Effect of polymerization degree of polyethylene glycol on microtopography and adsorbability of mesoporous η-Al₂O₃ fibers

The mesoporous η-Al₂O₃(PEG600)and η-Al₂O₃(PEG2000)fibers were synthesized by hydrothermal method, using polyethylene glycol (PEG)of different polymerization degree (PEG600 and PEG2000)as the templates, respectively. The prepared samples were characterized by XRD, TEM and N₂ adsorption, and the effect of polymerization degree of PEG on the properties of the mesoporous η-Al₂O₃ fibers was investigated. The absorption property of mesoporous η-Al₂O₃ fibers toward methylene blue was studied by static equilibrium adsorption experiments. The results show that both of the two templates can be used to synthesize the mesoporous η-Al₂O₃ fibers. It is found that the polymerization degree of PEG has great effect on mesoporous structure, surface area, pore volume and pore diameter. The surface area and pore volume of η-Al₂O₃(PEG600)are 189.899 m²·g^-1 and 0.329 cm³·g^-1, which are 1.4 times and 1.2 times of that of η-Al₂O₃(PEG2000), respectively. And the average pore diameter of η-Al₂O₃(PEG600) is also bigger than η-Al₂O₃(PEG2000). The adsorption mechanism of the two kinds of mesoporous η-Al₂O₃ fibers is multi molecular layer adsorption. According to the calculation of BET multi molecular layer adsorption equations, the equilibrium adsorption capacities of η-Al₂O₃(PEG600)and η-Al₂O₃(PEG2000)towards methylene blue are 256.391 3 mg·g^-1 and 204.045 9 mg·g^-1, respectively.