Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO2 composites

Multi-walled carbon nanotubes (MWCNTs)/TiO₂ composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and UV-vis absorption spectra. Compared to pure TiO₂, the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region. The photocatalytic performances of the MWCNTs/TiO₂ composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G (K-6G) and Mordant black 7 (MB 7) azo dyes solution under solar light irradiation. The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO₂ for the degradation of azo dyes K-6G and MB 7. The effect of MWCNTs content, catalyst dosage, pH, and initial dye concentration were examined as operational parameters. The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law. The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%. A plausible mechanism is also proposed and discussed on the basis of experimental results.     

H2O2-固载型TiO2光催化对城市污水消毒作用研究

以泡沫镍作为载体,利用电沉积技术将纳米TiO2负载在泡沫镍上,制成固载型TiO2光催化反应器,在光催化反应器中加入H2O2,研究H2O2-固载型TiO2光催化反应系统对城市污水消毒效果。试验表明,固载型TiO2光催化反应中加入10 ppm H2O2,能大大提高紫外消毒效果,降低原水浊度对紫外消毒系统的影响,同时显著减少紫外消毒系统出水光复活现象。H2O2-固载型TiO2光催化反应系统,对降低紫外消毒投资和运行成本,提高紫外消毒效果稳定性,促进城市污水紫外消毒技术的推广具有重要意义。     

纳米二氧化钛制备与表征

通过水热反应法合成出了两种纳米二氧化钛粉体材料,通过差热分析、X衍射分析、扫描电镜分析,粉体的平均直径小于100nm,通过光催化试验分析,纳米二氧化钛的光催化性能可以达到47%.     

镍掺杂二氧化钛光催化剂的制备与光催化性能研究

利用溶胶-凝胶法制备了镍掺杂的二氧化钛,采用紫外可见分光光度计、傅里叶红外分光光度计、X衍射仪(XRD)、扫描电镜(SEM)等测试手段对结果进行了表征。表征结果表明在550℃下煅烧的产物主要是锐钛型二氧化钛,镍的掺杂使得二氧化钛的紫外可见反射光谱明显红移,且镍掺杂二氧化钛的粒度减小,团聚程度下降。以活性艳蓝KN-R为模型降解目标物,通过比较镍掺杂二氧化钛、纯二氧化钛以及标准P25二氧化钛的光催化性能发现镍掺杂二氧化钛的光催化活性最好。当钛酸正丁酯/乙醇比为1:25;钛酸正丁酯/冰乙酸比为1:1;钛酸正丁酯/硝酸镍比为1 000:3;煅烧温度为550℃,煅烧时间为2 h时,镍掺杂二氧化钛的光催化效率最高,达到73.3%。     

UV/H2O2/

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Ti02光催化剂的掺杂改性和固定化研究

纳米TiO2作为光催化剂,由于其化学性质稳定、无毒、价廉等优点,使得纳米TiO2光催化氧化技术在环境领域具有广阔的应用前景,而针对其对可见光利用率低,光生电子一空穴对易复合,在使用过程中回收难,光催化效率不高等问题,近年来科研人员致力于Ti02光催化剂的改性和固定化研究。本文介绍了掺杂改性的不同方法及负载技术的研究进展,其中包括贵金属沉积、金属离子掺杂、非金属掺杂、共掺杂、表面光敏化、复合半导体等,并提出了TiO2光催化剂今后的研究方向及存在的问题。     

二氧化钛光催化降解双酚AF研究

系统研究了双酚AF在二氧化钛溶液中的光催化降解行为。就溶解氧、二氧化钛投加量、氟离子浓度和双酚AF的初始浓度等因素对双酚AF降解的影响进行了详细讨论。研究重点是双酚AF的降解动力学以及在降解过程中所产生的氟离子浓度。当双酚AF的初始浓度是40μmol/L时,经过540 min的光催化降解,反应体系的总有机碳去除率超过97%,此时溶液中氟离子的浓度为0.98 mg/L。双酚AF在二氧化钛溶液中的降解符合Langmuir-Hinshelwood动力学模型,其降解动力学常数是1.21μmol/(L·min)。结果表明,二氧化钛光催化可以有效的去除双酚AF,并且不产生其它二次污染物。     

