Abstract
Hierarchical Zn-ZSM-5 photocatalyst structures were synthesized via a hydrothermal one-pot synthesis route using a double template. Activated attapulgite (Si-ATP) and zinc nitrate (Zn(NO3)2) precursors were used as silicon and zinc sources, respectively. The structural properties, morphology, photocatalytic activity and the texture properties of the synthesized Zn-ZSM-5 photocatalysts were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), diffracted ultraviolet–visible (UV–Vis) spectrometry (DRUV–Vis) and N2 adsorption/desorption, respectively. It was found that the composites exhibit a typical MFI framework structure, a hexahedral twin structure and typical UV absorption peaks at 292 nm and 246 nm, when the Zn/Si mole ratio reaches its optimum value of 1:100. The hierarchical nanocrystals exhibit a similar Brunauer–Emmett–Teller surface area (309 m2 g−1) and a high mesopore ratio (37.47%) as compared to commercial zeolites. Sub-nano-sized zinc oxide (ZnO) particles with small size moieties were implanted and isolated in the silica matrices of micro-mesoporous zeolite, which had a significant photocatalytic activity and reusability of degrading methylene blue (MB) dyeing wastewater. Using a 500 W mercury lamp with the wavelength range from 185–500 nm operating during an illumination time of 30 min, the concentration of MB decreases significantly in the presence of Zn-ZSM-5 photocatalyst leading to a 95.56% of degradation, where the ratio still remained at 94.32% after six times of reuse.
Highlights
Printing and dyeing wastewaters are a complex mixture of pollutants including some carcinogenic, teratogenic and mutagenic organic compounds derived from aromatic hydrocarbons and heterocyclic compounds
In order to test the reusability of the material further, the recycling experiments are conducted under the same conditions, the result showed in Figure 12.The photocatalytic activity of hierarchical Zn-ZSM-5 (Zn/Si = 1:100) still reaches 94.32% after being reused for
It was shown that the Zn/Si ratio has a significant impact on the crystal structure, surface morphology, photo-response activity and texture characteristics
Summary
Printing and dyeing wastewaters are a complex mixture of pollutants including some carcinogenic, teratogenic and mutagenic organic compounds derived from aromatic hydrocarbons and heterocyclic compounds. The technique of photocatalysis enables an efficient use of solar energy to degrade organic matter and has, attracted considerable research interest recently to be utilized for printing and dyeing wastewater degradation [4,5,6] In this context, the semiconducting photocatalyst ZnO has become a major research target in the field of photocatalytic degradation of water pollutants, since it offers several advantages such as facile synthesis, good practicability, an environmentally-friendly nature and no secondary pollution [7,8,9]. ZnO particles can agglomerate, resulting in a low recovery rate and poor performance in industrial applications To overcome such disadvantages of pristine ZnO, different approaches have been followed to increase the specific surface area and to generate more reaction sites to improve the photocatalytic activity [10,11,12]. The effects of the pore structure and Zn/Si ratio on the photocatalytic performance of the synthesized products were investigated, and further details about the photocatalytic mechanism could be revealed
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