Characterization and Optimization of Calcination Process Parameters for Extraction of Aluminum from Ethiopian Kaolinite

Table 1

Experimental level for central composite design (CCD) in coded and actual values.

Factors	Coded factors	Coded values		Actual values
		Low	High	Low	High
Temperature (^oC)	X1	−1	+1	600	700
Time (min)	X2	−1	+1	120	180
Particles size (μm)	X3	−1	+1	106	355