Uranium removal by sulfate reducing biofilms in the presence of carbonates

2005 ◽  
Vol 52 (7) ◽  
pp. 49-55 ◽  
Author(s):  
E. Marsili ◽  
H. Beyenal ◽  
L. Di Palma ◽  
C. Merli ◽  
A. Dohnalkova ◽  
...  
Keyword(s):  
Continuous Flow ◽  
Desulfovibrio Desulfuricans ◽  
Bicarbonate Buffer ◽  
Flow Reactors ◽  
Sulfate Reducing ◽  
Hexavalent Uranium ◽  
Uranium Removal ◽  
Nanocrystalline Structures ◽  
Continuous Flow Reactors ◽  
Reducing Bacteria

Hexavalent uranium [U(VI)] was immobilized in biofilms composed of the sulfate reducing bacteria (SRB), Desulfovibrio desulfuricans G20. The biofilms were grown in two flat-plate, continuous-flow reactors using lactate as the electron donor and sulfate as the electron acceptor. The growth medium contained uranium U(VI) and the pH was maintained constant using bicarbonate buffer. The reactors were operated for 5 months, and during that time biofilm activity and uranium removal were evaluated. The efficiency of uranium removal strongly depended on the concentration of uranium in the influent, and was estimated to be 30.4% in the reactor supplied with 3 mg/L of U(VI) and 73.9% in the reactor supplied with 30 mg/L of U(VI). TEM and SAED analysis showed that uranium in both reactors accumulated mostly on microbial cell membranes and in the periplasmic space. The deposits had amorphous or poor nanocrystalline structures.

Impact of organic ligands on uranium removal during anaerobic biological treatment

1998 ◽  
Vol 37 (8) ◽  
pp. 73-80 ◽  
Author(s):  
Kevin G. Robinson ◽  
Rajagopalan Ganesh ◽  
Gregory D. Reed
Keyword(s):  
Complex Formation ◽  
Pure Culture ◽  
Biological Treatment ◽  
Desulfovibrio Desulfuricans ◽  
Organic Ligands ◽  
Ligand Concentration ◽  
Batch Experiments ◽  
Sulfate Reducing ◽  
Uranium Removal ◽  
Reducing Bacteria

Anaerobic batch experiments were conducted to evaluate the reduction and precipitation of U6+ complexed to acetate, oxalate, citrate and tiron using a pure culture of sulfate reducing bacteria (Desulfovibrio desulfuricans). These ligands were chosen to evaluate the nature of complex formation on uranium bioreduction. Experiments in which uranium was initially complexed to the ligand (>92%) indicated that bacteria reduce U6+ to U4+ in the presence of each ligand tested. The rate of acetate complexed uranium reduction was fastest and that of citrate complexed uranium was slowest. Precipitation of reduced uranium was evaluated by filtering the reduced complex through 0.2 μm filters. The U4+ formed after biotransformation in acetate solutions was retained on the filter whereas U4+ in the oxalate, citrate and tiron solutions passed through the filter. When ligand concentrations were lowered (44–50% of the uranium initially complexed) a greater amount of UO2 precipitate from oxalate samples was collected on the filter indicating that ligand concentration can impact uranium removal via precipitation. Little or no precipitate was collected from citrate or tiron containing solutions. The preferred reaction of U4+ appeared to be recomplexation with these ligands rather then precipitation as UO2.

Continuous flow reactors: a perspective

2012 ◽  
Vol 14 (1) ◽  
pp. 38-54 ◽  
Author(s):  
Charlotte Wiles ◽  
Paul Watts
Keyword(s):  
Continuous Flow ◽  
Flow Reactors ◽  
Continuous Flow Reactors

Synthesis of Tailored Segmented Polyurethanes Utilizing Continuous-Flow Reactors and Real-Time Process Monitoring

2021 ◽  
Author(s):  
Xabier Lopez de Pariza ◽  
Tim Erdmann ◽  
Pedro L. Arrechea ◽  
Leron Perez ◽  
Charles Dausse ◽  
...  
Keyword(s):  
Real Time ◽  
Process Monitoring ◽  
Continuous Flow ◽  
Time Process ◽  
Flow Reactors ◽  
Segmented Polyurethanes ◽  
Continuous Flow Reactors

