Table 1.
Main physicochemical features of the three types of MWCNTs (CNT, CNTf, and CNTa). TEM: Transmission Electronic Microscopy, FEG-SEM: Field Emission Gun Scanning Electronic Microscopy, XPS: X-ray photoelectron spectroscopy, SSA: Specific Surface Area, BET method: Brunauer–Emmet–Teller method, ICP-AES: Inductively Coupled Plasma—Atomic Emission spectroscopy. Zeta potentials and Isoelectric points were measured using a Zetasizer Nano ZS.
| PHYSICOCHEMICAL CHARACTERISTICS | CNT | CNTf | CNTa |
|---|---|---|---|
| Diameter (nm) with FEG-SEM and TEM | 17 ± 5 | 18 ± 5 | 17 ± 5 |
| O (% atomic proportion) by XPS | 8.7 | 7.7 | 3.5 |
| SSA (m2 g−1) using BET method | 212 ± 2 | 279 ± 1 | 209 ± 3 |
| Catalytic iron metallic impurities (wt%) by XPS and ICP-AES | 0.19 | 0.02 | 0.01 |
| Structural defects indication (Id/Ig ratio) with Raman spectroscopy | 1.18 ± 0.10 | 1.33 | 0.77 ± 0.13 |
| Zeta potential in water (mV) | −23.3 ± 7 | −28.7 ± 2.1 | −36.4 ± 4.3 |
| Isoelectric point in water (pH) | 3.12 ± 0.32 | 2.6 ± 0.1 | 2.82 ± 0.02 |