Sonochemical reactors for waste water treatment: comparison using formic acid degradation as a model reaction

Sonochemical reactors find a promising future in the area of wastewater treatment as one of the advanced oxidation methods. The degradation of formic acid has been studied using different cavitation equipments such as ultrasonic horn, ultrasonic bath, dual frequency flow cell, and triple frequency flow cell. The effect of several operating parameters such as time of destruction, initial concentration of the pollutant, intensity and frequency of irradiation, introduction of air, and liquid level in the case of ultrasonic bath on the extent of degradation has been investigated. Comparison of these types of equipment has been made using the two characteristic parameters, i.e. energy efficiency and the cavitational yield. The triple frequency hexagonal flow cell has been found to be more efficient in the destruction of formic acid. The present work clearly illustrates that the multiple frequency multiple transducer reactors can be used with higher energy efficiency and cavitational yield at a larger scale of operation. A new design in terms of hexagonal flow cell and also combination of bath and horn has been used for the first time with improved results.