1 Introduction
- Shells and husks from nuts and other agricultural products
- Fruit stone waste
- Adsorbents from other wastes such as vehicle tyres, waste plastics and seafood shell waste
2 Adsorption technology
2.1 Adsorption
2.2 Advantages of adsorption in wastewater treatment
2.3 Adsorbent types and characteristics
2.3.1 Characteristics of adsorbents
- Reasonably high surface area or micropore volume to achieve a high adsorption capacity.
- The pore diameter must be sufficiently large appropriate to the size of the adsorbate molecule.
- The appropriate surface functional groups to attract the adsorbate molecule (or the large surface area may become of secondary importance).
- A relatively large porous network providing access to the internal surface area by diffusion.
2.3.2 Naturally occurring resources
2.3.3 Shells and husks
2.3.4 Fruit stone wastes
2.3.5 Adsorbents from other wastes
2.4 Advantages of activated carbons as adsorbents
2.5 Activation methodology
3 Olive stones
Analysis | % |
---|---|
Ultimate analysis | |
C | 46.5 |
H | 6.4 |
N | 0.4 |
S | 0 |
Cl | 0.34 |
Proximate analysis | |
Fixed carbon | 16.2 |
Volatile matter | 72.7 |
Ashes | 2.3 |
Moisture | 8.8 |
Cellulose | 28.1–40.4 |
Hemicellulose | 18.5–32.2 |
Lignin | 25.3–27.2 |
HHV* (MJ/kg) | 19.4 |
Precursor | Activation method | Pollutant | Adsorption capacity (mg/g) | Removal efficiency (%) | Time (h) | Temp (°C) | pH | Area (m2/g) | Ref. |
---|---|---|---|---|---|---|---|---|---|
Olive stone | Chemical (H3PO4) | Cadmium (II) | 9.01 | 68.0 | 4 | 20 | 2 | 1169 | [16] |
24.83 | – | 4 | 20 | 5 | |||||
Olive mill waste | Chemical (KOH) with carbonisation | Chromium (III) | 0.61a | – | * | 25 | 7 | 1641 | [151] |
Bisphenol A | 2.58a | – | * | 25 | 7 | ||||
Chemical (KOH) without carbonisation | Chromium (III) | 0.47a | – | * | 25 | 7 | |||
Bisphenol A | 1.75a | – | * | 25 | 7 | ||||
Olive stone | Chemical (KOH) | Toluene | 720.00 | – | – | – | – | 883 | [152] |
Olive pulp | Chemical (H2O) | Arsenic (III) | 1.39 | – | – | – | – | 1030 | [153] |
Olive pulp | Chemical (K2CO3) | 0.86 | – | – | – | – | 1850 | ||
Olive stone | Chemical (K2CO3) | 0.74 | – | – | – | – | 1610 | ||
Olive pulp | Chemical (HNO3) | 0.21 | – | – | – | – | 732 | ||
Olive seed | Chemical (KOH) (800/1 h) | Methylene blue | 190.00 | – | – | – | NA | 367 | [154] |
Chemical (KOH) (800/2 h) | Methylene blue | 217.00 | – | – | – | 419 | |||
Chemical (KOH) (800/3 h) | Methylene blue | 208.00 | – | – | – | 401 | |||
Chemical (KOH) (800/4 h) | Methylene blue | 255.00 | – | – | – | 492 | |||
Chemical (KOH) (900/1 h) | Methylene blue | 236.00 | – | – | – | 455 | |||
Chemical (KOH) (900/2 h) | Methylene blue | 263.00 | – | – | – | 508 | |||
Chemical (KOH) (900/3 h) | Methylene blue | 241.00 | – | – | – | 465 | |||
Chemical (KOH) (900/4 h) | Methylene blue | 262.00 | – | – | – | 506 | |||
Olive cake | Chemical (HCl) | Cadmium (II) | 0.10 | – | 1 | – | 6.5 | NA | [155] |
Chromium (III) | 1.05 | – | 1 | – | 6.5 | ||||
DBSNa | 0.57 | – | 6 | – | 6.5 | ||||
Phenol | 0.40 | – | 16 | – | 6.5 | ||||
Silver (I) | 5.03 | – | 1 | – | 6.5 | ||||
Methylene blue | 0.40 | – | 16 | – | 6.5 | ||||
Chemical (HNO3) | Cadmium (II) | 0.08 | – | 1 | – | 6.5 | |||
Chromium (III) | 0.58 | – | 1 | – | 6.5 | ||||
DBSNa | 0.48 | – | 6 | – | 6.5 | ||||
Phenol | 0.25 | – | 16 | – | 6.5 | ||||
Silver (I) | 0.39 | – | 1 | – | 6.5 | ||||
Methylene blue | 0.42 | – | 16 | – | 6.5 | ||||
Chemical (H2SO4) | Cadmium (II) | 0.17 | – | 1 | – | 6.5 | |||
Chromium (III) | 2.93 | – | 1 | – | 6.5 | ||||
DBSNa | 0.52 | – | 6 | – | 6.5 | ||||
Phenol | 0.13 | – | 16 | – | 6.5 | ||||
Silver (I) | 72.00 | – | 1 | – | 6.5 | ||||
Methylene blue | 0.31 | – | 16 | – | 6.5 | ||||
Solvent-extracted olive pulp | Chemical (H2SO4) | Iodine | 494.00 | – | – | – | 6–7 | NA | [156] |
