Effect of thin film titanium dioxide characteristics on photocatalytic reduction of chromium (VI) using fixed bed photoreactor

Abstract

This research focused on the effect of thin film Ti02 characteristics on chromium (VI) removal in the photocatalytic reduction using a fixed bed photoreactor. The goal of this work was to verify the optimum synthesis condition of nanocrystalline Ti02 thin layers derived from the sol-gel process to be used in the fixed bed photoreactor. The factors influencing the thin layers properties were the addition of acetyl acetone used as an additive, the calcination temperatures, the number of coating cycles and the appropriate wavelengths. The mole ratio of Ti02 was titanium (IV) butoxide: ethanol: HCI: acetyl acetone at 1: 30: 0.5: 1, respectively. From this work, It was found that acetyl acetone prevented the cracking of the surface morphology as shown in the SEM micrographs and gave the high efficiency of photocatalytic reduction. The optimum condition to produce the immobilized Ti02 on stainless steel was found at 500 °c calcination temperature and the 3-coating cycles which gave the highest photocatalytic activities due to the highest amount of the anatase phase and smallest size of nanocrystalline Ti02. Moreover, the recombination of electrons and holes was found at 4- coating cycles in which the thickness higher than 91 nm. The appropriate wavelength was found at 380 nm provided the optimum energy to the thin film Ti02. Photocatalytic reduction of Cr (VI) in all experiments followed zero order pattern and the kinetic coefficients in all cases were also reported in this work.