Fig. 2: The response surface plots.

The influence of interaction term between variables onto removal of ENF (a, b) and RhB (c, d). X1: GO amount, X2: ENF concentration, X3: RhB concentration, X4: pH of solution, and X5: sonication time.
The influence of interaction term between variables onto removal of ENF (a, b) and RhB (c, d). X1: GO amount, X2: ENF concentration, X3: RhB concentration, X4: pH of solution, and X5: sonication time.