The effect of frequency on sonochemical reactions III: dissociation of carbon disulfide

Abstract

Investigations were made of the effects of frequency, temperature, intensity and gases on the rate of sonochemical dissociation of carbon disulfide. Application of 900 kHz ultrasound did not produce any noticeable change. When carbon disulfide was irradiated with 20 kHz, the liquid formed a heterogeneous mixture of black particles in a yellow solution. The rate of dissociation decreased with increasing temperature, in agreement with most sonochemical reactions. The rate also decreased with decreasing area of the horn tip, keeping total power constant. This dependence on the horn tip area, as well as that on the frequency, is in opposition to the dependence for the formation of iodine from the sonication of aqueous potassium iodide solution [See Part II, Ultrasonics Sonochemistry 3 (1996) 19]. The X-ray spectrum of the black particles and the yellow residue obtained after evaporation showed the presence of amorphous carbon and monoclinic sulfur. The rate of sono-dissociation of carbon disulfide in the presence of different gases is in the order He > H2 > Air > Ar > O2 > CO2.

Degradation of pharmaceuticals by ultrasound-based advanced oxidation process

“…This is the reason with highly efficient degradation in the presence of these gases. In addition to this, the solubility of gas possesses a role in the degradation, and the order is found to be He (Entezari et al 1997), and thus, the enhancement of the cavitational event is in the same order. Similarly as the thermal conductivity of dissolved gas increases, the amount of heat loss due to thermal dissipation also increases.…”

Sonochemical reactions: mass transfer and kinetic studies of a solid-liquid system

“…In the past, typical sonochemical reactions were carried out at frequencies between 20 and 50 kHz. la some reactions, alteration of frequency has no apparent effect, sudi as the in the dissociation of carbon disulfide (Entezari et al, 1997). However, in other reactions, such as oxidations, current research is finding that higher frequencies may lead to higher reaction rates.…”

“…The dependence of cavitational intensity on the characteristics of the dissolved gases has been studied by Entezari et al (1997) vsdio investigated the effect of ultrasound on the rate of carbon disulfide dissociation. Th^ found that He gave the hi^est reaction rate and CO2 gave the lowest, with the rate decreasing in the following ordra^ of gases present: He > H2 > air > Ar > O2 > C02-Since argon has a hi^er ^edfic heat ratio that helium, th^ were piuzled with the observations.…”

“…In addition, probe systems are capable of delivering large amounts of power directly to the reaction mixture which can be regulated by varying the anq>]itude delivered the transducer. Disadvantages in using a probe system include erosion and pitting of the probe t^, which may contaminate the reaction solution, as found by Entezari et al (1997) ^en investigating the dissociation of carbon disulfide. Several probes are available with removable t^s, maldng replacement relatrvefy ineTqiensive.…”

“…The thermal conductivity of the gas is also in^ortant because, although the course is modeled as adiabatic, there is a small amount of heat which is transferred to the bulk liquid mixture during collapse. As the thermal conductivity of the gas increases, the amount of heat loss due to thermal diss^ation also increases.The dependence of cavitational intensity on the characteristics of the dissolved gases has been studied by Entezari et al (1997) vsdio investigated the effect of ultrasound on the rate of carbon disulfide dissociation. Th^ found that He gave the hi^est reaction rate and CO2 gave the lowest, with the rate decreasing in the following ordra^ of gases present: He > H2 > air > Ar > O2 > C02-Since argon has a hi^er ^edfic heat ratio that helium, th^ were piuzled with the observations.…”