Solid-phase synthesis of amphiphilic dendron-surface-modified silica particles and their application toward water purification

Surface modification of silica particles by an amphiphilic poly(amido amine) (PAMAM) dendron and investigation of their advanced application toward water purification have been demonstrated. The amphiphilic dendron-surface-modified silica particles (C18GnS, n = 1-3) were prepared by solid-phase synthetic strategy including the propagation of PAMAM dendrons on silica surface through conventional divergent pathway and the end-group functionalization of dendrons by long aliphatic chains. Infrared absorption analyses confirmed the characteristic vibration modes of amide and methylene groups on the dendritic backbone and long alkyl peripherals, respectively. The gradual increasing amount of organic grafts determined by thermogravimetric and elemental analyses also supported the successful modification of amphiphilic dendron on the silica surface. C18GnS effectively adsorbed anionic targets such as organic dyes and surfactants in water, and the adsorption behavior obeyed a Langmuir adsorption isotherm. Moreover, the adsorption isothermal studies indicated that adsorption of surfactants on C18GnS was due to the assistance of hydrophobic interaction between the aliphatic peripherals on the dendron and the alkyl tail on the surfactant, while the electrostatic interaction with C18GnS mainly played a role for the adsorption of dyes. Anionic adsorbates were released from C18GnS in an alkaline environment because of the pH-dependent nature of PAMAM dendron, and thus the surface-modified silica particles were recovered and reused.