A sonophotochemical reactor for the removal of formic acid from wastewater

The efficacy of a sonophotochemical reactor coupling ultrasonic irradiation with photocatalytic oxidation has been evaluated using formic acid degradation as the model reaction. The reactor used in the present work is a hexagonal flow cell irradiated with multiple-frequency transducers placed at the wall of the reactor and by ultraviolet radiation positioned at the center of the reactor. The various operating parameters studied in the present work include the concentration of the photocatalyst, initial concentration of the pollutant, and effect of aeration for the case of photocatalytic oxidation. The sonophotochemical operation has been studied in two ways: simultaneous irradiation and sequential irradiation with the aim of understanding the expected synergism between the two modes of energy transmission. The effect of the addition of hydrogen peroxide on the extent of degradation has also been studied. The hybrid technique of sonophotochemical degradation in the presence of aeration and hydrogen peroxide has been compared with the individual techniques of photocatalysis, ultrasonic irradiation, and addition of hydrogen peroxide alone, and recommendations about the effective techniques have been made for wastewater treatment applications.