Chemical ((NH4)2S2O8 in H2SO4) | Iodine | 270.00 | – | – | – | ||||
Zinc (II) | 4.61 | 98.0 | – | – | |||||
Olive stone | Chemical (H2SO4) | Iodine | 570.00 | – | – | – | |||
Olive seed | Chemical (H3PO4) (400 °C) | Methylene blue | 110.00 | – | – | – | – | NA | [157] |
Chemical (H3PO4) (600 °C) | 112.50 | – | – | – | – | ||||
Chemical (H3PO4) (800 °C) | 115.00 | – | – | – | – | ||||
Olive stone | Chemical (ZnCl2) | Cadmium (II) | 1.85 | – | – | 20 | – | 790 | [158] |
Olive pomace | Chemical (H3PO4) | Copper (II) | 0.50* | 1.5 | – | 5 | NA | [159] | |
Cadmium (II) | 0.10* | 1.5 | – | 5 | |||||
Chemical (H2O2) | Copper (II) | 0.19* | 1.5 | – | 5 | ||||
Cadmium (II) | 0.05* | 1.5 | – | 5 | |||||
Olive stone | Chemical (ZnCl2) | Remazol Red B | 790 | [131] | |||||
Olive tree pruning | Chemical (HNO3) | Lead (II) | 25.54 | – | – | – | 3–5 | 425 | [160] |
Chemical (H2SO4) | Lead (II) | 23.87 | – | – | – | 3–5 | 611 | ||
Chemical (NaOH) | Lead (II) | 26.63 | – | – | – | 3–5 | 3526 | ||
Olive stone | Chemical (H3PO4) | Amoxicillin | 57.00 | 93.0 | 116 | 20 | – | 1174 | [161] |
Olive stone | Chemical (H3PO4) | Phenol | 110.30 | – | 4 | 30 | – | NA | [162] |
Olive stone | Chemical (H3PO4) | Cobalt (II) | 10.25 | – | 10 | 30 | 5 | 1194 | [163] |
Nickel (II) | 12.91 | – | 10 | 30 | 5 | ||||
Copper (II) | 14.16 | – | 10 | 30 | 5 | ||||
Chemical (H3PO4) + O3 post-treat | Cobalt (II) | 16.20 | – | 10 | 30 | 5 | 798 | ||
Nickel (II) | 12.44 | – | 10 | 30 | 5 | ||||
Copper (II) | 17.91 | – | 10 | 30 | 5 | ||||
Chemical (H3PO4) + HNO3 post-treat | Cobalt (II) | 14.08 | – | 10 | 30 | 5 | 173 | ||
Nickel (II) | 20.49 | – | 10 | 30 | 5 | ||||
Copper (II) | 34.16 | – | 10 | 30 | 5 | ||||
Olive stone | Chemical (H3PO4) | Phenol | 32.36 | – | – | – | 6 | 1242 | [164] |
Methylene blue | 454.54 | – | – | – | 6.8 | ||||
Chemical (H3PO4 + 2 M HNO3) | Phenol | 28.57 | – | – | – | 4.95 | 1163 | ||
Methylene blue | 625.00 | – | – | – | 4.45 | ||||
Chemical (H3PO4 + 3 M HNO3) | Phenol | 24.39 | – | – | – | 4.35 | 614 | ||
Methylene blue | 666.66 | – | – | – | 4.25 | ||||
Chemical (H3PO4 + 4 M HNO3) | 666.66 | – | – | – | 4.05 | 222 | |||
Chemical (H3PO4 + 5 M HNO3) | 526.31 | – | – | – | 3.8 | 13 | |||
Olive wood** | Washing (ethanol) | Phenol | 1.09 | 67–84 | 72 | 20 | 7 | 78 | [96] |
2-Chlorophenol | 6.54 | ||||||||
3-Chlorophenol | 7.69 | ||||||||
4-Chlorophenol | 9.09 | ||||||||
2-Nitrophenol | 0.64 | ||||||||
4-Nitrophenol | 2.25 | ||||||||
2,4-Di-nitrophenol | 0.57 | ||||||||
Washing (tetrahydrofuran) | Phenol | 1.11 | 13–84 | 72 | 20 | 7 | 103 | ||
2-Chlorophenol | 6.85 | ||||||||
3-Chlorophenol | 10.42 | ||||||||
4-Chlorophenol | 11.36 | ||||||||
2-Nitrophenol | 0.67 | ||||||||
4-Nitrophenol | 2.31 | ||||||||
2,4-Di-nitrophenol | 0.63 | ||||||||
Washing (ether) | Phenol | 1.05 | 17–81 | 72 | 20 | 7 | 135 | ||
2-Chlorophenol | 7.19 | ||||||||
3-Chlorophenol | 9.71 | ||||||||
4-Chlorophenol | 10.87 | ||||||||
2-Nitrophenol | 0.62 | ||||||||
4-Nitrophenol | 2.36 | ||||||||
2,4-Di-nitrophenol | 0.57 | ||||||||
Washing (dichloromethane) | Phenol | 1.10 | 33–53 | 72 | 20 | 7 | 123 | ||
2-Chlorophenol | 7.30 | ||||||||
3-Chlorophenol | 9.90 | ||||||||
4-Chlorophenol | 11.36 | ||||||||
2-Nitrophenol | 0.66 | ||||||||
4-Nitrophenol | 2.46 | ||||||||
2,4-Di-nitrophenol | 0.62 | ||||||||
Washing (hexane) | Phenol | 1.05 | 28–68 | 72 | 20 | 7 | 106 | ||
2-Chlorophenol | 7.09 | ||||||||
3-Chlorophenol | 9.26 | ||||||||
4-Chlorophenol | 10.64 | ||||||||
2-Nitrophenol | 0.63 | ||||||||
4-Nitrophenol | 2.40 | ||||||||
2,4-Di-nitrophenol | 0.59 | ||||||||
Olive stones | Succinylation (succinic acid + NaHCO3) | Cadmium (II) | 200.00 | – | 1.5 | 20 | 4 | NA | [165] |
Olive stone | Chemical (H2SO4 + NaOH reflux) | Cadmium (II) | 128.20 | – | 1 | 25 | 4 | NA | [166] |
Safranin | 526.30 | – | 1 | 25 | 6.8 | ||||
