February 7, 2012
Title: Acid Ionization Constants, Electrostriction and Ionic Transport in D2O at Elevated Temperatures and Pressures. How is heavy water solution chemistry different from light water?
Abstract: Heavy water (D2O) provides an important tool for studying hydrogen-bonding and solvation effects in aqueous solutions. While deuterium isotope effects have been determined for many systems at 25 oC, there are only a handful of measurements on D2O systems at temperatures above 100 oC. Differences in the properties of heavy and light water at elevated temperature are of considerable fundamental interest. For example, the critical temperature of D2O (Tc = 370.9 C; pc = 21.67 MPa ) is 3.2 C below the critical temperature of H2O (Tc = 374.1 C; pc = 22.06 MPa ), even though it is a heavier molecule with triple point and boiling point several degrees higher than those of light water. Deuterium isotope effects are also important to carbon-free electricity production, because D2O is used as the heat transfer medium between the reactor core and steam generator in Canadian CANDU nuclear reactors. An accurate understanding of heavy water solvent isotope effects is required to optimize heavy-water pH (pD) and redox chemistry in primary coolant systems at temperatures between 250 and 320 C. This talk will present results from a long-term research project to measure and model the thermodynamic and transport properties of simple acids, bases and electrolytes in heavy water at high temperatures and pressures. The study uses a novel high-precision AC conductance instrument,1 vibrating-tube densimeter,2 UV-visible spectroscopy3 and Raman spectroscopy to determine the effect of D2O on the ionization constants of organic and inorganic acids and bases, pK = pKD2O - pKH2O up to 300 C. Thermally stable colorimetric indicators are being developed, to measure in situ pD at tempera tures up to 320 C, and we are working with colleagues at Thompson River University and St. Marys University to develop thermodynamic and ab initio models to predict pK at elevated temperatures. The limiting conductivities of a number of electrolytes in D2O and H2O, from these measurements, are being used as a probe to examine hydration and water structure effects up to sub-critical and supercritical conditions.
Biography: Dr. Peter Tremaine, FCIC, is a Professor in the Department of Chemistry at the University of Guelph, and former Dean of the College of Physical and Engineering Science (2001-2006). Before moving to Guelph, he was Head of the Department of Chemistry at Memorial University of Newfoundland (1990-1996), Manager of the AOSTRA In Situ Oils Sands Research Program, at the Alberta Research Council (1986-1990), and a Research Officer at both ARC (1980-1990) and Atomic Energy of Canada Ltd. (1975-1980). Tremaine's research is centered on the use of small-scale flow techniques for high-precision measurements on the properties of aqueous chemistry at very high temperatures and pressures. His work has had an impact on both underlying science and on applied problems in thermal and nuclear power generation, heavy oil recovery, geochemistry and materials science. His contributions to basic research have been recognized by his Fellowship in the Chemical Institute of Canada (FCIC) and the Calorimetry Conference Stig Sunner Award. Tremaines contributions to applied research have been recognized by his appointment as Honorary Fellow by the International Association of Water and Steam (IAPWS) and by the International Water Conference Paul Cohen Award. He is a former President of IAPWS, and has just completed a two-year term as Chair of the R & D Advisory Panel to the Board of Directors of Atomic Energy of Canada Ltd. He currently supervises a research group of six graduate students, three postdoctoral fellows and a research associate, who are engaged in fundamental and applied studies on the physical chemistry and geochemistry of aqueous solutes and materials in high-temperature water.
