T5 Desorption kinetics and irreversibility in applications of technical adsorbents for water treatment
Doctoral student: Geert Aschermann 
Supervisors: Prof. Dr. Martin Jekel , Prof. Dr. Eckhard Worch , Prof. Dr. Juliane Hollender 
Organic contaminants such as pharmaceuticals, household chemicals or radiocontrast agents can be found in all parts of urban water cycles, from waste water over surface waters to drinking water [1, 2]. According to their in low concentration ranges of µg/L to ng/L these compounds are often called organic micropollutants. Due to their unknown effects on human health as well as the aquatic environment action concerning their reduction in aquatic systems is under discussion . The application of activated carbon is a promising method for the removal of these compounds, in water works as well as in waste water treatment plants . During this technical treatment step dissolved water constituents (including micropollutants) are removed by adsorption onto the activated carbon surface. This process is generally expected to be reversible . Thus, it seems likely that adsorbed micropollutants can also desorb again under certain conditions (e.g. due to strong fluctuations of the micropollutant concentration in the raw water). This can then lead to an undesired increase of micropollutant concentration in the treated water. Whereas the adsorption of organic micropollutants onto activated carbon was investigated extensively, the knowledge about their potential desorption is still limited.
- Desorption of micropollutants in an activated carbon filter
- © Aschermann
Aim of the work
The aim of this project is therefore to get a better mechanistic understanding of the desorption processes in activated carbon applications, with respect to the extent as well as to the kinetic. Initially, the general desorption behavior of micropollutants (under ideal conditions) will be studied. Furthermore, factors will be indentified that influence micropollutant desorption. One main goal of the current study is to study the effects of dissolved organic matter on the desorption of micropollutants. It is known that the adsorption of micropollutants onto activated carbon is strongly reduced by the presence of background organic matter due competition effects . It can therefore be expected that it also influences desorption. Moreover, it will be studied how activated carbon properties affect this process. There is a broad pool of commercially available activated carbons which differ in their characteristics. These characteristics have impact on the adsorption , and probably also on the desorption of micropollutants .
The projected research will be based on lab scale investigations, where potential desorption scenarios will be simulated. Experimental methods that are established in adsorption research will adapted and expanded with a subsequent desorption step. This includes batch tests (to study the potential extent of desorption) as well as small scale column tests (to study the kinetics and dynamics of desorption).
These tests are accompanied by modern analytics. Liquid chromatography coupled with tandem quadrupole mass spectrometry (LC-MS/MS) is used to determine micropollutant concentration in the range of µg/L to ng/L. This allows experiments under environmentally relevant concentrations of micropollutants.
- Other UWI projects: N3  (Sonia Herrero), N4  (Clara Romero), N6  (Jonas Schaper), T6  (Fatima El-Athman)
- Common topics: Micropollutants 
- Heberer, T., K. Reddersen, and A. Mechlinski, From municipal sewage to drinking water: fate and removal of pharmaceutical residues in the aquatic environment in urban areas. Water Science and Technology, 2002. 46(3): p. 81-88.
- Reemtsma, T., S. Weiss, J. Mueller, M. Petrovic, S. Gonzalez, D. Barcelo, F. Ventura, and T.P. Knepper, Polar pollutants entry into the water cycle by municipal wastewater: A European perspective. Environmental Science & Technology, 2006. 40(17): p. 5451-5458.
- Jekel, M., A. Ruhl, F. Meinel, F. Zietzschmann, S. Lima, N. Baur, M. Wenzel, R. Gnirss, A. Sperlich, U. Dunnbier, U. Bockelmann, D. Hummelt, P. van Baar, F. Wode, D. Petersohn, T. Grummt, A. Eckhardt, W. Schulz, A. Heermann, T. Reemtsma, B. Seiwert, L. Schlittenbauer, B. Lesjean, U. Miehe, C. Remy, M. Stapf, and D. Mutz, Anthropogenic organic micro-pollutants and pathogens in the urban water cycle: assessment, barriers and risk communication (ASKURIS). Environmental Sciences Europe, 2013. 25(1): p. 20.
- Zietzschmann, F., G. Aschermann, and M. Jekel, Comparing and modeling organic micro-pollutant adsorption onto powdered activated carbon in different drinking waters and WWTP effluents. Water Research, 2016. 102: p. 190-201.
- Worch, E., Adsorption Technology in Water Treatment, Fundamentals, Processes, and Modeling. 2012.
- Zietzschmann, F., E. Worch, J. Altmann, A.S. Ruhl, A. Sperlich, F. Meinel, and M. Jekel, Impact of EfOM size on competition in activated carbon adsorption of organic micro-pollutants from treated wastewater. Water Research, 2014. 65: p. 297-306.
- Zietzschmann, F., J. Altmann, A.S. Ruhl, U. Dunnbier, I. Dommisch, A. Sperlich, F. Meinel, and M. Jekel, Estimating organic micro-pollutant removal potential of activated carbons using UV absorption and carbon characteristics. Water Research, 2014. 56: p. 48-55.
- Tanthapanichakoon, W., P. Ariyadejwanich, P. Japthong, K. Nakagawa, S. Mukai, and H. Tamon, Adsorption–desorption characteristics of phenol and reactive dyes from aqueous solution on mesoporous activated carbon prepared from waste tires. Water Research, 2005. 39(7): p. 1347-1353.
Initial project plan