Synthesis of bifunctional mesoporous silica spheres as potential adsorbent for ions in solution

The immobilization of EDTA on Si–APTS composite was observed to occur in a stoichiometric relation of 2(APTS):1(EDTA) with a degree of functionalization of 0.56 mmol g−1. Based on IR and NMR data it was suggested that the immobilization results in a cavity with four nitrogen atoms inside and two carboxylate groups outside. Surface area, total pore volume and average pore diameter, of the Si–APTS–EDTA spheres were determined, respectively, as 177.6 m2 g−1, 0.35 cm3 g−1 and 73.6 Å. Zeta potential (PZC = 5.0) and adsorption assays indicated a potential applicability of the Si–APTS–EDTA spheres as a bifunctional material since it was observed the adsorption of cations and anions.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The immobilization of EDTA on Si–APTS composite was observed to occur in a stoichiometric relation of 2(APTS):1(EDTA). ► IR and NMR data suggest a cavity-like structure with four nitrogen atoms inside and two carboxylate groups outside. ► Adsorption assays for ions indicated a potential applicability of the Si–APTS–EDTA spheres as a bifunctional material.