Stability of Tetrabutylphosphonium Beidellite Organoclay

Organoclays originating by interaction of clays with organic cations/molecules are important in industrial processes for their physicochemical properties. The beidellite (Bd) mineral is an interesting material, e.g., as a potential sorbent of waste and pesticides. For this reason, its behavior at the atomic scale is of great interest. The DFT method is used to investigate the stability of Bd intercalated with a tetrabutylphosphonium cation (TBP). The interlayer distances (d₀₀₁) of the proposed models agree well with the experimental values. The ab initio molecular dynamics (AIMD) is successfully employed in a detailed explanation of the experimental FTIR spectrum of the TBP-Bd which has a complicated structure with overlapped bands. Detailed analysis of the present hydrogen bonds and calculated intercalation energies shows that the TBP-Bd is a highly stable intercalate. Its stability decreases with growing amount of water, but the high stability is still preserved (−87.5 kJ mol^–1).