Olive stone | Physico-chemical (ZnCl2 + CO2) | Ethanol | 73.70 | – | – | – | – | 1448 | [167] |
Chemical (ZnCl2 + HNO3) | 97.60 | – | – | – | – | 1264 | |||
Chemical (ZnCl2 + HNO3) (400 °C) | 81.50 | – | – | – | – | 1319 | |||
Chemical (ZnCl2 + HNO3) (700 °C) | 70.70 | – | – | – | – | 1444 | |||
Olive stones | Chemical (H3PO4) | Copper (II) | 17.78 | 62.0 | 10 | 30 | 5 | 1081 | [168] |
Nickel (II) | 24.07 | 78.0 | 10 | 30 | 5 | ||||
Lead (II) | 148.77 | 100.0 | 10 | 30 | 5 | ||||
Olive stones | Chemical (HCl + ZnCl2 0.5 g) | Phenol | 78.74 | 40.4 | 48 | 25 | 7.5 | 834 | [169] |
Chemical (HCl + ZnCl2 1 g) | 84.03 | 41.9 | 1093 | ||||||
Chemical (HCl + ZnCl2 2 g) | 85.47 | 44.8 | 1266 | ||||||
Olive stones | Chemical (H3PO4) | Cyanide | 57.35 | – | 5 | 20 | 10.9 | 680 | [170] |
Olive stones | Chemical (H3PO4) | Copper (II) | 17.67 | 68.0 | 10 | 30 | 5 | 1194 | [171] |
Cadmium (II) | 57.10 | 23.0 | 5 | ||||||
Lead (II) | 147.53 | – | 5 | ||||||
Olive stones | Chemical (H2SO4) | Lead (II) | 14.11 | 2 | 25 | 5 | 0.51 | [172] | |
Chemical (HNO3) | 15.33 | 2.45 | |||||||
Chemical (NaOH) | 16.25 | 0.25 |
Precursor | Activation method | Pollutant | Adsorption capacity (mg/g) | Removal efficiency (%) | Time (h) | Temp (°C) | pH | Area (m2/g) | Ref. |
---|---|---|---|---|---|---|---|---|---|
Olive stones | Conventional heating | Copper (II) | 17.83 | 98.6* | 3 | – | 4.5 | 883 | [173] |
Iron (II) | 57.47 | 99.3* | 3 | – | 4.5 | ||||
Lead (II) | 22.37 | 98.8* | 3 | – | 4.5 | ||||
Olive stone waste | Conventional heating | Cadmium (II) | 7.80 | 95.0 | * | 30 | 5 | 886 | [174] |
Nickel (II) | 8.42 | 99.1 | * | 30 | 5 | ||||
Zinc (II) | 11.14 | 99.2 | * | 30 | 5 | ||||
Olive cake | Thermal | Cadmium (II) | 0.14 | 22.5 | 1 | – | 6.5 | NA | [155] |
Chromium (III) | 2.09 | 90.4 | 1 | – | 6.5 | ||||
DBSNa | 0.67 | 34.5 | 6 | – | 6.5 | ||||
Phenol | 0.73 | 22.5 | 16 | – | 6.5 | ||||
Silver (I) | 6.72 | 82.7 | 1 | – | 6.5 | ||||
Methylene blue | 0.72 | – | 16 | – | 6.5 | ||||
Solvent-extracted olive pulp | Physical (H2O/N2) | Iodine | 478.00 | – | – | – | 6–7 | 364 | [156] |
Zinc (II) | 32.68 | 68.6 | – | – | |||||
Olive stone | Physical (H2O/N2) | Iodine | 550.00 | – | – | – | 474 | ||
Zinc (II) | 16.08 | – | – | – | |||||
Olive mill waste | Thermal | Methylene blue | 14.95 | – | 2 | – | – | [175] | |
Olive waste cake | Physical (H2O/N2) (70 min/800 °C) | Methylene blue | 373.00 | – | 4 | 20 | NA | 1201 | [176] |
Iodine | 1261.00 | – | 2 | ||||||
Physical (H2O/N2) (30 min/800 °C) | Methylene blue | 115.00 | – | 4 | 514 | ||||
Iodine | 796.00 | – | 2 | ||||||
Physical (H2O/N2) (60 min/850 °C) | Methylene blue | 490.00 | – | 4 | 1271 | ||||
Iodine | 1495.00 | – | 2 | ||||||
Physical (H2O/N2) (40 min/750 °C) | Methylene blue | 121.00 | – | 4 | 687 | ||||
Iodine | 741.00 | – | 2 | ||||||
Physical (H2O/N2) (60 min/750 °C) | Methylene blue | 197.00 | – | 4 | 700 | ||||
Iodine | 996.00 | – | 2 | ||||||
Physical (H2O/N2) (40 min/850 °C) | Methylene blue | 364.00 | – | 4 | 1127 | ||||
Iodine | 1017.00 | – | 2 | ||||||
Physical (H2O/N2) (50 min/800 °C) | Methylene blue | 285.00 | – | 4 | 1025 | ||||
Iodine | 930.00 | – | 2 | ||||||
Olive pomace | Untreated | Copper (II) | 0.18* | 1.5 | – | 5 | NA | [159] | |
Cadmium (II) | 0.03* | 1.5 | – | 5 | |||||
Olive cake | Untreated | Cadmium (II) | 65.36 | 66.0 | 24 | 28 | 6 | NA | [177] |
60.61 | 61.0 | 24 | 35 | 6 | |||||
44.44 | 50.0 | 24 | 45 | 6 | |||||
Olive pomace | Solvent extracted and incompletely combusted | Total phenols | 11.40 | 90.0 | 24 | – | 4–10 | NA | [178] |
Olive pomace | Solvent extraction, packed bed | Methylene blue | 13.85 | 52.0 | 7 | – | – | NA | [29] |
Olive stone | Thermal (with CO2 and steam) | – | – | – | – | – | – | 1187 | [179] |
Olive stone | Plasma enhanced (N2 plasma 30 min) | Phenol | 635.20 | – | 4 | 30 | – | 988 | [162] |
