Table 1. Independent Variables and Their Levels for Box-Behnken Design

Independent variables	Units	Symbol	Range and Levels
			-1	0	1
Sonocatalyst dosage	g/L	X1	0.2	0.4	0.6
Dye concentration	mg/L	X2	5	10	15
Ultrasound treatment time	min	X3	90	120	150