Effect of Naturally Occurring Organic Matter (NOOM) Type and Source on NOOM Adsorption onto Titanium Dioxide Nanoparticles under Varying Environmental Condition

In many studies, different humic acid sources and naturally occurring organic matter (NOOM) types are used interchangeably to evaluate the effect of organic matter on geochemical processes in the environment. This research looks more specifically at the effect of humic acid source and different fractions of NOOM on NOOM adsorption onto nano-TiO2 and how NOOM adsorption affects the fate and transport of nano-TiO2, as a function of pH, ionic strength and electrolyte. For NOOM source, seven HAs were studied, including soil HA (SHA), freshwater sedimentary HA (FSDHA) and estuarine sedimentary HA (ESDHA) all originating from the state of Florida. For NOOM type, three NOOM were studied, including Suwannee River humic acid (SRHA), fulvic acid (SRFA), and natural organic matter (SRNOM), all from the same source. Ultraviolet-Visible (UV-Vis) absorption spectroscopy was used to monitor the NOOM adsorption onto nano-TiO2 and the sedimentation of NOOM-coated and uncoated nano-TiO 2. Synchronous scan fluorescence (SSF) spectroscopy was used to provide more information about NOOM adsorption onto nano-TiO2. Selected samples of NOOM-coated and uncoated nano-TiO2 were analyzed by transmission electron microscopy (TEM).