Valorization of Wasted Black Tea as a Low-Cost Adsorbent for Nickel and Zinc Removal from Aqueous Solution

Table 4

The capacity of different adsorbents for Ni²⁺ and Zn²⁺ removal.

Adsorbent	Adsorbent mass to solution volume ratio	Sorption capacity (mg/g)	Reference
Ni^2+ removal
Sphagnum moss peat	0.4 : 100	9.18	[31]
Baker’s yeast	0.1 : 100	11.40	[32]
Chlorella sorokiniana (FBCS)	0.1 : 100	48.08	[33]
Powdered activated carbon	1.2 : 100	31.08	[34]
Waste tea	1.5 : 100	18.42	[24]
Waste tea (formaldehyde-treated)	0.2 : 100	120.50	[35]
Black wasted tea	2 : 100	90.91	This study
Zn^2+ removal
Olive oil mill residues	0.4 : 100	52.91	[36]
Bagasse-based activated carbon	0.6 : 100	54.00	[37]
Date pits-based activated carbon	0.02 : 100	120.5	[38]
Chitosan	0.25 : 100	58.83	[39]
Waste tea leaves	0.15 : 100	11.76	[40]
Black tea waste	1 : 100	12.24	[41]
Tea factory waste	0.4 : 100	8.9	[25]
Tea leaves (hydrazine monohydrate-exhausted)	0.125 : 100	79.76	[42]
Wasted black tea	2 : 100	166.67	This study