Table 2 Properties of modified biochars obtained from various treatments.

Steam activation

Tea waste

300

Un-modified

7.90

70.10

5.20

19.60

5

5.70

0.006

2.30

¹⁰

Modified

8.60

71.50

4.80

18.20

5.50

6.40

0.004

1.50

Steam activated

Invasive plant

300

Un-modified

10.90

66

5.60

23.10

5.10

25.40

0.004

0.90

¹¹

Modified

11.10

68.10

5.10

21.40

5.10

28.70

0.003

1.20

Steam activation

Tea waste

700

Un-modified

11

85.10

2

8.90

3.9

10.90

0.022

342.2

¹²

Modified

10.50

82.40

2.1

11.60

3.9

16.70

0.109

576.1

Steam activation

Invasive plant

700

Un-modified

12.30

69.40

1.30

24.40

4.60

43.70

0.008

2.30

¹³

Modified

11.70

50.60

1.70

44.90

2.50

70.70

0.038

7.10

Zn-loading

Pine cone

500

Un-modified

–

67.90

3.90

22.10

0.5

2.1

0.016

6.60

¹⁵

Modified

–

71.20

3

20.40

0.5

2.1

0.028

11.50

FeCl₃-modified

Wheat straw

450

Un-modified

7

47.20

2.40

18.40

1.10

–

0.012

9.50

¹⁶

Modified

8.30

25.90

1.70

21.60

0.60

–

0.038

50

Amino-modified

Sawdust

500

Un-modified

4

68.70

3.80

–

0.30

–

0.005

2.60

¹⁷

Modified

6

62.10

4.20

–

4.60

–

0.005

2.50

Methanol-treatment

Rice husk

450

Un-modified

–

70.60

3.50

24.10

0.80

1

51.90

¹⁸

Modified

–

71.10

3.60

23.40

0.80

0.90

66

KOH modification

Rice husk

450–500

Un-modified

7

42.10

2.20

0.50

12.10

42.20

0.028

34.40

¹⁹

Modified

7

76.40

3.30

0.90

16.90

3.50

0.073

117.80

H₂O₂ oxidation

Peanut hull

300

Un-modified

6.2

56.30

5.60

36.60

0.90

–

–

1.30

¹³

Modified

4.4

48.30

5.80

43.80

0.80

–

–

96.90

Clay-loaded composite (montmorillonite)

Hickory chips

600

Un-modified

–

81.80

2.20

14

0.70

–

–

401

²⁰

Modified

–

80.90

2.20

15.10

0.30

–

–

376.10

Clay-loaded composite (montmorillonite)

Bagasse

600

Un-modified

–

76.40

2.90

18.30

0.80

–

–

388.30

²¹

Modified

–

75.30

2.20

18.90

0.70

–

–

407

Clay-loaded composite (Kaolinite)

Bamboo

600

Un-modified

–

80.90

2.30

14.90

0.10

–

–

375.50

²²

Modified

–

83.30

2.40

12.40

0.20

–

–

408.10

CO₂-ammonia treatment

Cotton stalk

600

Un-modified

–

–

–

–

1.10

–

0.070

224

²³

Modified

–

–

–

–

1

–

0.130

351

MnOx-loading

Corn straw

600

Un-modified

–

85.30

1.70

5.20

0.80

5

0.036

61

²⁴

Modified

–

73

0.30

10.90

0.70

13.10

0.006

3.20

Metal coating

Pulverized sub-bituminous

600–1000

Un-modified

6.4

81.60

–

17.90

–

–

0.079

190

²⁵

Modified

–

65.50

–

13.20

–

–

0.126

245

MnO₂-loading

Pinewood

700

Un-modified

4.5

–

–

–

–

–

0.200

369

²⁹

Modified

–

–

–

–

–

–

0.194

361

MnO₂-loading

Pinewood

600

Un-modified

–

85.70

2.10

11.20

0.30

4.0

0.003

209.60

²⁶

Modified

–

61.50

1.90

27.60

0.20

33.40

0.066

67.40

CO₂/NH₂-modified

Cotton stalks

600

Un-modified

–

–

–

–

1.10

–

0.070

224.10

²⁷

Modified

–

–

–

–

3.50

–

0.130

351.50

Magnetic biochar (Zero-valent iron)

Paper waste

700

Un-modified

–

–

–

–

–

–

0.083

67

²⁸

Modified

–

–

–

–

–

–

0.079

102.20

Magnetic biochar (Fe²⁺/Fe³⁺)

Orange peel

700

Un-modified

–

67

1.50

–

2

14.90

0.390

501

³⁰

Modified

–

0.40

0.20

–

0.20

95.70

0.033

19.40

Magnetic biochar (Fe²⁺/Fe³⁺)

Orange peel

400

Un-modified

–

65.70

3.50

–

1.80

6.90

0.041

28.10

³⁰

Modified

–

29.40

2.20

–

0.50

35

0.042

23.40

Magnetic biochar (Fe²⁺/Fe³⁺)