Plasma enhanced (N2 plasma 10 min) | 323.26 | – | 4 | 30 | – | 1055 | |||
Plasma enhanced (N2 plasma 5 min) | 226.35 | – | 4 | 30 | – | 1140 | |||
Olive stone | No treatment | Alizarin Red S | 16.10 | – | 72 | 20 | 7.2 | 0.16 | [180] |
Methylene blue | 13.20 | – | 72 | 20 | 7.2 | ||||
Olive stone | Physical (H2O) | Nitrogen dioxide | 131.00 | – | – | – | – | 807 | [181] |
Olive wood** | Pyrolysis (100 °C) | Phenol | 0.80 | 13–87 | 72 | 20 | 7 | 110 | [96] |
2-Chlorophenol | 4.51 | ||||||||
3-Chlorophenol | 5.00 | ||||||||
4-Chlorophenol | 5.53 | ||||||||
2-Nitrophenol | 0.49 | ||||||||
4-Nitrophenol | 2.46 | ||||||||
2,4-Di-nitrophenol | 0.47 | ||||||||
Pyrolysis (150 °C) | Phenol | 0.78 | 12–77 | 72 | 20 | 7 | 9 | ||
2-Chlorophenol | 4.05 | ||||||||
3-Chlorophenol | 4.93 | ||||||||
4-Chlorophenol | 5.38 | ||||||||
2-Nitrophenol | 0.48 | ||||||||
4-Nitrophenol | 2.38 | ||||||||
2,4-Di-nitrophenol | 0.45 | ||||||||
Pyrolysis (200 °C) | Phenol | 0.72 | 47–76 | 72 | 20 | 7 | 176 | ||
2-Chlorophenol | 3.34 | ||||||||
3-Chlorophenol | 4.00 | ||||||||
4-Chlorophenol | 4.44 | ||||||||
2-Nitrophenol | 0.46 | ||||||||
4-Nitrophenol | 2.16 | ||||||||
2,4-Di-nitrophenol | 0.44 | ||||||||
Pyrolysis (250 °C) | Phenol | 0.76 | 22–75 | 72 | 20 | 7 | 26 | ||
2-Chlorophenol | 3.66 | ||||||||
3-Chlorophenol | 4.35 | ||||||||
4-Chlorophenol | 4.76 | ||||||||
2-Nitrophenol | 0.48 | ||||||||
4-Nitrophenol | 2.34 | ||||||||
2,4-Di-nitrophenol | 0.45 | ||||||||
Pyrolysis (300 °C) | Phenol | 0.72 | 13–55 | 72 | 20 | 7 | 18 | ||
2-Chlorophenol | 3.66 | ||||||||
3-Chlorophenol | 4.41 | ||||||||
4-Chlorophenol | 4.88 | ||||||||
2-Nitrophenol | 0.46 | ||||||||
4-Nitrophenol | 2.28 | ||||||||
2,4-Di-nitrophenol | 0.43 | ||||||||
Olive stone | Untreated | Cadmium (II) | 4.90 | 45–82 | 2 | 25 | 7 | NA | [182] |
5.71 | 2 | 40 | 7 | ||||||
6.00 | 2 | 60 | 7 | ||||||
Chromium (III) | 6.96 | 86–90 | 2 | 25 | 4 | ||||
6.99 | 2 | 40 | 4 | ||||||
7.03 | 2 | 60 | 4 | ||||||
Lead (II) | 6.66 | 76–88 | 2 | 25 | 5 | ||||
6.06 | 2 | 40 | 5 | ||||||
5.40 | 2 | 60 | 5 | ||||||
Olive stone | Untreated | Chromium (III + VI) | 2.17 | 5 | 25 | 2 | NA | [183] | |
2.45 | 5 | 60 | 2 | ||||||
3.67 | 5 | 80 | 2 | ||||||
Chromium (VI) | 1.73 | 5 | 25 | 2 | |||||
2.35 | 5 | 60 | 2 | ||||||
4.82 | 5 | 80 | 2 | ||||||
Olive stones | Untreated | Cadmium (II) | 0.93 | 96.0 | 1.3 | 25 | 7 | 0.38 | [184] |
0.92 | 1.3 | 30 | 7 | ||||||
0.90 | 1.3 | 50 | 7 | ||||||
0.88 | 1.3 | 70 | 7 | ||||||
0.86 | 1.3 | 90 | 7 | ||||||
Physical (CO2 1 h) | 78.74 | 44.8 | NA | ||||||
Physical (CO2 1 h) | 83.33 | 43.7 | |||||||
Physical (CO2 1 h) | 156.25 | 61.5 | |||||||
Olive stones | Untreated | Iron (III) | 1.50 | 90.0 | – | 20 | – | 0.6 | [185] |
Olive stones | Untreated | Lead (II) | 4.57 | 2 | 25 | 5 | 0.16 | [172] | |
Olive stones | Pyrolysis (500 °C) | Sulphonic compounds | 570.00 | – | 2 | 25 | – | 760 | [186] |
Phenolic compounds | 500.00 | – | |||||||
80% OS/novolac resin/hexamethylenetetramine mix | Physical (CO2) | Methylene blue | 2.66 | – | 300 | 25 | – | 760 | [31] |
2.75 | 60 | ||||||||
60% OS/novolac resin/hexamethylenetetramine mix | 3.13 | 25 | |||||||
3.19 | 60 |
Precursor | Activation method | Pollutant | Adsorption capacity (mg/g) | Removal efficiency (%) | Time (h) | Temp (°C) | pH | Area (m2/g) | Ref. |
---|---|---|---|---|---|---|---|---|---|
Olive stone | Chemical (KOH) + microwave | Cadmium (II) | 11.72 | 95.3 | The maximum capacities were determined via the Langmuir isotherm model by modelling of experimental data with various experimental factors and levels. | 1281 | [187] | ||
Copper (II) | 22.73 | 98.6 | |||||||
Iron (II) | 62.50 | 99.3 | |||||||
Lead (II) | 23.47 | 98.8 | |||||||
Nickel (II) | 12.00 | 98.2 | |||||||
Zn (II) | 15.08 | 98.4 | |||||||
