Silanization of natural Na+-maghnite algerian clay pre-intercalated with a cationic alkylphosphonium salt

Abstract

In this investigation sodium Maghnite (Na+-Mag) clay was functionalized by the combination of two consecutive treatments. The first treatment was the intercalation of the clay by means of a cationic surfactant; namely: 1-butyl (triphenyl)phosphonium chloride (BTPPC). In the second step, the alkylphosphonium-modified clay was functionalized with three silane coupling agents; namely: N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), 3-methacryloxypropyltrimethoxysilane (MPTMS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) in order to introduce functional groups on the silicate layers. The modified clays were fully characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), solid state 29Si NMR and contact angle measurements. The FT-IR results demonstrated the presence of alkylphosphonium cations and the grafting of the silane coupling agents on the clay surface. The XRD analysis showed an increase of the d001 value with the introduction of alkylphosphonium cations (d-value∼2 nm). Nevertheless, no variation of the interlayer distance was observed after the silanization processes. Furthermore, the TGA characterization indicated a successful intercalation and silanization of the clay. The 29Si NMR analysis of the different modified materials showed the presence of two additional resonance signals T3 and T2 corresponding to [RSi*(OSi)3] and [RSi*(OSi)2(OH)] species respectively, which confirmed the successful grafting of the silanes on the clay surface. The contact angle results revealed that the polar and specific components of the surface energy of the clay can be enhanced after the silanization treatment.