Orange peel

250

Un-modified

–

56.50

5.10

–

1.70

3.10

0.059

51.60

³⁰

Modified

–

35.10

3.60

–

1.10

42.40

0.052

41.20

Zn(NO₃)₂-modified

Pine cones

500

Un-modified

4.70

67.90

3.90

22.10

0.50

2.10

0.016

6.60

³¹

Modified

4

71.20

3

20.40

0.50

2.10

0.028

11.50

Mg-Ca loaded

Corn cob

300

Un-modified

–

35.50

6.30

–

0.70

4

–

–

³²

Modified

–

43.30

5

–

0.60

5

–

378

H₂O₂ oxidation

Apple tree branch

550

Un-modified

9.79

72.53

14.85

2.49

1.49

–

–

6.67

³³

Modified

5.93

62.69

21.58

2.86

1.42

–

–

7.95

HNO₃-modified

Tea waste

300

Un-modified

7.16

57.80

4.42

34.12

3.66

6.15

–

–

³⁴

Modified

2.40

57.03

4.47

32.99

5.51

2.80

–

–

Chemically modified (H₂SO₄)

Tea waste

300

Un-modified

7.16

57.80

4.42

34.12

3.66

6.15

–

–

³⁵

Modified

3.40

60.79

4.69

30.65

3.87

4

–

–

Chemically modified (HCl)

Tea waste

300

Un-modified

7.16

57.80

4.42

34.12

3.66

6.15

–

–

³⁵

Modified

2.55

63.15

4.75

28.18

3.92

3.10

–

–

HNO₃-modified

Tea waste

500

Un-modified

7.04

69.66

2.96

24.82

2.55

11.40

–

–

³⁵

Modified

2.44

56.57

4.39

33.78

5.26

3.10

–

–

HNO₃-modified

Tea waste

700

Un-modified

10.09

71.03

2.11

23.74

3.12

9.26

–

–

³⁵

Modified

2.57

71.30

2.21

22.69

3.80

2.50

–

–

Chemically modified (H₂SO₄)

Tea waste

500

Un-modified

7.04

69.66

2.96

24.82

2.55

11.40

–

–

³⁵

Modified

2.35

61.27

4.55

30.26

3.96

3.50

–

–

Chemically modified (H₂SO₄)

Tea waste

700

Un-modified

10.09

71.03

2.11

23.74

3.12

9.26

–

–

³⁵

Modified

4.16

71.37

2.14

23.45

3.04

6.50

–

–

Chemically modified (HCl)

Tea waste

500

Un-modified

7.04

69.66

2.96

24.82

2.55

11.40

–

–

³⁵

Modified

2.65

63.35

4.17

28.07

3.88

3.80

–

–

Chemically modified (HCl)

Tea waste

700

Un-modified

10.09

71.03

2.11

23.74

3.12

9.26

–

–

³⁵

Modified

2.49

74.02

2.22

20.62

3.15

7.83

–

–

HCl-modified

Peanut shells

500

Un-modified

9.20

–

–

–

–

32.54

–

³⁶

Modified

8.60

–

–

–

–

8.52

–

–

H₃PO₄-modified

Swine manure

700

Un-modified

–

31.96

0.66

4.77

1.60

60.73

0.07

227.56

³⁷

Modified

–

48.35

0.66

4.41

2.23

43.98

0.09

319.04

H₃PO₄-modified

Rice straw

700

Un-modified

–

31.77

0.98

7.23

0.96

58.97

0.23

369.26

³⁹

Modified

–

37.77

0.43

5.31

1.05

55.27

0.23

372.21

H₂O₂ oxidation

Eucalyptus saligna

500

Un-modified

5.60

82.10

0.97

9.20

0.17

–

0.138

333.72

⁴⁰

Modified

6.48

78.40

1.29

12.70

0.14

–

0.146

347.46

HNO₃ + H₂SO₄

wheat straw

450

Un-modified

8

66.15

2.09

7.21

0.87

–

–

–

⁴¹

Modified

7.30

60.57

1.60

14.82

1.21

–

–

–

H₂O₂ oxidation

Yak manure

350

Un-modified

–

37.44

5.87

26.76

2.71

27.22

–

1.03

⁴²

Modified

–

40.04

3.99

29.17

2.90

23.91

–

6.36

H₂O₂ oxidation

Eucalyptus wood

550

Un-modified

–

75.5

2.90

21.50

0.1

–

–

249

⁴³

Modified

–

64.8

2.30

32.60

0.3

–

–

261

H₂O₂ oxidation

Corn stover

600

Un-modified

8.30

41.60

1.50

8.10

0.40

–

–

178

⁴⁴

Modified

7

40.60

1.30

8.30

0.40

–

–

179

HNO₃-modified

Pinewood chips

300

Un-modified

6.20

54.80

4.10

41

0.12

0.15

–

–

⁴⁵

Modified

5.80

56.50

1.20

40.30

1.99

0.11

–

–

H₂SO₄/HNO₃ treatment

Alternanthera philoxeroides

350

Un-modified

9.56

47.70

4.19

25.83

2.68

19.36

–

4.78

⁴⁶

Modified

2.12

60.34

1.91

28

1.85

5.46

–

7.14