Sample name

Zeta potential (ζ) value (mV)

S₁ (pH 3)

(−) 16.1 ± 0.1

S₂ (pH 5)

(−) 25.2 ± 0.3

S₃ (pH 8)

(−) 43.4 ± 0.2

S₄ (pH 10)

(−) 80.1 ± 0.2

S₅ (pH 12)

(−) 57.4 ± 0.3