Solar assisted photocatalytic and photochemical degradation of Reactive Black 5

The photocatalytic oxidative degradation of Reactive Black 5 (RB 5) has been investigated using TiO(2)-P25 as photocatalyst and sunlight as irradiation source in slurry form. The degradation was carried out at different experimental conditions to optimize the parameters such as amount of catalyst, concentration of dye and pH. A complete degradation of 3.85 x 10(-4) M dye solution under solar irradiation was observed in 3.5 h. The photochemical degradation using hydrogen peroxide results in the partial removal of the dye.     

Visible light active photocatalytic degradation of bisphenol-A using nitrogen doped TiO2

Nitrogen doped titania was prepared by low temperature sol-gel method using titanium precursor and nitrogen containing bases like triethylamine and tetramethyl ammonium hydroxide compounds. The materials were characterized by XRD, BET, SEM, XPS, DRS-UV, and FT-IR techniques. DRS-UV study substantially indicates shift of the absorption edge of TiO2 to lower energy region. The phase composition, crystallinity, specific surface area, and visible light activity of nitrogen doped titania depend upon the preparation conditions. Photocatalytic degradation of bisphenol-A in aqueous medium was investigated by TiO2 and nitrogen doped TiO2 under visible light irradiation in a batch photocatalytic reactor. The results indicate higher visible light activity for nitrogen doped TiO2 than commercial TiO2 (Degussa P25) for bisphenol-A degradation. The influence of various parameters such as initial concentration of bisphenol-A, catalyst loading and pH was examined for maximum degradation efficiency.     

Effect of deposition of Ag on TiO2 nanoparticles on the photodegradation of Reactive Yellow-17

Nanoparticles of TiO(2) were synthesized by sol-gel technique and the photodeposition of about 1% Ag on TiO(2) particles was carried out. Ag-deposited TiO(2) catalyst was characterised by XRD, TEM and UV-vis spectroscopy. The Ag-TiO(2) catalyst was evaluated for their photocatalytic activity towards the degradation of Reactive Yellow-17 (RY-17) under UV and visible light irradiations. Then the results were compared with synthesized nano-TiO(2) sol and P-25 Degussa and the enhanced degradation was obtained with Ag-deposited TiO(2). This enhanced activity of Ag-TiO(2) may be attributed to the trapping of conduction band electrons. The effect of initial dye concentration, pH and electron acceptors such as H(2)O(2), K(2)S(2)O(8) on the photocatalytic activity were studied and the results obtained were fitted with Langmuir-Hinshelwood model to study the degradation kinetics and discussed in detail.     

TiO2 mediated photocatalytic degradation studies of Reactive Red 198 by UV irradiation

Photocatalytic degradation of an aqueous solution of azo dye (Reactive Red 198) used in textile industries by UV irradiation was investigated. The effect of initial dye concentration, TiO(2) loading, pH and H(2)O(2) on degradation rate was ascertained and optimized conditions for maximum degradation were determined. The kinetics of photocatalytic degradation was found to follow a pseudo-first order according to Langmuir-Hinshelwood model. The degradation experiment under optimized reaction conditions was investigated under sunlight.     

Photocatalytic decolorization and degradation of dye solutions and wastewaters in the presence of titanium dioxide

In this study, the photocatalytic degradation of two commercial azo dyes in the presence of TiO(2) suspensions as photocatalyst has been investigated. The degradation of the dyes follows a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Under the certain experimental conditions, in the presence of TiO(2) P-25 decolorization is achieved within 100 min of illumination, while in the presence of TiO(2) Hombikat UV-100 complete color disappearance is accomplished in less than 50 min of light exposure. The influence of various parameters, such as the type and mass of the catalyst, the initial concentration of the dye, etc. on the degradation process was examined. The mineralization of organic carbon was also evaluated by measuring the dissolved organic carbon (DOC) of the dye solutions. Moreover, the toxic properties of the dye solutions treated by photocatalysis were examined by the use of a Microtox bioassay (Vibrio fischeri). Finally, experiments using real textile wastewater were also carried out, in order to examine the effectiveness of the method to a more complex substrate.     

