Graphitic-C₃N₄ coated floating glass beads for photocatalytic destruction of synthetic and natural organic compounds in water under UV light

Many drinking water reservoirs can contain organic pollutants such as artificial synthesized dye and drugs. On the other hand, some naturally occurring microorganisms such as cyanobacteria, are capable of producing toxic secondary metabolites (cyanotoxins) causing detrimental health effects in humans and animals are also present in water reservoirs. Photocatalytic destruction of organic pollutants in-reservoir requires not only good photo-catalytically activity but also efficacy of distribution and recycling. We report here, a facile calcination method of coating graphitic carbon nitride (g-C₃N₄) onto porous glass beads. Influences of precursor and heating temperature on photocatalytic activity were evaluated by photocatalytic degradation of methyl orange. The yellow floating beads show comparable activity to P25 (TiO₂) coated beads in the removal of two of the most frequently occurring cyanobacterial toxins, microcystin-LR and cylindrospermopsin, in artificial freshwater under UV light irradiation. Microcystin-LR was destroyed within 60 min and cylindrospermopsin was removed after 100 min UV irradiation. The coated g-C₃N₄ layer is very robust and shows negligible degradation on photocatalytic performance when recycled. The recycling of the photocatalyst is very simple because of the large size of the catalyst-coated beads. A large batch was successfully produced in a lab tube furnace. For further application, the ability of g-C₃N₄ absorbing visible light could pave the way to utilise sunlight for the destruction of toxins in the water.