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。     

二氧化钛/还原氧化石墨烯复合材料的制备及其光催化降解脱色性能

为比较二氧化钛/ 还原氧化石墨烯(TiO2 / rGO)复合材料和TiO2 的光催化降解脱色性能,以钛酸丁酯为前驱体,采用水热法制备了不同晶型的TiO2 和TiO2 / rGO 复合材料,借助紫外漫反射吸收光谱仪、傅里叶红外光谱仪、拉曼光谱仪、X 射线衍射仪和扫描电子显微镜等对TiO2 及其复合材料进行表征。分析混晶TiO2 和混晶TiO2 / rGO复合材料对活性红3BS 染料废水的降解脱色效果。结果表明：在150 ℃水热12 h,再经过650 ℃煅烧4 h 后,可制得锐钛矿型和金红石型同时存在的混晶TiO2 体系;在碱性条件下,于140 ℃水热72 h,不经过煅烧可制得较为纯净的板钛矿型TiO2;锐钛矿型和金红石型混晶结构TiO2 体系对染料有一定的降解脱色效果,混晶TiO2 / rGO 复合材料降解染料120 min 后,降解脱色率高达99%。     

17 beta-estradiol degradation by TiO2 photocatalysis as a means of reducing estrogenic activity

The degradation of 17 beta-estradiol (E2) in water by TiO2 photocatalysis was investigated; concurrently the estrogenic activity of the treated water was evaluated during the photocatalytic reactions by an estrogen screening assay. As a result, 10(-6) M of E2 was totally mineralized to CO2 in 1.0 g L-1 TiO2 suspension under UV irradiation for 3 h. 10 epsilon-17 beta-Dihydroxy-1,4-estradien-3-one and testosterone-like species were elucidated as intermediate products by GC/MS analysis. The mechanisms of E2 degradation by TiO2 photocatalysis were discussed not only experimentally but also theoretically by calculating the frontier electron densities of the E2 molecule. On the basis of the results obtained, it was concluded that the phenol moiety of the E2 molecule, one of the essential functional groups to interact with the estrogen receptor, should be the starting point of the photocatalytic oxidation of E2. This means that the estrogenic activity should be almost lost concurrently with the initiation of the photocatalytic degradation. Actually, the estrogenic activities of the intermediate products were negligible. TiO2 photocatalysis could be applied to water treatment to effectively remove natural and synthetic estrogens without producing biologically active intermediary products.     

Photocatalytic degradation of organic compounds over combustion-synthesized nano-TiO2

The photocatalytic degradation of various organics such as phenol, p-nitrophenol, and salicylic acid was carried out with combustion-synthesized nano-TiO2 under UV and solar exposure. Under identical conditions of UV exposure, the initial degradation rate of phenol with combustion-synthesized TiO2 is 2 times higher than the initial degradation rate of phenol with commercial Degussa P-25 TiO2. The intermediates such as catechol (CC) and hydroquinone (HQ) were not detected during the degradation of phenol with combustion-synthesized TiO2, while both the intermediates were detected when phenol was degraded over Degussa P-25. This indicates that the rates of secondary photolysis of CC and HQ occur extremely faster than the rates at which they are formed from phenol and further implies that the primary hydroxylation step is rate limiting for the combustion-synthesized TiO2 aided photodegradation of phenol. The degradation rates of salicylic acid and p-nitrophenol were also investigated, and the rates were higher for combustion-synthesized titania compared to Degussa P-25 TiO2. Superior activity of combustion-synthesized TiO2 toward photodegradation of organic compounds can be attributed to crystallinity, higher surface area, more surface hydroxyl groups, and optical absorption at higher wavelength.     

