Table 5 Comparison of Cr(VI) adsorption by persulfate-modified AC adsorbent with other types of AC adsorbents.

Granulated activated carbon (GAC-S)

nitric acid, ammonium persulphate and hydrogen peroxide

Cr (VI) = 20–1000 mg/L, ambient temperature

30

–

⁴⁶

Activated carbon prepared from coconut tree sawdust

H₂SO₄

Dosage = 50–750 mg, V_solution = 50 mL, Time = 180 min, pH = 3, Cr (VI) = 5–20 mg/L, shaker = 150 rpm, ambient temperature

3.46

–

⁴⁷

Commercial coconut activated carbon

HNO₃ and NaOH

Dosage = 0.2 g, V_solution = 100 mL, Cr (VI) = 5–50 mg/L, Temp = 303.15 K

13.88

–

¹²

Activated carbon

Modification of AC with 7 mol/L of HNO₃ at 90 ^oC

Dosage = 2 g, V_solution = 100 mL, Cr (VI) = 10 mg/L, Temp = 301.15 K

10.929

83

¹³

Activated carbon

HNO₃

Dosage = 0.2–2.5 g, Time = 180 min, pH = 2–9, Cr (VI) = 25 mg/L, ambient temperature

16.10

99

¹⁸

Activated carbon (Made from palm bark)

polyethylene amine (228.2 mg/g PEI on AC)

Dosage = 0.1 g, V_solution = 50 mL, Time = 24 h, pH = 3–4, Cr (VI) = 200 mg/L, shaker = 150 rpm, ambient temperature

20.5

76.64

¹⁴

Activated carbon

Fe (III)

Dosage = 0.25–5 g/L, Time = 1–500 min, pH = 2–11, Cr (VI) = 3.5–20 mg/L, shaker = 300 rpm, ambient temperature

11.83

100

¹⁵

Commercial activated carbon

–

Dosage = 6 g/L, Time = 24 h, pH = 6, Cr (VI) = 50 mg/L, shaker = 250 rpm, ambient temperature

52.60

–

¹⁶

Activated carbon

(NH₄)₂S₂O₈

Dosage = 0.03 g, V_solution = 10 mL Time = 180 min, pH = 2–5, Cr (VI) = 100 mg/L, shaker = 150 rpm, ambient temperature

108.69

90.49

Present study