In this work, photoactive nanocomposites of ZnO/SiO2 porous heterostructures (PCHs) were prepared from montmorillonite clay. The effects of preparation methods and Zn content on the physicochemical features and photocatalytic properties were investigated. Briefly, a comparison of the use of hydrothermal and microwave-assisted methods was done. The Zn content was varied between 5 and 15 wt% and the characteristics of the nanomaterials were also examined. The physical and chemical properties of the materials were characterized using X-ray diffraction, diffuse-reflectance UV-Vis, X-ray photoelectron spectroscopy, and gas sorption analyses. The morphology of the synthesized materials was characterized through scanning electron microscopy and transmission electron microscopy. The photocatalytic performance of the prepared materials was quantified through the photocatalytic degradation of methyl violet (MV) under irradiation with UV and visible light. It was found that PCHs exhibit greatly improved physicochemical characteristics as photocatalysts, resulting in boosting photocatalytic activity for the degradation of MV. It was found that varied synthesis methods and Zn content strongly affected the specific surface area, pore distribution, and band gap energy of PCHs. In addition, the band gap energy was found to govern the photoactivity. Additionally, the surface parameters of the PCHs were found to contribute to the degradation mechanism. It was found that the prepared PCHs demonstrated excellent photocatalytic activity and reusability, as seen in the high degradation efficiency attained at high concentrations. No significant changes in activity were seen until five cycles of photodegradation were done.
Microwave-assisted synthesis method was applied for producing porous clay heterostructure-Zn/Si heterostructure from Indonesian natural montmorillonite. The porous montmorillonite heterostructure was prepared by previously intercalating cetyl trimethyl ammonium as templating agent and surfactant, and trimethyl ammonium hydroxide as co-surfactant, followed by the introducing Zn–Si precursor solution for the sol-gel reaction of porous formation. The comparison of the use of microwave-assisted synthesis and hydrothermal method for the porous formation was studied. Physicochemical characterization by using XRD, SEM-EDX, TEM, gas sorption analysis, and FTIR method. Effect of the evolution of the surface characters on its catalytic activity in citronellal conversion into isopulegol was studied. The characterization by XRD informed the increasing basal spacing d001 from 1.57 nm into 3.71 nm by the microwave-assisted method, meanwhile the hydrothermal method produced 3.56 nm spacing. The increasing specific surface area from 98.82 m2 g−1 into 752.95 m2 g−1 and 409.95 m2 g−1 for microwave-assisted synthesized and hydrothermal synthesized composites, were obtained. These profiles are attributed to the increasing surface acidity determined by pyridine-adsorption method and n-butylamine titration method, and contributed to the significant increasing catalytic activity. The time-efficient synthesis method obtained by the microwave-assisted method is good alternative for the preparation of highly active montmorillonite heterostructure composite for acid-catalyzed organic reaction.
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