Photocatalytic decomposition of bisphenol A in water using composite TiO2-zeolite sheets prepared by a papermaking technique

Titanium dioxide (TiO2) photocatalyst and zeolite adsorbent were made into a paper-like composite by a papermaking technique using pulp and ceramic fibers as sheet matrix. The photocatalytic performance for the degradation of bisphenol A (BPA) dissolved in water was investigated under UV irradiation. The TiO2 sheet prepared was easier to handle than the original TiO2 powders in aqueous media. The TiO2 sheet could decompose the BPA under UV irradiation, although at a lower degradation efficiency than the TiO2 suspension. The TiO2-free zeolite sheet could not remove the BPA from water completely because of its adsorption equilibrium. Furthermore, the composite TiO2-zeolite sheets exhibited a higher efficiency for BPA removal than the zeolite-free TiO2 sheets, the efficiency of the former being equivalent to that of the TiO2 suspension. The enhancement in removal efficiency was not attributed to the simple adsorption of BPA on zeolite but rather to the synergistic effect obtained through the combined use of TiO2 photocatalyst and zeolite adsorbent in the paper-like composite sheet, which is believed to accelerate the BPA photodegradation in water.     

TiO2-based photocatalytic degradation of 2-chlorophenol adsorbed on hydrophobic clay

The combination of adsorption and heterogeneous photocatalysis has been investigated as a promising technology for the removal of organic water pollutants. A laboratory study of the removal and decomposition of 2-chlorophenol (2-CP) as a toxic organic pollutant was carried out under various conditions with an organophilized clay mineral (hexadecylpyridinium chloride-modified montmorillonite; HDPM) as adsorbent and Degussa P25 TiO2 as photocatalyst. Three different oxidation processes leading to the degradation of 2-CP were compared: direct photolysis, heterogeneous photocatalysis in a TiO2 suspension, and the decomposition of substrate adsorbed on HDPM in the presence of TiO2. Both the degradation of 2-CP and the formation of intermediates were analyzed by HPLC, the total organic carbon content and the total organic and inorganic chloride contents were measured to monitor the mineralization process, and X-ray diffraction and thermoanalytical measurements were made to characterize the hydrophobic clay adsorbent. The heterogeneous photocatalytic degradation of dissolved (2-CP/UV/TiO2) and desorbed 2-CP (2-CP/HDPM/UV/TiO2) appeared to be equally efficient, whereas direct photolysis of 2-CP was far less efficient in the oxidative destruction. HDPM proved to be a suitable adsorbent, capable of adsorbing toxic organics from water. It was demonstrated that the adsorbent (at relatively high concentration) did not decrease the rate of mineralization of 2-CP. The results confirmed that the adsorbent retains its structure and composition during the mineralization process, and thus it can be reused without regeneration. The combination of adsorption and heterogeneous photocatalysis studied may be an efficient and economical means of accumulating, removing, and oxidizing organic water contaminants, and its application is in accordance with the growing environmental demands.     

Antifungal activity of TiO2 photocatalysis against Penicillium expansum in vitro and in fruit tests

The antifungal activity of TiO2 photocatalytic reaction in the form of TiO2 powder and TiO2 coated on a plastic film against Penicillium expansum was investigated in vitro and in fruit tests. The mixture of P. expansum conidial suspension and TiO2 powder was added to potato dextrose agar (PDA) plates for vitro test. The TiO2 photocatalytic reaction reduced conidial germination of the fungal pathogen. It was found that the ability of the TiO2 photocatalytic reaction to suppress P. expansum growth correlated to the amount of TiO2 added. Lower numbers of viable colonies of P. expansum were observed with increasing amount of TiO2. Regardless of the kind of selected fruit inoculated with P. expansum, both TiO2 powder and TiO2-coated film exhibited antifungal activity to control fruit rot. Development of Penicillium rot in apple was significantly (P = 0.05) retarded by the TiO2 photocatalytic reaction. Similarly the TiO2 photocatalytic reaction was the only treatment where no tomato fruit rot was noticeable after 1 week of storage. TiO2-coated film also decreased brown lesions and Penicillium rot infection in lemons. The mean severity fruit rot scores (browning and softening flesh) were 3.2 and 1.9 for uncoated and TiO2-coated film, respectively. Our findings suggest that "TiO2 photocatalytic reaction" shows antifungal activity against P. expansum which may have potential for postharvest disease control.     

