Uranyl Arsenate Complexes in Aqueous Solution: Insights from First-Principles Molecular Dynamics Simulations

Area of Science:

• Geochemistry
• Solution Chemistry
• Computational Chemistry

Background:

• Uranyl arsenate complexes are significant in environmental and nuclear waste contexts.
• Understanding their speciation and stability is crucial for predicting behavior in aqueous solutions.

Purpose of the Study:

• To elucidate the structures and acidity constants (pKa) of uranyl arsenate complexes.
• To determine the pH-dependent speciation of these complexes in solution.

Main Methods:

• First-principle molecular dynamics simulations were employed.
• Free energy and pKa calculations were performed to derive speciation-pH distributions.

Main Results:

• Stable uranyl arsenate complexes with U/As ratios of 1:1 and 1:2 were identified.
• Bidentate complexation between uranium (U) and arsenic (As) is highly favored.
• Specific uranyl arsenate species dominate across different pH ranges, from acidic to highly alkaline conditions.

Conclusions:

• The study provides detailed insights into uranyl arsenate complexation and speciation.
• These findings are vital for geochemical modeling and environmental risk assessment involving uranium and arsenic.