Preparation and functionalization of DE with APDMS

Amine-functionalization of the diatomaceous earth (DE) was performed via a silanization process in which the surface of the DE reacted with the amine group on silane using APDMS (97%, Sigma-Aldrich St. Louis, MO, USA). Biocompatible DE mineral powder (18 μm; Sigma-Aldrich) was washed with distilled water (DW) for 10 min with vigorous stirring. Impurities were removed after brief gravity settling of the mixture. After being washed with 99% ethanol and DW with stirring, clean DE was collected by centrifugation. Two grams of the DE sample was suspended in 25 mL of toluene and stirred for 1 h at 60 °C, and then 0.5 mL of DW was added to this mixture, which was then stirred for 1 h at 65 °C. Subsequently, 1 mL of APDMS was added dropwise to the mixture and stirred for 1 h at 65 °C. The APDMS-DE was collected by centrifugation and washed several times with isopropanol and toluene. Subsequently, the functionalized AD was dried to a desiccator at ambient temperature in a vacuum.