Synthesis of 12-tungestophosphoric acid supported on Zr/MCM-41 composite with excellent heterogeneous catalyst and promising adsorbent of methylene blue

In this study, zirconia-supported mesoporous MCM-41 composite was synthesized through the surfactant-assisted sol-gel technique. Then, different weight percentages of phosphotungstic acid (PTA) were loaded over Zr-MCM41 composites by wet impregnation method. The composites were characterized by different techniques like TEM, XRD, FTIR, and N2 adsorption isotherms (BET). Potentiometric titration was used to study the surface acidity of the prepared catalysts, while pyridine adsorption was used as a probe molecule to distinguish between Bro center dot nsted and Lewis acid sites. Characterization techniques reveal that the insertion of PTA and ZrO2 improved the acidic strength and surface acidity of mesoporous MCM-41. The catalytic performance of the composites was studied through the synthesis of 7-hydroxy-4-methyl coumarin. Both catalytic activity and surface acidity raised sharply after addition of PTA and 25.0 wt% PTA/Zr-MCM-41 displayed the highest catalytic activity and surface acidity. As well as, the adsorption activity of PTA/Zr-MCM-41 composites was tested in the removal of Methylene Blue (MB) from an aqueous solution. Among the synthesized composites, 25.0 wt% PTA/Zr-MCM-41 has a maximum adsorption capacity equal 259.1 mg/g at pH = 10.0. The adsorption and kinetics data are well fitted with Langmuir isotherm model and pseudo-second-order model.

Automated summary

The insertion of phosphotungstic acid (PTA) and zirconia (ZrO2) into mesoporous MCM-41 significantly improved the acidic strength and surface acidity of the composite material. After determining the optimal catalytic activity and surface acidity of 25.0 wt% PTA/Zr-MCM-41, adsorption experiments revealed that this composite has high adsorption capacity for Methylene Blue (MB).