Adsorbate

Adsorbent

Removal capacity (mg/g)

Percentage removal (%)

Ref

Co(II)

Ni(II)

Natural iron oxide

103.9

85.2

90.33

75.60

This work

Co(II)

Ni(II)

Synthetic goethite

117.8

100.6

N/A

N/A

This work

Co(II)

Ni(II)

AFWC

9.89

10.12

96.5

96.8

[37]

Co(II)

Ni(II)

FWC

2.91

2.97

26.3

26.8

Co(II)

Ni(II)

PAC

1.86

2.29

16.7

17.7

Co(II)

Mesoporous silica nano-conjugate material

170.17 (calculated)

96

[38]

Ni(II)

Ni²⁺-imprinted chitosan Foam

69.93 (calculated)

N/A

[39]

Ni(II)

MWCNTs

2.90

N/A

[40]

Ni(II)

HNO₃-treated MWCNTs

12.50

N/A

[41]

Co(II)

MWCNTs/iron oxide

2.88

N/A

[42]

Co(II)

Oxidized CNTs sheets

69.63

N/A

[43]

Co(II)

Ni(II)

Chitosan-coated perlite beads

56.18

66.66 (calculated)

N/A

[44]

Co(II)

Ni(II)

γ-Fe₂O₃ nanotubes

56.83

65.62

N/A

[45]