Nanosized Spinel Ferrites Synthesized by Sol-Gel Autocombustion for Optimized Removal of Azo Dye from Aqueous Solution

Table 5

Input variables and their coded and actual values used for adsorption experiments.

Input variables (factors)	Coded variables	Coded levels versus actual values
		−α		0	+1	+α
Contact time, (min)		14	30	105	180	196
Initial dye concentration, (mg/L)		13.6	20.0	50.0	80.0	86.5
Sorbent dosage (NiFe2O4), SD (g/L)		0.57	1.00	3.00	5.00	5.43

Note: (value of axial point for orthogonal CCD in case of three factors).