Colloid Systems and Interfaces Stability of Cerium Oxide Nanoparticles in Aqueous Environments: Effects of pH, Ionic Composition, and Suwanee River Humic and Fulvic Acids

Table 1

Solutions created for experimentation on the stability and aggregation of cerium oxide NPs in aqueous systems as a function of pH, electrolyte type and concentration, and the absence and presence of humic substances.

Systems				Humic substances
				Humic acid 5 mg/L			Fulvic acid 0.14 mg/L
	pH 8.2 + electrolyte concentration (mM)	pH 10.2 + electrolyte concentration (mM)	pH 12.2 + electrolyte concentration (mM)	pH 8.2 + electrolyte concentration (mM)	pH 10.2 + electrolyte concentration (mM)	pH 12.2 + electrolyte concentration (mM)	pH 8.2 + electrolyte concentration (mM)	pH 10.2 + electrolyte concentration (mM)	pH 12.2 + electrolyte concentration (mM)
DI water	0	0	0	0	0	0	0	0	0
NaCl				0.01	0.01	0.01	0.01	0.01	0.01
	0.05	0.05	0.05
	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
	0.5	0.5	0.5
	1	1	1	1	1	1	1	1	1
CaCl2				0.01	0.01	0.01	0.01	0.01	0.01
	0.05	0.05	0.05
	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
	0.5	0.5	0.5	1	1	1	1	1	1
	1	1	1

These solutions include pH solutions ranging from 1 to 14, and aqueous systems with electrolytes (monovalent cation Na⁺ at concentrations ranging from 0. to 1 mM, and divalent cation Ca²⁺ at concentrations ranging from 0 to 1 mM), at pH values of 8.2, 10.2, and 12.2, and in both the absence and presence of HA at 5 mg/L and FA at 0.14 mg/L.