Simple fabrication of carbon/TiO2 composite nanotubes showing dual functions with adsorption and photocatalytic decomposition of Rhodamine B

Carbon/TiO2 composite nanotubes were fabricated via a very simple electrospinning process and their dual functionalities of adsorptivity and photocatalytic activity were evaluated using Rhodamine B (RhB) as a model organic pollutant. A poly(vinyl alcohol) (PVA) aqueous solution was directly electrospun into a coagulation bath containing titanium (IV) tetraisopropoxide (TTIP) solution so that PVA-core/TiO2-shell composite nanofibers were formed through the in situ sol-gel reaction of TTIP. The carbon/TiO2 composite nanotubes were then fabricated by heat treatment of composite nanofibers under nitrogen atmosphere. By using several characterization methods, we confirmed that the resultant nanotubes consisted of anatase TiO2 nanocrystallites embedded in a carbonaceous matrix. The prepared nanotubes exhibited fast adsorption of RhB with high capacity compared with a commercial porous carbon, and they also showed the photocatalytic decomposition activity for the dye molecules under UV irradiation comparable to the degradation by P-25 and ST-01 (commercial TiO2). Finally, the carbon/TiO2 composite nanotubes exhibited several cycle performances of adsorption-photodegradation for RhB. This indicates that the composite nanotubes can adsorb and photodecompose organic pollutants repeatedly without additional activating processes.     

Photocatalytic properties of silver nanoparticles decorated nanobranched TiO2 nanofibers

In this study, nanobranched TiO2 nanofibers and silver loaded nanobranched TiO2 nanofibers were prepared by electrospinning technique followed by TiCl4 aqueous solution treatment and silver photodeposition method. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to investigate the morphology of the products. X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were conducted on the samples to study their chemical composition as well as crystallographic structure. The photocatalytic activities of these produced nanofibers were examined with two organic dyes, methylene blue and methyl orange, under ultraviolet (UV) light irradiation. The effect of nanobranches and silver modification on TiO2 nanofibers was revealed in the photocatalysis process. The photocatalytic degradation rates of silver loaded on nanobranched TiO2 nanofibers were 1.6 and 1.7 times as that of pure TiO2 nanofibers in the presence of methylene blue and methyl orange, respectively, which indicated silver nanoparticles combined nanobranches modified on the surface of TiO2 nanofibers could enhance the photocatalytic ability.     

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water

TiO(2) photocatalyst (P-25) (50mgL(-1)) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO(2) were obviously increased. Pulsed high-voltage discharge process with TiO(2) had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10x10(-6) to 1.50x10(-6)Ms(-1), the ozone formation rate from 1.99x10(-8) to 2.35x10(-8)Ms(-1), respectively. In addition, this process had no influence on the photocatalytic properties of TiO(2). The introduction of TiO(2) photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants.     

碳纤维负载钐掺杂纳米TiO_2复合材料的制备与表征

采用静电纺丝法和热处理工艺制备了纳米碳纤维负载掺杂1.5%(摩尔分数)Sm的纳米Ti O2复合材料(Sm-Ti O2/CNFs),利用SEM、EDX、TEM、FTIR和XRD对其组成和结构进行了表征,并以甲基橙为降解对象,考察了Sm-Ti O2/CNFs复合材料在紫外光照射下对甲基橙的光催化降解效果。结果表明,掺杂Sm3+的Ti O2以锐钛矿晶型均匀分散在碳纳米纤维的表面和内部,质量分数为20%左右;相对于未掺杂的Ti O2/CNFs样品,Sm-Ti O2/CNFs的光催化活性提高约37%。     

Fabrication characterization and activity of a solar light driven photocatalyst: cerium doped TiO2 magnetic nanofibers

A novel magnetic separable composite photocatalytic nanofiber consisting of TiO2 as the major phase, CeO(2-y) and CoFe2O4 as the dopant phase was prepared by sol-gel method and electrospinning technique, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectrum (UV-vis DRS) and vibrating sample magnetometer (VSM). The photocatalytic activity of the resultant CoFe2O4-TiO2 and CeO(2-y)/CoFe2O4-TiO2 nanofibers was evaluated by photodegradation of methylene blue (MB) in an aqueous solution under xenon lamp (the irradiation spectrum energy distribution is similar to sunlight) irradiation in a photochemical reactor. The results showed that the dopant of Ce could affect the absorbance ability and photo-response range. The sample containing 1.0 wt% CeO(2-y) exhibited the highest degradation with 35% for MB under simulate solar light irradiation. Furthermore, the as-synthesized composite photocatalytic nanofibers could be separated easily by an external magnetic field, thus it might hold potential for application in wastewater treatment.     

