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The study provides insights into the silanisation process of sepiolite nanoparticles. The nanoparticles were modified applying acidic and basic silanisation methods using Methacryloxypropyltrimethoxysilane (g-MPS) as coupling agent. The silanisation reaction was performed in the following conditions: (1) acidic ethanolÀwater solution with a pH of 5 and (2) basic cyclohexane with a pH of 9. The influence of the conditions on the surface chemistry of modified particles was then investigated. To characterise the surface of sepiolite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-Ray diffraction (XRD), scanning electron microscopy (SEM), and zeta potential analyses were applied. In addition, the colloidal stability of the modified nanoparticles was studied using a separation analysis. According to XRD and SEM, the basal interlayer distance of pristine sepiolite is not altered by silanisation process. TGA reveals that the grafting percentage of organosilane synthesised by basic method is approximately two times of that of acidic method. The silane coverage on the surface of the sepiolite and the per cent of hydroxyl groups covalently bound to g-MPS were calculated. Separation analysis indicates decline in dispersion stability of the modified nanoparticles in ethanol due to increment of their hydrophobicity.

Molecular dynamics (MD) simulations were performed at 298.15 K and 1 atm in order to study microstructure and transport behaviors of polydimethylsiloxane (PDMS) membranes containing 0%–8% SiO2 nanoparticles used for the separation of thiophene from n-octane. It was found that the fractional free volume (FFV) of 0% SiO2 was the highest (47.24%) among five nanocomposite membranes and addition of 2%–8% silica nanoparticles led to dramatic decrease in the FFV of the cells. The x-ray diffraction (XRD) patterns of all membranes showed that they had a semi-crystalline structure containing a broad peak around 15°–18°. The radial distribution function (RDF) analysis proved that the smallest C(CH2-octane)–O(SiO2), C(PDMS)–O(SiO2) and H(thiophene)–O(SiO2) distances were present in 4% SiO2 membrane reflecting the silica–octane, silica–polymer and silica–thiophene interactions were the strongest in this membrane. The mean squared displacement (MSD) and diffusion coefficients of n-octane were both small in the 6% silica membrane but they were high for thiophene suggesting this membrane was the most suitable for the desulfurization process and separation of thiophene from n-octane.

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