Olive stones | Microwave (KOH impregnated) | Copper (II) | 22.73 | 98.6 | 3 | – | 4.5 | 1281 | [173] |
Iron (II) | 62.50 | 99.3 | 3 | – | 4.5 | ||||
Lead (II) | 23.47 | 98.8 | 3 | – | 4.5 | ||||
Olive waste cake | Physical (H2O/N2) (70 min/800 °C) | Methylene blue | 373.00 | – | 4 | 20 | – | 1201 | [176] |
Iodine | 1261.00 | – | 2 | ||||||
Physical (H2O/N2) (30 min/800 °C) | Methylene blue | 115.00 | – | 4 | 514 | ||||
Iodine | 796.00 | – | 2 | ||||||
Physical (H2O/N2) (60 min/850 °C) | Methylene blue | 490.00 | – | 4 | 1271 | ||||
Iodine | 1495.00 | – | 2 | ||||||
Physical (H2O/N2) (40 min/750 °C) | Methylene blue | 121.00 | – | 4 | 687 | ||||
Iodine | 741.00 | – | 2 | ||||||
Physical (H2O/N2) (60 min/750 °C) | Methylene blue | 197.00 | – | 4 | 700 | ||||
Iodine | 996.00 | – | 2 | ||||||
Physical (H2O/N2) (40 min/850 °C) | Methylene blue | 364.00 | – | 4 | 1127 | ||||
Iodine | 1017.00 | – | 2 | ||||||
Physical (H2O/N2) (50 min/800 °C) | Methylene blue | 285.00 | – | 4 | 1025 | ||||
Iodine | 930.00 | – | 2 | ||||||
Olive stone | Thermal | Methylene blue | 38.00 | – | – | – | 9 | 368 | [188] |
Iodine | 238.00 | – | – | – | 9 | ||||
Olive pulp | Thermal | Methylene blue | 46.00 | – | – | – | 9 | 396 | |
Iodine | 294.00 | – | – | – | 9 | ||||
Olive stone | Thermal + K2CO3 | Methylene blue | 394 | 1610 | |||||
Iodine | 1540 | ||||||||
Olive pulp | Thermal + K2CO3 | Methylene blue | 420 | 1850 | |||||
Iodine | 1720 | ||||||||
Olive stone | Thermal and chemical (KOH) | Lead (II) | 100.0 | 6 | 1203 | [189] | |||
Thermal and chemical (ZnCl2) | Lead (II) | 34.0 | 6 | 735 | |||||
Olive stone | Physico-chemical (ZnCl2 + CO2) | Ethanol | 73.70 | – | – | – | – | 1448 | [167] |
Olive stones | Physico-chemical (HCl + ZnCl2 0.5 g + CO2) | Phenol | 126.58 | 67.4 | 48 | 25 | 7.5 | 985 | [169] |
Physico-chemical (HCl + ZnCl2 1 g + CO2) | 147.06 | 68.5 | 1546 | ||||||
Physico-chemical (HCl + ZnCl2 2 g + CO2) | 158.73 | 73.0 | 1793 |
3.1 Chemical activation of olive stones
3.2 Physical activation of olive stones
3.3 Physico-chemical activation treatment of olive stones
3.4 Experimental details of the various treatment studies
Carbonisation | Impregnation characteristics | Comments | Ref. | ||
---|---|---|---|---|---|
Temp (°C) | Time (min) | Chemical | Ratio (chemical:precursor) | ||
400/500/600 | 60 | Phosphoric acid | 0.75/1.0/1.5:1 | – | [16] |
500 | 120 | Potassium hydroxide | 2:1 | After impregnation of KOH, mixture was heated to 300 °C for 1 h and then at 800 °C for 2 h | [151] |
– | 120 | Potassium hydroxide | 2:1 | ||
840 | 60 | Potassium hydroxide | 1/2/4/5:1 | Samples were pyrolysed at 300 °C for 3 h followed by 800 °C for 2 h in N2 posterior to KOH impregnation | [152] |
800 | 60 | Potassium hydroxide | 2:1 | ||
800 | 10 + 120 | Water vapour | – | Carbonisation of raw olive stone at 800 °C for 10 min, further activated with water vapour at 800 °C for 2 h | [153] |
950 | 720 + 10 | Potassium carbonate | 1:1 | Chemically activated olive pulp and olive stones are considered different | |
800 | 10 + 120 | Nitric acid | 3:1 | The carbonised raw olive stone was treated with HNO3 for 1 h, then washed and dried | |
700 | 60 | Hydrochloric acid | 1:1 | Carbonisation was carried out at 700 °C for 60 min and activation carried out using 2 N HCl and HNO3 | [155] |
700 | 60 | Nitric acid | 1:1 | ||
700 | 60 | Sulphuric acid | 1.8:1 | Air-dried olive cake was treated with conc. H2SO4 and then carbonised at 700 °C for 60 min | |
600/900 | 60/60 | Potassium hydroxide (75% w/w) | 1:1 | Carbonisation at 600 °C for 1 h followed by chemical activation with KOH, and further activation after drying at 900 °C for 1 h. The activated carbon was then washed and dried | [190] |
Potassium hydroxide (50% w/w) | 1:1 | ||||
