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 1

Proximate analysis using the American Society for Testing and Materials (ASTM).

St.	Proximate analysis parameter	Standard methods	Reference	Experimental results
1.	Ash content	ASTM D 1102–84	[14]	3.51
2.	Moisture content	ASTM 2867–99	[23, 27]	10.85
3.	Volatile matter content	ASTM D4607-86	[28]	68.33
4.	Fixed carbon content	ASTM 2867–99	[29]	17.31