The Preparation And Photocatalvtic Studv Of Novel Visible-light Photocatalysts

Dye wastewater is among the largest groups of water pollutants in the world. With the rapid development of the dye industry, the removal of these non-biodegradable dye molecules from the environment is a crucial ecological problem due to their toxicity and potential carcinogenicity. It has drawn much attention to the vital need for ecologically clean chemical technologies. Over the past few decades, semiconductor-based photocatalysis for its high efficiency and promising economy has been extensively developed to treat dye wastewater. However, it should be noted that the traditional photocatalyst can only utilize the ultraviolet light (about4%solar spectrum). Moreover, due to its low quantum efficiency as well as the difficulty in separation and reuse of the powder catalysts, the practical application of the photocatalyst is greatly limited. Thus, it is urgently required to develop effective strategies to explore novel, highly efficient visible light driven photocatalysts to the environmental pollution control.In the present work, based on the two excellent photocatalyst of TiO2and Ag3PO4, we try to synthesize a series of visible light driven photocatalysts such as Ti-Cr-MCM-48、Ag3PO4/MWCNT. AgBr/Ag3PO4/Fe3O4with various structures and morphology. The morphology and photocatalytic activity of the as prepared photocatalysts were characterized through a variety of characterization methods and the degradation of methyl orange dye under visible light.The main results of the present work were summarized as follows:1. Ti-Cr-MCM-48photocatalyst was successfully synthesized via a facile and rapid one-step approach at room temperature, which takes CTAB as a template, Cr(NO3)3·9H2O and titanium isopropoxide as metallic precursors, and TEOS as source of silicon. The results shows that the Ti-Cr-MCM-48exhibits good visible light activity. The degradation of MO over Ti-Cr-MCM-48was reached to81%in5h, which is much higher than that of Cr-MCM-48(45%in5h). The high activity of Ti-Cr-MCM-48was closely associated with the formation of Ti-O-Cr structure.2. A high-performance Ag3PO4photocatalyst was prepared with different phosphate salts (Na3PO4, Na2HPO4, and NaH2PO4) through a precipitation method. Due to the different pH in preparation system, the type of phosphate salt used as a precipitating agent can affect the purity, morphology, particle size, and photocatalytic activity of the prepared Ag3PO4powder. The results indicate that the Ag3PO4sampled prepared from NaH2PO4showed better photocatalytic efficiency of MO under visible light (100%in40min), compared with those prepared from Na2HPO4andNa3PO4. The degradation rate of MO over the Ag3PO4sampled prepared from NaH2PO4was about5.2times faster than that of the Ag3PO4sampled prepared from Na3PO4.3. Ag3PO4/MWCNT composite was successfully synthesized via in-situ precipitation method. The MWCNTs play a key role for the enhanced pho-tocatalytic activity and stability of Ag3PO4. The Ag3PO4/1.4wt%MWCNT sample shows optimal photocatalytic ability over MO (100%in12min), which improved by nearly55%compared with pure Ag3PO4. The rate constant of MO degradation over Ag3PO4/1.4wt%MWCNT is5.84times that of pure Ag3PO4. Moreover, The photocatalytic activity of Ag3PO4/MWCNT sample decreased slowly in three successive experimental runs.4. A novel magnetically recoverable AgBr/Ag3PO4/Fe3O4hybrid was successfully synthesized via in-situ precipitation method. Because of the magnetism of Fe3O4and the matching band between AgBr and Ag3pO4, the as-synthesized AgBr/Ag3PO4/Fe3O4nanoparticles exhibited efficient photocatalytic activity, good stability and recyclability toward decomposition of methyl orange (MO) dye under visible light irradiation. The AgBr-80/Ag3PO4/Fe3O4sample shows optimal photocatalytic ability over MO (100%in15min), which is much higher than that of pure Ag3PO4(50%in15min). Moreover, after three successive experimental runs, the photocatalytic activity of AgBr/Ag3PO4/Fe3O4still reached to95%of the initial efficiency. Besides, the as-prepared AgBr/Ag3PO4/Fe3O4can be conveniently collected from the solution by applying an external magnetic field within3min.