Table 2.
Detailed information on the adsorbents used for fluoride removal.
| Adsorbent | Concentration Range (mg/L) | pH Range | Contact Time (min) | Model Used to Calculate Adsorption Capacity | Maximum Adsorption Capacity (mg/g) | Ref. |
|---|---|---|---|---|---|---|
| Waste mud | - | 2–8 | 0–480 | Langmuir and Freundlich | 27.2 | [220] |
| Red Mud | 5–150 | 4.7 | 15–540 | Freundlich | 0.851 | [215] |
| 5 | 4.7 | 360 | Redlich–Peterson and Freundlich | 0.644 | [215] | |
| 100–1000 | 5.5 | 120 | Langmuir and Freundlich | 3.12 and 6.29 | [165] | |
| Modified red mud with AlCl3 (MRMA), heat activated red mud (MRMAH) | - | 7–8 | Langmuir | MRMA-68.07 MRMAH-91.28 |
[216] | |
| Zirconium hydroxide modified red mud porous material Zr-modified RMPM |
- | 3 | 60 | pseudo-second-order rate kinetics and pore diffusion models | 0.6 | [217] |
| Red mud | - | 5.5 | 120 | - | [218] | |
| Alum sludge | - | 5.5–6.5 | - | - | 5.35 | [221] |
| Sludge produced during the manufacturing of aluminium sulphate (alum) from kaolin | 10 | 3–8 | - | - | 332.5 | [222] |
| Spent Bleach Earth (SBE) | - | 3.5 | - | - | 7.75 | [223] |
| Fly ash A and S | - | - | - | Freundlich | 1.22 (A) 1.01 (S) |
[226] |
| Calcium hydroxide treated fly ash (CFA) | 10 | 7 | 120 | 10.86 | [227] | |
| Bottom ash | - | 6 | 105 | BDST | 16.26 | [228] |
| Magnesia-loaded fly ash cenospheres (MLC) | 10 | - | - | Thomas | 5.884 | [230] |
| aluminium-treated bagasse fly ash (ABF) | 1–10 | 6 | 300 | - | 10 | [232] |
| Maize husk fly ash | 2.0 g/50 mL | 2 | 120 | Redlich-Peterson | [233] | |
| Activated tea ash (AcTAP) | 6 | 180 | Langmuir | 8.55 | [231] | |
| Waste carbon slurry obtained from fuel oil | 15 | 7.58 | 120 | Langmuir | 4.861 | [234] |
| Coal mining waste | - | 3.5 | - | Langmuir | 15.67 | [235] |
| Shale (coal mine waste) in the form of native shale (NS) and heat activated shale (HAS) at 350 °C, 450 °C and 550 °C | 10-HAS550 | 3 | 24 h | Langmuir | 0.358 | [236] |
| Blast furnace slag generated from steel industry | 10 mg/l | 6–10 | 35 | Langmuir | 8.07 | [237] |
| Spent catalyst (a by-product of petrochemical industry) | - | 4 | - | 28 | [238] | |
| Iron coated spent catalyst | - | 5.5–6.0 | - | Langmuir | 7.2–20.7 | [239] |
| Thermally activated titanium rich bauxite (TRB) | 10 | 5.5–6.5 | - | Langmuir | 3.8 | [240] |
| High alumina (81.5%) content bauxite | - | - | - | Freundlich | 3.125 | [243] |
| Bauxite | 10 | 6 | 90 | Freundlicha, Langmuira Tempkina, | 3 | [241] |
| Hydrated cement (HC), brick powder (BP) marble powder (MP). |
30 | 7 8 7 |
60 | Langmuir | 1.72 0.84 0.18 |
[254] |
| Bleaching powder | - | 6–10 | - | - | - | [244] |
| Rice husk ash, which was coated with aluminium hydroxide | 10–60 | 7 | 60 | 15.08 | [183] | |
| Activated rice husk ash (ARHA) | 100 | Langmuir | 0.402 | [231] | ||
| Ceramic adsorbents consisting of Kanuma mud, with zeolite, starch, and FeSO4·7H2O | 20–100 | 4–11 | 0–48 h | pseudo-second-order | 2.16 | [253] |
| Porous granular ceramic adsorbents containing dispersed aluminium and iron oxides | 10 | 4–9 | 48 h | Langmuir and Freundlich | 1.79 | [249] |
| Iron-impregnated granular ceramics | 7, 4 | Langmuir and Freundlich | - | [167] | ||
| Recycled phosphogypsum in a form of HAP nanoparticles | 7 | Langmuir-Freundlich | 19.742–25 °C 26.108–35 °C 36.914–45 °C 40.818–55 °C |
[186] | ||
| HAP-calcium phosphate based bioceramic | - | - | - | Langmuir and pseudo-second-order | 32.57 | [250] |
| HAP Apatitic tricalcium phosphate. |
up to 20 up to 60 |
4.16 4 |
Langmuir Langmuir |
13.88–25 °C 14.70–30 °C 15.15–37 °C |
[118,119] |