静电纺丝法制备Fe3+/TiO2纳米纤维及表征

以聚乙烯吡咯烷酮(PVP)为纤维模板,钛酸四丁酯(Ti[O(CH2)3CH3]4)和Fe3+为前驱体,乙醇为溶剂,醋酸为催化剂,采用静电纺丝法制备不同含铁量的复合纳米纤维Fe3+/TiO2,经500℃煅烧得到以锐钛矿为主的Fe3+/TiO2纳米纤维。采用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分别表征了Fe3+/TiO2纳米纤维的形貌与晶态,计算了样品的晶粒尺寸和锐钛矿所占的比例,并比较了5%Fe3+/TiO2纳米纤维、5%Fe3+/TiO2粉体以及纯TiO2纳米纤维三者光催化降解亚甲基蓝(MB)的效果。研究表明:由静电纺丝法制备的5%Fe3+/TiO2纳米纤维的光催化降解效果比相同含铁量的粉体的降解效果好,TiO2纳米纤维比5%Fe3+/TiO2纳米纤维的光催化活性高。     

Fabrication of TiO2 nanoparticles loaded on coal fly ash composite with enhanced photocatalytic activity

By immobilized on the coal fly ashes, the TiO2 nanoparticles photocatalysts were obviously improved in removing organic compounds of the contaminated water. These composite catalysts were fabricated by three different methods involving hydrothermal method, physical blending and sol-gel method. The resulting materials have been characterized by XRD, SEM and FTIR. The photocatalytic activity of these as-prepared samples was assessed by photocatalytic degradation of methylene blue (MB) aqueous solution at ambient temperature under UV-light irradiation. The experimental results indicated that TiO2 nanoparticles were tightly dispersed on the surface of spherical coal fly ash particles, where the adsorption ability of the catalysts is effectively promoted. It was found that the catalysts prepared by hydrothermal method exhibited the highest photocatalytic activity than that prepared by physical blending or sol-gel method which mainly resulted from the synergistic effect of TiO2 nanopartcles and coal fly ashes.     

Direct formation of reusable TiO2/CoFe2O4 heterogeneous photocatalytic fibers via two-spinneret electrospinning

A reusable photocatalytic TiO2/CoFe2O4 composite nanofiber was directly formed by using a vertical two-spinneret electrospinning process and sol-gel method, followed by heat treatment at 550 degrees C for 2 h. The high photocatalytic activity of the composite nanofibers depends on the good morphology of the fibers and the appropriate calcination temperature. The crystal structure and magnetic properties of the fibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The photocatalytic activity of the TiO2/CoFe2O4 fibers was investigated through ultraviolet-visible absorbance following the photo-oxidative decomposition of phenol. Meanwhile, the presence of CoFe2O4 not only broadens the response region of visible light, but also enhances the absorbance of UV light. Furthermore, these fibers displayed photocatalytic activity associated with magnetic activity of CoFe2O4 ferrites, allowing easy separated of the photocatalysts after the photo-oxidative process and effectively avoided the secondary pollution of the treated water.     

Capability of coupled CdSe/TiO(2) for photocatalytic degradation of 4-chlorophenol

The photocatalytic process using TiO(2) and coupled semiconductor in the photodegradation reaction of 4-chlorophenol (4-CP) was investigated. Nanosized titanium dioxide powder was synthesized via the sol-gel procedure and modified via the coupled photocatalysts. The microstructural and chemical properties of TiO(2) and coupled CdSe/TiO(2) were also examined. For CdSe/TiO(2) samples, the specific surface area was 7.0 m(2)/g and the deposition proportion of CdSe was approximately 27.6%. In the photocatalysis results, higher photodegradation efficiency of 4-CP was observed at higher pH values. In the UV 254 nm system, the degradation efficiency of 4-CP and TOC with sol-gel produced TiO(2) (TiO(2)(SG)) powder was higher than with commercial TiO(2)(RdH) powder. For the coupled semiconductor system (CdSe/TiO(2)), the apparent first-order rate constants were 1.35 x 10(-2), 4.33 x 10(-2), 2.0 x 10(-3) and 1.9 x 10(-3)min(-1) at the conditions of pH 7 (254 nm), pH 11 (254nm), pH 7 (365 nm), and pH 11 (365 nm). The disappearance of 4-CP under CdSe/TiO(2)(RdH) photoreaction at pH 7 and 365 nm condition is better than that of TiO(2)(RdH) system, with 30% versus 22% 4-CP reduction in 180 min. In the same condition, CdSe/TiO(2)(RdH) provided more photomineralization efficiency than that of TiO(2)(RdH) in terms of TOC reduction. Both 4-CP and TOC reduction were significant for systems illuminated at 254 nm. Considering the direct photolysis effect at 254 nm where 4-CP reduction is near 100% and TOC removal is nil, CdSe/TiO(2)(RdH) exhibits a 50% photomineralization efficiency and a nearly four times faster reaction rate than the single TiO(2)(RdH) semiconductor.     

