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:
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Synthesize nanosize MnO2
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Create three different MnO2 with different MnIII surface concentrations using Mn2+ spiking
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Measure the average oxidation state (AOS) of the mineral surfaces Mn using XPS
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Unravel the oxidation state dependency of IDMP oxidation by MnO2
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Conduct transformation experiments (IDMP) on MnO2 with different MnIII/IV ratios
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Is there a clear trend between AOS and kinetics?
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Does this lead to different transformation products?
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Find possible explanations for the findings
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