Biosorption Studies of Cd²⁺ and Cr⁶⁺ from Aqueous Solution Using Cola-Nut Leaves as Low-Cost Biosorbent

Table 4

q_m of various adsorbents for the removal of Cd (II) and Cr (VI) ions.

Adsorbent used for the removal of metal ions from solution	Type of metal ion adsorbed	Maximum monolayer adsorption capacity (qm mg/g)	Reference
Activated coal	Cr III	13.552	[23]
Oxidized MW carbon nanotubes	Cr VI	4.262	[32]
Rhizopus arrhizus for removal	Cr VI	23.92	[33]
Dried activated sludge	Cd II	84.30	[34]
Tamarindus indica seeds	Cr VI	0.098	[35]
Coconut copra meal	Cd II	4.92	[36]
Crude tamarind fruit shells (CTFS)	Cr VI	74.62	[37]
HCl-treated shells (H-TS)	Cr VI	140.84
Oxalic acid-treated shells (O-TS)	Cr VI	151.51
Orange peels	Cd II	123.65	[38]
Pinus bark	Cd II	10.384	[24]
Pinus bark	Cr VI	−10.661
ATK cola nut leaves	Cr VI	178.57
UTK cola nut leaves	Cr VI	555.56
ATK cola nut leaves	Cd II	200
UTK cola nut leaves	Cd II	185.19