Table 1 Comparison of removal efficiencies [adsorption capacity] of various biochars

1

Buck wheat, corn cobs,

mulberry wood, poultry manure and peanut shells BC pyrolyzed at 350, 450, 550 and 650 °C

(1) Lead

(2) Cadmium

(3) Arsenic

(1) 97.5% [2.5 mg g^− 1]

(2) < 90% [1.5 mg g^− 1]

(3) 42% [0.5 mg g^− 1]

[12]

2

Rape straw BC-NaOH

Cadmium

90% [72 mg g^− 1]

[16]

Rape straw BC-MnO_x

95% [81 mg g^− 1]

Rape straw BC-FeO_x

47% [67 mg g^− 1]

3

Hard wood and corn stalk BC

Copper

95%

[17]

Zinc

90%

4

Activated HTC BC

(1) Copper

(2) Cadmium

(1) 100% [31 mg g^− 1]

(2) 100% [34 mg g^− 1]

[18]

HTC BC

(1) 16% [4.0 mg g^− 1]

(2) 5.6% [1.5 mg g^− 1]

5

Compost BC

93.6% [3.6 mg g^− 1]

[19]

Rice husks BC

Copper

90.1% [2.5 mg g^− 1]

Olive pomace BC

77.8% [2.2 mg g^− 1]

Orange waste BC

88.7% [3.3 mg g^− 1]

6

Non-impregnated rice husk BC

Arsenic

25%

[20]

Ca impregnated rice husk BC

Arsenic

95%

Fe⁰ impregnated rice husk BC

Arsenic

58%

7

Soybean stalk BC

Mercury

86.4% [0.7 mg g^− 1]

[21]

8

Oak bark BC

Arsenic

70% [7.4 mg g^− 1]

[22]

Cadmium

50% [5.4 mg g^− 1]

Lead

Nearly 100% [13.1 mg g^− 1]

9

Sugar beet tailings BC

Chromium (VI)

98% [123 mg g^− 1]

[23]

10

Pinewood (P) BC

Rice husk (R) BC

Lead

P: Nearly 80% [4.1 mg g^− 1]

R: Nearly 60% [2.4 mg g^− 1]

[24]

11

Chitosan modified bamboo BC

Lead

50% [25.1 mg g^− 1]

[25]

Cadmium

45% [14.3 mg g^− 1]

Copper

Close to 55%

12

Olive mill solid waste BC

Lead

>  80%

[26]

Copper

>  80%

Selenium

<  20%

13

Groundnut shell BC

Cadmium

99.93% [0.14 mg g^− 1]

[27]

Mercury

99.99% [0.14 mg g^− 1]

Lead

100% [0.18 mg g^− 1]

14

Groundnut shell BC

Cadmium

99.20% [29.0 mg g^− 1]

[28]

15

Corn straw BC

Cadmium

99.24% [38.9 mg g^− 1]

[29]

16

Dairy manure derived BC

Lead

92.8–99.8%

[30]

17

Carbon microspheres derived from walnut shell

Chromium

Lead

Cadmium

Copper

[792 mg g^− 1]

[638 mg g^− 1]

[574 mg g^− 1]

[345 mg g^− 1]

[31]