Destruction of Aqueous Phase Organic Pollutants Using Ultraviolet Light Emitting Diodes and Photocatlaysis
Abstract
The photocatalytic degradation of dyes (Allura Red AC and Brilliant Blue FCF) in water using ultraviolet light emitting diodes (UV-LED) and an immobilized titanium dioxide (TiO2) as a photocatalyst; was investigated using a novel bench-top Teflon reactor. This reactor has been uniquely designed to contain low-powered UV-LEDs combined with TiO2 immobilized substrates. A sol-gel method was used to anneal TiO2 to three different substrates: standard microscope quartz slides, quartz cylinders and borosilicate beads. TiO2 characterization was performed using Scanning Electron Microscope (SEM), Raman spectroscopy, and mass comparisons. High resolution SEM images confirmed the presence and morphology of TiO2 on the substrates. SEM and Raman analyses demonstrated the TiO2 coating was uniform and predominantly has the anatase crystalline phase structure. The slide had the largest individual TiO2 surface area of 0.187 mg cm-2. Size, shape, packing and stirring properties were factors that determine overall photocatalytic properties and degradation. For an ideal completely mixed batch reactor (CMBR), the largest adjusted rate constants were 1.69 x10-3, 5.39 x10-3 and 4.46 x10-3 min-1 for the slide, beads and cylinders respectively. Borosilicate beads were the best performing substrate as determined by the greatest degradation rate for Allura Red AC. The beads and cylinders showed 58 and 51 degradation of a model organic compound, Allura Red AC. Actinometry experiments revealed quartz cylinders had the largest fluence value of 0.0461 J L-1s-1. Optimization of the sol-gel application method and reactor operating parameters was performed to maximize the degradation rate and overall degradation of Allura Red AC. Electric energy per order (EEO) was calculated and optimized at 9.20, 10.5 and 12.7 kWh m-3order-1 for the glass beads, cylinders and slides, respectively.