AWARD ACS FOR CREATIVE ADVANCES IN ENVIRONMENTAL SCIENCE AND TECHNOLOGY: HONORING DR. MICHAEL R. HOFFMANN (Sponsored by Air Products and Chemicals, Inc.) Wednesday, April 4, 2001 American Chemical Society National Meeting San Diego, CA Chemical Transformations and Phase Transfer
Organizers: M.R. Hoffmann R.A. Hathaway Presiding: M.R. Hoffmann
Time 8:00 a.m.
Paper Kinetics of surfactant degradation by sonolysis. L.K. Weavers, M.G.Y. Pee and J.F. Rathman Environmental photochemistry of decabromodiphenyl ether and related compounds. I. Hua and C. Jafvert Conditions during cavitation. K.S. Suslick, W.B. McNamara III and Y. Didenko Microporous oxides as electrolytes in proton exchange membrane fuel cells. M.A. Anderson and M.I. Tejedor Intermission Redox transformation and bioavailability of mercury. F.M.M. Morel Degradation of methylmercury by OH radicals in natural waters. S.O. Pehkonen and C.Jing Concentrations and spatial variations of polybrominated diphenyl ethers in fish and air from the northeastern United States. R.A. Hites, N. Dodder and B.Strandberg Partitioning of anthropogenic and natural lead in soils. Y. Erel, S. Emmanuel, N. Teutsch, L. Halicz and A. Veron
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ABSTRACTS
Kinetics of surfactant degradation by sonolysis. Linda K. Weavers1, Maggie G. Y. Pee1 and James F. Rathman2; 1Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, 470 Hitchcock Hall, 2070 Neil Ave., Columbus, OH 43210, Fax: [phone], [e-mail]; 2Department of Chemical Engineering, The Ohio State University. The application of sonochemistry to the degradation of surfactants was explored in this study. The surface-active properties of t-octylphenoxy polyethoxyethanol (OPE) and 4-octylbenzene sulfonic acid (OBS) surfactants enhanced their degradation rate constants by a factor of 3 to 2, respectively, compared to two non-surfactant compounds, 4-nitrophenol and ethylbenzene sulfonate in a 20 kHz low power intensity reactor. Enhanced degradation was not observed in a high power intensity reactor at 20 kHz. Enhanced degradation of surfactants was attributed to the ability of surfactants to accumulate on cavitation bubble surfaces and faster growth of bubbles by rectified diffusion. The lack of enhanced degradation of surfactants in the probe was attributed to the higher power intensity resulting in rapid bubble growth cycles with insufficient time for surfactants to accumulate on the cavitation bubble surface.
Environmental photochemistry of decabromodiphenyl ether and related compounds. Inez Hua and Chad Jafvert; Environmental Engineering and Hydraulics, School of Civil Engineering, Purdue University, 1284 Civil Engineering Building, West Lafayette, IN 47906, Fax: [phone], [e-mail]. Decabromodiphenyl ether (DBDE) is a flame retardant currently under intense scrutiny. Once released into the environment, brominated flame retardants are very persistent, transforming slowly by physical, chemical, and biological processes. Photolysis studies are conducted with hydrated DBDE and selected lower congeners, including tetrabromodiphenyl ether and dibromodiphenyl ether. The substrates are adsorbed onto quartz particles and quartz cuvettes and irradiated under well-defined conditions of light intensity, wavelength, temperature, and soil phase characteristics. After 64 hrs of sunlight exposure in quartz tubes, approximately 50% of the DBDE remained. Irradiation was also performed (=250 - 400 nm) in a photochemical reactor, and decay of DBDE occurred much more rapidly. Bromide ion accumulates during photolysis with sunlight and in the photochemical reactor, and the bromide ion concentration approaches the theoretical maximum under the conditions of the photochemical reactor.
Conditions during cavitation. Kenneth S. Suslick, William B. McNamara III and Yuri Didenko; School of Chemical Sciences, University of Illinois, 600 S. Mathews, Urbana, IL 61801, [e-mail]. Sonoluminescence from cavitating clouds of bubbles ("multi-bubble sonoluminescence", MBSL) in room temperature liquids closely resembles flame emission. Effective emission temperatures have been obtained for MBSL from excited state metal atom emission (from sonolysis of several volatile metal carbonyls). From the relative intensities of multiple line emissions from Cr, Mo, and Fe, emission temperatures have been calculated and are all in close agreement with each other. The effects of bubble contents can alter the observed temperatures and this has been now directly observed for the first time. In addition, effective pressures can be estimated from line broadening and line shifts of the metal atom emission. The effective transient conditions formed during cavitation of bubble clouds under Ar in low volatility solvents are roughly 5000 K, 500 atm, which implies heating and cooling rates in excess of 110 K/s. The effect of polyatomic gas or vapor in the bubble have been probed and dramatically reduce the effective measured temperature in a manner quantitatively consistent with a very simple adiabatic compression model. The effect of thermal conductivity of the bubble contents on the measured temperature has also been determined and is found to be significantly less than prior calculations.
