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Effect of Humic Acid and Sunlight on the Generation of aqu/C60
Citation:
Isaacson, C. AND D. BOUCHARD. Effect of Humic Acid and Sunlight on the Generation of aqu/C60. Presented at Nano 2010: Environmental Effects of Nanoparticles and Nanomaterials, Clemson, SC, August 22 - 26, 2010.
Impact/Purpose:
Presentation of research at a scientific meeting.
Description:
Little is known about the effect of sunlight and natural organic matter, such as humic acid, on the aqueous suspension of fullerene C60. This knowledge gap limits our ability to determine the environmental impact of potential environmental releases of these materials. Aqueous suspensions of C60 nanoparticles (aqu/C60) were generated by stirring in the presence and absence of sun light in deionized water, 0.1, 1.0, and 10 mg/L Suwanee River Humic Acid (SRHA) (adjusted to 1 µS/cm ionic strength with NaCl and pH 7 with NaOH) and in a water collected from a Call’s Creek, a primary tributary of the Oconee River, Athens GA (pH 8, conductivity 26 µS/cm, TOC 2.8 mg/L and TSS 35 mg/L). For both light and dark suspensions the mass of C60 suspended increased over the course of 400 hours with sunlight generating significantly more concentrated aqu/C60 suspensions than the dark treatments. For suspension generated in the presence of sun light, the C60 concentrations were greater than the dark controls with 0.1, 1,0 and 10 mg/L SRHA suspensions having C60 concentrations of 310 ± 88, 461 ± 120 and 384 ± 110 µg C60 / L, respectively. Sun light suspensions generated in de-ionized and Call’s Creek water were lower and the difference between them was not statistically significant, 150 ± 20 and 150 ± 40 µg C60 / L, respectively. Batch dynamic light scattering size determinations of aqu/C60 aggregate hydrodynamic diameters (Dh) generated in sunlight and dark suspensions indicate that sunlight only effected the size for the aqu/C60 aggregates generated in deionized water. While the concentration of humic acid did not effect aggregate size, the presence of humic acid resulted in reduced aggregate size, 170 – 180 nm Dh, compared to suspensions generated in deionized water, 200-250 nm Dh. Additionally, aggregates generated in Call’s Creek water were larger than those generated in deionized water or in the presence of humic acids, 250-300 nm Dh.