负载银纳米TiO2光催化活性染色废水的脱色

采用负载银纳米TiO2光催化对活性艳红K-2BP染料废水脱色，分析了不同光照时间、不同染料浓度、不同pH值下的光催化脱色效果。试验结果表明，负载银纳米TiO2对活性艳红K-2BP染料废水的光催化是可行的；低浓度染色废水的脱色率较高；pH值对光催化脱色影响很大。     

二氧化钛纳米管的制备及其光催化性能

为提高TiO_2的光催化性能,通过电化学阳极氧化法在金属钛箔基体上制备了结构有序的TiO_2纳米管(TiO_2NTs),并以此为基础通过连续离子层吸附反应技术(SILAR)制备了Ag、CdS共修饰的TiO_2纳米管(AgCdS/TiO_2NTs)。采用X射线衍射仪、扫描电子显微镜、透射电子显微镜、元素分析仪和紫外可见漫反射光谱等表征手段,对Ag-CdS/TiO_2NTs形貌结构、元素组成和光吸收特性等进行了表征,并研究了Ag、CdS修饰后的TiO_2纳米管的光催化性能。结果表明:Ag和CdS纳米粒子被成功沉积在TiO_2纳米管上;与纯TiO_2纳米管的吸收光谱相比,Ag-CdS/TiO_2NTs对光的吸收范围延伸到整个可见光区域;与纯TiO_2纳米管或CdS修饰的TiO_2纳米管相比,Ag(3)-CdS/TiO_2NTs对甲基橙脱色率最高,70 min后脱色率达100%。     

Supercritical preparation of a highly active S-doped TiO2 photocatalyst for methylene blue mineralization

Sulfur-modification of the TiO2 was achieved by treating the TiO2 precursor (xerogel) under supercritical conditions in CS2/ethanol fluid. Nuclear magnetic resonance, X-ray photoelectron spectroscopy and Fourier transform infrared spectra demonstrated that the TiO2 was modified by the S-species incorporated into the TiO2 network by forming S-Ti-O bonds rather than by the adsorbed CS2. During liquid-phase photocatalytic degradation of methylene blue (MB) under visible light irradiation (> 420 nm), the as-prepared S-doped TiO2 exhibited much higher activity than the undoped TiO2 obtained via either supercritical treatment or direct calcinations and even the N-doped TiO2 obtained via supercritical treatment. The promoting effects of both the supercritical treatment and S-modification on the photocatalytic activity were discussed by considering the high surface, large porous channels, well crystallized anatase phase, excellent thermal stability, and strong absorbance for visible lights, corresponding to the high quantum efficiency. The maximum activity was obtained at 1.8% S/Ti molar ratio, nearly 8 times higher than that of the commercially available P25 TiO2.     

多孔TiO2薄膜在PET纤维上的负载及其光催化性能

采用浸渍法将低温制备的TiO2溶胶在普通和碱减量PET纤维上负载成膜,并以聚苯乙烯（PS）微球为模板剂使TiO2膜多孔化,制备了一系列TiO2/PET光催化纤维。采用XRD、SEM对TiO2和纤维进行了表征,并通过对甲基橙的降解来考察其光催化性能。结果表明：溶胶经室温陈化后可得到具有较高光催化活性的纳米锐钛矿型TiO2。PET纤维上TiO2的负载率随着溶胶在浸渍液中的含量增加而增大。PET纤维的碱减量有利于TiO2的负载和光催化活性的提高,且随着TiO2负载率的增加,甲基橙降解率具有先增加后缓慢减小的趋势。当碱减量纤维的TiO2负载率为4.2%时,光催化活性最好。利用PS为模板剂使TiO2薄膜多孔化可以进一步提高光催化纤维的比表面积和吸附能力,从而提高光催化活性。     

TiO2/蒙脱土复合光催化材料的制备与结构性能

以钛酸丁酯为原料,采用溶胶-凝胶法制备TiO2光催化材料,研究了水、硝酸用量和反应温度对TiO2性能的影响.以蒙脱土为复合基质制备TiO2/MMT复合材料,采用XRD和FT-IR表征了产物的结构,并考察了该材料对亚甲基蓝的降解行为.结果表明:锐钛矿型TiO2已插层柱化到蒙脱土层间,形成分子级别的TiO2支柱,钛的掺入导致原土层间域内离子性质发生变化,从而使TiO2/MMT复合材料的光降解效率远远高于纯TiO2粉体,并形成吸附-光降解协同作用,在降解40 min后对亚甲基蓝溶液的降解率可达到95%.     

