Factors influencing interactions of organophosphorus pesticides with montmorillonite

• Published in: Geoderma 1983-02, Vol.29 (2), p.107-118
• Main Authors: Sánchez Camazano, M., Sánchez Martín, M.J.
• Format: Article
• Language: English
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(83)90035-6

A summary is made of the results obtained from the study of the adsorption and interaction mechanisms of a series of organophosphorus pesticides (phosphates, phosphorothiolates, phosphorothionates and phosphorothiolothionates) with montmorillonite, with the aim of establishing relationships between the chemical structure of these compounds and the adsorption and interaction mechanisms with this clay. Many of the organophosphorus pesticides studied are adsorbed into the interlayer space of montmorillonite. The intercalation causes different degrees of expansion (different types of complexes) principally as a function of the chemical structure of the organic compound. The presence in the organic molecules of the P0 and PS groups and the size and composition (functional groups present) of the radicals are the two most important factors. Both the nature of interlayer cations and the previous hydration status of montmorillonite influence adsorption. In some cases the polarizing power of the interlayer cation is a conditioning factor of the degree of interlayer expansion, whereas in others the cation charge is responsible for this. Results of infrared spectroscopy show that interaction is of the dipole ion type and that it depends on the presence of the P0 or PS group in the molecule and also on the functional groups present in the side chains. These factors, together with the situation of these latter groups in the side chains, condition the arrangement adopted by the molecules of a pesticide in the interlayer space.