GWC2 Wednesday Afternoon Research Seminars: Peter Tremaine

Wednesday, October 20, 2021 3:00 pm - 3:00 pm EDT (GMT -04:00)

Deuterium isotope effects on acid-base ionization and metal hydrolysis equilibria in high temperature water up to near-critical conditions

Peter Tremaine
Department of Chemistry
University of Guelph

Wednesday, October 20, 2021
3:00 p.m.
Online via Microsoft Teams

Please contact with your Teams ID/email address to attend the seminars. 
All are welcome to attend!

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 = 374.9 ; pc = 22.06 MPa ), even though it is a heavier molecule. 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 pressurized heavy water reactors. Quantitative understanding of heavy-water solvent isotope effects is required to optimize heavy-water pH (“pD”) and redox chemistry (D2 concentration) in primary coolant systems at temperatures between 250 °C and 320 °C. This talk will present recent results from a long-term research project to measure and model the thermodynamic and transport properties of simple acids and bases in heavy water. The project is aimed at predicting accurate metal hydrolysis constants and oxide solubilities at high temperatures and pressures. Our most recent studies use a novel high-precision AC conductance instrument,1 Raman spectroscopy3,4 and computational (DFT) methods5 to determine the effect of D2O on the ionization constants of acids and bases, ΔpK = pKD2O - pKH2O, from 25 to 300 °C. The limiting conductivities of a number of electrolytes in D2O and H2O from these measurements, λ°, are being used as a probe to examine proton hopping, hydration and “water structure” effects up to sub-critical and supercritical conditions.