Urea-containing mesoporous silica for the adsorption of Fe(III) cations

A urea-containing mesoporous silica with intraframework urea groups ( UreaMS) was synthesized via a surfactant-templated route by co-condensation of an organosilane precursor and tetraethoxysilane. The material possesses hexagonal pores with a high degree of uniformity and shows long-range order as confirmed by the measurement of powder X- ray diffraction and N-2 adsorption isotherms. A detailed characterization by chemical analysis, Si-29 MAS NMR, X- ray photoelectron spectroscopy, thermogravimetric analysis, and FT- IR spectroscopy confirmed the integrity of urea groups inside the walls of the material. The results revealed a density of one urea group per ca. 13- 16 silicon atoms. The efficiency of UreaMS for the adsorption of Fe( III) cations was tested. A distribution coefficient of K-d = 700 mL g(-1) and an adsorption capacity of 0.19 mmol g(-1) were determined. X- ray photoelectron spectroscopy confirmed the conservation of the oxidation state + 3 for the iron within the mesoporous silica material.