Thermal and electrochemical studies of the interaction of organophilic montmorillonite and chlorpyrifos

Abstract

This work investigates the thermal and electrochemical interaction of montmorillonite Clay (Mt) and a modified montmorillonite Clay (Mt-M) with a peptide sequence, which mimics the active site of the enzyme acetylcholinesterase, as well as their interactions with the chlorpyrifos pesticide. The methods used include thermal analysis techniques (DSC), X-ray diffraction, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrochemical study was carried out in KCl 0.1 mol L−1, pH 7, containing a redox species Fe(CN)6–3/−4. The electrode surface coverage (θ) was 0.42 for Mt and 0.65 for Mt-M. The interpretation of the electrochemical impedance spectroscopy results was based on the charge transfer reaction involving the [Fe(CN)6]−3/−4 species at high frequencies, followed by diffusion through the monolayer at low frequencies. The heterogeneity of the Mt and Mt-M film formed on electrode surface limits the transport of [Fe(CN)6]−3/−4 through the montmorillonite layer since the Mt particles formed non-regular overlapping plates, observed under microscopy. The DSC analyses revealed disorganization in the structure of the organophilic clay with the insertion of the pesticide, reflected in the appropriate waters of the system.