Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review

Abstract

As one of several types of pollutants in water, chlorinated compounds have been routinely subjected to sonochemical analysis to check the environmental applications of this technology. In this review, an extensive study of the influence of the initial concentration, ultrasonic intensity and frequency on the kinetics, degradation efficiency and mechanism has been analyzed. The sonochemical degradation follows a radical mechanism which yields a very wide range of chlorinated compounds in very low concentrations. Special attention has been paid to the mass balance comparing the results from several analytical techniques. As a conclusion, sonochemical degradation alone is not an efficient treatment to reduce the organic pollutant level in waste water.

Sonochemical Formation of Hydrogen Peroxide

“…All experiments showed R 2 value greater than 0.9. Previous studies have confirmed that, during sonication at constant intensity, the rate of generation of hydroxyl radicals can be assumed constant, with a prominent product of sonication being hydrogen peroxide (reactions 1.6, 1.9 and 1.10), with this acting as an OH scavenger and accumulating linearly in solution during the process of ultrasonic irradiation [2,23]. In addition, conducted statistical analysis have shown that the highest correlation coefficient was observed for 90 min (R 2 = 0.9998).…”

“…The hydroxyl radical exhibits a high oxidation potential and can oxidize organic substrates directly, causing their degradation or mineralization [1,4,5]. However, hydroxyl radicals have a very short lifetime, and tend to combine with one another to form H2O2 [2,3,10]. The production of hydrogen peroxide in the circumstances of different intensities of ultrasonic irradiation is as shown in Figure 2a.…”

“…The range of ultrasound frequencies used commonly in sonochemistry is 20 kHz to 1 MHz [1,2]. Ultrasonic irradiation of liquids causes acoustic cavitations, i.e., the formation, growth and implosive collapse of bubbles.…”

A new bipyridyl cobalt complex for reductive dechlorination of pesticides

“…Several physicochemical methods have been proposed for their degradation [1][2][3][4][5][6]. Among them, the catalytic reduction of chlorinated compounds has been the subject of numerous investigations because of its high importance both for synthetic chemistry and environment [6][7][8][9][10][11].…”

Preliminary investigation on ultrasound frequency determination in TNT, RDX and HMX degradation

“…The extreme conditions created by cavitation leads to the thermal destruction of pollutants and generation of reactive hydroxyl radicals (Mason, 1991). Therefore, by pyrolytic processes, volatile pollutants are degraded inside the cavitation bubbles while non-volatile pollutants are degraded by the hydroxyl radical in the bulk liquid (Tiehm, 1999;González-García et al, 2010).…”