Photocatalytic oxidation of aqueous ammonia over microwave-induced titanate nanotubes

Characterizations of microwave-induced titanate nanotubes (NaxH(2-x)Ti3O7, TNTs) were conducted by the determinations of specific surface area (S(BET)), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS), ionic coupled plasma-atomic emission spectrometry(ICP-AES), scanning electron microscopy/ energy dispersive X-ray (SEM/EDX), and high-resolution transmission electron microscopy (HR-TEM). The applied level of microwave irradiation during the fabrication process is responsible for both the intercalation intensity of Na atoms into TNTs and the type of crystallization phase within TNTs, which dominate the efficiency of photocatalytic NH3/NH4+. A pure TNT phase presents no powerful ability toward photocatalytic NH3/ NH4+, while the photocatalytic efficiency can be enhanced with the presence of a rutile phase within TNTs. In addition, the mixture of anatase and rutile phase within P25 TiO2 prefers forming NO3-, whereas TNTs yield higher NO2- amount Regarding the effect of acid-washing treatment on TNTs, the acid-treated TNTs with enhanced ion exchangeability considerably improve the NH3/NH4+ degradation and NO2-/NO3- yields. This result is likely ascribed to the easy intercalation of NH3/ NH4+ into the structure of acid-washing TNTs so that the photocatalytic oxidation of intercalated NH3/NH4+ is not limited to the shielding effect resulting from the overload of TNTs.     

金红石型高品质二氧化钛的制备

钛白粉具有良好的光学特性、易分散性、耐老化性和化学稳定性,在造纸行业有着广泛的应用。本文介绍了纳米金红石型二氧化钛的性质、生产方法,并主要探索采用硫酸法制备纳米金红石型二氧化钛,采用马尔文激光粒度分析仪、扫描电镜、透射电镜和X-射线衍射仪对实验产物进行表征。实验结果表明,该方法制得的二氧化钛具有较小的粒径以及较好的白度。     

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%。     

Semiconductor-mediated Photocatalyzed degradation of a herbicide derivative, chlorotoluron, in aqueous suspensions

The photocatalytic degradation of a herbicide derivative, chlorotoluron [3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 1], has been investigated in aqueous suspensions of titanium dioxide (TiO2) under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics of the model compound was investigated under different conditions such as type of TiO2, pH, catalyst concentration, substrate concentration, temperature, and in the presence of different electron acceptors such as hydrogen peroxide (H2O2), potassium persulfate (K2S2O8), and potassium bromate (KBrO3) besides molecular oxygen. TiO2 Degussa P25 was found to be a more efficient photocatalyst for the degradation of the model compound as compared with other photocatalysts. The degradation products were analyzed using GC/MS analysis technique and probable pathways for the formation of different products have been proposed.     

Mass production and photocatalytic activity of highly crystalline metastable single-phase Bi₂₀TiO₃₂ nanosheets

Highly crystalline metastable bismuth titanate (Bi??TiO??) nanosheets are prepared via a simple green wet chemical route for the first time. The Bi??TiO??)photocatalysts were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy dispersive spectrum analysis (EDS), X-ray diffraction (XRD), N? adsorption-desorption (BET), and UV-vis diffuse reflectance spectroscopy (DRS). Inspiringly, Bi??TiO?? nanosheets showed high photocatalytic activity for the degradation of nonbiodegradable azo dye under simulated sunlight and visible-light irradiation. The experimental results showed that the photocatalytic activity of the Bi??TiO?? nanosheets was superior to the commercial Degussa P25 TiO?, and demonstrated that the morphology and crystal structure have a distinct effect on the photocatalytic activity. The reasons for the high photocatalytic activity and the formation mechanism of Bi??TiO?? nanosheets are also discussed.     

Enhanced photocatalytic activity of nafion-coated TiO2

Photocatalytic degradation (PCD) of aqueous paraquat was accelerated by the addition of either phosphate or sulfate salt. Attachment of these anions to the TiO2 surface possibly results in increased adsorption of the cationic paraquat species and in turn its photocatalysis rate. The same effect was obtained more consistently using the Nafion (an anionic polymer)-coated TiO2. Enhanced PCD of paraquat and some amine compounds was noted. However the anionic and neutral compounds were not affected significantly. Nafion proved to be stable against photocatalysis. It has been suggested that the degradation rate is larger for the cationic compounds with higher pK(B). For a phenol-paraquat-TiO2 system, paraquat degradation did not begin till near-complete phenol removal. Using the Nafion-coated TiO2, both phenol and paraquat degradations started simultaneously. Nevertheless, complete paraquat removal still took longer than phenol.     