Nanocomposite of Cu-TiO2-SiO2 with high photoactive performance for degradation of rhodamine B dye in aqueous wastewater

The nanocomposite of Cu-TiO2-SiO2 photocatalyst have been prepared by a sol-gel method, which is used for the degradation of Rhodamine B (RB) as a probe that is notorious organic compound present in dyes wastewater. Morphological and structural characteristics of the Cu-TiO2-SiO2 nanocomposite were studied with low temperature N2 adsorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectroscopy (DRS). The Fourier transformed infrared spectroscopy (FT-IR) analysis shows the enhanced chemical bonding of O-Ti and O-Ti-O after the composition of Cu and SiO2 species into TiO2. It is found that the Cu-TiO2-SiO2 nanocomposite exhibits much higher photocatalytic activity under both UV light and visible light irradiation as compared with that over commercial titania (Degussa P25) toward the dyes wastewater containing RB. The photodegradation rate of RB (5 mg/L) can reach above 95.0% under sunlight after 3 h. The addition of SiO2 not only inhibites the crystal growth and anatase-to-rutile transformation of TiO2 nanocatalyst, but also enhances the adsorption of organic compounds. Cu-doping extends the light response to the visible region. Synergetic effects between Cu-SiO2 and TiO2 have been investigated, which provides a good way and material in the degradation field of dyes wastewater.     

Photocatalytic degradation of Congo Red by hydrothermally synthesized nanocrystalline TiO2 and identification of degradation products by LC-MS

Degradation of Congo Red (CR) dye in aqueous solutions was investigated by means of photocatalysis of TiO2 which was hydrothermally synthesized at 200 degrees C in 2 h, in anatase phase with 8 nm crystallite size. Efficiency of TiO2 in photocatalytic degradation under visible irradiation was studied by investigating the effects of amount of TiO2, irradiation time, initial CR concentration and pH. It was found that complete decolorization is achieved within 30 min of irradiation. Effects of nitrate and sulphate ions and humic acid on the degradation were also tested. The results were compared with Degussa P-25 TiO2 at the same degradation conditions. Degradation products were detected using LC-MS technique. The probable pathways for the formation of degradation products were proposed.     

Application of novel copolymer-TiO(2) membranes for some textile dyes adsorptive removal from aqueous solution and photocatalytic decolorization

Novel low density polyethylene-grafted-poly(4-vinylpyridine-co-acrylamide) (LDPE-g-P(4-VP/AAm)) films were prepared by means of gamma-radiation-induced graft copolymerization as support for photocatalytic application. Nanometer-sized TiO(2) particles were immobilized to the grafted LDPE via dip coating technique. The efficiency of immobilized photocatalyst is tested on two target pollutants (textile azo dyes: Remazol red RB-133 (RR RB 133) and reactive blue 2 (RB2)). The efficient photocatalytic ability as reflected in determined photobleaching rate of both dyes was observed and is comparable to that for the non-supported TiO(2) used in a typical slurry photoreactor. The LDPE-g-(4-VP/AAm) copolymers supported TiO(2) photocatalyst has the practical advantages of easy separation and removal from the polluted environment. It could be a viable technique for the safe disposal of textile wastewater into the water streams.     

Photocatalytic degradation of methyl red by TiO2: comparison of the efficiency of immobilized nanoparticles versus conventional suspended catalyst

