Direct Immersion Sonic Horn

Horn design is a very important aspect of ultrasonic engineering. The vibrational amplitude of the piezoelectric crystal itself is normally so small that the intensity of sonication attainable by direct coupling of the transducer to the chemical system is not large enough to cause cavitation. The horn acts as an amplifier for the vibration of the transducer and the precise shape of the horn will determine the gain or mechanical amplification of the vibration. It is for this reason that it is sometimes referred to as a 

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Ultrasonic irradiation of aqueous solutions of the chlorophenols was carried out with a Vibra Cell Model VC-250 direct immersion ultrasonic horn (Sonics Materials Newtown, CT) operated at a frequency of 20 kHz with a constant power output of 50 W (the actual insonation power at the solution was 49.5 W, and the power density was 52.1 W/cm2). Reactions were done in a glass sonication cell (4.4 cm i.d. by 10 cm), similar to the one described by Suslick (1988). The temporal course of the sonochemical processes was monitored by HPLC. 

The mathematical model presented here was first used to simulate the oxidation of S(-II) at pH 10, [S(-II)]0 = 196 jxM, and [O2]0 = 240 p,M (air saturation). These initial conditions correspond to the conditions of one of the sonication experiments conducted in a stainless steel cell at 20 kHz and —75 W/cm2 with a Branson 200 sonifier and a Vfe-inch direct-immersion horn (3). The rates of H202 and NOz input to the system (i.e., H202input and N02input, respectively) were set at the experimentally observed zero-order formation rates for those species in deionized water buffered at pH 10 and sonicated under the same conditions. Various runs were performed with different values of OHmp, . 

Experiments using the same direct-immersion horn that was used ir S(-II) sonication, but in a completely different reaction vessel under different... 

Molecular oxygen is important for the sonolysis of S(-II) at alkaline pH because it propagates a free-radical chain reaction that is initiated by OH. Furthermore, the enhancement of oxygen transfer upon sonication with a direct-immersion horn is considerable. These results may have important implications for the application of ultrasonic irradiation for the destruction of chemical contaminants in water systems. 

By directly immersing a vibrating metal plate or a horn into the reaction medium (direct sonication)... 

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