Affordable phosphonic- and phenyl-functionalized silicate adsorbent for metal and dye cations uptake

A mesoporous sample of SBA-15 type was prepared by co-condensation of sodium metasilicate as a structure-forming reagent and silanes with phosphonic and phenyl groups. The proposed synthesis approach involves a minimum of stages during template synthesis to produce bifunctional material. Physicochemical methods have shown that the sample has an ordered mesoporous (4.4 nm) hexagonal structure and contains 0.41 × 10 –3 mol/g of ion-exchange phosphonic groups, as well as phenyl groups. The benefits of incorporating such diverse groups which are capable of different types of adsorbate interactions have been demonstrated in the adsorption of Eu(III) (70.3 mg/g) and methylene blue (MB) (200 mg/g) cations. It was determined that the Eu(III) ions adsorption equilibrium was established within 1 h, while for MB—within 16 h. Kinetics data were best fitted by the pseudo-second order equation indicating several mechanisms that control the rate of sorption removal of cations. IR spectra and compliance of Eu(III) and MB sorption isotherms with the Langmuir adsorption model prove chemisorption. Still, the ratio between the content of phosphonic groups and adsorbed cations represents the existence of additional interactions. Such types of mesoporous silica materials have been shown to be promising for application in water treatment.