| The application of ultrasound to environmental problems relies on the process of acoustic cavitation: the formation, growth, and implosive collapse of bubbles in a liquid. The collapse of such bubbles creates hot spots with temperatures as high as 5000 K, pressures up to 800 atm, and cooling rates in excess of 1010K/s. This thesis describes the use of ultrasound for the dissolution of gas into water, an investigation the sonochemistry of ionic liquids, and the sonochemical preparation of nanostructured materials for the catalytic hydrodehalogenation of organic halides.; A variety of ultrasonic methods and configurations were designed and tested for the dispersion and dissolution of O2 in water. Ultrasonic methods examined include 20 kHz Ti horns, 336 to 1.41 MHz transducers, specially designed ultrasonic gas dispersion cell including the hollow horn extensions, Ti frits, and a modified 20 kHz cup horn. Most methods increased the dispersion rate when compared to non-ultrasonic control runs.; Room-temperature ionic liquids were examined for their potential application as green solvents for sonochemical reactions. The effects of ultrasound on room-temperature ionic liquids were investigated using butylmethyl imidazolium chloride (BuMeImCl), butylmethyl imidazolium tetrafluoroborate (BuMeImBF 4), and decylmethyl imidazolium tetraphenylborate. Gas-chromatography mass-spectrometry head-gas analysis and multibubble sonoluminescence were used to show that room-temperature ionic liquids decomposed in the presence of ultrasound.; As previously reported, molybdenum carbonyl and tungsten carbonyl were decomposed sonochemically in hexadecane to form porous aggregates of 2–3 nm high surface area Mo2C and W2C particles. The activity of these materials was studied for the catalytic hydrodehalogenation of aliphatic and aromatic halocarbons at low temperatures (T = 200–300°C). Both catalysts were selective, active, and stable for all substrates tested. The HDH of substrates bearing aliphatic C-Cl bonds occurs faster than those with aryl C-Cl bonds. Characterization of post catalytic materials with x-ray diffraction and x-ray photoelectron spectroscopy revealed no change in the bulk structure of the catalyst and chlorination of the surface metal species, respectively. |