TiO2/SiO2的制备与光催化降解甲基橙

为了探讨Ti02晶粒形貌对光催化过程的作用规律,研究吸附法和浸渍法制备的TiO2光催化剂降解甲基橙的过程,并考察制备反应条件对催化剂形貌和活性的影响.通过剖析反应的基本过程后得出,扩散过程与表面反应过程耦合,催化剂活性与甲基橙浓度的相对高低决定反应过程的控制步骤,从而对表观级数产生影响.在催化剂活性的考评中发现,低Ti含量以及小粒径情况下影响光催化的关键因素是晶型,其次为含量、粒径.吸附法制备的光催化剂Ti含量高,粒径小,可控性好,具有比浸渍法制备的材料更好的催化性能.随着水量的增加,吸附相反应技术的优势越来越显著.     

纳米TiO2光催化氧化技术在造纸废水处理中的应用

TiO2光催化氧化是一种新兴的高效水处理技术，其在处理废水中的难降解毒性有机污染物等方面具有广阔的应用前景。文章介绍了纳米TiO2光催化氧化技术的原理、影响因素及其在制浆造纸废水处理方面的研究进展，并对存在的问题作了探讨。     

Selective photocatalytic oxidation of NH3 to N2 on platinized TiO2 in water

Selective photocatalytic oxidation of NH3 to N2 is proposed as a new treatment method for controlling the levels of ammonia in water. The photocatalytic oxidation of ammonia on naked and metallized TiO2 in water saturated with air, nitrogen, or NO2 gas was investigated. While the slow photocatalytic oxidation of NH3 to NO2-/NO3- is the only pathway for decomposition of NH3 on naked TiO2 and Au/TiO2, a new pathway, that of selective oxidation of ammonia to dinitrogen, opens up on Pt/TiO2. The formation of dinitrogen from the oxidation of 15NH3 was confirmed by mass spectrometric detection of 15N2. The photocatalytic conversion of NH3 to N2 greatly increases when the Pt/TiO2 suspension is saturated with NO2 gas, whereas NO2 itself shows little reactivity with naked TiO2 and Au/TiO2. Over 80% of the total nitrogen available in ammonia (0.1 mM) is converted into N2 within 40 min illumination of the N2O-saturated Pt/TiO2 suspension. The ability of N2O to accept the conduction band electrons of Pt/TiO2 was verified by photoelectrochemical measurements. NO2 reductively decomposes to generate OH radicals on Pt/TiO2; the rate of ammonia degradation in the NO2-saturated Pt/TiO2 suspension significantly decreases in the presence of excess tert-butyl alcohol, an OH radical scavenger. The presence of Pt deposits on the TiO2 particles changes the photocatalytic pathway of ammonia conversion by both enhancing OH radical production from NO2 and stabilizing intermediate NHx (x=0, 1, 2) species to facilitate their recombination into N2.     

Enhanced degradation in nanocomposites of TiO2 and biodegradable polymer

Nanocomposites of titamium dioxide (TiO2) particles and biodegradable poly (butylene succinate) (PBS) were fabricated by melt-blending using a high-shear extruder. TiO2 particles were highly dispersed in the PBS matrix by high-shear processing, and the addition of TiO2 particles into PBS did not decrease its mechanical strength. The photocatalytic decomposition and biodegradable properties of the nanocomposites were evaluated by UV irradiation or enzymatic degradation methods in vitro. It was found that both the esterase enzyme and UV irradiation decomposed the nanocomposites. Photocatalytic decomposition of PBS clearly depended on the size and dispersibility of TiO2 particles in PBS polymer. Higher dispersibility and smaller size of TiO2 particles were effective on the photocatalytic oxidation of PBS. In addition, decomposition rate under a simultaneous UV irradiation treatment and immersion in an enzyme solution was higher than those under UV irradiation or immersion in an enzyme solution. These results indicate that the nanocomposites can easily be decomposed not only by an enzyme in soil or compost, but also by photocatalytic oxidation of TiO2 under sunlight.     

