Characterization of montmorillonites modified with organic divalent phosphonium cations

Abstract Montmorillonite was surface modified by the cation exchange method with o-xylylenebis(triphenylphosphonium bromide) (Dim-Br), a compound consisting of two phosphonium groups. The modification yield of the exchange reaction was characterized by means of several analytical methods (Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and thermogravimetry analysis (TGA)). The obtained organoclays (OC) exhibited higher thermal stability than the pristine montmorillonite due to the hydrophobization effect that produced the organic modification with Dim-Br. The basal space determined by means of X-ray diffraction (XRD) increased gradually with surfactant concentration, until it reached a maximum, and was well correlated with the organic content of the modified montmorillonites. Moreover, EDX results showed that with increasing surfactant concentration, the sodium content corresponding to the unmodified surface decreased and the phosphorus content related to the modifier increased. EDX technique is proposed as an additional analytical tool that might be applied in the chemical characterization of modified nanoclays.