TY  - JOUR
A1  - Tippkötter, Nils
A1  - Roikaew, Wipa
A1  - Ulber, Roland
A1  - Hoffmann, Alexander
A1  - Denzler, Hans-Jörg
A1  - Buchholz, Heinrich
T1  - Paracoccus denitrificans for the effluent recycling during continuous denitrification of liquid food
JF  - Biotechnology Progress
N2  - Nitrate is an undesirable component of several foods. A typical case of contamination with high nitrate contents is whey concentrate, containing nitrate in concentrations up to 25 l. The microbiological removal of nitrate by Paracoccus denitrificans under formation of harmless nitrogen in combination with a cell retention reactor is described here. Focus lies on the resource-conserving design of a microbal denitrification process. Two methods are compared. The application of polyvinyl alcohol-immobilized cells, which can be applied several times in whey feed, is compared with the implementation of a two step denitrification system. First, the whey concentrate's nitrate is removed by ion exchange and subsequently the eluent regenerated by microorganisms under their retention by crossflow filtration. Nitrite and nitrate concentrations were determined by reflectometric color measurement with a commercially available Reflectoquant® device. Correction factors for these media had to be determined. During the pilot development, bioreactors from 4 to 250 mg·L-1 and crossflow units with membrane areas from 0.02 to 0.80 m2 were examined. Based on the results of the pilot plants, a scaling for the exemplary process of denitrifying 1,000 tons per day is discussed.
Y1  - 2010
U6  - http://dx.doi.org/10.1002/btpr.384
SN  - 8756-7938
VL  - 26
IS  - 3
SP  - 756
EP  - 762
PB  - Wiley
CY  - Hoboken, NJ
ER  - 
TY  - JOUR
A1  - Hoffmann, Andreas
A1  - Rohrbach, Felix
A1  - Uhl, Matthias
A1  - Ceblin, Maximilian
A1  - Bauer, Thomas
A1  - Mallah, Marcel
A1  - Jacob, Timo
A1  - Heuermann, Holger
A1  - Kuehne, Alexander J. C.
T1  - Atmospheric pressure plasma-jet treatment of polyacrylonitrile-nonwovens—Stabilization and roll-to-roll processing
JF  - Journal of Applied Polymer Science
N2  - Carbon nanofiber nonwovens represent a powerful class of materials with prospective application in filtration technology or as electrodes with high surface area in batteries, fuel cells, and supercapacitors. While new precursor-to-carbon conversion processes have been explored to overcome productivity restrictions for carbon fiber tows, alternatives for the two-step thermal conversion of polyacrylonitrile precursors into carbon fiber nonwovens are absent. In this work, we develop a continuous roll-to-roll stabilization process using an atmospheric pressure microwave plasma jet. We explore the influence of various plasma-jet parameters on the morphology of the nonwoven and compare the stabilized nonwoven to thermally stabilized samples using scanning electron microscopy, differential scanning calorimetry, and infrared spectroscopy. We show that stabilization with a non-equilibrium plasma-jet can be twice as productive as the conventional thermal stabilization in a convection furnace, while producing electrodes of comparable electrochemical performance.
KW  - batteries and fuel cells
KW  - electrospinning
KW  - fibers
KW  - irradiation
KW  - porous materials
Y1  - 2022
U6  - http://dx.doi.org/10.1002/app.52887
SN  - 0021-8995 (Print)
SN  - 1097-4628 (Online)
N1  - Weitere Informationen: Bundesministerium für Bildung und Forschung, Fördernummer: 13XP5036E. Deutsche Forschungsgemeinschaft, Fördernummern: 390874152, 441209207, 327886311
VL  - 139
IS  - 37
SP  - 1
EP  - 9
PB  - Wiley
ER  - 
TY  - JOUR
A1  - Hoffmann, Andreas
A1  - Uhl, Matthias
A1  - Ceblin, Maximilian
A1  - Rohrbach, Felix
A1  - Bansmann, Joachim
A1  - Mallah, Marcel
A1  - Heuermann, Holger
A1  - Jacob, Timo
A1  - Kuehne, Alexander J.C.
T1  - Atmospheric pressure plasma-jet treatment of PAN-nonwovens—carbonization of nanofiber electrodes
JF  - C - Journal of Carbon Research
N2  - Carbon nanofibers are produced from dielectric polymer precursors such as polyacrylonitrile (PAN). Carbonized nanofiber nonwovens show high surface area and good electrical conductivity, rendering these fiber materials interesting for application as electrodes in batteries, fuel cells, and supercapacitors. However, thermal processing is slow and costly, which is why new processing techniques have been explored for carbon fiber tows. Alternatives for the conversion of PAN-precursors into carbon fiber nonwovens are scarce. Here, we utilize an atmospheric pressure plasma jet to conduct carbonization of stabilized PAN nanofiber nonwovens. We explore the influence of various processing parameters on the conductivity and degree of carbonization of the converted nanofiber material. The precursor fibers are converted by plasma-jet treatment to carbon fiber nonwovens within seconds, by which they develop a rough surface making subsequent surface activation processes obsolete. The resulting carbon nanofiber nonwovens are applied as supercapacitor electrodes and examined by cyclic voltammetry and impedance spectroscopy. Nonwovens that are carbonized within 60 s show capacitances of up to 5 F g⁻¹.
Y1  - 2022
U6  - http://dx.doi.org/10.3390/c8030033
SN  - 2311-5629
N1  - This article belongs to the Collection "Nanoporous Carbon Materials for Advanced Technological Applications"
VL  - 8
IS  - 3
PB  - MDPI
CY  - Basel
ER  -