Table 5.
Removal of contaminants and associated mechanisms through non-metallic heteroatom-doped biochar.
| Doping agent | Biochar type | Pyrolysis temperature (°C) | Contaminants | Removal capacity | Mechanism involved | References |
|---|---|---|---|---|---|---|
| Nitrogen | Bamboo | 500 | Chlorotetracyclin | 92% |
Non-radical pathways 1O2 Radical pathway: SO4·− |
68 |
| Boron | Wheat straw | 700 | Phenol | 33 mg g−1 |
Non-radical pathways 1O2 Radical pathway: SO4·− |
70 |
| S and N | Peanut shell | 300 | Diethyl phthalate | 14 mg g-1 | Increased removal via pyridinic-N formation and the oxidized sulfur groups on doped-biochar | 71 |
| Nitrogen | Pomelo peel | 800 | Sulfamethoxazole | 95% | Non-radical oxidation involving electron transfer and 1O2 | 72 |
| Sulfur | Tapioca peel | 800 |
Rhodamine B Malachite green |
33 mg g−1 30 mg g-1 |
H- bonding, surface interaction, and electrostatic attraction | 73 |
| Sulfur | Wood pellets | 800 | Bisphenol A | 91% | Driven via hydroxyl radicals and surface-bound singlet O2 | 71 |
| Co-doped (boron and nitrogen) | Wheat straw | 700 | Oxytetracycline | 60% | High defect sites and large SSA | 75 |
| Sulfur | Bamboo | 600 | Oxytetracycline | 89% |
Non-radical pathways 1O2 Radical pathway: SO4·- |
77 |
| Boron | Wheat straw | 900 | Sulfamethoxazole | 90% | Boron-doping restrained the electron transfer | 78 |
| Co-doped (copper and nitrogen) | Glucose | 700 | Tetracycline | 100% | Radical degradation such as electron transfer and ·OH | 84 |
| Nitrogen | Hickory chip | 600 | Reactive red | 37 mg g-1 | zeta potential enhancement and electrostatic interaction | 79 |
| Co-doped (nitrogen and sulfur) | Wood shaving | 800 | Methylene blue | 40% | Activation through the thiophenic S and graphitic-N active sites | 74 |
| Nitrogen | Enteromorpha prolifera | 800 |
Phenanthrene Acenaphthene Naphthalene |
90 mg g−1 51 mg g−1 86 mg g−1 |
Partition effect, π–π stacking, mass transfer, and pore-filling | 81 |
| Nitrogen | Glucose | 700 | Pnitrophenol | 94% | New sorption sites of pyrrolic-N and pyridinic-N | 75 |
| Nitrogen | Maize straw | 600 |
Methyl blue Acid orange 7 |
436 mg g−1 292 mg g−1 |
π–π stacking and pore-filling Lewis acid–base interaction, π–π stacking, and electrostatic attraction |
33 |
| Nitrogen | Phragmites australis | 280 | Phenanthrene | 1.9 mg g−1 | Electrostatic attraction, hydrophobic effect, and π–π interaction | 82 |
| Nitrogen | Alfalfa | 600 |
Methyl orange Methyl blue |
326 mg g−1 906 mg g−1 |
H-bonding, electrostatic interactions, and π–π stacking | 69 |
| Nitrogen | Sawdust | 800 | Bisphenol A | 50 mg g-1 | π-π EDA interactions | 67 |
| Nitrogen | Pomelo peel | 200 | Orange II | 100% | 1O2 and ·OH expedited the degradation | 72 |
| Nitrogen | Peanut shell | 350 | Pb2+ | 130 mg g−1 | ion exchange and surface complexation | 23 |
| Co-doped (phosphorus and nitrogen) | Lotus leaf | 600 | Pb2+ | 321 mg g−1 | Precipitation and surface complexation | 32 |
| Sulfur | Corn straw | 800 | Pb2+ | 181 mg g−1 | Precipitation, reduction, and complexation | 69 |
| Nitrogen | Loofah sponge | 400 | Cr (IV) | 238 mg g−1 | In-situ reduction, complexation, and electrostatic attraction | 44 |
| Nitrogen | Hemicelluloses | 200 | Cr (VI) | 349 mg g−1 | Chelation, redox, and electrostatic attraction | 71 |
| Nitrogen | Maize straw | 600 |
Cd2+ Cu2+ |
197 mg g−1 104 mg g−1 |
Complexation and cation-π bonding with hydroxyl groups and graphitic-N | 74 |
| Boron | Maize straw | 800 | Fe2+ | 50–132 mg g−1 | Co-precipitation, ions exchange, and chemical complexation | 75 |
| Co-doped (nitrogen and oxygen) | Rice husk | 500 |
Zn2+ Ni2+ Cu2+ |
12 mg g−1 8 mg g−1 13 mg g−1 |
Electrostatic attraction and surface complexation | 80 |