Acid Rain and Flue Gas: Quantum Chemical Hydrolysis of NO2

Abstract

Despite decades of efforts, much is still unknown about the hydrolysis of nitrogen dioxide (NO2), a reaction associated with the formation of acid rain. From the experimental point of view, quantitative analyses are hard, and without pH control the products decompose to some reagents. We resort to high-level quantum chemistry to compute Gibbs energies for a network of reactions relevant to the hydrolysis of NO2. With COSMO-RS solvation corrections we calculate temperature dependent thermodynamic data in liquid water. Using the computed reaction energies, we determine equilibrium concentrations for a gas-liquid system at controlled pH. For different temperatures and initial concentrations of the different species, we observe that nitrogen dioxide should be fully converted to nitric and nitrous acid. The thermodynamic data in this work can have a potential major impact for several industries with regards to the understanding of atmospheric chemistry and in the reduction of anthropomorphic pollution.