nitrophenols and titanium-dioxide

This investigation implemented the nanomaterial rGOTiO

Topics: Catalysis; Graphite; Light; Models, Theoretical; Nanostructures; Nitrophenols; Photolysis; Titanium; Water Pollutants, Chemical

In this study, a horizontally rotating disc recirculated (HRDR) photoreactor equipped with two UV lamps (6 W) was designed and fabricated for photocatalytic removal of p-nitrophenol (PNP). Photocatalyst (TiO

Topics: Catalysis; Nanoparticles; Nitrophenols; Photolysis; Polyethylene; Titanium; Ultraviolet Rays; Water Purification

Catalytic activity of Zr and Ag co-doped TiO2 nanoparticles on the reduction of 4-nitrophenol, degradation of methylene blue and methyl orange was studied using sodium borohydride as reducing agent. The nanoparticles were characterized using X-ray diffraction, energy dispersive X-ray, high resolution transmission electron microscopy, selected area electron diffraction and UV-Vis spectroscopy. The rate of the reduction/degradation was found to increase with increasing amount of the photocatalyst which could be attributed to higher dispersity and small size of the nanoparticles. The catalytic activity of Zr and Ag co-doped TiO2 nanoparticles showed no significant difference even after recycling the catalyst four times indicating a promising potential for industrial application of the prepared photocatalyst.

Topics: Azo Compounds; Catalysis; Environmental Pollutants; Light; Metal Nanoparticles; Methylene Blue; Microscopy, Electron, Transmission; Nitrophenols; Oxidation-Reduction; Silver; Spectrometry, X-Ray Emission; Spectrophotometry, Ultraviolet; Titanium; X-Ray Diffraction; Zirconium

In this work, a new hybrid nanocatalyst, namely titanium dioxide (TiO2) composite nanowires, encapsulated with graphene (G) and palladium nanoparticles (Pd NPs) (designated as G-Pd@TiO2-CNWs), was prepared. In preparing the nanowires, a combination of electrospinning and hydrothermal approaches was employed. The visible-light-driven photocatalytic performance of G-Pd@TiO2-CNWs was investigated using the reduction of 4-nitrophenol (4-NP) as a model reaction. The results showed that G-Pd@TiO2-CNWs converted nearly 100% of 4-NP under visible light irradiation. The reaction kinetics of the photocatalytic reduction of 4-NP was studied by UV-vis spectrophotometry and the apparent rate constant was determined and compared with those for other supported TiO2 catalysts. Furthermore, the spent G-Pd@TiO2-CNWs could be recovered by simple centrifugation and reused. The work is expected to shed new light on the development of G-incorporated hybrid nanostructures for harvesting light energy and on the development of new photocatalysts for the removal of environmental pollutants.

Topics: Graphite; Nanowires; Nitrophenols; Photolysis; Titanium; Water Pollutants, Chemical

A unique Ag-bridged Ag2O nanowire network/TiO2 nanotube array p-n heterojunction (Ag-Ag2O/TiO2 NT) was fabricated by simple electrochemical method. Ag nanoparticles were firstly electrochemically deposited onto the surface of TiO2 NT and then were partly oxidized to Ag2O nanowires while the rest of Ag mother nanoparticles were located at the junctions of Ag2O nanowire network. The Ag-Ag2O/TiO2 NT heterostructure exhibited strong visible-light response, effective separation of photogenerated carriers, and high adsorption capacity. The integration of Ag-Ag2O self-stability structure and p-n heterojunction permitted high and stable photocatalytic activity of Ag-Ag2O/TiO2 NT heterostructure photocatalyst. Under 140-min visible light irradiation, the photocatalytic removal efficiency of both dye acid orange 7 (AO7) and industrial chemical p-nitrophenol (PNP) over Ag-Ag2O/TiO2 NT reached nearly 100% much higher than 17% for AO7 or 13% for PNP over bare TiO2 NT. After 5 successive cycles under 600-min simulated solar light irradiation, Ag-Ag2O/TiO2 NT remained highly stable photocatalytic activity.