Functional Group Interconversion Reactions in Continuous Flow Reactors

2021 ◽  
Vol 25 ◽  
Author(s):  
Alexander Leslie ◽  
Angel Maria Joseph ◽  
Marcus Baumann
Keyword(s):  
Continuous Flow ◽  
Functional Group ◽  
Modern Synthesis ◽  
Flow Reactors ◽  
Flow Synthesis ◽  
Specific Reaction ◽  
Solid Foundation ◽  
Continuous Flow Reactors ◽  
Flow Techniques

: An overview of the current uptake of continuous flow techniques for various functional group interconversion reactions is presented. Besides highlighting a variety of prominent examples and their main features, this review provides insights into specific reaction classes, such as oxidations, reductions, rearrangements as well as different C-H functionalization processes. While this review can only include key examples from the last decade, the reader will find a solid foundation of important transformations along with further references to inform and appreciate the opportunities arising from modern synthesis technologies such as flow synthesis.

Visible light-induced iniferter polymerization of methacrylates enhanced by continuous flow

2017 ◽  
Vol 8 (42) ◽  
pp. 6496-6505 ◽  
Author(s):  
Maarten Rubens ◽  
Phanumat Latsrisaeng ◽  
Tanja Junkers
Keyword(s):  
Block Copolymers ◽  
Visible Light ◽  
Continuous Flow ◽  
Flow Reactors ◽  
Continuous Flow Reactors

Visible-light induced photoiniferter polymerization in continuous flow reactors is very efficient in yielding low dispersity methacrylate block copolymers.

Experimental Investigation on the Active Range of Sulfate-Reducing Bacteria for Geological Disposal

1994 ◽  
Vol 353 ◽  
Author(s):  
S. Fukunaga ◽  
H. Yoshikawa ◽  
K. Fujiki ◽  
H. Asano
Keyword(s):  
Experimental Investigation ◽  
Environmental Conditions ◽  
Desulfovibrio Desulfuricans ◽  
Sulfate Reducing Bacteria ◽  
Geological Disposal ◽  
Sulfate Reducing ◽  
Buffer Material ◽  
Ph Range ◽  
High Level ◽  
Reducing Bacteria

AbstractThe active range ofDesulfovibrio desulfuricans. a species of sulfate-reducing bacteria, was examined in terms of pH and Eh using a fermenter at controlled pH and Eh. Such research is important because sulfate-reducing bacteria (SRB) are thought to exist underground at depths equal to those of supposed repositories for high-level radioactive wastes and to be capable of inducing corrosion of the metals used in containment vessels.SRB activity was estimated at 35°C, with lactate as an electron donor, at a pH range from 7 to 11 and Eh range from 0 to -380 mV. Activity increased as pH approached neutral and Eh declined. The upper pH limit for activity was between 9.9 and 10.3, at Eh of -360 to -384 mV. The upper Eh limit for activity was between -68 and -3 mV, at pH 7.1. These results show that SRB can be made active at higher pH by decreasing Eh, and that the higher pH levels of 8 to 10 produced by use of the buffer material bentonite does not suppress SRB completely.A chart was obtained showing the active range ofDesulfovibrio desulfuricansin terms of pH and Eh. Such charts can be used to estimate the viability of SRB and other microorganisms when the environmental conditions of a repository are specified.

scholarly journals Diels–Alder reactions of myrcene using intensified continuous-flow reactors

2017 ◽  
Vol 13 ◽  
pp. 120-126 ◽  
Author(s):  
Christian H Hornung ◽  
Miguel Á Álvarez-Diéguez ◽  
Thomas M Kohl ◽  
John Tsanaktsidis
Keyword(s):  
Continuous Flow ◽  
Flow Reactor ◽  
Scale Up ◽  
Reaction Times ◽  
Alder Reaction ◽  
Diels Alder ◽  
Flow Reactors ◽  
Diels Alder Reaction ◽  
Naturally Occurring ◽  
Continuous Flow Reactors

This work describes the Diels–Alder reaction of the naturally occurring substituted butadiene, myrcene, with a range of different naturally occurring and synthetic dienophiles. The synthesis of the Diels–Alder adduct from myrcene and acrylic acid, containing surfactant properties, was scaled-up in a plate-type continuous-flow reactor with a volume of 105 mL to a throughput of 2.79 kg of the final product per day. This continuous-flow approach provides a facile alternative scale-up route to conventional batch processing, and it helps to intensify the synthesis protocol by applying higher reaction temperatures and shorter reaction times.

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