织物负载S-N共掺杂TiO2薄膜的光催化降解活性染料研究

采用溶胶-凝胶法制备S-N共掺杂改性纳米TiO2溶胶,通过浸溃工艺对棉织物进行整理,制备出织物负载S-N共掺杂TiO2薄膜.探讨了在日光灯照射下,其对活性红MS模拟活性染料废水的光催化活性.结果表明,在日光灯照射下,织物负载S-N共掺杂TiO2薄膜的光催化降解率大大高于织物负载TiO2薄膜的降解率;对活性红MS的光催化降解效果随染液中氯化钠浓度的升高而降低,随碳酸钠浓度的升高而提高.     

钨杂二氧化钛负载棉织物的微波法制备及光催化性能

采用(NH4)2TiF6为原料,钨酸钠和钨酸铵作为钨源在微波加热的条件下反应生成钨掺杂的锐钛矿W-TiO2,并采用微波辅助法原位处理到棉织物上从而赋予棉织物光催化性能。讨论了(NH4)2TiF6和H3BO3的摩尔比、微波加热温度、钨掺杂比等因素对TiO2晶型的影响,结果表明：(NH4)2TiF6和H3BO3以不同比例混合、微波加热温度、钨掺杂对TiO2晶型没有影响。研究了前驱体浓度、钨掺杂量、微波反应时间及温度对织物光催化性能的影响。制备具有光催化性能的W-TiO2/棉织物的最优工艺是：前驱体浓度为0.05mol/L,95℃微波加热45min,钨的最佳掺杂比例是5%。     

A new route for degradation of volatile organic compounds under visible light: using the bifunctional photocatalyst Pt/TiO2-xNx in H2-O2 atmosphere

The bifunctional photocatalyst Pt/TiO2-xNx has been successfully prepared by wet impregnation. The properties of Pt/ TiO2-xNx have been investigated by diffuse reflectance spectra, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, a photoluminescence technique with terephthalic acid, and electric field induced surface photovoltage spectra. The photocatalytic activity of the sample was evaluated by the decomposition of volatile organic pollutants (VOCs) in a H2-O2 atmosphere under visible light irradiation. The results demonstrated that nitrogen-doped and platinum-modified TiO2 in a H2-O2 atmosphere could enormously increase the quantum efficiency of the photocatalytic system with excellent photocatalytic activity and high catalytic stability. The increased quantum efficiency can be explained by enhanced separation efficiency of photogenerated electron-hole pairs, higher interface electron transfer rate, and an increased number of surface hydroxyl radicals in the photocatalytic process. A mechanism was proposed to elucidate the degradation of VOCs over PtTiO(2-x)Nx in a H2-O2 atmosphere under visible light irradiation.     

Plasma surface modified TiO2 nanoparticles: improved photocatalytic oxidation of gaseous m-xylene

Titanium dioxide (TiO(2)) is a preferred catalyst for photocatalytic oxidation of many air pollutants. In an effort to enhance its photocatalytic activity, TiO(2) was modified by pulsed plasma treatment. In this work, TiO(2) nanoparticles, coated on a glass plate, were treated with a plasma discharge of hexafluoropropylene oxide (HFPO) gas. By appropriate adjustment of discharge conditions, it was discovered that the TiO(2) particles can be either directly fluorinated (Ti-F) or coated with thin perfluorocarbon films (C-F). Specifically, under relatively high power input, the plasma deposition process favored direct surface fluorination. The extent of Ti-F formation increased with increasing power input. In contrast, at lower average power inputs, perfluorocarbon films are deposited on the surface of the TiO(2) particles. The plasma surface modified TiO(2) nanoparticles were subsequently employed as catalysts in the photocatalytic oxidation of m-xylene in air, as carried out inside a batch reactor with closed loop constant gas circulation. Both types of modified TiO(2) were significantly more catalytically active than that of the unmodified particles. For example, the rate constant of m-xylene degradation was increased from 0.012 min(-1) with untreated TiO(2) to 0.074 min(-1) with fluorinated TiO(2). Although it is not possible to provide unequivocal reasons for this increased photocatalytic activity, it is noted that the plasma surface treatment converted the TiO(2) from hydrophilic to highly hydrophobic, which would provide more facile catalyst adsorption of the xylene from the flowing air. Also, based on literature reports, the use of fluorinated TiO(2) reduces electron-hole recombination rates, thus increasing the photocatalytic activity.     

