TiO₂/AC Composites for Synergistic Adsorption-Photocatalysis Processes: Present Challenges and Further Developments for Water Treatment and Reclamation

Abstract

Titanium dioxide supported on activated carbon, or TiO₂/AC composite, exhibits bifunctionality of adsorption and photocatalysis in synergism. The authors review the TiO₂/AC synthesis techniques, characteristics, and performances in removing organic pollutants in water. Practical issues pertinent to applications of the TiO₂/AC composite in water treatment and reclamation are discussed. These include dispersing the particles and recovering from the product water, UV introduction and attenuation in the photoreactor, long-term photostability and mechanical stability of the composite, potential TiO₂ deactivation by the organic and inorganic matrices, assessment of intermediates and byproducts, and regeneration techniques for the exhausted or fouled TiO₂/AC. Coupling with a membrane separation process to recover and regenerate TiO₂/AC in various continuous flow-through system configurations is proposed. There are also possible integrations of TiO₂/AC treatment systems with other treatment processes that may result in effective pollutant removal with reduced energy and chemical cost. Future developments including incorporation of solar energy are proposed. A modified TiO₂/AC that can be photoexcited by solar light has been developed by the authors, and its performance in adsorbing and photocatalytic degradation (PCD) of bisphenol-A is presented.

KEY WORDS:

• activated carbon
• organic contaminants
• photocatalysis
• solar light
• titania
• water reclamation

ACKNOWLEDGMENTS

National Research Foundation (NRF), Singapore, is acknowledged for the financial support through the project EWI RFP 0802-11 for development of new-generation adsorptive-photocatalysts to be used for solar-driven water purification. Pow-Seng Yap is grateful to Nanyang Technological University (NTU) for providing his PhD research scholarship.