Photocatalytic degradation of methyl orange using ZnO/TiO2 composites

ZnO/TiO₂ composites were synthesized by using the solvothermal method and ultrasonic precipitation followed by heat treatment in order to investigate their photocatalytic degradation of methyl orange (MO) in aqueous suspension under UV irradiation. The composition and surface structure of the catalyst were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). The degradation efficiencies of MO at various pH values were obtained. The highest degradation efficiencies were obtained before 30 min and after 60 min at pH 11.0 and pH 2.0, respectively. A sample analysis was conducted using liquid chromatography coupled with electrospray ionization ion-trap mass spectrometry. Six intermediates were found during the photocatalytic degradation process of quinonoid MO. The degradation pathway of quinonoid MO was also proposed.     

纳米TiO2光催化降解海水中的有机物

以无水四氯化钛为原料,采用溶胶-凝胶法制备出纳米TiO2粉末作为光催化剂,在高压汞灯的光源照射下对模拟海水进行了光催化降解。考察了TiO2光催化剂的焙烧温度、用量、反应pH、反应时间等因素对模拟海水COD降解率的影响。研究表明:经460℃焙烧1 h的TiO2光催化效果较好,在海水COD浓度约10 mg/L,溶液的初始pH为6.0、光催化剂用量1.8 g/L、反应时间2.5 h条件下,COD去除率可达99.58%。     

废水中染料的TiO2光催化氧化降解机理研究现状

系统论述了废水中TiO2光催化氧化降解染料的机理、动力学机制、染料的反应活性、研究中间降解产物的方法和结果等的研究现状，指出了目前研究中最大难点是分析手段的不足，对此提出了自己的看法，这为今后实际废水处理工艺过程中起到指导控制作用。     

热处理温度对TiO2z结构性质及光催化活性的影响

从晶相组成、晶格缺陷密度、表面羟基含量、晶粒尺寸以及比表面积等方面阐述了热处理温度与TiO2光催化剂结构性质的关系，并就混晶效应、载流子输运/俘获以及尺寸量子效应等对光仙伦活性的影响进行了讨论。此外，还汇总了对水中典型有机污染物的光催化氧化研究以及相关的催化剂结构性质。     

Synergistic effect of N- and F-codoping on the structure and photocatalytic performance of TiO2

Three types of TiO₂ nanostructures were synthesized via a facile hydrolysis method at 195 °C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of TiO₂ were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller porosimetry, ultraviolet–visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase TiO₂ had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure TiO₂. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N–F-TiO₂ nanomaterial shows considerable potential for water treatment under sunlight irradiation.     

凹凸棒负载TiO2对偶氮染料和纺织永废水催化脱污

通过浸渍的方法，制备了天然粘土矿石凹凸棒负载的P25 TiO2固化催化剂。实验了催化剂的负载量和煅烧温度对催化剂活尾的影响，研究了最佳固化催化剂对5种生物难降解的偶氮染料和纺织废水的太阳光催化脱污偶氮染料及毛纺织废水，而且具有高的稳定性，可重复使用。     

锰前驱体对MnO_x/TiO_2催化剂低温选择性催化还原NO_x影响

以醋酸锰和硝酸锰为前趋体通过浸渍法制备了MA和MN两种系列的MnOx/TiO2催化剂,结合BET、XRD、TPR及FT-IR等手段对催化剂进行了表征,并进行了比较,同时对两种系列的催化剂进行了选择催化还原脱硝的活性测试。结果表明,MA和MN均具有良好的低温催化活性,脱销效率随温度的变化趋势基本相同,在80℃时已经达到80%的脱硝效率;随着温度的升高,在200℃时效率上升至接近100%。通过对催化剂性能测试比较表明,锰的含量对于催化剂的活性有一定的影响。总体上看,MN具有更好的活性,脱销效率较高,并且其活动的窗口也是相对更宽,可能是因为以硝酸锰为前躯体制的的催化剂中MnO2的含量相对较多,即两类前驱体在制备过程中与载体之间的相互作用不同,导致最终催化剂表面活性组分MnOX结构和价态的不同,从而影响催化剂的低温活性。     

