Relating structure of organic chemicals to their sorption at biogeochemical interfaces by combining macroscopic, spectroscopic and calorimetric methods with molecular modelling

Principal investigators: Prof. Dr. M. Kaupenjohann, Dr. F. Lang, Dr. J. Siemens

Co-worker: Dipl.-Ing. J. Kr├╝ger

Physicochemical and steric properties of organic chemicals on the one hand and physicochemical surface properties and structural properties of the sorbent on the other hand determine sorptive interactions at biogeochemical interfaces. In order to gain a mechanistic understanding of these interactions we want to combine macroscopic, micro-calorimetric and spectroscopic methods. We hypothesise that sorption and distribution of a polar organic chemical at biogeochemical interfaces is either determined by the molecules hydrophobic R-groups ("R-determined") or its functional groups ("F-determined"). To test our hypothesis we will study sorption of bisphenol A and fenhexamid (R-determined chemicals) and bentazone and naproxen (F-determined chemicals) in pure systems of minerals (kaolinite, illite, gibbsite and quartz), in model substances of biofilms (polygalacturonic acid and dextran), in combined systems of mineral phases with organic layers and in topsoils and subsoils. Interpretation and modelling of sorption isotherms and sorption kinetics derived from batch experiments together with results from diffusion experiments with polysugars of variable cross-linking will provide macroscopic insight into sorptive interactions. Information regarding the thermodynamics of sorption will by derived from micro-calorimetry. Spectroscopic (ATR-FTIR, NMR) measurements deliver information on molecular interactions and structure.

Cooperation within the pririty programme:
Prof. Dr. M.H. Gerzabek, Prof. Dr. Dr. h.c. M. Spiteller

Mikrokalorimeter

Micro-calorimeter (TAM III, Thermometric)

Al2O3

Al2 O3 coated with polygalacturonic acid

Poster Kaupenjohann1