Table 5.

Surface charge density (σ ₀; c = 100 ppm) and zeta potential (ζ) values for Cr₂O₃ in the absence and presence of ionic polyamino acids

System	pH	σ 0 (μC/cm2)	ζ (mV)
Cr2O3–NaCl	4	11.9	19.1
	7.6	0.0	−10.6
	10	−10.5	−34.6
Cr2O3–ASP 6,800	4	3.9	−22.6
	7.6	−21.0	−68.3
	10	−35.1	−72.8
Cr2O3–ASP 27,000	4	4.6	−49.4
	7.6	−20.3	−70.7
	10	−34.3	−73.9
Cr2O3–LYS 4,900	4	2.8	58.7
	7.6	−14.5	50.2
	10	−42.2	32.8
Cr2O3–LYS 33,000	4	−1.5	54.9
	7.6	−19.3	49.7
	10	−45.4	27.9

The ζ potential values were obtained at a polymer concentration equal to 1 ppm