Topics: Azo Compounds; Benzenesulfonates; Catalysis; Coloring Agents; Light; Nanotubes; Nanowires; Nitrophenols; Oxides; Silver; Silver Compounds; Titanium; Water Pollutants, Chemical

In this study we use a straightforward experimental method to probe the presence and activity of the proteolytic enzyme α-chymotrypsin adsorbed on titania colloidal particles. We show that the adsorption of α-chymotrypsin on the particles is irreversible and pH-dependent. At pH 8 the amount of adsorbed chymotrypsin is threefold higher compared to the adsorption at pH 5. However, we observe that the adsorption is accompanied by a substantial loss of enzymatic activity, and only around 6-9% of the initial enzyme activity is retained. A Michaelis-Menten kinetics analysis of both unbound and TiO2-bound chymotrypsin shows that the K(M) value is increased from ∼10 μM for free chymotrypsin to ∼40 μM for the particle bound enzyme. Such activity decrease could be related by the hindered accessibility of substrate to the active site of adsorbed chymotrypsin, or by adsorption-induced structural changes. Our simple experimental method does not require any complex technical equipment, can be applied to a broad range of hydrolytic enzymes and to various types of colloidal materials. Our approach allows an easy, fast and reliable determination of particle surface-bound enzyme activity and has high potential for development of future enzyme-based biotechnological and industrial processes.

Topics: Adsorption; Catalytic Domain; Chymotrypsin; Colloids; Enzyme Assays; Enzymes, Immobilized; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Kinetics; Nitrophenols; Titanium

To overcome the drawback of poor solar light utilization brought about by the narrow photoresponse range of TiO₂, a silver and sulfur co-doped TiO₂was synthesized. Using the prepared catalyst, solar photocatalytic degradation of 2-nitrophenol (2-NP) by a TiO₂-based catalyst was studied for the first time. Effects of the co-doping on the structural, optical and morphological properties of the synthesized nanoparticles were investigated by different characterization methods: X-ray diffraction, N2 adsorption-desorption measurements, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy. Solar experiments showed that the co-doping with silver and sulfur significantly increased the photocatalytic activity. In various initial concentrations of 2-NP more than 99% of the contaminant was decomposed by Ag-S/TiO₂in less than 150 minutes, while the degradation efficiency was much less in the presence of bare TiO₂. Kinetic studies suggested that solar photocatalytic degradation of 2-NP is consistent with the Langmuir-Hinshelwood model. The rate constant of the reaction and adsorption constant of the modified photocatalyst were found to be 2.4 and 4.1 times larger than that of bare TiO₂, respectively.

Topics: Catalysis; Coloring Agents; Kinetics; Nitrophenols; Photolysis; Silver; Sulfur; Sunlight; Titanium; Water Pollutants, Chemical

The photocatalytic properties of functionalized TiO2 with silver nanoparticles (AgNPs) for the conversion of 4-nitrophenol to 4-aminophenol in the presence of hydrazine were investigated. The TiO2 semiconductor synthesized by the sol-gel method was functionalized with AgNPs at different loadings, and their structural and optical properties were characterized by several techniques. The functionalized TiO2 with 1.5wt% AgNPs presented the highest photocatalytic activity for the conversion of 4-nitrophenol with appropriate hydrazine concentrations (0.5M). The photoefficiency enhancement under UV light irradiation was attributed to the electron transfer from the TiO2 semiconductor surface to the adsorbed acceptor reactant (4-nitrophenol) through the deposited AgNPs.

Topics: Catalysis; Hydrazines; Metal Nanoparticles; Microscopy, Electron, Transmission; Nitrophenols; Phase Transition; Photochemical Processes; Semiconductors; Silver; Surface Properties; Titanium

