Silanization of sepiolite with various silane coupling agents for enhancing oil uptake capacity

Eskisehir sepiolite (SEP) was given a hydrophobic surface through acid treatment followed by silanization. The silanization process was realized with trimethoxy(octadecyl)silane (TMODS), (3-aminopropyl)triethoxysilane (APTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS) coupling agents. The effects of temperature and reaction time on the silanization degree were studied within the ranges 25–50°C and 2–48 h, respectively. The efficiency of silanized SEP as an oil absorbent was investigated in pure olive oil media. The structural changes in sepiolite samples were monitored by X-ray diffraction (×RD), N2 adsorption (BET), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Fourier Transform Infrared spectroscopy (FTIR). Accordingly, maximum organic loading was achieved as 20.6% (w.) corresponding to 0.69 mmol silane/g SEP, when silanization was conducted with TMODS at 50°C for 24 h. Acid activation with hydrochloric acid removed the dolomite fraction and thus was in favor of silanization. The oil uptake capacities followed the order: GPTMS modified acid-activated SEP > APTES modified acid-activated SEP> TMODS modified acid-activated SEP > acid-activated SEP > SEP reaching as high as 2.77 ± 0.01 g/g at utmost. The augmentation in oil uptake capacity was not solely related to increased hydrophobicity, but also to altered surface area and porosity. Absorbed oil was recoverable at nearly 90% after three absorption – desorption cycles.