Peter R. Tentscher - Scientific Services

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Organic Micropollutants

Organic micropollutants (pharmaceuticals, pesticides, personal care products, etc.) are present in virtually all water bodies, from surface freshwater bodies, over groundwater, to seawater. As organic micropollutants are bioactive substances, recent efforts across Europe are focusing on their removal during wastewater treatment and during drinking water production.
Chemical oxidation plays a crucial role for micropollutant abatement- either in water treatment systems, or during natural attenuation through photo-induced chemistry in sunlit surface waters. Depending on the system of interest, a multitude of oxidants can react with micropollutants, for example hydroxyl radical, ozone, HOCl, HOBr, Cl2O, ClO2, chloramines, triplet states of photosensitizers, carbonate radical anion...
These abatement reactions can usually be described by second order rate laws:
Rate expression for dosed oxidants.
where MPj is the jth micropollutant, and Oxi is the ith oxidant present in the system. Owing to the sheer number of micropollutants (several 10000s of compounds), it will be impossible to study the kinetics and the potentially toxic transformation products in all relevant systems. Instead, it is necessary to guide and complement experimental work with predictive models for abatement kinetics and product formation.

In this context, I am interested in experimental work on micropollutant oxidation: applied studies as well as oxidation work on structurally simpler model substances that allow conclusions on the underlying reaction mechanisms. This can be combined with computational approaches described below.

Computational Quantum Chemistry

My research in computational chemistry revolves primarily around the application of quantum chemical methods- ab initio calculations and density functional theory- to practical problems of oxidation chemistry.
In the context of aqueous oxidation reactions (vide infra), a primary goal of my research is to study the applicability of such methods to problems relevant to oxidation chemistry: the description of open-shell (radical) species, the estimation of redox properties, the estimation of equilibrium constants and pKa values, and the elucidation of reaction mechanisms of oxidation reactions.
Another area that I entered recently is the estimation of second order reaction rate constants with quantitative structure-property relationship based on quantum chemically computed descriptors. In contrast to traditional structure-rate relationships based on Hammett or Taft constants, quantum chemical descriptors can be calculated for any type of structure. Such descriptors should also allow for more general relationships with a larger domain of applicability. I'm currently working on the selection of appropriate electronic structure methods and descriptors that are best suited for the estimation of reaction rate constants.