite activation by a low-leaching silica-supported copper catalyst for oxidation of As(III) in water at circumneutral pH

2019 ◽  
Vol 359 ◽  
pp. 1518-1526 ◽  
Author(s):  
Wei Ding ◽  
Xingyun Huang ◽  
Weidong Zhang ◽  
Feng Wu ◽  
Jinjun Li
Keyword(s):  
Copper Catalyst ◽  
Supported Copper Catalyst ◽  
Circumneutral Ph

scholarly journals Terraced Iron Formations: Biogeochemical Processes Contributing to Microbial Biomineralization and Microfossil Preservation

Geosciences ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 480 ◽  
Author(s):  
Jeremiah Shuster ◽  
Maria Rea ◽  
Barbara Etschmann ◽  
Joël Brugger ◽  
Frank Reith
Keyword(s):  
Iron Oxidation ◽  
Open Pit ◽  
Annual Rainfall ◽  
Biogeochemical Processes ◽  
Iron Oxyhydroxide ◽  
Iron Oxidizing Bacteria ◽  
Ph Conditions ◽  
Laminated Structures ◽  
Iron Formations ◽  
Circumneutral Ph

Terraced iron formations (TIFs) are laminated structures that cover square meter-size areas on the surface of weathered bench faces and tailings piles at the Mount Morgan mine, which is a non-operational open pit mine located in Queensland, Australia. Sampled TIFs were analyzed using molecular and microanalytical techniques to assess the bacterial communities that likely contributed to the development of these structures. The bacterial community from the TIFs was more diverse compared to the tailings on which the TIFs had formed. The detection of both chemolithotrophic iron-oxidizing bacteria, i.e., Acidithiobacillus ferrooxidans and Mariprofundus ferrooxydans, and iron-reducing bacteria, i.e., Acidobacterium capsulatum, suggests that iron oxidation/reduction are continuous processes occurring within the TIFs. Acidophilic, iron-oxidizing bacteria were enriched from the TIFs. High-resolution electron microscopy was used to characterize iron biomineralization, i.e., the association of cells with iron oxyhydroxide mineral precipitates, which served as an analog for identifying the structural microfossils of individual cells as well as biofilms within iron oxyhydroxide laminations—i.e., alternating layers containing schwertmannite (Fe16O16(OH)12(SO4)2) and goethite (FeO(OH)). Kinetic modeling estimated that it would take between 0.25–2.28 years to form approximately one gram of schwertmannite as a lamination over a one-m2 surface, thereby contributing to TIF development. This length of time could correspond with seasonable rainfall or greater than average annual rainfall. In either case, the presence of water is critical for sustaining microbial activity, and subsequently iron oxyhydroxide mineral precipitation. The TIFs from the Mount Morgan mine also contain laminations of gypsum (CaSO·2H2O) alternating with iron oxyhydroxide laminations. These gypsum laminations likely represented drier periods of the year, in which millimeter-size gypsum crystals presumably precipitated as water gradually evaporated. Interestingly, gypsum acted as a substrate for the attachment of cells and the growth of biofilms that eventually became mineralized within schwertmannite and goethite. The dissolution and reprecipitation of gypsum suggest that microenvironments with circumneutral pH conditions could exist within TIFs, thereby supporting iron oxidation under circumneutral pH conditions. In conclusion, this study highlights the relationship between microbes for the development of TIFs and also provides interpretations of biogeochemical processes contributing to the preservation of bacterial cells and entire biofilms under acidic conditions.

Achnanthidium palmeti (Bacillariophyta, Achnanthidiaceae), a new freshwater species from Réunion Island 

Phytotaxa ◽  
2013 ◽  
Vol 119 (1) ◽  
pp. 21 ◽  
Author(s):  
GILLES GASSIOLE ◽  
RENÉ LE COHU ◽  
MICHEL COSTE
Keyword(s):  
New Species ◽  
Recent Survey ◽  
Running Waters ◽  
Freshwater Species ◽  
Reunion Island ◽  
Epilithic Diatoms ◽  
Réunion Island ◽  
A New Species ◽  
Circumneutral Ph

Recent survey of the epilithic diatoms in the running waters of Réunion Island led to the discovery of a new species of Achnanthidium. Achnanthidium palmeti sp. nov. belongs to the group of Achnanthidium taxa with terminal raphe fissures curved to the same side of the valve. The new species differs from other taxa in this group by a higher stria density and the areolae morphology along the axial area; moreover, apart from Achnanthidium latecephalum H. Kobayasi, A. palmeti sp. nov. is the only species having raphe vestiges. The new species was found in oligotrophic waters with very low conductivity and circumneutral pH. 