The photocatalytic efficiency of supported TiO2 nanoparticles (mean size 6 nm), immobilized onto the inner walls of a cylindrical glass photoreactor was compared versus the performance of conventional TiO2 Degussa P25 catalyst. For this purpose the degradation of methyl red dye was used as evaluation test. The obtained results showed that the TiO2 Degussa P25 catalyst is more efficient than the supported nanoparticles. The poorer performance of the nanosized catalyst can be ascribed to the fact that the immobilization procedure turns out, in spite of the extremely high surface to volume ratio, in an overall reduction of active surface area available for target molecule adsorption, due to the low porosity of the supported catalyst layer. The kinetics of the investigated processes were monitored and a study on the reaction products and intermediates was carried out in order to evaluate possible difference in the reaction pathway in presence of immobilized nanoparticles versus suspended catalyst. The results demonstrate that the mechanisms of parent dye degradation in presence of supported TiO2 nanoparticles are the same as those occurring in presence of TiO2 Degussa P25 catalyst. The present work describe the results obtained on the feasibility of scaling up the colloidal nanocrystal-based photocatalysis experiment: the comparison with a well standardized degradation method performed with a known material can allow a realistic evaluation of the advantages and the limits of the investigated nanoparticle towards the ultimate technology transfer.     

A visible light response TiO2 photocatalyst realized by cationic S-doping and its application for phenol degradation

S-doped TiO2 photocatalyst with high visible light activity was prepared by acid catalyzed hydrolysis method using thiourea (TU) as sulfur source. The catalyst was characterized by DRS, XPS, XRD, FTIR, SEM and N2 adsorption. It was found that cation S6+ was homogeneously incorporated into the bulk phase of TiO2 and substitutes for some of the lattice titanium (Ti4+). Doped S can form a new band above the valence band and narrow the band-gap of the photocatalyst, giving rise to a second absorption edge in the visible light region. The activity of the catalyst was examined by photodegradation of phenol in aqueous solution under both artificial visible light and solar light irradiation. The activity of catalyst was found to be dependent on the doping amount of S and the maximum activity was observed when the catalyst was obtained by calcinated at 600 degrees C with the mass ratio of TU/TiO2=1. Too much of new-generated band-gap structures due to higher S-doping could act as recombination centers for electron-hole pairs. Catalyst with optimum S-doping exhibited the highest activity under both artificial light and solar irradiation for phenol degradation. In addition, doped S also beneficial for the better dispersion, large S(BET) and phase transformation retardation of TiO2.     

TiO2-UV photocatalytic oxidation of Reactive Yellow 14: effect of operational parameters

The photocatalytic decolourisation and degradation of an azo dye Reactive Yellow (RY14) in aqueous solution with TiO(2) as photocatalyst in slurry form has been carried out using UV-A radiation (365 nm). The effect of various parameters such as catalyst loading, radiation intensity and initial dye concentration on the dye removal was investigated to find optimum conditions. The decolourisation and degradation kinetics have been analysed. Both follow modified Langmuir-Hinshelwood kinetic (L-H) model. A study on the effect of electron acceptors on photooxidation reveals that both decolourisation and degradation increase in the presence of H(2)O(2), (NH(4))(2)S(2)O(8), KBrO(3), to certain dosage beyond which the enhancement effect is negligible. But negative effects are observed in the presence of NaCl or Na(2)CO(3).     

Semiconductor-mediated photocatalysed degradation of two selected azo dye derivatives, amaranth and bismarck brown in aqueous suspension

Semiconductor-mediated photocatalysed degradation of two selected azo dye derivatives such as amaranth (1) and bismarck brown (2) has been investigated in aqueous suspension by monitoring the change in substrate concentration employing UV spectroscopic analysis technique as a function of irradiation time. The degradation was studied under different conditions such as types of TiO(2), pH, substrate concentration, catalyst concentration, and in the presence of electron acceptors such as hydrogen peroxide (H(2)O(2)), potassium bromate (KBrO(3)) and ammonium persulphate (NH(4))(2)S(2)O(8) besides air. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 showed comparatively highest photocatalytic activity. The dye derivative, bismarck brown (2) was found to degrade faster than amaranth dye (1).     

