2019 CSCE Annual Conference - Laval (Greater Montreal) Conference
Dr. Linlong Yu, University of Calgary
Dr. Gopal Achari, University of Calgary (Presenter)
Photocatalysis is an advanced oxidation process (AOP) that uses light energy to activate a substance known as a photocatalyst, which then triggers a series of reactions that breakdown organic contaminants in water. Photocatalysis offers the possibility to harness sunlight, posing as a low cost and energy saving approach for treating organic contaminants from water. Titanium dioxide (TiO2), the most commonly used photocatalyst, can be excited by photons with wavelengths shorter than 385 nm. Only 5% of solar radiation received by the earth’s surface accounts for this spectrum of wavelengths. Therefore, there is a demand for photocatalysts that can be activated by light with longer wavelengths in order to maximize the use of sunlight. Combining photocatalysts with graphene has been shown to enhance the performance due to its strong adsorption capacity, photocatalytic activity and overall stability. Graphene based photocatalysts have been used to effectively remove many water-borne organic dyes under visible irradiation. However, this application has not yet been extended for use in emerging contaminants.
In this study, composites of graphene and titanium dioxide (Gr-TiO2) were synthesized using the hydrothermal method, where graphene oxide is reduced to graphene and simultaneously deposited onto the TiO2 surface. The effectiveness of Gr-TiO2 was then evaluated by testing its use in the removal of organic dye (methyl orange) and emerging contaminants. Both ultraviolet A(UVA)-LED and blue LED were used for experiments as the source of irradiation. Light emitting diodes (LED's) are a novel and robust light source that offer better energy utilization than conventional mercury lamps. Sulfolane and phenol are selected as candidates for emerging contaminants in these experiments. Sulfolane is a solvent used to remove acidic component from sour natural gas and has been reported to contaminate soil and water near gas plants in North America. Phenol is a precursor for many chemical products and causes adverse effects to biota when released into aquatic environments.
The results show that the performance of Gr-TiO2 varied for each contaminant and light condition. Gr-TiO2 can effectively degrade sulfolane and phenol with UVA irradiation, but barely any degradation was observed using the blue light. Further investigation indicated that Gr-TiO2 showed better performance than powdered TiO2 in dye removal. However, powdered TiO2 exhibited better overall performance for the degradation of sulfolane and phenol than Gr-TiO2.