| The secondary effluent of municipal wastewater is a good potential water source due to its large quantity and stable quality. It can be reused after proper advanced treatment, which alleviates the water shortage to a large extent in cities. Generally, the secondary effluent has some biochemical non-degradable organic matters which are difficultly removed by traditional biochemical treatment. Photocatalytic oxidation is often used in treating micro-polluted waste water due to its considerable photocatalytic activity, high stability, non-environmental impact and non-selective degradation of organic compounds. However, TiO2 powder is hardly recycled in aqueous solution. Besides, the easily recombination of electron-hole pair reduces the photocatalytic oxidation efficiency. To overcome these problems, Nanocrystalline TiO2 codoped with La3+and Fe3+ was synthesized by using sol-gel method. Modified TiO2 catalyst was immobilized on pumices by using Sol-Gel method and dip-coating method. The La3+ and Fe3+ codoped TiO2/pumice was used for the advanced treatment of secondary effluent aiming at water reuse.La3+ and Fe3+ codoped TiO2/pumice was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the extent of water use, the amount of acetyl acetone, calcination temperature, thin films have an important influence on crystalline phases and surface morphology of the catalysts.When the ration of La3+ and Fe3+ were 0.5%and 0.05%, the particle size of pumice were from 20 to 40 meshes, the number of TiO2 films were 4 and the dosage of catalysts were 15 g/L, the reduction rate of TOC was 50.8%.The overall stability of the TiO2 catalyst made in this work was acceptable in the first use of 5 times. After having been used 5 times, the reduction rate of TOC still had 44.1%. For the deactivated photocatalyst, it can be used for 10 more times after 3 times of regeneration treatment.The main anions in the secondary effluent were HCO-,NO3-,Cl-,SO42- and HPO42-. The HCO3- and HPO42- were found to inhibit the activity of photocatalyst by their adsorption onto the surface of TiO2 and trapping positive holes and·OH. No significant effect was observed by the Cl" and SO42". On the contrary, the NO3" did not lead to the retardation effect of the photodegradation under 1 mmol/L.The organics with molecular weight< 1 k Dalton in the secondary effluent accounted for 41.2%. The SUVA was 7.35 m-1L/mg. The secondary effluent was poorly biodegradable since the BDOC/DOC accounted for 0.13. Furthermore the concentration of 16 sorts of polycyclic aromatic hydrocarbons amount to 294.7 ng/L. The photocatalytisis of the secondary effluent indicated that the removal of DOC, UV254 and PAHs were 49.0%,76.5% and 80.2%. It also enhanced the biodegradability of the secondary effluent by raising BDOC/DOC to 0.51.In conclusion, TiO2 Photocatalytic oxidation was an effective as well as promising process for advanced treatment of the secondary effluent for reuse purpose.
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