Abstract: Natural organic matter (NOM) has a profound effect on the colloidal stability of discharged C₆₀ nanoparticles in the water environment, which influences the environmental behaviors and risks of C₆₀ and therefore merits more specific studies. This study investigates the effects of humic acid (HA), as a model NOM, on the aqueous stabilization of C₆₀ powder and the colloidal stability of a previously suspended C₆₀ suspension (aqu/nC₆₀) with variations of pH values and ionic strengths. Our results reveal that HA could disperse C₆₀ powder in water to some degree, but was unable to stably suspend them. The aqu/nC₆₀ could remain stable at pH>4 but was destabilized at lower pH values. However, the colloidal stability of aqu/nC₆₀ in the presence of HA was insensitive to pH 3–11, owing to the adsorption of HA onto nC₆₀ and the increased electrosteric repulsions among nC₆₀ aggregates. The colloidal stability of aqu/nC₆₀, with and without HA, decreased as we increased the valence and concentration of the added cations. HA was found to mitigate the destabilization effect of Na⁺ on the colloidal stability of aqu/nC₆₀ by increasing the critical coagulation concentration (CCC) of Na⁺, while HA lowered the CCCs of Ca²⁺ and La³⁺ probably by the bridging effect of nC₆₀ with HA aggregates formed through the intermolecular bridging of the HA macromolecules via cation complexation at high concentrations of cations with high valences.

Key words: Fullerene, Humic acid, Colloidal stability, Natural organic matter, Nanomaterial

Please provide your name, email address and a comment

Your Name: Affili: E-Mail Address:

Comment (Please comment in English):


Verification Code(click to change a pic):