Surfactant-Encapsulated Polyoxometalate Compound With Two Morphologies

In this paper, we successfully synthesized two morphologies of surfactant-encapsulatedpolyoxometalate (POM) complexes by electrostatic interaction. POMs with Keggin structure(α-K4SiW12O40) have been interacted with cetyltrimethylammonium bromide (CTAB) tofabricate two inorganic-organic hybrid functionalized materials,cetyltrimethylammonium-encapsulated α-K4SiW12O40(CTA-SiW12) microtubes and powder.Synthetic methods were very facile and green. The two complexes were characterized byelemental analysis, emission environmental scanning electron microscope (SEM), infraredspectroscopy (IR), X-ray powder diffraction (XRD), and thermogravimetric analysis (TGA)measurements.Amazingly, in the ethanol solution, adsorption rate of powder was more than40timesfaster than the microtubes, but adsorption capacity of CTA-SiW12microtubes and CTA-SiW12vesicles was almost consistent (91%). however, we found the similar results was obtained inthe mixed solution of water and ethanol (volume ratio=9:1). These are due to two reasonsbelow. Firstly, adsorption rate of powder is much faster than the microtubes due to a higherproportion of surfactant and a relatively larger specific surface area for the powder; Secondly,adsorption capacity of CTA-SiW12microtubes and CTA-SiW12powder is almost consistentdue to a steric hindrance on the powder surface. So CTA-SiW12powder is a small particle thatadsorption capacity for small organic molecules is restricted. The adsorption rate was slowerin the mixed solution than in the ethanol solution, which due to the high polarity of watermolecules. There is larger repulsive force between the water molecules and complexes in themixed solution, so the final adsorption rate and adsorption capacity is less than in the ethanolsolution.Thus it can be seen, the organic-inorganic composite material have a lot of advantages asadsorbents for the MB ethanol solution. Obviously, the above-mentioned adsorption processhas a certain application value in dispose of sewage and decoloration in the ethanol and watersolution.