Heterogeneous precipitation of barium sulfate (barite) is an important geochemical process and a technological problem in the petroleum industry. The fundamental physical chemistry of this process must be understood at a molecular level in order to make predictions of behavior in the environment and to design strategies for pipe scale prevention. This work uses periodic density functional theory (DFT) calculations in the Vienna Ab-initio Simulation Package (VASP) to model Ba2+ and SO42- ions in various states at the quartz (101)-water interface. The purpose of this work is to connect the molecular structure with the thermodynamics of BaSO4 in solution, in ion pairs near a surface and as a precipitate on the surface. In addition, we plan to use these DFT results to help parameterize tight-binding DFT calculations for simulations of larger scale models. Models of Si72O144 + 4Ba2+ + 4SO42- + 57H2O and Si216O432 + 2Ba2+ + 2SO42- + 203H2O were constructed to investigate the relative energy differences among configurations with Ba2+ and SO42- in solution, as adsorbed species both as individual ions and as ion pairs and as a monolayer of BaSO4 on the quartz (101) surface.

Density functional theory modeling of Ba2+ and SO42- adsorption onto the quartz (101) surface

ACS Spring Meeting 2021

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