A series of lead dioxide electrodes developed on titania nanotube arrays with different matrix were fabricated by electrodeposition. Before the deposition of PbO₂, the matrix of this anode was electrochemically reduced in (NH₄)₂SO₄ solution and/or pre-deposited with certain amounts of copper. To gain insight into these pretreatments, the PbO₂ electrodes were characterized by SEM, LSV, and XRD, and their electrocatalytic activities for pollutant degradation were compared using p-nitrophenol (p-NP) as a model. It was confirmed that the electrochemical reduction with (NH4)₂SO₄ resulted in the partial conversion of TiO₂ into Ti₄O₇ and Ti₅O₉, which increased the conductivity of PbO₂ anode, but decreased its electrochemical activity, while the Ti/TNTs*-Cu/PbO₂ electrode with both pretreatments possessed the highest oxygen evolution overpotential of 2.5 V (vs. SCE) and low substrate resistance. After a 180-min treatment on this electrode, the removal efficiency of p-NP reached 82.5% and the COD removal achieved 42.5% with the energy consumption of 9.45 kWh m(-3), demonstrating the best performance among these electrodes with different matrices. Therefore, this titania nanotube array-based PbO₂ electrode has a promising application in the industrial wastewater treatment.

Topics: Biological Oxygen Demand Analysis; Copper; Electrochemistry; Electrodes; Electroplating; Lead; Nanotubes; Nitrophenols; Oxidation-Reduction; Oxides; Titanium; Waste Disposal, Fluid; Water Pollutants, Chemical

A novel visible light sensitized photoelectrochemical sensing platform was constructed based on the perylene-3,4,9,10-tetracarboxylic acid/titanium dioxide (PTCA/TiO(2)) heterojunction as the photoelectric beacon. PTCA was synthesized via facile steps of hydrolysis and neutralization reaction, and then the PTCA/TiO(2) heterojunction was easily prepared by coating PTCA on nano-TiO(2) surface. The resulting photoelectric beacon was characterized by transmission electron microscope, scanning electron microscopy, X-ray diffractometry, FTIR spectroscopy, and ultraviolet and visible spectrophotometer. Using parathion-methyl as a model, after a simple hydrolyzation process, p-nitrophenol as the hydrolysate of parathion-methyl could be obtained, the fabricated derivative photoelectrochemical sensor showed good performances with a rapid response, instrument simple and portable, low detection limit (0.08 nmol L(-1)) at a signal-to-noise ratio of 3, and good selectivity against other pesticides and possible interferences. It had been successfully applied to the detection of parathion-methyl in green vegetables and the results agreed well with that by GC-MS. This strategy not only extends the application of PTCA, but also presents a simple, economic and novel methodology for photoelectrochemical sensing.

Topics: Carboxylic Acids; Electrochemical Techniques; Electrodes; Gas Chromatography-Mass Spectrometry; Light; Metal Nanoparticles; Methyl Parathion; Nitrophenols; Perylene; Pesticides; Titanium; Vegetables

Three porphyrins containing different functional groups (-OH, C-O2C2H5, -COOH), 5-(4-hydroxy) phenyl-10,15,20-triphenyl porphyrin (1a), 5-(4-ethylacetatatomethoxy) phenyl-10,15,20-triphenyl porphyrin (1b), 5-(4-carboxylatomethoxy) phenyl-10,15,20-triphenyl porphyrin (1c), were synthesized and characterized spectroscopically. The CuPp(2a, 2b, 2c)-TiO2 photocatalysts were then prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis-DRS), Fourier-transform infrared spectroscopy (FT-IR). The photocatalytic activities of the photocatalysts were investigated by carrying out the photodegradation of 4-nitrophenol in aqueous solution under simulated solar irradiation. It was found that the CuPp(2a, 2b, 2c)-TiO2 enhanced the photocatalytic efficiency of bare TiO2 in photodegrading the 4-NP due to the interaction between CuPp(2a, 2b, 2c) and TiO2, resulted in the enhancement of the photogenerated electron-hole separation. The reasons of this enhanced photocatalytic activity were also discussed. Based on the present study, it could be considered as a promising photocatalyst for the further industrial application.

