Synthesis of sulfated zirconium supported MCM-41 composite with high-rate adsorption of methylene blue and excellent heterogeneous catalyst

Abstract

Zirconia-based mesoporous MCM-41 was successfully prepared then loaded with different content of sulfate (5, 10, 15, 25, 40 and 50 wt.%) through the wet impregnation method. The prepared samples were characterized by numerous methods like N2 adsorption (T= - 196 °C), FT-IR, XRD and TEM images. FTIR spectra of chemically adsorbed pyridine and non-aqueous potentiometric titration were applied to measure the acidity of SO42−/ZrO2@MCM-41 (SZ/MCM-41) catalysts. XRD results showed that the lattice cell parameter (a0) is increased from 37.8 to 39.5 Ǻ with increasing the sulfate content. TEM images of SZ/MCM-41 samples exhibit ordered arrays of mesoporous structure with light and dark contrast and also the formation of nanorods with a diameter of 50 nm. The resulting materials showed a large surface area with a uniform pore diameter distribution. All samples displayed both Lewis and Brønsted acid sites. The catalytic activity of SZ/MCM-41 samples was examined for the preparation of 7-hydroxy-4-methyl coumarin which dramatically enhanced when compared with MCM-41 and Z/MCM-41 and the reaction continued efficiently with a yield of 99.3–89.8 % after reused four times. Furthermore, the adsorption behavior of as-synthesized samples was examined over methylene blue (MB) in the aqueous solution with varying parameters such as dye concentration, pH of the solution and contact time. The prepared samples have a good ability to eliminate the methylene blue from aqueous solution with adsorption capacity equal to 186 mg/g and the equilibrium time of 60 min.