Effect of cationic surfactant HDPy+ on the acidity and hydrophilicity of Tunisian clay

Abstract Surfaces of Tunisian montmorillonite clays were modified using batch method through intercalation of cationic surfactant hexadecylpyridinium (HDPy+) by an exchange reaction. The structural, textural and surface properties of clays, before and after modification, were investigated using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Specific Surface Area (BET method) and Differential Scanning Calorimetry (DSC). XRD patterns showed that the interlayer spacing expanded from 12.31 to 44.51 A as HDPy concentration was increasing. These results were confirmed by the changes in frequencies and intensities of symmetric and antisymmetric stretching bands of CH2 at 2852 and 2922 cm−1 showed in FTIR specta. The decrease of the specific surface area from 109 to 0.85 m2/g was explained by the compact packing of the surfactant between the aluminosilicate sheets. DSC data showed better thermal stability with an amount of HDPy+ adsorbed equivalent to 1.0 time the cationic exchange capacity (CEC) of purified clay. The uptake of cationic surfactant which exceeded the CEC of montmorillonite led to the exposure of HDPy+ polar head, consequently, acid-base potentiometric and contact angle indicate more positive surface charge with increasing of surfactant concentration.