Silica grafted with a silsesquioxane containing the positively charged 1,4-diazoniabicyclo[2.2.2]octane group used as adsorbent for anionic dye removal

The present study reports the development of an alternative adsorbent, based on silica modified with a water soluble silsesquioxane containing a double charged 1,4-diazoniabicyclo[2.2.2]octane, employed for removal of the dye brilliant yellow from aqueous solution. The dye removal ability of this adsorbent was determined by batch adsorption procedure. Effects such as pH value and adsorbent dosage on the adsorption capacity were studied. Four kinetic models were applied. The adsorption was best fitted to a fractionary-order kinetic model. The kinetic data were also adjusted to an intra-particle diffusion model resulting three linear regions, indicating that the adsorption kinetics follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models. The maximum adsorption capacity was 54 mg g−1.