Photocatalytic Degradation Of Aniline Wastewater By NaNO-TiO₂

With the economic development and social progress of China, water pollution problem is a major social concern environmental issue and has become increasingly prominent. Photocatalytic degradation with nano-TiO2 is a potential effective technology to degrade wastewater, and has received much attention in recent years because of its advantages such as low cost, mild reaction condition and high degradation effect. In previous, people have mostly researched degradation of wastewater by undoped TiO2. In the paper, photocatalytic degradation of aniline wastewater by metal and nonmetal ions co-doped, rare earth doped and heteropoly acid load TiO2 was investigated.Nano-TiO2 doped with Fe3+, Fe3+/F?, Nb5+/F? were prepared by sol-gel method. The photocatalytic were characterized with Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), spectrometer, and energy dispersion X-ray spectrum (EDS). The photocatalysis activity and the major influencing factors for degradation of aniline were studied. IR spectra analysis shows that similar peaks apear around characteristic peaks of TiO2 at 2 366.66 cm?1 and 472.56 cm?1with the amount of Fe-doped 0.05%, but the intensity has increased and the peak of 472.56 cm?1 red shift. The reasons are that the joint action of Fe-O bond with the Ti-O bond and the larger of doped nano-powder particle size. From IR spectra can be seen that the Fe3+ ions on the TiO2 crystal play a role has combined with TiO2. The results of XRD showed that the crystal structure of catalysts were of anatase type. Although the average size of TiO2 doped with Fe3+/F? increases from 12.57 nm to 13.16 nm, the photocatalytic activity increases after doping. The best doping amounts of the three different doped TiO2 catalysts are 0.05%, 0.05%/2%, 0.1%/1%. After reaction for 2 hours under UV irradiation, the degradation rate of aniline wastewater is about 97.64%, 98.20%, 98.32%, respectively.Rare earth ion-doped TiO2 nano-crystals were also obtained. The photocatalysts were characterized with FT-IR, XRD, and EDS. The results showe that the photocatalytic properties of rare earth ion-doped TiO2 can be improved obviously. And the activities vary with the different doping ions and concentration. The optimal doping concentration of Nd is 0.1% and the degradation rate can reach 98.47%; the optimal doping concentration of Ce is 0.5% and the degradation rate can reach 99.20%. The rare earth elements and fluorine element codoped TiO2 can improve the photocatalysis activity. The effects of Nd 0.05% and F 2% co-doping are better than that of pure titanium dioxide, and the degradation rate up to 99.08%. The degradation rate with Ce 1% and F 2% co-doped TiO2 is 96.14%.Two kinds of heteropolyacid supported on titanium dioxide photocatalysts were prepared by immersing TiO2 powder in each corresponding aqueous solution of heteropolyacid, and then drying at a certain temperature. The effects of immersing time, temperature, dosage, concentration of heteropolyacid aqueous solution were studied. The photocatalysts were characterized with FT-IR. The highest activity catalyst can be obtained under the conditions of dipping time of 28 h, soaking solution concentration of 0.04 mol/L, drying temperature of 85℃, muffle furnace sintering temperature of 400℃, sintering time of 2 h, and the amount of titanium dioxide immobilized of 0.5 g. Compared to the pure TiO2, phosphotungstic acid-immobilized TiO2 has higher catalytic activity under visible light and the degradation rate of aniline increase from 34.2% to 60.3%. Phosphorus molybdate impregnated TiO2 powders with the highest activity could be obtained when the soaking time was 26 h, soaking solution concentration 0.04 mol/L, drying temperature was 85℃, muffle furnace sintering temperature was 450℃, sintering time was 2 h, and the amount of titanium dioxide immobilized was 0.6 g. And compared to the pure TiO2 photocatalyst, the catalytic activity of phosphomolybdate-immobilized TiO2 has been greatly improved under visible light and the degradation rate of aniline increase from 34.2% to 74.5%. Results show that phosphotungstic acid and phosphomolybdic acid are loaded on the surface of TiO2. The supported photocatalysts have higher catalytic activies than that of unloaded TiO2 and its photodegradation efficiency for aniline wastewater increase by 26.1% and 40.3%, respectively, under visible light irradiation.