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

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.