Organically modified Urea-sepiolite to application in caffeine removal

This study aimed to assess the capacity of sepiolite (SEP) modified with Trietoxymethylsilanopropyl Urea (SEP-TEMSPU) to adsorb and remove caffeine from aqueous solutions. Powder X-ray diffraction (PXRD) revealed no increased basal spacing in the modified sepiolite proving that the clay present non-expansive characteristics. Thermal analyses (TG/DTG/DSC) for modified clay present a mass loss at 347.55 °C (7.86%), characteristic of the decomposition of organic matter resulting from TEMSPU, previously not observed for SEP. The infrared spectroscopy shows functionalization due to deformation vibrations of N-H bonds (1556 to 1263 cm-1) and NH (3341 cm-1) bonds in the urea. The C-H stretching at the propyl groups (2925-2921 cm-1) is also a good indication for the modification, since the sepiolite does not have any peaks around this region. The textural analyses confirmed functionalization of the natural sepiolite too, there was a decrease in the specific surface area from SEP (149 m².g-1) to SEP-TEMSPU (17 m².g-1) due to the presence of the organic groups of the alkoxy. The maximum adsorption capacity at equilibrium (Figure 1) indicate that the sepiolite and urea-sepiolite constitutes an efficients and suitables caffeine adsorbents.