Table 2. ζ-Potential and MB Removal (at Equilibrium) of Doped Titanate Nanotubes.

samples	ζ-potential (mV)	((C0 – Ct)/C0) × 100 (%)a
Mg-TNT	–37	97
Ca-TNT	–33.2	95
Zn-TNT	–36.5	97
K-TNT	–35	97
Cr-TNT	–33	84
Ce(IV)-TNT	1	36
Ce(III)-TNT	–36	95
Mo(V)-TNT	–36	96
La-TNT	–31	94
Na-TNT	–37	96

^aMB removal percentage (%) = ((C₀ – C_t)/C₀) × 100.