Isomorphous substitution of Zr in the framework of aluminosilicate HY by an electrochemical method: Evaluation by methylene blue decolorization

Isomorphous substitution of Zr in the framework of aluminosilicate HY occurred during the preparation of electrogenerated zirconia supported HY (EGZrO2/HY) catalyst via a simple electrochemical method. Dealumination accompanied by an ion exchange with Zr4+ formed SiOZr bond, which controlled the formation of active species EGZrO2 that influenced the efficiency of the photodecolorization of methylene blue (MB). An amount of 0.375 g L−1 1 wt% EGZrO2/HY was found to be the optimum dosage for 10 mg L−1 MB, which resulted in 97% decolorization after 6 h of contact time at pH 11. The kinetics study indicates that the reaction follows the Langmuir–Hinshelwood model, where the reaction may occur both on the surface of the catalyst and in the bulk solution. The mineralization of MB was measured by removal of chemical oxygen demand (COD), five days biochemical oxygen demand/chemical oxygen demand (BOD5/COD), and total organic carbon (TOC/TOC0), and the results obtained were 95%, 7.14, and 0.08, respectively. After five cycling runs, the catalyst was still stable and showed no leaching effect. This study is believed to be extendable to the synthesis of other catalysts with different characteristics and be used in various applications.

.Figure optionsDownload as PowerPoint slideHighlights
► Electrochemical method can generates nanosize zirconia in average of 8–18 nm.
► Isomorphous substitution of Al with Zr was taken place.
► A new structural model for EGZrO2/HY is proposed.
► SiOZr bonds were formed as evidenced by MAS NMR, XPS, and IR.
► 1 wt% EGZrO2/HY exhibited the best performance for the photodecolorization of MB.