用吸附相反应技术制备弱光响应的铈掺杂TiO2复合光催化剂

为拓展多相光催化的实际应用和满足环境治理的严格要求,利用吸附相反应技术设计并制备了弱紫外光响应高效的TiO2 多组分催化剂。借助透射电子显微镜、高分辨率透射电子显微镜和X 射线衍射分析了不同焙烧温度下铈离子掺杂量对催化剂形貌的影响,并结合光致发光光谱和弱光降解甲基橙过程,探索了催化剂结构变化对光生载流子复合率和弱光催化活性的影响。结果表明,当掺杂量较低（小于0.10%）时,铈离子掺入引起TiO2 晶格膨胀,从而引入光生载流子的浅能级捕获中心,提升了催化活性;在较高掺杂量（0.20% 以上）时, 铈离子掺入抑制了TiO2 结晶,催化剂中大量无定形TiO2 严重抑制了其活性;焙烧温度越高,铈离子掺杂量对催化剂结构和活性的影响越显著;降解高浓度甲基橙时,催化性能最好的催化剂的活性是商用P 25 的2 倍多。     

Photocatalytic degradation of pesticide pyridaben. 3. In surfactant/TiO2 aqueous dispersions

The effective TiO2 photocatalytic degradation of pyridaben in an acetronitrile/water dispersion has been investigated in previous work, but could not be achieved in the case of real waters. In this paper, photocatalytic degradation of pyridaben on TiO2 particles under UV light (lambda> 360 nm) illumination in surfactant CTAB (cetyltrimethyl ammonium bromide) aqueous dispersions was studied. 1H NMR was used to determine quantitative information about the adsorption mode of pyridaben in CTAB micelles. The results showed that the upfield 1H shifts were largest for long chain protons of CTAB, indicating that the hydrophobic aromatic rings were primarily located in this region. Adsorption models on TiO2 surface were thus proposed. The reaction rates decreased with the increase of pH value, which can be attributed to the surface charge variations of pyridaben adsorbed onto TiO2 particles. The adsorption isotherms at different pH values confirmed that preadsorption on the surface of TiO2 particles was prerequisite for efficient degradation. Furthermore, an oxidation reagent such as H2O2 was added to the photocatalytic system, which may act as an alternative electron acceptor and result in a notably enhanced rate of pollutant destruction. On the basis of intermediates identified by GC/MS, a degradation pathway was proposed.     

反相微乳液水热法合成锐钛矿TiO2微球及其光催化性能

以钛酸丁酯（TBT）为钛源、辛烷基苯酚聚氧乙烯醚(Triton X-100)为表面活性剂,采用反相微乳液水热法制备锐钛矿TiO2微球,并研究了反应体系中水含量对生成的锐钛矿TiO2微球性能的影响。采用粉末X射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）、场发射扫描电子显微镜（FE-SEM）、透射电子显微镜（TEM）、荧光光谱（PL）对锐钛矿TiO2微球的结构、形貌和物相等进行表征。结果表明：在一定范围内增加钛酸丁酯/水（TBT/H2O）摩尔比,锐钛矿TiO2微球形貌由无规则形态向规则形貌转变,颗粒尺寸也随之变均匀。同时,以亚甲基蓝为目标降解物,对其光催化活性进行评价,结果表明颗粒尺寸和形貌的变化对其催化活性有较大影响,当TBT/H2O摩尔比为1:25时,微球尺寸均匀,催化活性最好,优于商业化P25。     

镧掺杂TiO2光催化降解酸性红B的研究

采用溶胶-凝胶法制备了La^3＋／TiO2光催化剂，在模拟太阳光照射下，考察了该催化剂对酸性红B的光催化降解效果。结果表明：掺杂量ω（La^3＋）1％、催化剂用量1g／L、通气量100 mL／min、体系pH值是7时，50mg/L的酸性红B经3 h光催化降解，其降解率可达92．9％：与纯TiO2相比，La^3＋／]TiO2光催化剂显示出良好的太阳光催化活性：