响应面法优化TiO2光催化预处理树脂废水

为探讨不同环境因素对TiO₂光催化对树脂废水预处理效果的影响,采用响应面法对影响树脂废水Ti0₂光催化处理过程中的3个主要因素pH、TiO₂量及废水初始COD进行优化,并以COD去除率为响应值。经统计学分析和响应面模型建立,确定了悬浮态TiO₂光催化处理树脂废水的最佳控制条件为:pH值4.06、TiO₂投加量2.45 g/L、初始COD 2 007mg/L。在因素最优组合的条件下,废水COD去除率可达39.8%,与响应面模型最大预测值41%非常接近。与其他物化预处理方式相比,Ti0₂光催化对废水COD和挥发酚的去除率最高,且对废水生化性有很大提高,具有良好的应用前景。     

银、钕掺杂TiO_2催化光解甲基橙的实验研究

实验用水热合成法制备出银、钕掺杂TiO2催化剂粉体,然后以高压汞灯为光源,掺杂TiO2催化剂粉体为光化降解催化剂,探究对甲基橙模拟印染废水光催化分解的效果。光解实验研究采用正交设计法,以模拟废水浓度、催化剂用量、光照时间以及pH为因素,各因素选取4个水平,对催化光解甲基橙染料的降解率进行评价。分析结果表明:银、钕掺杂TiO2催化剂对甲基橙光化降解有良好的效果,最佳实验条件为:溶液pH为5,甲基橙的初始质量浓度为2 mg/L,催化剂投加量60 mg/L和光照时间80 min。在最佳条件下,连续光照8 h后甲基橙的降解率达到92%以上。     

Inactivated properties of activated carbon-supported TiO2 nanoparticles for bacteria and kinetic study

The activated carbon-supported TiO₂ nanoparticles (TiO₂/AC) were prepared by a properly controlled sol-gel method. The effects of activated carbons (AC) support on inactivated properties of TiO₂ nanoparticles were evaluated by photocatalytic inactivation experiments of Escherichia coli. The key factors affecting the inactivation efficiency were investigated, including electric power of lamp, temperature, and pH values. The results show that the TiO₂/AC composites have high inactivation properties of E. coli in comparison with pure TiO₂ powder. The kinetics of photocatalytic inactivation of E. coli was found to follow a pseudo-first order rate law for TiO₂/AC composites, and kinetic behavior could be described in terms of a modified Langmuir-Hinshelwood model. The values of the adsorption equilibrium constants for the bacteria, K_c, and for the rate constants, k_r, were certainly depended on TiO₂ content. At 47 wt.% TiO₂ coatings with the highest rate constant, the K_c and k_r were 1.17 × 10⁻⁸L/cfu and 1.43 × 10⁶ cfu/(L·min), respectively. The variety of parameters shows significant effects on inactivation rate. The outer layer of bacteria decomposed first resulting in inactivation of cell, and with further illumination, the cells nearly decomposed.     

Tricrystalline TiO2 with enhanced photocatalytic activity and durability for removing volatile organic compounds from indoor air

It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO₂-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO₂ with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO₃. The obtained samples were characterized by X-ray diffraction and N₂ adsorption–desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO₂ exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO₂, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO₂ prepared at R_HNO3 = 0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO₂ will enrich the chemistry of the TiO₂-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.     

Photocatalytic degradation of methylbutandioic acid (MBA) in aqueous TiO2 suspension: influences of MBA adsorption on the solid semi-conductor

In the present work we describe the photocatalytic degradation of methylbutandioic acid (MBA), focusing particularly on adsorption of the MBA on TiO₂ surface. We observe a very fast surface carboxylate formation, a decrease of the surface carboxylates during the reaction and an apparent zero order kinetic for the degradation of MBA. We conclude that the main way of MBA degradation is its reaction in the solution, and not on the surface of TiO₂. The influence of the surface carboxylates on the efficiency of the catalyser is under study.     

Contribution of winter fluxes to the annual CH4, CO2 and N2O emissions from freshwater marshes in the Sanjiang Plain

Introduction C arbon dioxide, m ethane and nitrous oxide play im portant roles in the radiation balance of the earth contributing to the greenhouse effect (Rodhe, 1990). N 2O also takes part in the destruction of stratospheric ozone (W ang, 1999). N atura…