TiO2 hydrosols with high activity for photocatalytic degradation of formaldehyde in a gaseous phase

Two types of TiO2 hydrosols (TOSO and HTO) were prepared from titanium sulfate (TiOSO4) and metatitanic acid (H2TiO3) by a chemical precipitation-peptization method, respectively. The prepared hydrosols were characterized by means of X-ray diffraction, particle size distribution, scanning electron microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller and Barret-Joyner-Halender methods. The results showed that the TiO2 hydrosols with an anatase crystal structure had smaller particle sizes, higher surface areas, larger pore volume, and higher transparence than Degussa P-25 suspension. The photocatalytic activity of the TiO2 hydrosols was evaluated for formaldehyde degradation under UVA illumination in a gaseous phase. The results demonstrated that the photocatalytic activity with the catalyst loading of 2mgcm(-2) was ranked as an order of HTO>TOSO>P-25. The photocatalytic activity was further studied using the HTO catalyst under different experimental conditions. The results showed that catalyst loading, relative humidity, and initial concentration could influence the efficiency of HCHO photocatalytic degradation. It was found that a catalyst loading of more than 2mgcm(-2) and a relative humidity of 55% were two essential conditions for achieving the best performance under these experimental conditions. The repeated experiments indicated that the HTO catalyst was reasonably stable and could be repeatedly used for the HCHO oxidation under UVA irradiation. This investigation would be helpful to promote the application of TiO2 photocatalytic technique for indoor air purification.     

介孔TiO2微球水热法合成及在染料敏化太阳能电池中的应用

以Ti(SO4)2为钛源,采用尿素辅助水热法合成了介孔TiO2微球,利用XRD、FESEM和比表面积分析仪对样品的晶型、形貌和比表面积进行分析,探讨了尿素加入量对TiO2微球的颗粒尺寸、比表面积、孔径和孔容的影响。采用刮涂法,用所合成的介孔TiO2微球制备了染料敏化太阳能电池(DSSC)的光阳极,结果表明,尿素用量为1.2g合成的介孔TiO2微球所组装的电池在模拟太阳光的照射下(100mW/cm2,AM1.5),光电转换效率为6.2%,明显高于商用P25纳晶所组装的电池光电转换效率(4.24%)。     

Heterogeneous photocatalyzed degradation of uracil and 5-bromouracil in aqueous suspensions of titanium dioxide

Photocatalyzed degradation of uracil (1) and 5-bromouracil (2) has been investigated in aqueous suspensions of titanium dioxide 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 of the compounds under investigation was studied using various parameters such as, different types of TiO2 powders, pH, catalyst concentration, substrate concentrations, and in the presence of electron acceptors like hydrogen peroxide (H(2)O(2)) and potassium bromate (KBrO(3)) besides molecular oxygen. Photocatalyst Degussa P25 was found to be more efficient for the degradation of both compounds as compared with other TiO2 powders such as UV100, PC500 and TTP.     

Application of surfactant enhanced permanganate oxidation and bidegradation of trichloroethylene in groundwater

Fe-C-TiO(2) photocatalysts were prepared by mechanical mixing of commercial anatase TiO(2) precursor with FeC(2)O(4) and heating at 500-800 degrees C under argon flow. These photocatalysts were tested for dyes decomposition: Methylene Blue (MB), Reactive Black (RB) and Acid Red (AR). The preliminary adsorption of dyes on the photocatalysts surface was performed. Modification of anatase by FeC(2)O(4) caused reducing of zeta potential of the photocatalyst surface from +12 to -7mV and decreasing of their adsorption ability towards RB and AR, which were negatively charged, -46.8 and -39.7, respectively. Therefore, unmodified TiO(2) showed the highest degree of RB and AR decompositions in the combination of dyes adsorption and UV irradiation. Methylene Blue, which had zeta potential of +4.3 in the aqueous solution was poorly adsorbed on all the tested photocatalysts and also slowly decomposed under UV irradiation. The high rate of dyes decomposition was noted on Fe-C-TiO(2) photocatalysts under UV irradiation with addition of H(2)O(2). It was observed, that at lower temperatures of heat treatment such as 500 degrees C higher content of carbon is remained in the sample, blocking the built in of iron into the TiO(2) lattice. This iron is reactive in the photo-Fenton process resulting in high production of OH radicals and also high activity of the photocatalyst. At higher temperatures of heat treatment, less active FeTiO(3) phase is formed, therefore Fe-C-TiO(2) sample prepared at 800 degrees C showed low photocatalytic activity for dyes decomposition. Fe-C-TiO(2) photocatalysts are active under visible light irradiation, however, the efficiency of a dye decomposition is lower than under UV light. In a dark Fenton process there is observed an insignificant generation of OH radicals and very little decomposition of a dye, what suggests the powerful of photo-Fenton process in the dyes decomposition.     

