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

Table 1

Efficiencies of the current methods and sorption technique in removal of Ni²⁺ and Zn²⁺.

Technique	Removal efficiency (%)		Reference
	Ni^2+	Zn^2+
Chemical precipitation	98.4	99	[13, 14]
Electrochemical	98	96	[15, 16]
Ion exchange	93.6	100	[17, 18]
Filtration	99.1	98	[19, 20]
Reverse osmosis	99.3	98.9	[21]
Adsorption	82	99.8	[17, 22]

Initial metals concentrations of less than 200 mg/L.