400/600/800 | 60 | Phosphoric acid (85%) | 0.2:1 | The seeds were treated with 85% pure H3PO4 (for 1 l of seeds, 200 cm3 of acid was added) for 2 days and then activated at 400/600/800 °C for 1 h | [157] |
650 | 120 | Zinc chloride | – | Olive stone samples were mixed with ZnCl2 (10/20/30% conc.) and then carbonised in a muffle furnace at 650 °C for 2 h, subsequently washed and dried | [158] |
– | 1440* | Phosphoric acid (50%) | 5:1 | 50 g of olive pomace was added to t250 ml of chemical of varying concentrations. (* contact time for the chemical/olive pomace) | [159] |
180* | Hydrogen peroxide (1 M) | 5:1 | |||
170/380 | 30/150 | Phosphoric acid | 1:1 | Impregnation with H3PO4 was carried out at 110 °C for 9 h, followed by carbonisation at 170 °C for 30 min and then at 380 °C for 150 min | [161] |
170/410 | 30/150 | Phosphoric acid | 1:1 | Impregnation with H3PO4 was carried out at 110 °C for 9 h, followed by carbonisation at 170 °C for 30 min and then at 380 °C for 150 min | [162] |
500 | 120 | Phosphoric acid | 4.5/5.3/6:1 | Impregnation was carried out at 85 °C for 4 h | [191] |
410 | 150 | Phosphoric acid | 1:1 | Impregnation with H3PO4 was carried out at 110 °C for 9 h, followed by carbonisation at 410 °C for 150 min. The AC were post-treated with ozone and HNO3 | [163] |
25 | 240 | Ozone treatment | – | AC was exposed to O3 at room temperature for 4 h at 12 mg/l conc. in an air–ozone mixture, washed and dried after treatment | |
100 | 600 | Nitric acid | – | 500 ml 2 M nitric acid was added to 50 g AC sample and then washed and dried after treatment | |
170/380 | 30/150 | Phosphoric acid/nitric acid | 1:1 | Impregnation with H3PO4 was carried out at 110 °C for 9 h, followed by carbonisation with steam and nitrogen at 170 °C for 30 min and then at 380 °C for 150 min. The samples were then further activated using 2/3/4/5 mol/l HNO3 | [164] |
90 | 1440 | Succinic anhydride + NaHCO3 | – | A suspension of olive stone and pyridine (30 ml) in toluene (200 ml) heated at 60 °C was added at once to succinic anhydride (20 g). The resulting mixture was stirred overnight at 90 °C. After cooling, the solid was filtered off and washed thoroughly and treated with NaHCO3 | [165] |
400/500/600/700 | 60 | Phosphoric acid | 1/2/4:1 | [192] | |
20 | 1440 | Sulphuric acid + NaOH reflux for 1 h | 8:1 | The olive stone was mixed with conc. H2SO4 at rtp for 24 h and then neutralised using NaOH and subsequently washed and dried | [166] |
500 | 180 | Zinc chloride | – | Olive stones were impregnated in a ZnCl2 solution at 85 °C for 7 h under constant stirring | [167] |
500 + 400/700 | 180 | Zinc chloride + HNO3 | – | Olive stone AC was further oxidised using 6 M HNO3 for 1 h and heat treated at 400 and 700 °C under He | |
410 | 150 | Phosphoric acid | 1:1 | Olive stones were impregnated in H3PO4 at 110 °C for 9 h, followed by carbonisation at 410 °C for 150 min | [168] |
800 | 60 | Zinc chloride + HCl | 0.5/1/2:1 | Olive stones and ZnCl2 (0.5/1/2 g ratios) were both carbonised at 800 °C for 1 h followed by chemical treatment (reflux) with HCl for 3 h and washed and dried afterwards | [169] |
300 | 60 | Phosphoric acid | 2:1 | Olive stones are carbonised at 300 °C for 1 h followed by H3PO4 impregnation. Further activation is carried out at 700 °C for 2 h followed by washing and drying | [170] |
380 | 150 | Phosphoric acid | 1:1 | Raw milled olive stones were impregnated with a phosphoric acid solution (50% by weight) at 110 °C for 9 h, followed by thermal activation at 380 °C for 2.5 h | [171] |
50 | 1440 | Sulphuric acid | 2:1 | OS was chemically treated by soaking and shaking in a 2-M H2SO4, HNO3 or NaOH (Merck p.a.) solutions in a rotary shaker for 24 h, at 50 °C, followed by washing and drying | [172] |
Nitric acid | |||||
Sodium hydroxide |
Carbonisation | Impregnation characteristics | Comments | Ref. | ||
---|---|---|---|---|---|
