Optimized Removal of Hydroquinone and Resorcinol by Activated Carbon Based on Shea Residue (Vitellaria paradoxa): Thermodynamics, Adsorption Mechanism, Nonlinear Kinetics, and Isotherms

Table 2

Matrix of coded variables.

Variables	Symbols	Units	Coded variables	Variables levels
				−1	0	+1
Concentration	C0	(mg/L)	A	20	100	180
pH	pH	—	B	2	6	10
Time	t	(min)	C	30	75	120
Mass	m	(mg)	D	50	150	250