TiO_2光催化还原重金属离子的研究进展

光催化还原技术越来越得到人们的认可。文章综述了TiO2光催化还原技术在废水中重金属离子处理方面的应用,从重金属离子的光催化还原机理、反应驱动力、光催化剂的失活与再生以及各种光催化还原重金属的影响因素等方面,阐述了重金属离子的光催化还原新进展。     

用光触媒抑制淡水藻类增殖作用的研究

为维护和改善湖水、水库等大型蓄水设施的水质而寻找一种新的方法,在人工的明／暗光照射条件下,探讨了运用粉末状TiO2作为光触媒,抑制各种淡水藻类增殖的效果。粉末状的TiO2,在100mg／L的浓度下,对蓝藻的铜绿微囊藻原变种、鱼腥藻和绿藻的空星藻有明显的抑制增殖的效果;而对硅藻的钝脆杆藻,在此条件下则没有效果。     

TiO2晶须在深度净化饮用水过程中失活原因分析

研究了TiO₂晶须在光催化深度净化饮用水过程中失活的原因及相应的再生方法.对TiO₂薄膜失活前后的AFM、XRD表征,以及对失活前后TiO₂晶须酸洗液的ICP分析表明,TiO₂晶须失活的主要原因是难溶性碳酸钙在催化剂表面的沉积.由于自来水中钙离子的存在以及有机物光催化降解过程中产生的二氧化碳,生成的难溶性碳酸钙覆盖在催化剂的表面,影响了紫外光的透光率,限制了光生电子和光生空穴的生成,导致催化剂的光催化能力逐渐下降直至失活;失活的催化剂通过1 mol/L的盐酸酸洗4　h后,光催化活性可以恢复到95%左右;多次失活/再生的催化剂的光催化活性保持较好的稳定性.     

Photocatalytic degradation of 4-chlorophenol under P-modified TiO2/UV system:Kinetics, intermediates, phytotoxicity and acute toxicity

A series of phosphorus-modified titanium dioxide samples with varying P/Ti atomic ratio were conveniently prepared via a conventional solgel route. The effects of phosphorus content and calcination temperature on the crystalline structure, grain growth, surface area, and the photocatalytic activity of P-modified TiO₂ were investigated. The XRD results showed that P species slow down the particle growth of anatase and increase the anatase-to-rutile phase transformation temperature to more than 900℃. Kinetic studies on the P-modified TiO₂ to degraded 4-chlorophenol had found that the TP5₅₀₀ prepared by adopting a P/Ti atomic ratio equal to 0.05 and calcined at 500℃ had an apparent rate constant equal to 0.0075 min^-1, which is superior to the performance of a commercial photocatalyst Degussa P25 K_app = 0.0045 min^-1 and of unmodified TiO₂ (TP0₅₀₀) K_app = 0.0022 min^-1. From HPLC analyses, various hydroxylated intermediates formed during oxidation had been identified, including hydroquinone (HQ), benzoquinone (BQ) and (4CC) 4-chlorocatechol as main products. Phytotoxicity was assessed before and after irradiation against seed germination of tomato (Lycopersicon esculentum) whereas acute toxicity was assessed by using Folsomia candida as the test organism. Intermediates products were all less toxic than 4-chlorophenol and a significant removal of the overall toxicity was accomplished     

Kinetics study of photocatalytic process for treatment of phenolic wastewater by TiO2 nano powder immobilized on concrete surfaces

In this study, kinetics of photocatalytic degradation of phenolic wastewater in immobilized photocatalytic reactor was investigated. Immobilization of titanium dioxide (TiO₂) nano powders on concrete surfaces were accomplished with epoxy concrete sealer. Kinetics of photocatalytic reactions has been proposed to follow the Langmuir–Hinshelwood model in different initial phenol concentration, pH, and UV lamp intensity. First-order reaction kinetics with respect to the pollutant concentration was obtained for the reaction. Effect of UV lamp intensity showed that kinetic constants were proportional to the power of 0.73–1 of the photonic flow. In all cases kinetic constant increases as pH of the system reached up to 12 units. Several reaction intermediates were identified using the GC/Mass analysis. Products at the initial stage of the reaction were aromatic compounds, contained hydroquinone, benzoquinone, and catechol. These intermediates underwent further photocatalytic oxidation to aliphatic compounds and finally into CO₂ and H₂O after 4?h. Kinetic constants of intermediate compounds were determined using mathematical–chemical equations and nonlinear regression. Data showed that the differences between the mathematical model and Langmuir–Hinshelwood model for the kinetic constant was less than 5%.     

