| As the most commonly-used antibiotic in livestock and poultry in our country, Tetracycline has astrong inhibitory effect on biological process, and most of them will be discharged with feces, causingenvironmental pollution. Photocatalytic technology can degradate tetracycline in wastewater effectivelywith no secondary pollution. However, the utilization of photocatalytic technology still facedsome problems. First, the photocatalyst can only utilize UV. Second, it is difficult to separatepowdered photocatalyst and wastewater. Third, photocatalytic reactor can not support high catalyticefficiency. The purpose of this study is to prepare anew photocatalyst through multiple-doping method, which can not only use sunlight, but canbe effectively recovered by magnet. Based on this, developing the photocatalytic reactor, aeration wasutilized to improve the photocatalytic efficiency in the reactor. And researches were carried out in threeaspects:1. Magnetic substrate was prepared by explosive burning, then loading TiO2/WO3layer in the surfacesof substrate above by sol-gel method, then Solar-irradiated Magnetic Photocatalyst (MTW) wasobtained. By scanning electron microscopy, X-ray analysis, energy spectrum analysis and othermodern characterization techniques, the characterization of the magnetic TiO2particles was performed.Based on the results, MTW owned honeycomb surface with its honeycomb size of1.5μm in diameter,and its specific surface area was75.6m2·g-1, the main components were Fe3O4and anatase TiO2, themaximum saturation magnetization was21.7emu·g-1, which was enough for recycling. Besides, theintroduction of W element promoted the adsorption wavelength of light to visible region。As a result,the removal rate of methylene blue with MTW reached95.3%,1.1%and2.8%larger than that with theother Fe3O4/AC/TiO2and Fe3O4/TiO2, respectively.2. The catalytic property of MTW was studied with tetracycline as pollutant. The removal rate was65.2%under sunlight,24.8%lower than that under UV,38.7%and52.2%higher than that under visiblelight and darkness, respectively. The removal constant (kobs) increased from2.26×10-2h-1to6.23×10-2h-1when MTW dosage increased from0.25g·L-1to1.0g·L-1. Meanwhile, kobsdecreased by33.8%withdosage increasing from1g·L-1to3g·L-1. kobsincreased from3.19×10-2h-1to6.23×10-2h-1whentetracycline concentration increased from6mg·L-1to15mg·L-1, and decreased to5.18×10-2h-1atconcentration of18mg·L-1.3. The effect of aeration in the reactor was investigated with the upgrading photocatalytic reactor. Thesaturated adsorption amount of MTW on tetracycline under aeration of40m3·h-1was11.25mg·L-1, which was2.9times than that without aeration. It was indicated that aeration caneffectively improve the adsorption ability of MTW. However, the aeration flux increased from 10m3·h-1to40m3·h-1, the removal rate of tetracycline by photocatalysis increased from30.3%to47.4%, but there was no significant difference among removal rates under four different aerationfluxes (p<0.05). The removal rate of tetracycline increased from80%to94%with the increase of pHvalue from5to7. and there was no significant difference with the increase of pH from7to9. As for theeffect of water hardness on photocatalysis process, the removal rate of tetracycline withCa2+concentration in the range of0.01mol·L-1-0.1mol·L-1was3-13%lower than that without Ca2+, andthe removal rate of tetracycline decreased from71.1%to61.2%when Mg2+concentration increasedfrom0to0.1mol·L-1. The result showed that Ca2+and Mg2+had inhibitory effect on the removal oftetracycline.In the study, noval photocatalysts were prepared by loading TiO2through sol-gel method on the surfaceof magnetic material, compared to conventional magnetic material with TiO2as matrix, threeadvantages were as following:(1) increasing the available active sites on the surface of photocatalysts,then improving the photocatalytic ability;(2) improving magnetism and the recovery ability ofthe photocatalyst;(3) reducing the cost of photocatalysts. Based on this, photocatalytic reactor isdeveloped with the introduction of aeration, breaking through the limit of propagation ability of light inwater effectively, improving the photocatalytic efficiency. |
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