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。     

Kinetics of simultaneous photocatalytic degradation of phenolic compounds and reduction of metal ions with nano-TiO2

The simultaneous photocatalytic degradation of phenol and 4-nitrophenol and reduction of metal ions like copper (Cu2+) and chromium (Cr6+) was studied with solution combustion synthesized nanoanatase TiO2 (CS TiO2) and commercial titania, Degussa P-25. The presence of metal ion reduces the rate of degradation of phenol and 4-nitrophenol. It was found that Cu2+ reduction to Cu+ is accelerated in the presence of phenol. In the case of Cr6+, CS TiO2 enhances the initial adsorption of Cr6+ and complete reduction is achieved within the first 10 min of UV irradiation. The presence of phenol or 4-nitrophenol also enhances the initial adsorption of Cr6+ and its reduction. The metal ion reduction in the presence of CS TiO2 is compared with that of Degussa P-25. The rate of reduction of metal ions in presence of Degussa P-25 is twice as slow as that of CS TiO2 in presence of both phenol and 4-nitrophenol. The presence of Cu2+ and Cr6+ also induces the formation of the intermediates which were not observed for the phenol-CS TiO2 system. The formation and consumption of the intermediates are modeled with a simple series reaction mechanism. A detailed dual-cycle, multistep reaction mechanism of TiO2 photocatalysis for the simultaneous degradation and reduction is proposed and the model is developed following the network reduction technique. The kinetic rate constants in the model are evaluated for the systems studied.     

Effect of platinum deposits on TiO2 on the anoxic photocatalytic degradation pathways of alkylamines in water: dealkylation and N-alkyation

Most photocatalytic degradation (PCD) reactions of aquatic pollutants require the presence of dissolved oxygen and hence do not occur in anoxic suspensions. We investigated the PCD reactions of alkylamines in anoxic water using TiO2 deposited with Pt nanoparticles. Unlike typical PCD reactions, the absence of dissolved oxygen increases the PCD rates of alkylamines on Pt/TiO2 and generates products that are different from those formed on pure TiO2. In particular, N-alkylated amines (e.g., (CH3)3N produced from (CH3)2NH) as well as dealkylated amines are generated in a deaerated Pt/TiO2 suspension. This anoxic N-alkylation pathway is enabled only in the presence of Pt deposits on TiO2 and is applicable only to neutral alkylamines and not to alkylammonium cations. The Pt surface appears to interactwith the lone-pair electron on the N atom and catalyze the anoxic degradation of alkylamines mainly through a radical mechanism. Methyl radicals generated on Pt participate in the N-methylation reaction. The presence of intermediate methyl radicals on the Pt surface was verified by the detection of CH4 and CH3CH3 gases evolved during the PCD of (CH3)3N in an anoxic Pt/TiO2 suspension, whereas no such products were observed in a pure TiO2 suspension. The anoxic PCD of N-methylethylamine on Pt/TiO2 also produces both N-ethylated and N-methylated amines as byproducts, which indicates that both methyl and ethyl radicals are generated during the anoxic degradation process. From a practical point of view, the present finding that undesirable alkylated amines can be produced on Pt/TiO2 in anoxic conditions indicates that caution is necessary when applying Pt/TiO2 photocatalyst to the treatment of water that contains amines.     

Novel approach to enhance photosensitized degradation of rhodamine B under visible light irradiation by the ZnxCd1-xS/TiO2 nanocomposites

In order to exploit efficient photosensitizers with appropriate electronic states to enhance the transfer of electrons, ZnxCd1-xS/TiO2 nanocomposites were first synthesized by a simple hydrothermal method. The samples were characterized by X-ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron spin resonance, and photoluminescence techniques. The results showed that the composite of the two inorganic semiconductors largely enhanced the photosensitized degradation of rhodamine B (RhB) under visible light irradiation (420 nm<λ<800 nm). These photocatalytic reactions were driven mainly by the light absorption of RhB molecules and to a lesser extent by the excitation of ZnxCd1-xS. They were supposed to arise mainly from the electron transferred from the adsorbed dye in its singlet excited state to the conduction band of ZnxCd1-xS and TiO2. Such a heterogeneous photocatalytic reaction has much significance in the degradation of organic pollutants in ordinary photocatalysis.     

