Table 2.
Remediation efficiency of biochar on HM (heavy metal)-contaminated soil.
| Metals | Types of Biomass Feedstock | Pyrolysis Temperature | Dosage | Duration a | Soil Types | Total Metal Content | Immobilization Efficiency (Evaluation Method) | Reference |
|---|---|---|---|---|---|---|---|---|
| Cu | Chicken manure | 500 °C | 5% | 14 d | Sedimentary alfisol | 800 mg kg−1 | 73% (NH4NO3-extractable) | [36] |
| Orange bagasse | 500 °C | 60 t ha−1 | 24 m | Fallow field soil | 100 mg kg−1 | 28% (citric acid-extractable) | [90] | |
| Chicken manure | 550 °C | 5% | 14 d | Mine soil | 1805 mg kg−1 | 79% (NH4NO3-extractable) | [91] | |
| Orange bagasse | 500 °C | 60 t ha−1 | 6 m | Fallow field soil | 100 mg kg−1 | 41% (citric acid-extractable) | [92] | |
| Bamboo | 600 °C | 15% | 20 d | Sediment soil | 134.6 mg kg−1 | 79.7% (HOAc-soluble) | [93] | |
| Oat hull | 300 °C | 5% | 24 m | Sedimentary alfisol | 338 mg kg−1 | 68% (exchangeable fraction) | [22] | |
| Chicken manure | 550 °C | 5% | 14 d | Hills soil | 160 mg kg−1 | −45% (NH4NO3-extractable) | [91] | |
| Sewage sludge | 500 °C | 30 t ha−1 | 6 m | Fallow field soil | 100 mg kg−1 | −18% (citric acid-extractable) | [92] | |
| As | Rice straw | 500 °C | 3% | 30 d | Paddy soil | 120 mg kg−1 | As concentration increased by 234.5% in soil solution | [26] |
| Rice straw | 450 °C | 1−3% | 96 d | Paddy field soil | 212 mg kg−1 | As concentration increased in soil porewater | [94] | |
| Soybean stover | 700 °C | 10% | 90 d | Agricultural soil | 1945 mg kg−1 | As mobility increased greatly in soil | [25] | |
| Rice straw | 300 °C | 10% | 35 d | Paddy field soil | 92.3 mg kg−1 | As concentration increased in soil pore solution | [95] | |
| Oil palm fibers | 700 °C | 3% | 20 d | Paddy field soil | 0.3 mg kg−1 | As concentration increased in soil solution | [96] | |
| Sewage sludge | 200 °C | 3% | 6 d | Agricultural soil | 98.7 mg kg−1 | −81.9% (water-soluble) | [97] | |
| Sewage sludge | 350 °C | 3% | 6 d | Agricultural soil | 98.7 mg kg−1 | 42.2% (water-soluble) | [97] | |
| Corn straw | 600 °C | 0.5−2% | 100 d | Paddy soil | 73 mg kg−1 | As(Ⅴ): 11.7−28.5% (phosphate-extractable) As(Ⅲ): 54.0−81.6% (phosphate-extractable) |
[23] | |
| Cd | Wheat straw | 350−550 °C | 40 t ha−1 | 3 y | Paddy soil | 5 mg kg−1 | 59% (CaCl2-extractable) 24% (DTPA-extractable) |
[98] |
| Bamboo | 600 °C | 15% | 20 d | Sediment soil | 3.8 mg kg−1 | 31.2% (HOAc-soluble) | [93] | |
| Soybean straw | 350 °C | 3% | 6 d | Agricultural soil | 1.36 mg kg−1 | 65.7% (water-soluble) | [97] | |
| Maize straw | 550 °C | 30 t ha−1 | ~ 6 m | Paddy soil | 2.04 mg kg−1 | 50.4% (DTPA-extractable) | [29] | |
| Rice straw | 450 °C | 1−2% | 96 d | Paddy field soil | 10.8 mg kg−1 | Cd concentration decreased in soil porewater | [94] | |
| Sugarcane bagasse | 500 °C | 1.5% | 4 m | Agricultural soil | 50 mg kg−1 | 40.4% (DTPA-extractable) | [21] | |
| Corn stalk | 550 °C | 2% | 30 d | Arable land soil | 2.0 mg kg−1 | 91% (CaCl2-extractable) | [99] | |
| Hickory nut shell | 500 °C | 30 t ha−1 | ~ 6 m | Paddy soil | 2.04 mg kg−1 | 53.6% (DTPA-extractable) | [29] | |
| Pb | Soybean stover | 700 °C | 10% | 90 d | Agricultural soil | 1945 mg kg−1 | 95% (NH4OAc-extractable) 95% (TCLP-extractable) |
[25] |
| Vegetable waste | 500 °C | 5% | 45 d | Agricultural soil | 1445 mg kg−1 | 87% (NH4OAc-extractable) | [100] | |
| Bamboo sawdust | 600 °C | 37.5% | 30 d | Sediment soil | 589.7 mg kg−1 | 100% (TCLP-extractable) | [101] | |
| Red pepper stalk | 650 °C | 2.5% | 45 d | Agricultural soil | 1445 mg kg−1 | 65% (NH4OAc-extractable) | [100] | |
| Wheat straw | 350−550 °C | 40 t ha−1 | 3 y | Paddy soil | 100 mg kg−1 | 59% (CaCl2-extractable) 27% (DTPA-extractable) |
[98] | |
| Bamboo | 600 °C | 15% | 20 d | Sediment soil | 44.3 mg kg−1 | 73.2% (HOAc-soluble) | [93] | |
| Hg | Rice husk | 550 °C | 1−5% | 10 d | Field soil | 1000 mg kg−1 | > 94% (TCLP-extractable) | [102] |
| Rice hull | 480−660 °C | 24 t ha−1 | 118 d | Farmland soil | 129 mg kg−1 | Hg concentration decreased by 44% in soil porewater | [28] | |
| Wheat straw | 350−450 °C | 72 t ha−1 | 118 d | Farmland soil | 129 mg kg−1 | Hg concentration decreased by 26% in soil porewater | [28] | |
| Sewage sludge | 600 °C | 5% | 17 w | Paddy field soil | 2.1 mg kg−1 | MeHg concentration increased by 67% in soil | [41] | |
| Sewage sludge | 600 °C | 5% | 17 w | Paddy field soil | 65.3 mg kg−1 | MeHg concentration increased by 29% in soil | [41] | |
| Cr | Waste wood | 900 °C | 1−5% | 11 w | Tannery waste soil | 12285 mg kg−1 | 28−68% (CaCl2-extractable) | [103] |
| Sugarcane bagasse | 500 °C | 1.5% | 4 m | Agricultural soil | 50 mg kg−1 | 49.6% (DTPA-extractable) | [21] | |
| Rice straw | 500 °C | 40 t ha−1 | ~ 4 m | Paddy field soil | 432.8 mg kg−1 | Cr(total): 48.1% (HNO3/H2SO4-extractable) Cr(Ⅵ): 22.3% (HNO3/H2SO4-extractable) |
[104] | |
| Wheat straw | 600 °C | 0.25% | 180 d | Cr-spiked soil | 308 mg kg−1 | Cr(Ⅵ): 47.1% (TCLP-extractable) Cr(Ⅵ): 65.5% (CaCl2-extractable) |
[105] |
a Units explanation: d for days, w for weeks, m for months and y for years.