Photocatalytic degradation of phenol solution using Zinc Oxide/UV

The research on wastewater organic pollutant degradation has received substantial attention in the past few years. In this work, the effective use of ZnO nanoparticles as a photocatalyst in the photo-degradation process was studied in order to degrade phenol solutions. The photocatalytic oxidation of phenol solution occurred by using ZnO particles/254 nm UV system in a slurry type reactor sparged by air. The effect of various process parameters such as initial concentration of phenol, ZnO loading, initial solution pH, and air superficial velocity on the photo-degradation reaction was investigated to achieve maximum degradation efficiency. The degradation process was tracked by measuring the solution COD at many time intervals during the experiment period. The results showed that the percentage of COD reduction increases with increasing the air superficial velocity. On the other hand, it decreases with increasing the pH or the initial concentration of phenol. Also, the percentage of COD reduction increases with increasing ZnO loading up to 1.5 g/l then decrease with further increasing in the amount of ZnO. The maximum percentage of COD reduction was 78.2% at 25 ppm, pH 2, ZnO loading 1.5 g/l and air superficial velocity of 2.51 cm/s. The order of this reaction was determined using Lagergren's rate equation and linear pseudo second order equation and was found to be pseudo second order reaction. A correlation between Sherwood, Schmidt and Reynolds numbers was developed to describe the solid liquid mass transfer to understand, design, optimize, and control the system that is being studied.