Dye Wastewater Treatment Under Visable Light Irradiation Using A Dual Slant-placed Doped TiO₂/Ti-Cu Electrodes Thin-film Reactor

For its good photo-chemical stability,acid and alkali resisting,low cost,and no secondary pollution,TiO₂ photocatalytic water treament technology has aroused much concern.However,poor utilizaton of solar energy and low efficienty of photogenerated charge separation are two of the biggest challenges that influence the application of this technology.Metal doped and nonmetal doped are two good ways to improve the visible light photocatalytic performance of TiO₂.Generally,TiO₂ thin-film electrode was always completely immersed into the thick reaction solution in conventional photocatalytic reactors,which greatly affect the efficiency of light source and transfer speed of solution.In order to solve the problem,a dual slant-placed electrodes thin-film reactor was developed and successfully used to treat dye watewater by our research group.Single doped,co-doped and tri-doped TiO₂/Ti electrodes have been prepared by sol-gel method and dip-coating method using the cerium nitrate,ferric chloride,carbamide as raw materials.The preparation conditions of electrodes were optimized,and their characterization were tested by X-ray diffraction?XRD?and UV-Vis diffuse reflectance spectroscopy?UV-Vis DRS?.Finally,the doped TiO₂/Ti electrode was used as the photoanode to assemble a dual slant-placed electrodes thin-film reator with Cu cathode to degrade Amaranth solution,and the conditions were optimized.The main contents and results are following:1?Ce,Fe and N single doped TiO₂/Ti electrodes were prepared by sol-gol method.The main influence factors such as calcination temperature,doping concentration and coating layers were investigated.The results show that Fe-TiO₂/Ti has the best photocatalytic performance among the single doped and undoped TiO₂/Ti.The optimal preparation conditions are calcination temperature 500 ?,n?Fe:Ti?=8% and 4 layers coating.XRD analysis indicated that the TiO₂ crystal was main anatase,and the photocatalyst grain was about 15.30 nm.UV-Vis DRS analysis showed red shift of the light absorption spectrum was obvious.The photocatalytic conditions were investigated,and the optimal conditions are circulating flux 85 mL/min,initial pH 2.50 and Na₂SO₄ 1.0 g/L.Under these conditions,the decolourization efficiency of 20 mg/L Amaranth solution reached 91.20% for 90 min treatment.2?The Ce-Fe,Fe-N and Ce-N co-doped TiO₂/Ti electrodes were prepared through sol-gel method,and orthogonal tests were designed to optimize the preparation conditions.The results show that,compared with the single doped and undoped TiO₂/Ti electrodes,Ce,Fe-TiO₂/Ti has the best photocatalytic performance.Its optimal preparation conditions are calcination temperature 550?,n?Ce:Ti?=3% and n?Fe:Ti?=6%.XRD analysis indicated that the TiO₂ crystal was fully anatase.Ce and Fe co-doping effectively inhibited the crystal growth and rutile formation,and the photocatalyst grain was only 10.21 nm.UV-Vis DRS analysis and photoelectric performance test analysis showed red shift of the light absorption was more obvious.The photocatalytic conditions were investigated,and the optimal conditions are circulating flux 85 mL/min,initial pH 2.50 and Na₂SO₄ 0.5 g/L.Under these conditions,the decolourization efficiency of 20 mg/L Amaranth solution reached 93.42% for 60 min treatment.In addition,the reproducibility and repeatability of the Ce,Fe-TiO₂/Ti was investigated.The results show the decolourization efficiency of 8 pieces electrodes for 60 min treatment was 91.52±2.23%,and that of 1 piece electrode for 8 runs?60min treatment for each run?remained at 89.05±3.03%,which indicate the reproducibility and repeatability of the Ce,Fe-TiO₂/Ti is good.3?The Ce,Fe,N-doped TiO₂/Ti electrode were prepared by sol-gel method,and orthogonal tests were designed to optimize its preparation conditions.The optimal preparation condition is calcination temperature 550?,n?Ce:Ti?=4%,n?Fe:Ti?=6% and n?N:Ti?=15%.XRD analysis indicated that the photocatalyst crystal was main anatase,and its grain was about 13.46 nm.DRS analysis showed red shift of the light absorption was obvious,but a little less than that of Ce,Fe-TiO₂/Ti.The optimal treatment conditions are circulating flux 85 mL/min,initial pH 2.50 and Na₂SO₄ 0.5 g/L.Under these conditions,the decolourization efficiency of 20 mg/L Amaranth solution reached to 92.57% for 80 min treatment,which is slightly lower than that of Ce,Fe-TiO₂/Ti.4?UV-Vis spectrum of Amaranth solution was tested during the dual slant-placed electrodes thin-film photocatalytic process.The results indicate the degradation of Amaranth is mainly through azo bond cleavage and part naphthalene ring damage.In this way,the macromolecular organic was degraded to small molecule organic,and the Amaranth solution was decolorized.