Microporous oxides as electrolytes in proton exchange membrane fuel cells. Marc A. Anderson and M. Isabel Tejedor; Water Chemistry Program, University of Wisconsin, 660 N. Park Street, Madison, WI 53706, [e-mail]. We have been investigating the physical and electrochemical characteristics of inorganic membrane materials composed of microporous SiO2, TiO2 and Al2O3. All of these materials have high surface areas and high porosity. The Al2O3 membranes materials can be described as having slit-like pores of width less than 20 angstroms. SiO2 and TiO2 membrane materials contain randomly packed spherical nanoparticles and pore size in the mesoporous region. Our calculations indicate that for our oxide samples equilibrated under conditons of 81% relative humidity and at 25C number the of water molecules contained as expressed in mmols/cm3 are 20, 26 and 25 for SiO2, TiO2 and Al2O3 respectively. Measured proton conductivities of all three oxides increase with increasing relative humidity, SiO2 and TiO2 increasing over 3 orders of magnitude between RH values of 33% and 97%. We also find that, at 81% RH, conductivies generally increase with increasing temperature with SiO2 increasing lineraly but TiO2 and Al2O3 exponentially. Activation energies for our materials are 15.8 , 17.0 and 17.1 kJ.Mol-1 for SiO2, TiO2, and Al2O3 respectively. While our best values for the conductivities of our inorganic electrolytes are still about a factor of two less than an organic polymer membrane such as Nafion (5 x10-3 cm-1 vs at 80C versus 1.3 x 10-2 cm-1 at 79C), it should be noted that we are comparing absolute values for the conductivity. In practice, these ceramic membranes would be cast unto porous conducting supports with thicknesses less than 0.5 micron. Nafion membranes are
typically around 200mm thick. This means that we should be capable of greatly reducing the actual resistance of these membrane electrolytes, and this, along with higher possible operating temperatures should prove to make these systems commercially competitive.
Redox transformation and bioavailability of mercury. Franois M. M. Morel; Department of Geosciences, Princeton University, Guyot Hall, Room 153, Princeton, NJ 08544, Fax: [phone], [e-mail]. Exchange with the atmosphere represents a critical part of the cycle of mercury in natural waters: elemental mercury, Hg(0), is volatilized while ionic mercury, Hg(II), is brought down by rain. The relative rates of the redox transformations and of volatilization of mercury in surface waters which lead to the formation and elimination of Hg(0) thus largely control the total concentration of mercury in a given body of water. In contrast, the bioaccumulation of mercury in the food chain depends on the rate of methylation which occurs in anoxic bottom waters and sediments. This methylation is effected by sulfate reducing bacteria and thus depends on the bioavailability of mercury in anoxic environments. New laboratory and field data on the rate of photooxidation of elemental mercury in surface waters and on the bioavailability and methylation of mercury in sulfidic water will be presented and discussed.
Degradation of methylmercury by OH radicals in natural waters. Simo Olavi Pehkonen and Chen Jing; Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore, Fax: [phone], [e-mail]. The degradation of methylmercury by OH radicals has been investigated. The identified products are Hg2+, Hg2Cl2 and formaldehyde. The degradation rate has been calculated to be 1.57(0.189)E+10 (using benzene as the scavenger to maintain a steady state OH radical concentration) and 1.03(0.103)E+10 (using 1-octanol as the scavenger). The effect of chloride concentration and pH has been investigated. Based on the typical OH radical concentrations in surface waters, the results indicate that degradation by OH radicals may be the dominant pathway of methylmercury photodegradation in sunlit surface waters.
Concentrations and spatial variations of polybrominated diphenyl ethers in fish and air from the northeastern United States. Ronald A. Hites, Nathan G. Dodder and Bo Strandberg; School of Public and Environmental Affairs, Indiana University, SPEA 410 H, Bloomington, IN 47405, Fax: [phone], [e-mail]. Brominated flame-retardants, such as polybrominated diphenyl ethers (PBDEs), are added to different materials to...