Determination and prediction of surface coating composition, surface properties, and colloidal stability of nanoparticles after in situ exposure to natural waters

Despite the numerous studies about the sorption of dissolved organic matter (DOM) onto nanoparticles, most of the studies are conducted under controlled laboratory conditions with only a single compound or group of molecules with defined properties (e.g. humic acids). Also, the determination of only the molecular composition of the surface coating was conducted with an indirect measurement (difference between solution before and after sorption) using often unrealistic low ratios of organic carbon to nanoparticles. This results in a knowledge gap regarding the realistic mechanisms of surface coating formation and how this would affect the colloidal stability in the environment. This project aims to determine and predict the physico-chemical properties and structural features of the natural organic matter (NOM) coating forming on engineered (new and aged in formulation) nanoparticles after field exposure. This knowledge will be used to support the prediction of the colloidal stability of nanoparticles. In order to conduct the experiments under environmental conditions, five different types of nanoparticles will be loaded into a dialysis bag which works as passive sampler for in situ formation of the NOM-coating in different types of surface waters. Then, the characteristics of the formed natural coating will be explored using direct analysis method (LDI-FT-ICR MS). Multivariate predictive models will be used to identify the key parameters for the formation and stability of the NOM-coating, as well as the colloidal stability. These results will support building hypotheses on the sorption mechanisms and in combination with the aggregation rates of the NOM-coated particles, they will be used to explore the relationship between initial coating, natural coating, water composition, and aggregation.

Contact persons:
Michel Gad
Dr. Oliver Lechtenfeld

Project partner:
Dr. Allan Philippe (Uni Landau)