Analysis of optical properties of TiO2 nanoparticles and PAN/TiO2 composite nanofibers

The aim of the study was the production of thin composite nanofibrous mats PAN/TiO₂ nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO₂ nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO₂ rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer.     

Synthesis of anatase-silver nanocomposite fibers via electrospinning

There has been growing interest in new ways to produce composite nanofibers. Continuous TiO2 (anatase phase) nanofibers with silver nanoparticles were prepared successfully via sol-gel and electrospinning. A sol containing poly(vinyl pyrrolidone), titanium tetraisopropoxide, and silver nitrate was injected through a conductive capillary where high voltage was applied. As a result of electrospinning, continuous composite nanofibers were collected and they were calcined in air at 500 degrees C in order to complete the crystallization of anatase phase. The anatase-silver nanocomposite fibers were characterized with X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy.     

Nanofibrous TiO2-core/conjugated polymer-sheath composites: synthesis, structural properties and photocatalytic activity

Nanofibrous TiO2-core/conjugated polymer-sheath composite nanocables were synthesized by in-situ chemical oxidative polymerization of aniline with oxidant in the presence of TiO, nanofibers prepared through an electrospinning process. During the polymerization process, aniline molecules were adsorbed on the surface of TiO2. Upon the addition of oxidant, the polymerization of aniline takes place on the surface of the TiO2 nanofibers and polyaniline (PANI) is gradually deposited on their surface. The resulting TiO2-PANI nanocomposites have a coaxial nanocable structure. The morphological and structural properties of the composite nanocables were analyzed by using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and UV-visible spectroscopy (UV-vis), respectively. The HRTEM images proved that PANI (20 nm thickness) covered the surface of the TiO2 nanofibers. Also, the photocatalytic activity for the degradation of organic dyes on fibrous photocatalysts under UV-light was studied. The photocatalytic experiments showed that dye could be degraded more efficiently on the TiO2-PANI composite nanocables than on pure TiO2, due to the charge transfer from PANI to TiO2. The method for the synthesis of these unique structured composite nanocables is simple, rapid and reproducible. This facile method may be developed to produce multifunctional nanocomposites of various polymers with metal oxide fibers on a large scale for various technological applications such as sensors, solar cells, and catalysts.     

Facile fabrication and photocatalytic application of Ag nanoparticles-TiO2 nanofiber composites

A novel chemical method has been developed for the fabrication of Ag nanoparticles-coated TiO2 nanofiber composites. The method involves dispersion of TiO2 nanofibers in silver salt solution under ultrasonication, followed by addition of sodium citrate as a reducing agent. The Ag-coated TiO2 composites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron microscopy (XPS). Furthermore, the photocatalytic performance was evaluated by the photocatalytic degradation of methyl orange under UV-light irradiation. It was found that the heterogeneous Ag-TiO2 composite showed a higher activity than the pure TiO2 nanofiber; the enhanced activity can be attributed to the excellent distribution and interaction of Ag nanoparticles with the TiO2 nanofiber support. A plausible mechanism for the formation of the Ag-coated TiO2 composite and reasons for the enhancement of photocatalytic activity are also discussed.     

TiO_2/改性膨润土复合光催化材料的制备及其性能

本文采用无机和有机两种改性方法对钠基膨润土进行改性,在超声辅助下采用溶胶-凝胶法制备了TiO2/改性膨润土复合光催化材料。用X射线衍射(XRD)和红外光谱(IR)等测试技术对复合材料进行了表征,以TNT的吸附和降解为模型反应,考察了膨润土的改性对复合材料的吸附和光催化性能的影响。实验结果表明:无机改性的膨润土层间距减小,而有机改性膨润土的层间距增大;膨润土的改性提高了其对水中有机物的吸附性能,且能有效地抑制复合材料中TiO2晶粒尺寸,提高复合材料的光催化性能。     

Synthesis and Characterization of Cu Nanoparticles Embedded in PAN/β-Cyclodextrin (β-CD) Composite Nanofiber Films

In the study, PAN/β-cyclodextrin (β-CD) one dimensional composite nanofibers were synthesized with sol-gel method and electrospinning, and then, we dipped the composite nanofibers into NaBH₄ aqueous solution acted as reducing agent to fabricate PAN/β-CD/Cu composite nanofibers. We got the PAN/β-CD/Cu composite nanofibers with different concentration of β-CD, and Cu nanoparticles formed on its surface. The final products were characterized using scanning electronic microscope (SEM), fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM). The results of characterization showed that the Cu nanoparticles with small size were well-distributed on the composite nanofibers.     