Topics: Catalysis; Luminescence; Metalloporphyrins; Microscopy, Electron, Transmission; Nitrophenols; Photoelectron Spectroscopy; Photolysis; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Sunlight; Temperature; Titanium; X-Ray Diffraction

Inorganic-framework molecularly imprinted TiO2/WO3 nanocomposites with molecular recognitive photocatalytic activity were first prepared successfully by a facile one-step sol-gel method using 2-nitrophenol and 4-nitrophenol as template molecules, and tetrabutyl orthotitanate as titanium source as well as the precursor of functional monomer which could complex with template molecules. The template molecules could be completely removed by means of high-temperature calcination, avoiding the traditional extraction procedures that are time- as well as solvent-consuming. Compared to nonimprinted TiO2/WO3, the molecularly imprinted TiO2/WO3 shows a much higher adsorption capacity and selectivity toward the template molecules. The enhancement in terms of adsorption capacity and selectivity can be attributed to the chemical interaction between target molecules and imprinted cavities, as well as size matching between imprinted cavities and target molecules. The photocatalytic activity of molecularly imprinted TiO2/WO3 toward the target molecules is more than two times that of non-imprinted TiO2/WO3, a result of selective adsorption of target molecules on molecularly imprinted TiO2/WO3. The formation pathway of intermediate products in 2-nitrophenol and 4-nitrophenol degradation process was provided. Moreover, molecularly imprinted TiO2/WO3 exhibits high stability. The results indicate that inorganic-framework molecularly imprinted TiO2/WO3 nanocomposites have a promising prospect in the treatment of wastewater for irrigation.

Topics: Catalysis; Light; Molecular Imprinting; Nanocomposites; Nitrophenols; Oxides; Photolysis; Recycling; Titanium; Tungsten; Waste Disposal, Fluid; Water Pollutants, Chemical

We report a simple biogenic-route to narrow the band gap of TiO2 nanocrystals for visible light application by offering a greener method. When an electrochemically active biofilm (EAB) was challenged with a solution of Degussa-TiO2 using sodium acetate as the electron donor, greyish blue-colored TiO2 nanocrystals were obtained. A band gap study showed that the band gap of the modified TiO2 nanocrystals was significantly reduced (E(g) = 2.85 eV) compared to the unmodified white Degussa TiO2 (E(g) = 3.10 eV).

Topics: Bioelectric Energy Sources; Catalysis; Cerium; Electrochemical Techniques; Light; Methylene Blue; Nanoparticles; Nitrophenols; Titanium

Dissolved organic matter (DOM) is widespread in aquatic and terrestrial environments. Iron is the most abundant transition metal in the Earth's crust. The biogeochemistry of iron and the strength of Fe(II) as a reducing agent while adsorbed on minerals are affected by DOM. This study investigated the effects of Fe(II)/DOM interactions on the reduction of 2-nitrophenol (2-NP) in TiO2 suspensions. Kinetic measurements demonstrated that rates (k) of 2-NP reduction by adsorbed Fe(II) species are affected by adding DOM (denoted O-DOM), and the obtained k values under the impact of the Fe(II)/DOM interaction with different molecular weight DOM fractions [including MW<3500Da (L-DOM), 350014000Da (H-DOM)] showed significant differences. The enhanced rates of 2-NP reduction contributed to increases in the amount of adsorbed Fe(II) species and negative shifts in peak oxidation potential values (EP) in CV tests. For different molecular weight DOM fractions, increases in k (O-DOM

Topics: Adsorption; Electrochemistry; Electron Transport; Iron; Kinetics; Molecular Weight; Nitrophenols; Suspensions; Titanium

A novel magnetic double-shell Fe3O4@TiO2/Au@Pd@TiO2 microsphere composed of a Fe3O4 core and double TiO2 shells with Au and Pd nanoparticles encapsulated is created. The microsphere can be used as a highly efficient reusable catalyst with superior catalytic activity and stability and magnetic separable capability in reduction of 4-nitrophenol.