Degradation of benzene over a zinc germanate photocatalyst under ambient conditions

A rod-shaped Zn2GeO4 photocatalyst has been successfully prepared by a surfactant-assisted hydrothermal method. The photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, UV/vis, N2 adsorption-desorption, and FTIR techniques. The photocatalytic activity of the sample was evaluated by the decomposition of benzene in the gas phase under UV light illumination and was compared with that of bulk Zn2GeO4, commercial titania (Degussa P25), and Pt/P25. The results revealed that the Zn2GeO4 nanorods had the best photocatalytic activity for mineralizing benzene to CO2 among the catalysts examined. No obvious deactivation of Zn2GeO4 nanorods was observed during the prolonged operation of 140 h. It was found that the Zn2GeO4 was also more active and stable than TiO2-based catalysts toward photocatalytic decomposition of other volatile aromatic pollutants (e.g., toluene and ethylbenzene).     

Development of an E-H2O2/TiO2 photoelectrocatalytic oxidation system for water and wastewater treatment

In this study, an innovative E-H2O2/TiO2 (E-H2O2 = electrogenerated hydrogen peroxide) photoelectrocatalytic (PEC) oxidation system was successfully developed for water and wastewater treatment. A TiO2/Ti mesh electrode was applied in this photoreactor as the anode to conduct PEC oxidation, and a reticulated vitreous carbon (RVC) electrode was used as the cathode to electrogenerate hydrogen peroxide simultaneously. The TiO2/Ti mesh electrode was prepared with a modified anodic oxidation process in a quadrielectrolyte (H2SO4-H3PO4-H2O2-HF) solution. The crystal structure, surface morphology, and film thickness of the TiO2/Ti mesh electrode were characterized by X-ray diffraction and scanning electron microscopy. The analytical results showed that a honeycomb-type anatase film with a thickness of 5 microm was formed. Photocatalytic oxidation (PC) and PEC oxidation of 2,4,6-trichlorophenol (TCP) in an aqueous solution were performed under various experimental conditions. Experimental results showed that the TiO2/Ti electrode, anodized in the H2SO4-H3PO4-H2O2-HF solution, had higher photocatalytic activity than the TiO2/Ti electrode anodized in the H2SO4 solution. It was found that the maximum applied potential would be around 2.5 V, corresponding to an optimum applied current density of 50 microA cm(-2) under UV-A illumination. The experiments confirmed that the E-H2O2 on the RVC electrode can significantly enhance the PEC oxidation of TCP in aqueous solution. The rate of TCP degradation in such an E-H2O2-assisted TiO2 PEC reaction was 5.0 times that of the TiO2 PC reaction and 2.3 times that of the TiO2 PEC reaction. The variation of pH during the E-H2O2-assisted TiO2 PEC reaction, affected by individual reactions, was also investigated. It was found that pH was well maintained during the TCP degradation in such an E-H2O2/TiO2 reaction system. This is beneficial to TCP degradation in an aqueous solution.     

Integrating plasmonic nanoparticles with TiO₂ photonic crystal for enhancement of visible-light-driven photocatalysis

Aimed at enhancing photocatalysis through intensifying light harvesting, a new photocatalyst was fabricated by infiltrating Au nanoparticles into TiO(2) photonic crystals (TiO(2) PC/Au NPs). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed that the Au NPs with average diameter around 15 nm were dispersed uniformly into the porous TiO(2) material. The results of the transmittance spectra demonstrated that the light absorption by Au NPs was amplified after they were infiltrated into TiO(2) 240, which was fabricated from 240 nm polystyrene spheres. In the photocatalytic experiments of 2,4-dichlorophenol degradation under visible light (λ > 420 nm) irradiation, the kinetic constant using TiO(2) 240/Au NPs was 2.3 fold larger than that using TiO(2) nanocrystalline/Au NPs (TiO(2) NC/Au NPs). The excellent photocatalysis benefited from the cooperatively enhanced light harvesting owing to the localized surface plasmon resonance of Au NPs, which extended the light response spectra and the photonic effect of the TiO(2) 240 which intensified the plasmonic absorption by Au NPs. The hydroxyl radicals originated from the electroreduction of dissolved oxygen with photogenerated electrons via chain reactions were the main reactive oxygen species responsible for the pollutant degradation.     