Photocatalytic degradation of monocrotophos pesticide--an endocrine disruptor by magnesium doped titania

Mg-doped TiO(2) with different Mg concentrations were prepared using sol-gel method and characterized by XRD, UV-visible, XPS, SEM and FT-IR. The XRD results revealed that Mg(2+) goes into the TiO(2) lattice. SEM images of the doped and pure TiO(2) indicated that there is a smaller particle size for the doped catalyst compared to that of the pure TiO(2). UV-visible absorption spectra indicated that upon doping with Mg(2+) ion, the catalyst exhibits absorption in visible region. FT-IR and XPS spectra demonstrated that the presence of Mg(2+) ion in the TiO(2) lattice as substitutional dopant. Photocatalytic activity of doped TiO(2) has been evaluated by degradation of the monocrotophos (MCP) pesticide. The effect of solution pH, catalyst dosage and initial concentration of MCP on the photocatalytic activity of Mg-doped TiO(2) with different loadings was studied. It was observed that the rate of degradation of MCP over Mg-doped TiO(2) is better than Pure TiO(2) and Degussa P-25.     

层层组装技术制备纳米级TiO2/聚电解质复合中空纤维催化剂

采用静电纺丝技术和层层组装技术制备了聚电解质/TiO2复合中空纳米纤维膜.通过控制PS纤维模板直径和吸附层数,TiO2中空纤维的直径和壁厚得到了很好的控制.在光催化降解乙醛性能实验中,TiO2中空纤维具有比P25更好的光催化性能.     

Photocatalytic degradation of carbofuran using semiconductor oxides

The photocatalytic degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) was investigated in an aqueous solution using Degussa P-25 TiO2 and ZnO as photocatalysts. The progress of degradation was monitored using TOC analyzer, HPLC, GC-MS and UV-vis spectrophotometer. The effects of various experimental parameters such as initial concentration of carbofuran, pH of the solution, catalyst loading and light intensity were systematically studied in order to achieve maximum degradation efficiency. The complete mineralization of carbofuran was confirmed by TOC analyzer. The degradation with ZnO showed less efficiency than TiO2. The formation of NO(3)(-) was identified and quantified using HPLC. In addition, four different intermediates formed during the degradation process were also identified and characterized by GC-MS. The mineralization rate was compared with lamps of wavelength 254 and 365 nm under similar conditions. The rate with 254 nm was observed to be very close to that of 365 nm.     

Enhancement of the bleaching and degradation of textile wastewaters by Gliding arc discharge plasma in the presence of TiO2 catalyst

The degradation of two polluted textile wastewaters from SOITEX (silk and textile) industry using the plasma-catalytic process, has been studied by non-thermal Gliding arc technique coupled to Degussa P25 titanium dioxide (TiO(2)) as photo-catalyst. Experiments were carried out to optimise the amount of phtoto-catalyst. The results showed that maximum degradation was attained for 3 g L(-1) TiO(2) concentration. For wastewater (1) degradation was 95% at the end of 60 min of treatment time. The same wastewater was completely decolourised after only 30min of plasma-catalytic treatment time. In parallel, the biodegradability was significantly enhanced through 20 min of exposure to the plasmagenous source for both wastewater samples. Turbidity of wastewater (1) and wastewater (2) decreased with rate constants of 0.015 and 0.017m in(-1), respectively. The TiO(2)-mediated Gliding Arc discharge (GAD(TiO(2)) showed potential application for the treatment of liquid wastes, resulting in the mineralization of the wastewater samples confirmed by chloride, sulphate and phosphate ions formation. In both cases of GAD treatments, with and without photo-catalyst, the plasmagenous process proves efficient in the field of wastewaters degradation.