Topics: Catalysis; Ferrosoferric Oxide; Gold; Lead; Magnetics; Metal Nanoparticles; Microspheres; Nitrophenols; Oxidation-Reduction; Titanium

Conductive polypyrrole-polyaniline/TiO2 nanocomposites (PPy-PANI/TiO2) were prepared by in situ oxidative copolymerization of pyrrole and aniline monomers in the presence of TiO2. For comparison studies, polypyrrole/TiO2 (PPy/TiO2) and polyaniline/TiO2 (PANI/TiO2) were also prepared. The samples were characterized by X-ray diffraction, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, zeta potential analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis and photocurrent tests. In contrast to PPy/TiO2 and PANI/TiO2, PPy-PANI/TiO2 exhibits obvious absorption in the visible-light range, and is much superior to PPy/TiO2 and PANI/TiO2 in thermal stability. It is found that PPy-PANI/TiO2 performs well in the visible-light photocatalytic degradation of 4-nitrophenol. The optimized pyrrole : aniline : TiO2 molar ratio for best performance is 0.75 : 0.25 : 100. The efficacy of PPy-PANI/TiO2 is attributed to its conductivity, conjugated structure, as well as to the synergy amidst polypyrrole, polyaniline and TiO2.

Topics: Aniline Compounds; Catalysis; Light; Nitrophenols; Oxidation-Reduction; Photolysis; Polymers; Pyrroles; Temperature; Titanium

The degradation and detoxification towards the duckweed Lemna minor of 4-nitrophenol (4NP) was studied by means of bench-scale constructed wetlands (CWs), TiO(2)-photocatalysis and Fenton + photoFenton reactions. The main goal of this work was to compare the three treatment techniques to evaluate their possible combination for the efficient, low cost treatment of 4NP effluents. In CWs, adsorption on the substrate of 4NP was found to achieve 34-45%. Low concentrations (up to 100 ppm) of 4NP were successfully treated by CWs in 8-12 h. The microbial degradation of 4NP started after a lag phase which was longer with higher initial concentrations of the pollutant. The greatest degradation rate was found to occur at initial concentrations of 4NP between 60 and 90 ppm. Solar TiO(2)-photocatalysis was faster than the CWs. The greatest removals in terms of mass of 4NP removed after 6 h of irradiation were found to occur at 4NP concentrations of about 200 ppm. Fenton reaction provided complete 4NP degradation up to 500 ppm in only 30 min but TOC was removed by only about 40%. The resulting toxicities were below 20% for initial 4NP concentrations below 300 ppm. It was the Fenton + photoFenton combination (180 min in total) that provided TOC reductions up to 80% and negative L. minor growth inhibition for almost all the 4NP concentrations tested. The combination of solar TiO(2)-photocatalysis (6 h) with CWs (16 h) was able to completely treat and detoxify 4NP effluents with concentrations as high as 200 ppm of the organic.

Topics: Biodegradation, Environmental; Catalysis; Light; Nitrophenols; Oxidation-Reduction; Plants; Titanium; Water Microbiology; Wetlands

Titanium dioxide (TiO2) nanoparticles were prepared by sol gel route. The preparation parameters were optimized in the removal of 4-nitrophenol (4-NP). All catalysts were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). An artificial neural network model (ANN) was developed to predict the photocatalytic removal of 4-NP in the presence of TiO2 nanoparticles prepared under desired conditions. The comparison between the predicted results by designed ANN model and the experimental data proved that modeling of the removal process of 4-NP using artificial neural network was a precise method to predict the extent of 4-NP removal under different conditions.

Topics: Catalysis; Crystallization; Nanoparticles; Neural Networks, Computer; Nitrophenols; Temperature; Time Factors; Titanium; Ultraviolet Rays; X-Ray Diffraction

The TiO(2)/ZnO nanofibers embedded by Au nanoparticles (TiO(2)/ZnO/Au NFs) were fabricated by combining the electrospinning technique (for TiO(2)/ZnO nanofibers) and an in situ reduction approach (for Au nanoparticles). X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electronmicroscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy, were used to characterize the as-synthesized nanofibers. The results showed that small Au nanoparticles (Au NPs) were well dispersed on the TiO(2)/ZnO nanofibers (TiO(2)/ZnO NFs). And, the TiO(2)/ZnO/Au nanofibers showed high charge separation efficiency under ultraviolet excitation, as evidenced by photoluminescence spectra. The photocatalytic studies revealed that the TiO(2)/ZnO/Au NFs exhibited enhanced photocatalytic efficiency of photodegradation of Methyl orange (MO) and 4-nitrophenol (4-NP) compared with the pure TiO(2) nanofibers, ZnO nanofibers and TiO(2)/ZnO NFs under ultraviolet excitation, which might be attributed to the high separation efficiency of photogenerated electron-hole pairs based on the photosynergistic effect among the three components of TiO(2), ZnO and Au. And, the TiO(2)/ZnO/Au NFs could be easily separated and recycled due to their one-dimensional nanostructural property.