Pure and Mg-doped self-assembled ZnO nano-particles for the enhanced photocatalytic degradation of 4-chlorophenol

A novel self-assembled pure and Mg doped ZnO nano-particles （NPs） were successfully synthesized by a simple low temperature co-precipitation method. The prepared photocatalysts were characterized by X-ray diffraction, high resolution scanning electron mi- croscopy, high resolution transmission electron microscopy, diffuse reflectance spectroscopy and photoluminescence （PL） spectroscopy. The results indicated that the prepared photocatalysts showed high crystallinity with a uniform size distribution of the NPs. The degradation of cholorphenols is highly mandatory in today＇s scenario as they are affecting the environment adversely. Thus, the photocatalytic degradation of 4-chlorophenol （4-CP）, a potent endocrine disrupting chemical in aqueous medium was investigated by both pure and Mg-doped ZnO NPs under UV-light irradiation in the present study. The influence of the Mg content on the structure, morphology, PL character and photocatalytic activity of ZnO NPs were investigated systematically. Furthermore,the effect of different parameters such as 4-CP concentration, photocatalyst amount, pH and UV-light wavelength on the resulting photocatalytic activity was investigated.     

磁性CuS/γ-Fe2O3复合材料光催化处理染料废水

以氯化铜、纳米γ-Fe₂O₃和硫脲为原材料,乙二醇为溶剂,采用溶剂热法制备了磁性CuS/γ-Fe₂O₃复合光催化剂。考察了该光催化剂对刚果红染料废水的处理效果。在m（CuS）:m（γ-Fe₂O₃）=2:1、刚果红初始质量浓度为10 mg/L、光催化剂投加量为0.6 g/L的最佳工艺条件下,刚果红去除率达96.51%。阴离子Cl^-、NO₃^- 及SO₄^2-对该光催化剂的催化活性具有促进作用,其中SO₄^2–的促进作用最显著。该光催化剂具有较好的活性稳定性,重复使用6次后刚果红去除率仍高达90.50 %。     

Cr(VI)离子在TiO2表面的吸附与光催化还原消除

随着体系pH值增大,Cr(VI)离子在TiO₂表面的吸附下降。当Cr(VI)离子初始浓度为300μmol/L时,其在TiO₂表面具有最大值吸附。H₂PO₄^-阴离子及乙酸的存在对Cr(VI)离子的吸附有阻抑作用,甲酸存在会提高Cr(VI)离子的吸附。Cr(VI)离子在TiO₂半导体催化剂表面的光催化还原受体系的酸度影响较大。H₂PO₄^-阴离子或Mn²⁺离子存在会降低Cr(VI)离子的光催化还原效率。在太阳光照下,Cr(VI)离子在TiO₂上的光催化还原也可实现。通过调节反应结束后水溶液的酸碱度,Cr(VI)离子得以消除。反应后催化剂经酸处理,其活性恢复并可重复使用。     

Pathways and Kinetics on Photocatalytic Destruction of Aqueous Phenol

In this study, the TiO₂ photocatalytic decomposition process of aqueous phenol was investigated. The intermediate products generated in the elementary reaction steps in the mineralization process were experimentally identified as hydroquinone, catechol and hydroxyhydroquinone. The concentration variations of these intermediate products with time passage were traced by high performance liquid chromatograph. The pathways of the decomposition process were given. Based on Langmuir isothermal theory and Langmuir-Hinshelwood mechanism, the multi-compounds competition kinetic model was established. In this model, the observed time-dependent concentrations of phenol and the intermediate products were simulated.     

磁载光催化剂ZnO/SiO_2-Fe_3O_4的光催化活性

采用液相沉积法制备出了纳米SiO_2-Fe_3O_4复合粒子,并在其表面负载ZnO,得到了易于磁性固液分离的磁载光催化剂ZnO/SiO_2-Fe_3O_4,并通过傅立叶红外光谱仪、X射线衍射仪和透射电子显微镜等对光催化剂进行了表征.以亚甲基蓝为目标降解物,研究了光催化剂在紫外光下的光催化活性.实验结果表明,在Fe_3O_4和ZnO之间包覆一层无定形SiO_2可使亚甲基蓝降解率由20.34%提高到94.52%,所制备的ZnO/SiO_2-Fe_3O_4在3次重复使用后仍能保持较好的光催化性能.