Silver Decorated Carbon Nanospheres as Effective Visible Light Photocatalyst
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Silver Decorated Carbon Nanospheres as Effective Visible Light Photocatalyst W. Armstrong, B. Sapkota, and S. R. Mishra The Department of Physics, The University of Memphis, Memphis, TN 38152 Abstract The objective of this study was to assess usability of silver nanoparticles loaded on amorphous carbon (Ag-C) hollow nanospheres for the removal of Methylene Blue (MB) molecules from aqueous solutions. Using microwave technique, silver nanoparticles of different weight ratio was deposited onto amorphous carbon templates. The carbon hollow spheres were derived from glucose using hydrothermal technique. Interestingly crystallite size of Ag decreased with the silver loading on carbon nanospheres. Using UV-vis spectroscopy, the kinetics of MB removal from the solution was assessed. The degradation of MB followed pseudo-first-order kinetics. The obtained results showed that Ag-C particles are efficient MB degradation agent with the rate constant as high as 0.19 m-1 under visible light and 0.041 m -1 under UV light. Thus Ag-C particles are good alternative as low-cost scavenger of dye molecules in wastewater treatments. Introduction Large industrial wastes, mainly aqueous toxic dyes such as Azo dyes, from textile, paper, leather, food and cosmetic industries are routinely poured out in water as waste [1,2,3]. Due to high stability of organic dyes it is difficult to decompose the dye molecule which eventually causes serious environmental and health problems. Furthermore, sunlight penetration to the aquatic environment is hindered by dye molecules which significantly affect photosynthetic processes. Dyes are also known to reduce oxygen levels in water which lead to suffocation of aquatic flora and fauna [4,5].The widely used biological treatment of waste water is found ineffective in treating dye loaded water as these dyes are resistant to destruction to biological treatment using microbes. The advances in synthesis of nanoparticles opened up an alternative solution to waste water treatment. An advanced oxidation process using nanoparticles such as ZnO, TiO2, ZrO2 etc. in the presence of UV light is have been extensively studied for treating organic chemicals including dyes in wastewater. But TiO2 and ZnO have serious draw back as they cannot be utilized in visible spectrum due to their wide band gaps (~ 3eV). The UV radiation accounts for less than 4% of incoming solar energy, while visible light (λ~400 nm) constitute around 43% of the solar energy [6]. Hence one of the greatest challenges for photocatalyst study is to engineer new catalyst that exhibit high activity in visible region of sun light spectrum. This will allow us to sunlight efficiently to drive chemical reactions at a very low cost. In wastewater treatment, nanoparticles loaded slurry reactors may be used device because of its high specific surface area and good dispersion [7,8]. However, these slurry reactors find limited application mainly because of difficulty in separating nanoparticles form treated water. To overcome this difficulty various strategies inclu
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