TABLE 1.
Physicochemical parameters of tested absorbents along with maximum affinities toward Co retention from solution.
| Nanocomposites a | CNTs% b | Fe% b | Ti% b | SSA c m2/g | Saturation value (mg/g) d | Heterogeneity index e | Functionality e (mmol/g) | ||
|---|---|---|---|---|---|---|---|---|---|
| a | b | c | |||||||
| CNTs | 100 | — | — | 193.19 | 13.86 | 1.13 | 4.70 | 3.92 | 1.96 |
| O-CNTs | 100 | — | — | 207.28 | 15.27 | 0.75 | 1.88 | 9.80 | 4.90 |
| TiO2 | — | — | 100% | 122.12 | 10.42 | 0.66 | |||
| Ti-CNTs (69.6%) | 30.4 | — | 69.6 | 189.13 | 16.56 | 2.14 | 3.76 | 5.88 | 3.92 |
| Ti-CNTs (82.1%) | 17.9 | — | 82.1 | 179.31 | 21.43 | 1.02 | 2.82 | 4.90 | 1.96 |
| Ti-CNTs (87.4%) | 12.6 | — | 87.4 | 171.16 | 24.63 | 1.18 | 2.82 | 3.92 | 1.96 |
| Ti-CNTs (90.2%) | 9.8 | — | 90.2 | 168.61 | 29.80 | 1.71 | 1.88 | 2.94 | 0.98 |
| Fe3O4 | — | 100 | — | 129.10 | 7.68 | 0.88 | |||
| Fe-CNTs (18.9%) | 81.1 | 18.9 | — | 185.19 | 13.30 | 1.10 | 3.76 | 6.86 | 3.92 |
| Fe-CNTs (31.8%) | 68.2 | 31.8 | — | 179.31 | 21.16 | 1.88 | 3.76 | 5.88 | 2.94 |
| Fe-CNTs (48.2%) | 51.8 | 48.2 | — | 176.51 | 20.32 | 1.62 | 2.82 | 4.90 | 1.96 |
a
Values between brackets indicated the ratios the nano-materials in the final mix.
b
Percentages were calculated based on limiting reactant of the reagents involved in synthesis of Fe3O4 and TiO2.
cSSA is determined using methylene adsorption method.
d
Both saturation values and heterogeneity indices were estimated from Langmuir-Freundlich isotherm equation measured at 50°C, 5 mg adsorbent, Co range 1–40 mg/L, pH 6.4, and shaking time 24 h.
e
Based on Bohem’s method, a total basic group (mainly ketonics and amines), b total acidic groups (mainly alcoholic, phenolic and carboxylic acid groups) and c carboxylic acid group.