The interplay of hydrological, chemical and microbial processes in the formation of iron-rich floating films in aquatic environments at a circumneutral pH

Limnetica ◽  
2015 ◽  
pp. 365-380
Author(s):  
Reina, Marta ◽  
Portillo, M. Carmen ◽  
Serrano, Laura ◽  
Lucassen, Esther C.H.E.T. ◽  
Roelofs, Jan G. M. ◽  
...  
Keyword(s):  
Microbial Processes ◽  
Aquatic Environments ◽  
Circumneutral Ph

scholarly journals Solar Photo-Assisted Degradation of Bipyridinium Herbicides at Circumneutral pH: A Life Cycle Assessment Approach

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1117
Author(s):  
Alejandra Teutli-Sequeira ◽  
Ruben Vasquez-Medrano ◽  
Dorian Prato-Garcia ◽  
Jorge G. Ibanez
Keyword(s):  
Life Cycle Assessment ◽  
Life Cycle ◽  
Carbon Footprint ◽  
Electricity Consumption ◽  
Electrical Energy ◽  
Sensitivity Study ◽  
Fenton Process ◽  
Assessment Approach ◽  
Energy Share ◽  
Circumneutral Ph

This study investigated the degradation of the herbicides diquat (DQ) and paraquat (PQ) by a solar photo-Fenton process that is mediated by Fe(III)-oxalate complexes at circumneutral pH = 6.5 in compound parabolic collectors (CPC)-type reactors. The photo-Fenton process operates efficiently at acidic pH; however, circumneutral operation was key to overcome drawbacks, such as acidification and neutralization steps, reagent costs, and the environmental footprint of chemical auxiliaries. This work revealed a remarkable reduction of total organic carbon for PQ (87%) and DQ (80%) after 300 min (at ca. 875 kJ L−1). Phytotoxicity assays confirmed that the treatment led to a considerable increase in the germination index for DQ (i.e., from 4.7% to 55.8%) and PQ (i.e., from 16.5% to 59.7%) using Cucumis sativus seeds. Importantly, treatment costs (DQ = USD$8.05 and PQ = USD$7.72) and the carbon footprint of the process (DQ = 7.37 and PQ = 6.29 kg CO2-Eqv/m3) were within the ranges that were reported for the treatment of recalcitrant substances at acidic conditions in CPC-type reactors. Life cycle assessment (LCA) evidenced that H2O2 and electricity consumption are the variables with the highest environmental impact because they contribute with ca. 70% of the carbon footprint of the process. Under the studied conditions, a further reduction in H2O2 use is counterproductive, because it could impact process performance and effluent quality. On the other hand, the main drawback of the process (i.e., energy consumption) can be reduced by using renewable energies. The sensitivity study evidenced that carbon footprint is dependent on the energy share of the local electricity mix; therefore, the use of more renewable electrical energy sources, such as wind-power and photovoltaic, can reduce greenhouse gases emissions of the process an average of 26.4% (DQ = 5.57 and PQ = 4.51 kg CO2-Eqv/m3) and 78.4% (DQ = 3.72 and PQ = 2.65 kg CO2-Eqv/m3), respectively. Finally, from the economic and environmental points of view, the experimental results evidenced that photo-assisted treatment at circumneutral pH is an efficient alternative to deal with quaternary bipyridinium compounds.

Process-based modeling of arsenic(III) oxidation by manganese oxides under circumneutral pH conditions

2020 ◽  
Vol 185 ◽  
pp. 116195
Author(s):  
Bhasker Rathi ◽  
James Jamieson ◽  
Jing Sun ◽  
Adam J. Siade ◽  
Mengqiang Zhu ◽  
...  
Keyword(s):  
Manganese Oxides ◽  
Ph Conditions ◽  
Circumneutral Ph

Enhanced Fenton-like degradation of TCE in sand suspensions with magnetite by NTA/EDTA at circumneutral pH

2017 ◽  
Vol 24 (21) ◽  
pp. 17598-17605 ◽  
Author(s):  
Na Wang ◽  
Daqing Jia ◽  
Yaoyao Jin ◽  
Sheng-Peng Sun ◽  
Qiang Ke
Keyword(s):  
Circumneutral Ph
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