Adsorption of hazardous and noxious 4-nitrophenol by a silsesquioxane organic-inorganic hybrid material

This paper reports the synthesis and characterization of a silsesquioxane polymer based on a rigid silica inorganic core and 3-n-propyl(4-methylpyridinium) organic linker (Si-4Pic+Cl‒), an organic–inorganic hybrid material which showed great potential for the application as an adsorbent for 4-nitrophenol (4-NP), a hazardous organic compound. The silsesquioxane material was fully characterized by ATR-FTIR, solid-state 13C-NMR, and 29Si-NMR, TGA, potentiometric chloride titration and carbon, hydrogen, and nitrogen elemental analyses (CHN). The effect of pH, contact time on adsorption performance of Si-4Pic+Cl‒ to 4-NP and heterogeneous adsorption equilibrium were investigated systematically. The remarkable adsorption affinity of 4-NP onto Si-4Pic+Cl‒ obeys the Langmuir model and a π–π stacking interaction between adsorbent and adsorbate was proposed. Cycle rate experiments demonstrated that the ability to be recovered and reusable at least three times makes this silsesquioxane material a very promising adsorbent of noxious 4-NP in aqueous media.