Characterization of montmorillonites modified with organic divalent phosphonium cations: Fid-Bau Portal

Characterization of montmorillonites modified with organic divalent phosphonium cations

Ezquerro, Carlos Sáenz / Ric, Gemma Ibarz / Miñana, Cristina Crespo / Bermejo, Javier Sacristán

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.

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Highlights • Montmorillonite was modified with a compound consisting of two phosphonium groups. • After the modification, a hydrophobization of the montmorillonite was achieved. • The basal space increased due to the intercalation of phosphonium derivative. • EDX is a complementary technique to TGA in order to determine exchange efficiency. • A fraction of the surfactant was incorporated by means of physical adsorption.