Fast adsorption of p-nitrophenol from aqueous solution using β-cyclodextrin grafted silica gel

Renewable β -cyclodextrin ( β -CD) was grafted onto the surface of silica gel using (3-chloropropyl)trimethoxysilane and ethylenediamine as linking groups to construct adsorbent in water treatment (CD@Si), and the obtained CD@Si was characterized through FT-IR, XPS, contact angle measurement, TGA, solid-state 13 C NMR, SEM, and XRD analyses. The effects of initial pH, contact time on the adsorption performance of CD@Si to p -nitrophenol, and the adsorption kinetics, adsorption isotherms, adsorption thermodynamics, reusability and adsorption mechanism were investigated systematically, which indicate the adsorption of p -nitrophenol onto CD@Si is a very fast process and the adsorption equilibrium can be reached in 5   s with acceptable equilibrium adsorption capacity of 41.5   mg/g in pH ≥8.5, much faster than many reported adsorbents based on β -CD. The adsorption of p -nitrophenol onto CD@Si follows the pseudo-second-order model, obeys the Freundlich model, and is a feasible, spontaneous and exothermic process which is more favorable in lower temperature. And the formation of inclusion complex and hydrogen bond interaction are two origins of p -nitrophenol being adsorbed onto CD@Si. Additionally, CD@Si can be recycled and reused at least five runs with acceptable adsorption capacity, is a very promising adsorbent in the fast adsorption of p -nitrophenol or its analogues from aqueous phase.