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 2

Initial aggregation rate constant k₁₁ obtained from the linear regression of the experimental data during the first 600 s, under varying concentrations of NaCl or CaCl₂ ranging from 0 to 1 mM in the absence and presence of HA (5 mg/L) or FA (0.14 mg/L) at three different pH values (8.2, 10.2, and 12.2).

pH	Electrolyte concentration (mM)	Aggregation rate (nm/s)
		NaCl	CaCl2	HA		FA
				NaCl	CaCl2	NaCl	CaCl2
8.2	0.00	0.01	0.01	0.51	0.51	0.02	0.02
	0.05	0.01	0.01
	0.10	0.02	0.01	0.01	0.04	0.01	0.02
	0.50	0.02	0.01
	1.00	0.35	0.08	0.25	0.11	0.02	0.02
10.2	0.00	0.44	0.44	0.54	0.54	0.02	0.02
	0.05	0.45	0.25
	0.10	0.33	0.35	0.42	0.37	0.01	0.01
	0.50	0.40	0.41
	1.00	0.44	0.50	0.48	0.44	0.02	0.02
12.2	0.00	0.01	0.01	0.01	0.01	0.02	0.02
	0.05	0.01	0.02
	0.10	0.01	0.02	0.02	0.02	0.01	0.01
	0.50	0.01	0.47
	1.00	0.00	0.00	0.02	0.00	0.01	0.02