22 June 2022

Contact: anna.roehnelt@uni-tuebingen.de , philipp.martin@uni-tuebingen.de , Stefan.haderlein@uni-tuebingen.de  (Environmental Mineralogy and Chemistry) 

Environmental Background:
Aminopolyphosphonates (APPs) are increasingly used for several industrial and household applications in the past decades, e.g., as scale inhibitor or bleaching stabilizer. Insufficient removal in waste water treatment plants leads to increasing concentrations in WWTP discharges and thus in receiving waters. The main removal process is sorption onto sewage sludge, which means that the APPs are not eliminated but effectively just changing the compartment. A drawback of several transformation processes (e.g., oxidation on redoxactive minerals) is still, that incomplete mineralization leads to (potentially toxic) transformation products (TP), as in case of APPs – glyphosate or aminomethylenephosphonate (AMPA).
Iminodimethylenephosphonate (IDMP) has been shown to be a main TP of APPs and therefore serves as a model compound for oxidation on MnO₂ in our study. Next to phosphate, AMPA is the main TP of IDMP oxidation, which is also a TP of microbial glyphosate degradation. AMPA is regarded as toxicologically relevant, as it exhibits direct toxicity to water organisms and plants and is persistent in the environment.

Goals:

• Synthesize nanosize MnO₂ 

• Create three different MnO₂ with different MnIII surface concentrations using Mn²⁺ spiking

• Measure the average oxidation state (AOS) of the mineral surfaces Mn using XPS 

• Unravel the oxidation state dependency of IDMP oxidation by MnO₂ 

  • Conduct transformation experiments (IDMP) on MnO₂ with different Mn^III/IV ratios

  • Is there a clear trend between AOS and kinetics?

  • Does this lead to different transformation products?

• Find possible explanations for the findings

We are looking for a highly motivated master student, who is …

• Enjoying laboratory work and having some lab experience

• Working independently

• Communicating openly and asks questions

We offer …

• An outlined master thesis project

• Close lab supervision

• Flexibility

• HiWi position prior or subsequent to the MSc work