Organic compounds are ubiquitous and may exist as coatings in the environment, or as coagulants in water treatment systems. Iron oxide nanoparticles can act as sinks and/or carriers for heavy metal contaminants; therefore, it is crucial to investigate factors affecting their formation at mineral surfaces and organic coatings. We used a unique simultaneous small-angle X-ray scattering (SAXS) and grazing incidence (GISAXS) technique to monitor nanoparticle nucleation in solution and at substrate surfaces (quartz, and polyaspartate- and alginate-coated substrates). After 2 h of reaction, polyaspartate, the most negatively charged substrate, had 10 times less precipitation of positively-charged iron(III) hydroxide nanoparticles than quartz,  the least negatively charged substrate, implying that electrostatics do not govern nucleation. Based on contact angle measurements, we concluded that hydrophilicity was the dominant mechanism. This work provides in situ hetero- and homogeneous nucleation information to help predict nanoparticle fate and transport in the presence of organic matter.

Effects of surface hydrophilicity and functional group of organic coated substrates on iron(III) (hydr)oxide nucleation

245th National Meeting (2013)

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