Photoreactive TiO2/carbon nanotube composites: synthesis and reactivity

Electron-hole recombination limits the efficiency of TiO2 photocatalysis. We have investigated the efficacy with which anatase/carbon nanotube (CNT) composite materials reduce charge recombination and enhance reactivity. We synthesized nanostructured assemblies composed of different proportions of anatase (5 or 100 nm) and either single-or multi-walled CNTs. The composites were prepared using a simple low temperature process in which CNTs and anatase nanoparticles were dispersed in water, dehydrated at 80 degrees C, and dried at 104 degrees C. The structures of the various TiO2/CNT composites were characterized by scanning electron microscopy (SEM) and their function was tested by phenol oxidation. Charge recombination was compared by measuring the photoluminescence spectra of select composites. We found that a nanostructured composite assembled from the 100 nm anatase and single-walled CNTs (SWCNTs) exhibited enhanced and selective photocatalytic oxidation of phenol in comparison to both pure anatase and Degussa P25. A mechanism for the enhanced reactivity is proposed in which electrons are shuttled from TiO2 particles to the SWCNTs as a result of an optimal TiO2/ CNT arrangement that stabilizes charge separation and reduces charge recombination. In addition, the SWCNT assembly provides better catalyst-support (dispersal and connection) than multi-walled CNTs.     

TiO2/ACF光催化材料的制备与特性

 本文采用溶胶-凝胶法制得TiO_2溶胶,并将TiO_2溶胶和粘胶基非织造布通过浸渍-干燥、磷酸活化和煅烧工艺一步法制备得到TiO_2/ACF光催化材料。采用EDAX、XRD、SEM对样品进行表征,同时测试了样品对亚甲基蓝溶液的催化降解性能。结果表明：样品负载上了锐钛矿型和金红石型的混晶的TiO_2;而且在样品的纤维上出现了孔洞,形成活性碳纤维;同时在20w紫外灯照射下,TiO_2/ACF光催化材料表现出了优异的光催化降解性能,500℃碳化条件得到的TiO_2/ACF光催化材料光催化降解亚甲基蓝溶液的脱色率达到98.83%。     

Photocatalytic oxidation using a new catalyst--TiO2 microsphere--for water and wastewater treatment

Since the suspended TiO2 powder enjoys free contact with UV irradiation in a photoreactor system, it can generally achieve better efficiency than the immobilized TiO2 catalysts. However, the separation and reuse of this catalyst powder from treated water often limit its application in practice. In this study, a new type of TiO2 catalyst called TiO2 microsphere was prepared by a sol-spraying-calcination method, which can easily settle in its aqueous suspensions under gravity. The SEM image of the TiO2 microsphere samples demonstrated that they had an almost spherical shape with a particle size of 30-160 microm, while the XRD analysis indicated that these TiO2 microspheres still had a crystal size of 8.1 nm. Since these TiO2 microspheres had a porous structure with higher specific surface area and pore volume than normal TiO2 powders, they appeared to have strong adsorption ability in its aqueous suspensions. The photocatalytic activity of the TiO2 microspheres was evaluated in the photodegradations of salicylic acid (SA) and sulfosalicylic acid (SSA). The experimental results showed that the reaction rate using the TiO2 microspheres was similar to that using the TiO2 powders in the SA suspensions and even higher than that in the SSA suspensions. Chemical and physical properties of the TiO2 microspheres and powders that are attributed to photoactivity were discussed based on the Langmuir-Hinshelwood kinetic model. The prepared TiO2 microsphere samples were reused in the photooxidation reaction more than 50 times. It was found that there was no significant weakening in their photoactivity and no change in their particle shape. This TiO2 microsphere catalyst can be simply used to conduct an effective photooxidation in its suspension for water and wastewater treatment with ease of recovery from treated water.