Swellable hybrid silicas for the removal of rhodamine B dye from aqueous phase

This study is focused on the use of a hybrid organic-inorganic silica (Silica-SOM) for the removal of Rhodamine B dye (RhB) from water media. Because of its hybrid structure, Silica-SOM has the unique property of being swellable in the presence of an organic solvent, thus increasing the volume available for pollutants adsorption. The adsorption capacity of the Silica-SOM to adsorb RhB from water media has been determined. In particular, if the material is previously swollen with an organic solvent, it is able to sequester more than 99 % of dye molecules in a 1.0 x 10-5 M RhB solution in less than 1 h at ambient conditions. In addition, the ability of Silica-SOM to be re-generated by mild sonication in ethanol after one RhB adsorption cycle was tested for the first time: the material was easily regenerated and used for six consecutive adsorption cycles; in each of them there is no loss in adsorption performance, which remains quantitatively high and extremely fast.