Table 4.

Comparison of the performance between the dual frequency method reported herein and those of alternative techniques reported in the literature with added catalysts/additives for the degradation of methylene blue.

Method	Power density [W/L]	Treatment time [min]	Degradation efficiency [%]	Reference
•Ultrasound plus CCl4 •Ultrasound alone	5000 _	35 30	98.6 36.75	Li et al. [12]
•Ultrasound with H2O2 and TiO2 •Ultrasound alone	–	60	85 25	Shimizu et al. [13]
•Ultrasound with TiO2 •Sonophotodegradation	_ _	180	30 45	Yuan et al.[14]
Ultrasound with CaMgO2 under sunlight	–	60	95	Karuppusamy et al.[15]
Ultrasound with rGO/TiO2 under sunlight	–	30	91.3	Deshmukh et al. [16]
Ultrasound with Ag-ZnO nanocomposite	_	120	96.2	Satdeve et al, [17]
Ultrasound (490 kHz) with TiO2	80	30	–	Honma et al, [39]
Ultrasound with CeO2	800	120	90	Gadge et al, [31]
Ultrasound with β-NiMoO4 under sunlight	2000	150	98.2	Dhanasekar et al, [23]
Ultrasound only (20 and 37 kHz)	272.08 ± 3.92	20	87.29	This work
Ultrasound only (20 and 80 kHz)	209.63 ± 6.94	20	91	This work