Immobilisation of diuron herbicide employing smectites

The beidellite (Bd) and montmorillonite (Mt), clay minerals proposed as suitable adsorbents of the diuron (D) herbicide with a high toxic potential for animals and the environment, were studied by both theoretical and experimental approaches. The ab initio Density functional theory method with involved dispersion corrections according to the D3 scheme (DFT-D3) was employed together with the experimental techniques to examine the D-Bd/Mt complex structures. Further, the Density Derived Electrostatic and Chemical approach (DDEC6) method and the electron location function (ELF) were used to study the interactions between the D and Bd/Mt clays through the examination of different electron density distribution onto unmodified and organically modified clay surfaces. The four systems, the D-Bd, D-Mt and D in the modified Bd/Mt clays by tetramethylphosphonium cation (TMP), the D-TMP-Bd and D-TMP-Mt, were studied. The calculations have shown that the diuron molecule presented a planar arrangement in the interlayer space of both smectites. Furthermore, the higher stability of the diuron adsorbed on Bd was revealed. The presence of organic surfactant significantly increased the stability of D-smectite systems (e.g.,-118.7 kJ mol(-1) in the D-Bd and -258.5 kJmol(-1) in the D-TMP-Bd).