Nylon6-TiO_2杂化超细纤维的制备与表征

采用静电纺丝法制备了Nylon6-TiO2及其杂化超细纤维无纺布。使用SEM、TEM和FTIR等方法探讨了其微观形貌、结构,并通过抗菌性能方法验证其抗菌性能与不同金属离子掺杂Nylon6-TiO2纤维膜的关系。结果表明：Ag＋的掺杂可改善电纺纤维的形貌特征,使纤维尺寸均匀,珠状物减少;Cu2＋的掺杂降低了Nylon6-...     

Photocatalytic and antibacterial properties of a TiO2/nylon-6 electrospun nanocomposite mat containing silver nanoparticles

Silver-impregnated TiO(2)/nylon-6 nanocomposite mats exhibit excellent characteristics as a filter media with good photocatalytic and antibacterial properties and durability for repeated use. Silver nanoparticles (NPs) were successfully embedded in electrospun TiO(2)/nylon-6 composite nanofibers through the photocatalytic reduction of silver nitrate solution under UV-light irradiation. TiO(2) NPs present in nylon-6 solution were able to cause the formation of a high aspect ratio spider-wave-like structure during electrospinning and facilitated the UV photoreduction of AgNO(3) to Ag. TEM images, UV-visible and XRD spectra confirmed that monodisperse Ag NPs (approximately 4 nm in size) were deposited selectively upon the TiO(2) NPs of the prepared nanocomposite mat. The antibacterial property of a TiO(2)/nylon-6 composite mat loaded with Ag NPs was tested against Escherichia coli, and the photoactive property was tested against methylene blue. All of the results showed that TiO(2)/nylon-6 nanocomposite mats loaded with Ag NPs are more effective than composite mats without Ag NPs. The prepared material has potential as an economically friendly photocatalyst and water filter media because it allows the NPs to be reused.     

太阳光下Cr~(3+)掺杂TiO_2复合微粒光催化性能研究

利用酸催化的溶胶一凝胶法成功地合成了一系列不同CP3+掺杂量(x=0.01%～10%)的TiO2复合光催化剂(Cd3+/TiO2).在太阳光条件下,以亚甲基蓝溶液的光催化降解对复合材料的光催化性能进行了表征,并考察了催化剂投加量、Cr3+掺杂量和溶液pH值等因素对光催化降解反应的影响.结果表明,亚甲基蓝溶液在复合微粒上的光催化降解反应遵循Langmuir-Hinshelwood动力学模型,在催化剂投加量为lg/L、Cr3+掺入量为0.3%和pH=7时,Cr3+/TiO2复合微粒光催化活性达最佳,测得表观反应速率常数 K为7.27×10-3 rag(L·min)-1,t1/2为95min,反应4h后亚甲基蓝的降解率可达79%,与纯的TiO2相比较,反应速率提高了2倍,降解率提高了20%.中性或碱性条件下有利于亚甲基蓝溶液的光催化降解.     

Enhanced photocatalytic degradation of pollutants in petroleum refinery wastewater under mild conditions

A circulating photocatalytic reactor was used for removing aliphatic and aromatic organic pollutants in refinery wastewater. The TiO(2) added wastewater samples, while saturating with air, were irradiated with an immersed mercury UV lamp (400 W, 200-550 nm). Optimal catalyst concentration, fluid pH and temperature were obtained at amounts of near 100 mgL(-1), 3 and 318K, respectively. A maximum reduction in chemical oxygen demand of more than 90% was achieved after about 4h irradiation and hence, 73% after about only 90 min; significant pollutant removal was also achievable in the other conditions. The identification of the organic pollutants, provided by means of a GC/MS and a GC analysis systems, equipped with headspace injection technique, showed that the major compounds were different fractions of petroleum aliphatic hydrocarbons (up to C(10)) and the well-known aromatic compounds such as benzene, toluene and ethylbenzene. The results showed a high efficiency degradation of all of these pollutants.     

纳米α-Fe2O3/TiO2光催化剂的制备及其光催化性能研究

以硝酸铁为铁源,NaOH为沉淀剂合成单分散性良好的纳米α-Fe2O3粒子,然后与纳米TiO2胶体复合制备了纳米α-Fe2O3/TiO2光催化剂。利用动态光散射粒径分析仪、扫描电子显微镜、紫外-可见分光光度计、X射线衍射仪对光催化剂的物相、形貌进行了表征。在室温条件下,以甲醛作为有机污染物,在可见光照射下探讨了纳米α-Fe2O3粒径、α-Fe2O3摩尔分数等对甲醛光催化降解的影响。结果表明,在一定范围内,随着粒径的减小,纳米α-Fe2O3光催化活性增强,在120min内粒径40nm的纳米α-Fe2O3对甲醛的降解效果最好,降解率约为93.05%。与纯TiO2相比,纳米α-Fe2O3/TiO2光催化剂的可见光催化活性明显增强,纳米α-Fe2O3最佳含量为0.20%(摩尔分数)。纳米α-Fe2O3含量过大,纳米α-Fe2O3/TiO2光催化剂的催化活性将降低。