Green coconut shell	650˚C for 1 hour	ZnCl₂	Volatile matter (17.2%), fixed carbon (78.9%), ash content (0.9%), surface area (995 m²/g), micropore volume (0.37 cm³/g) in the obtained activated carbon were reported [51] . Removal of methylene blue greater than 90% when the contact time about 9 - 10 hours.
Apple pulp and apple peel	Modified microwave oven was used	Furnace was used during the activation process. Activation agent: phosphoric acid	The highest removal of methylene blue was 94.6% and 87.2% for pulp-based, and peel-based activated carbon [52] . BET surface area showed the highest value (1552 m²/g) in apple peel based activated carbon if compared to pulp based (1103 m²/g).
Orange peel	Tubular furnace was used, 1073 K for 1 hour	--	Removal of phenol onto activated carbon was 88 mg/g when the contact time is 3 hours [53] The adsorption data support pseudo second order model. The best pH values are in the range of 4 to 8.
Banana peel waste	350˚C for 1 hour	Sulphuric acid	The highest iodine number could be observed when H₂SO₄ was used during the activation process [54] . Percentage of yield increased from 33.56% to 61.4% as concentration of H₂SO₄ decreased from 6 N to 1 N. BET surface area increased from 367 to 426 m²/g with increasing the concentration of sulfuric acid.