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

Abstract

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 M 3+ 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

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
921593
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Theoretical Chemistry Accounts (Print); Journal Volume: 115; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AQUEOUS SOLUTIONS; FOREIGN EXCHANGE RATE; HYDROLYSIS; HYDROXIDES; PROTONS; TITRATION; WATER; Environmental Molecular Sciences Laboratory

Citation Formats

Rustad, James R, and Casey, William H. A Molecular Dynamics Investigation of the Titration of a Trivalent Aqueous Ion. United States: N. p., 2006. Web. doi:10.1007/s00214-005-0048-2.
Rustad, James R, & Casey, William H. A Molecular Dynamics Investigation of the Titration of a Trivalent Aqueous Ion. United States. doi:10.1007/s00214-005-0048-2.
Rustad, James R, and Casey, William H. Wed . "A Molecular Dynamics Investigation of the Titration of a Trivalent Aqueous Ion". United States. doi:10.1007/s00214-005-0048-2.
@article{osti_921593,
title = {A Molecular Dynamics Investigation of the Titration of a Trivalent Aqueous Ion},
author = {Rustad, James R and Casey, William H},
abstractNote = {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},
doi = {10.1007/s00214-005-0048-2},
journal = {Theoretical Chemistry Accounts (Print)},
number = 2,
volume = 115,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2006},
month = {Wed Mar 01 00:00:00 EST 2006}
}