Temp (°C) | Time (min) | Chemical | Ratio (chemical:precursor) | ||
715 | 120 | Potassium hydroxide | 1.53:1 | – | [173] |
715 | 120 | Potassium hydroxide | 1.53:1 | – | [174] |
840 | 60 | – | – | Samples were pyrolysed at 300 °C for 3 h followed by 800 °C for 2 h in N2 posterior to KOH impregnation | [152] |
700 | 60 | – | – | No chemical activation for this olive cake carbon | [155] |
850 | 90 | Steam/nitrogen | – | Activation of carbon was carried under steam/nitrogen mixture at 800 °C for 0.66/1.5/2 h for different samples | [156] |
150 | Until colour changed from brown to black | – | – | – | [175] |
400 | 60 | Steam/nitrogen | – | Activation times were varied between 30 and 70 min and temperatures between 750 and 850 °C. Activated carbons were boiled in distilled water for 30 min, dried, ground and sifted | [176] |
510–850 | 850 | CO2 | – | Carbonisation carried initially at 510 °C at 1 °C/min, and further from room temperature to 850 °C/min, followed by CO2 activation at 800 °C | [193] |
600 | 60 | Steam (70%) in N2 | – | Activation of the obtained char is realised at 750 °C under 70 vol% H2O in N2 during 360 min | [181] |
100/150/200/250/300/400 | 60 | – | – | Sample was placed in a furnace under N2 flow and temperature raised to the desired set point and maintained for 1 h | [96] |
800 | 60/120/180 | Carbon dioxide | – | Olive stone powder was carbonised at 800 °C for various times (1/2/3 h) in CO2 to obtain various activated carbons | [169] |
800 | 60 | Pyrolysed at 500 °C | – | OS was pyrolysed at 500 °C then activated at 800 °C for 1 h | [186] |
1000 | 30 | Carbon dioxide | – | OS/novolac/hexamethylenetetramine mix was formed into small cylinders and cured at 170 °C for 30 min, then was carbonised at 1000 °C. After the carbonisation, the samples were activated using CO2 at 900 °C | [31] |
Method | Carbonisation | Impregnation characteristics | Comments | Ref. | ||
---|---|---|---|---|---|---|
Temp (°C) | Time (min) | Chemical | Ratio (chemical:precursor) | |||
Microwave | 600 | – | Potassium hydroxide | 0.5/1.25/2.0:1 | Microwave with a frequency of 2.4 GHz at power levels from 264 to 616 W was used for 4/6/8 min for activation of impregnated char | [187] |
Microwave | 600 | 1440 | Potassium hydroxide | 1.87:1 | Microwave with a frequency of 2.4 GHz at power levels from 565 W for 7 min was used for activation of impregnated char | [173] |
Pyrolysis and chemical activation | 800/900 | 60/120/180/240 | Potassium hydroxide | 4:1 | Char created by pyrolysis at 800 °C and then activated by KOH and consequently washed and dried | [154] |
Physico-chemical | 850 | 90 | Steam/nitrogen → sulphuric acid | 10: 1 | Further activation after the steam/nitrogen was carried out in 10% H2SO4 solution for 6 h at 25 °C | [156] |
Physico-chemical | Steam/nitrogen → (NH4)2S2O8 in H2SO4 | 10: 1 | Further activation after the steam/nitrogen was carried out in (NH4)2S2O8 in 1 M H2SO4 for 10 h at 25 °C | |||
Hydrothermal | 160–240 | 60/120/240/360/480 | Water | 8: 1 | One hydrochar was further carbonised under N2 at 900 °C for 3 h | [194] |
Succinylation | 90 | 1440 | Succinic anhydride + NaHCO3 | – | A suspension of olive stone and pyridine (30 ml) in toluene (200 ml) heated at 60 °C was added at once to succinic anhydride (20 g). The resulting mixture was stirred overnight at 90 °C. After cooling, the solid was filtered off and washed thoroughly and treated with NaHCO3 | [165] |
Physico-chemical | 825 | 20/40/60/72/80 (h) | Carbon dioxide | – | The chemically activated carbons were physically activated using CO2 for different periods of time | [167] |
Physico-chemical | 800 | 60 | Carbon dioxide + zinc chloride + HCl | 0.5/1/2:1 | Zinc chloride and olive stones were both carbonised together under CO2 for 1 h using the same ratios as in the chemical method, followed by the same chemical treatment with HCl afterwards | [169] |
