University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Susanne Langer
(2017):
Influence of rhamnolipid on the reductive dechlorination of tetrachloroethene by nanoscale zero-valent iron.
Master / Diploma Thesis - Institut für Bodenforschung (IBF),
BOKU-Universität für Bodenkultur,
pp 61.
UB BOKU
obvsg
FullText
- Abstract:
- Tetrachloroethene (commonly known as perchloroethylene or PCE) is a severe groundwater contaminant which is difficult to remediate, hardly biodegradable and very persistent. Zero-valent iron reacts with PCE and by complete reductive dechlorination harmless end products (ethene and ethane) are formed. Nanoscale zero-valent iron (nZVI) has a high reactivity due to its high specific surface area and can be used to treat contaminated groundwater in-situ. However the nZVI particles tend to build aggregates due to their strong magnetic attractive forces and so lose their high surface area. The aim of this work was to investigate whether the addition of the biosurfactant rhamnolipid (RL) can help hinder the aggregation of the particles which would be seen in a higher degradation rate of PCE. Lab-scale batch experiments were conducted to investigate the possible effect of RL. Five different treatment groups were compared with concentrations of RL above and below its critical micelle concentration (CMC) and three (negative) controls were done with PCE + RL, PCE + nZVI and only PCE. The samples were analysed via GC-FID and GC-TCD. The observed degradation rate constant (kobs) of PCE of the samples with the lowest RL concentration (0.1 mg/L) was significantly higher than the kobs of the control with only PCE + nZVI. Moreover, a significant difference was found in the degradation of PCE of the samples with the highest RL concentration (above CMC). This treatment showed significant differences from the other treatments and controls by having the highest decrease in PCE, a higher kobs of PCE and a lower kobs for the production of H2. The higher degradation of PCE could not be attributed directly to a smaller particle size. There was also a shift in reaction pathway of PCE dechlorination from β-elimination to hydrogenolysis in the treatment with the highest RL concentration. Also, the production of ethene and ethane was lower and trichloroethene (TCE) accumulated.
- Beurteilende(r):
- 1.Mitwirkender: Fürhacker Maria