Understanding how cadmium adsorbs to mineral surfaces could aid in the attenuation of Cd2+ at hazardous waste sites. In this work, we used planewave density functional theory calculations on periodic structures of kaolinite (100) and gibbsite (100) to determine the energy differences among Cd2+ adsorption modes such as monodentate mononuclear, bidentate mono or binuclear, or out sphere. Water density in the models was set to 1g per cm3. The models were initially energy minimized, then they were subjected to 18-20 ps MD simulations to further relax their structures; the relaxed models were again energy minimized to obtain their final structures and energies. The calculated vibrational frequencies were used to obtain free energy corrections for the calculated electronic energies, and the energy differences among the models were used to predict which adsorption mode(s) were more thermodynamically favorable. In addition, structural properties of the models were compared with XAFS and XANES data to further verify the precision of the models.

Use of DFT thermodynamics calculations to better understand how Cd2+ adsorbs to kaolinite (100) and gibbsite (100) surfaces

251st National Meeting (2016)

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