Fe³⁺-bis-ethylenediamine complex bridged periodic mesoporous organosilica for the efficient removal of arsenate and chromate

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P><P>The direct removal of arsenate (AsO<SUB>4</SUB><SUP>3−</SUP>) and chromate (CrO<SUB>4</SUB><SUP>2−</SUP>) from water were achieved using a Fe<SUP>3+</SUP>-bis-ethylenediamine complex-bridged periodic mesoporous organosilica with a 20% organosilane content (Fe-EDPMO-20). The bridged Fe<SUP>3+</SUP>-bis-ethylenediamine complex was introduced to the pore wall of the PMO by combining the pre-complexation and co-condensation processes. N,N′-bis[3-(triethoxysilyl)propyl]ethylenediamine (TESEN) and tetramethyl orthosilicate (TMOS) as silica precursors were used with cetyltrimethylammonium bromide (CTABr) as a surfactant under basic conditions for the preparation of highly ordered Fe-EDPMO-20. Transmission electron microscopy, X-ray diffraction, and N<SUB>2</SUB>adsorption-desorption measurements confirmed that the Fe-EDPMO-20 had an ordered hexagonal p6mm mesostructure. The material had a Brunauer-Emmett-Teller surface area of 734 m<SUP>2</SUP>g<SUP>−1</SUP>, pore diameter of 2.6 nm, and pore volume of 0.61 cm<SUP>3</SUP>g<SUP>−1</SUP>. UV-vis and X-ray photoelectron spectroscopy confirmed that Fe<SUP>3+</SUP>was embedded in the coordination site by the nitrogen atoms from ethylenediamine. The adsorption efficiencies of arsenate and chromate ions by Fe-EDPMO-20 were examined as a function of pH, stirring time, amount of adsorbent, and initial concentration of metal ion solution. The maximum adsorption for arsenate and chromate were 156 and 102 mg g<SUP>−1</SUP>within 6 and 24 h, respectively, at pH 4.</P>