3.5 Comparison of olive stone AC with other adsorbents
S. no. | Adsorbate | Capacity (mg/g) | ||||
---|---|---|---|---|---|---|
Olive stone | Adsorbents | |||||
Reference | Reference | |||||
1 | Safranin | 526 | [166] | Spirulina sp. algae Clay MgO on graphene Fe3O4 nanoparticles | 54 18 14 92 | [195] [196] [197] [198] |
2 | Bisphenol A | 2.7 | [151] | Ulva prolifera Chitosan Vermiculite Montmorillonite | 9 35 93 4 | [199] [200] (Liu et al. 2017) [201] |
3 | Cadmium | 200 | [165] | Diplotaxis harra Glebionis coronaria Pcb e-waste Furnace slag Montmorillonite | 32 58 236 19 22 | [202] [203] [143] [204] [205] |
4 | Copper | 34 | [163] | Orange peel Sludge Pcb e-waste Chitosan Orange peel CNPs Sugarcane bagasse AC | 9 46 190 188 17 13 | [206] [207] [141] (Kalra et al. 2018) [206] [208] |
5 | Lead | 149 | [168] | Sludge Pcb e-waste Red mud Clinoptilolite | 64 704 65 18 | [207] [141] [209] [210] |
6 | Nickel | 24 | [168] | Sludge Pcb e-waste Chitosan Brown algae AC Green algae AC | 9.1 205 105 64 92 | [207] [143] [211] [212] [212] |
7 | Methylene blue dye | 667 | [164] | Sludge Bamboo Fox nutshell Biochar Milled biochar | 137 454 968 114 354 | [207] [213] [214] [215] [216] |
8 | Chromium | 7 | [182] | Sludge Alga Pterocladia CNTs Magnetic biochar Amino-crab shell Biochar | 15 66 113 8.4 41 21 | [207] [217] [218] [219] [220] [221] |
9 | Cobalt | 16 | [163] | Pcb e-waste Diplotaxis harra Glebionis coronaria Spirulina sp. Activated charcoal | 212 26 46 96 50 | [143] [202] [203] [222] [222] |
10 | Zinc | 16 | [156] | Bagasse pith Pcb e-waste Chitosan Furnace slag Zeolite | 147 124 104 18 55 | [223] [143] [211] [204] |
11 | Iodine | 1540 | [188] | Desert plant Acorn shell | 1178 1209 | [224] [225] |
12 | Phenol | 635 | [162] | Fox nutshell Sludge Avocado kernel AC Bentonite | 75 42 90 66 | [214] [207] [226] [227] |
13 | Chlorophenol | 11 | [96] | Filtrasorb AC Wheat husk biochar Muscovite-CTAB | 140 9.3 111 | [228] [] [] |
4 Criteria for producing quality activated carbons from olive stones
5 Conclusion
- A lack of reporting of all the experimental details, for example, heating rate, activation temperature, activating agent concentrations, yields and inert gas flow rates.
- A lack of reporting or determining all the characterisation parameters; in most cases, the surface areas are provided, but frequently mean pore size, pore size distribution and porosity are omitted; these are very important to ensure that large pollutant molecules can diffuse and adsorb into the pores.
- More information on surface functionality and zeta potential needs to be provided, since adsorption capacity is more dependent on surface functionality than surface area.
- A major criticism is that the design of tailor-made adsorbents for specific pollutant removal applications needs to be explored and applied by optimisation techniques such as RSM, response surface methodology; for practical applications, the pollutant must be defined first and then decide what properties of the activated carbon are needed, then optimise and design the industrial-scale system.
- More detailed temperature studies to establish more thermodynamic parameters such as enthalpy, entropy, Gibbs free energy and activation energy.
- More experimental conditions need to be investigated in both equilibrium and kinetics, especially the effect of pH and, in particular, the reporting of the final pH, which has a major influence on metal adsorption capacity.
- More fixed-bed and regeneration studies are essential to enhance the development and application of olive stone-derived activated carbons on a commercial scale.
- It is also important to test more equilibrium, kinetic/mass transport and fixed-bed models to enable accurate simulation and design models to be developed.