Photocatalysis in a packed bed: Degradation of organic dyes by immobilized silver nanoparticles

• Ag nanoparticles with anti-poisoning properties were synthesized and immobilized.
• The Ag nanoparticles are surfactant-free and have improved activity and efficiency.
• The Ag nanocatalysts were used in a packed bed for semi-continuous operation.
• Mixtures of model dyes were completely decolorized.

Complete photocatalytic degradation of methyl orange, methylene blue and rhodamine chloride was accomplished using immobilized silver nanoparticles as catalysts and tethered calix[7]hydroquinone molecules as nano-reactors. The nanoparticles were immobilized on quartz beads that were assembled in a packed bed configuration. The large interfacial area afforded by the packed bed geometry, presentation of the nanoparticles as a single, tethered layer, and the optically transparent packing material facilitated intimate interaction between the catalyst, dye solution and radiation. The degradation was accomplished using either UV or visible radiation and the nanoparticles displayed self-cleaning and anti-poisoning properties thereby demonstrating excellent durability and catalytic efficiency. The single-layer coverage of Ag nanoparticles facilitates use of very small amounts of the photocatalyst for degradation of relatively large amounts of dye. The method addresses multiple issues that constrain scale-up of photocatalytic systems that deploy nanoparticles as catalysts.

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