A Molecular Dynamics Investigation of the Titration of a Trivalent Aqueous Ion

Journal Article · Wed Mar 01 00:00:00 EST 2006 · Theoretical Chemistry Accounts (Print)

DOI:https://doi.org/10.1007/s00214-005-0048-2· OSTI ID:921593

Rustad, James R; Casey, William H

We carried out a series of molecular dynamics simulations of the hydrolysis of a model trivalent metal ion in aqueous solution. We use a dissociative model for water and examine the spontaneous speciation of M³⁺ into M(OH)_n^(3-n)+(n = 1, 4) both in neutral solution and as a function of added protons and hydroxide ions. The species distributions in neutral solution correspond reasonably well with those expected for real trivalent metal ions at neutral pH. However, the change in the species distributions as a function of either added protons or hydroxide ions is much less than expected with very large concentrations of protons or hydroxide ions required to shift the species equilibria in either direction. The influence of added protons and hydroxide ions on the species distributions appears to be proportional to the average charge of the hydrolysis couples, being highest for the 3+/2+ couple and lowest for the 1+/0 and 0/1- couples. Proton exchange rates varywith proton/hydroxide ion concentration giving a minimum at intermediate values ([H+]≈ 0.166) with increasing rates at both lower and higher pH

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 921593
• Journal Information: Theoretical Chemistry Accounts (Print), Vol. 115, Issue 2; ISSN 1432-881X
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AQUEOUS SOLUTIONS
FOREIGN EXCHANGE RATE
HYDROLYSIS
HYDROXIDES
PROTONS
TITRATION
WATER
Environmental Molecular Sciences Laboratory