Fig. 2

Contour Plot of Removal (%) Based on X1 to X6. pH (X1), moisture content (X2), applied voltage (X3), sodium persulfate concentration (X4), surfactant amount (X5), and ultrasonication time (X6).

Contour Plot of Removal (%) Based on X1 to X6. pH (X1), moisture content (X2), applied voltage (X3), sodium persulfate concentration (X4), surfactant amount (X5), and ultrasonication time (X6).