Optimization and Modeling of Cr (VI) Removal from Tannery Wastewater onto Activated Carbon Prepared from Coffee Husk and Sulfuric Acid (H₂SO₄) as Activating Agent by Using Central Composite Design (CCD)

Table 2

Proximate analysis performed for different biomass for AC preparation.

Proximate analysis of different biomass for AC preparation	Ash content (%)	Volatile matter (%)	Moisture content (%)	Fixed carbon content (%)	Reference
Coffee husk dry basis	2.01	24.62	6.03	67.34	[30].
Wet basis coffee husk	1–4%	65–72%	10–11%	17–20%	[31]
Wet basis coffee husk	3.51	68.33	10.85	17.31	Current study
Rise husk on a dry basis	21–32%	68–79%	6.0 to 7.7%	19–24%	[29]
Teff straw husk	4.88%	73.61%	6.98%	14.53%.	[14]
Durian shell	2.52	69.59	5.53	22.36	[32]