An Exploratory Study of a Photonic Crystal Monolith Reactor for Air Pollution Control

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ABSTRACTPI: Kalliat T. Valsaraj and Raghunathan RavikrishnaInstitution: Louisiana State UniversityProposal Number: 0520524ResearchThe overall objective of this project is the development of a monolith photocatalytic reactor using photonic band gap (PBG) titania for the treatment of dilute waste gases. The hypothesis is that, PBG titania produced in-situ and grafted on stripped fiber optic tubes using sol-gel chemistry and used in a monolithic configuration, can vastly improve UV absorption, quantum efficiency, the photocatalytic activity, and reduce the mass transfer limitations in a large scale reactor for photocatalytic degradation of organics in gaseous waste streams. The use of long range ordered porous structures of photonic band-gap exhibiting titania grown on optical fibers is expected to enhance the overall photocatalytic efficiency as compared to using powdered titania coating on stripped optical fibers due to improved light transmission properties and better mass transfer. The PBG titania will be manufactured on the optical fibers using two templates for solgel processing- a) polystyrene microspheres and b) polyaphrons (emulsions). The individual optical fiber monoliths with the PBG titania will be bundled together to form a composite monolith reactor. PBG material characteristics will be tailored at the synthesis stage in order to enhance the reactive efficiency of the composite monolith photocatalytic reactor in UV light. The composite monolith reactor will be used to degrade a test compound, 1,2-dichlorobenzene, in aqueous solutions. The specific objectives are:1. Preparation of PBG titania crystals on optical fibers using a sol/gel (solution) method2. Characterization of the PBG titania thin films and determination of their photonic properties.3. Construction of the internal configurations for the monolithic reactor.4. Testing the reactor on a candidate compound under various reaction conditions.5. Obtaining a mathematical model to extract kinetic rate constants and mass transfer characteristics useful for possible scale-up of the process.Broad ImpactThe proposal is high risk since the use of PBG materials in a continuous monolith photocatalytic reactor configuration is a concept that is yet to be tested. The development of this technology could have a significant impact on the application of photocatalytic processes to the treatment waste gas streams. It is high return because if successful, the reactor design offers a potential for scale up that can alleviate the current barriers to the use of photocatalytic reactors for industrial waste gas treatment. The broad impact is thus in the area of environmental sustainability.