Topics: Azo Compounds; Catalysis; Coloring Agents; Gold; Metal Nanoparticles; Nanofibers; Nitrophenols; Photolysis; Titanium; Ultraviolet Rays; Waste Disposal, Fluid; Zinc Oxide

In this work, we have synthesized eccentric Au@TiO(2) core-shell nanostructures and demonstrated their multiple reuse in the catalytic reduction of 4-nitrophenol.

Topics: Catalysis; Gold; Metal Nanoparticles; Nitrophenols; Oxidation-Reduction; Titanium

Cardanol, a well known hazardous byproduct of the cashew industry, has been used as starting material for the synthesis of useful differently substituted "cardanol-based" porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel composites prepared by impregnation of polycrystalline TiO₂ powder with an opportune amount of "cardanol-based" porphyrins, which act as sensitizers for the improvement of the photo-catalytic activity of the bare TiO₂, have been used in the photodegradation in water of 4-nitrophenol (4-NP), which is a toxic and bio-refractory pollutant, dangerous for ecosystems and human health.

Topics: Catalysis; Molecular Structure; Nitrophenols; Phenols; Photochemistry; Porphyrins; Titanium; Water

Nonthermal discharge plasma and TiO(2) photocatalysis are two techniques capable of organic pollutants removal in soil. In the present study, a pulsed discharge plasma-TiO(2) catalytic (PDPTC) technique by combining the two means, where catalysis of TiO(2) is driven by the pulsed discharge plasma, is proposed to investigate the remediation of p-nitrophenol (PNP) contaminated soil. The experimental results showed that 88.8% of PNP was removed within 10 min of treatment in PDPTC system and enhancing pulse discharge voltage was favorable for PNP degradation. The mineralization of PNP and intermediates generated during PDPTC treatment was followed by UV-vis spectra, denitrification, total organic carbon (TOC), and CO(x) selectivity analyses. Compared with plasma alone system, the enhancement effects on PNP degradation and mineralization were attributed to more amounts of chemically active species (e.g., O(3) and H(2)O(2)) produced in the PDPTC system. The main intermediates were identified as hydroquinone, benzoquinone, catechol, phenol, benzo[d][1, 2, 3]trioxole, acetic acid, formic acid, NO(2)(-), NO(3)(-), and oxalic acid. The evolution of the main intermediates with treatment time suggested the enhancement effect of the PDPTC system. A possible pathway of PNP degradation in soil in such a system was proposed.

Topics: Environmental Restoration and Remediation; Models, Chemical; Nitrophenols; Photochemistry; Soil Pollutants; Titanium

In this study, to investigate the application of heterogeneous photocatalysis in the removal of organic contaminants from aqueous media a novel tubular continuous-flow photoreactor with supported TiO2-P25 on glass plates was designed and constructed. The photoreactor comprises six quartz tubes and a UV lamp which was placed in the center of the quartz tubes. 4-nitrophenol (4-NP) as a most refractory pollutant was chosen as a probe pollutant to examine the photoreactor efficiency for environmental cleaning applications. Results of experiments show that the removal efficiency of 4-NP in this photoreactor is a function of photoreactor length, gas and liquid flow rates and 4-NP initial concentration. Kinetics analysis indicates that degradation of 4-NP in continuous-mode can be modeled with the Langmuir-Hinshelwood (L-H) model (k(L-H) = 1.5 mg L(-1) min(-1), K(ads) = 0.11 mg(-1) L). A design equation was obtained with a combination of L-H modified equation and tubular reactor design equation. This equation can be used for estimation of 4-NP concentration in different photoreactor lengths under various operational parameters. Mineralization study was followed through total organic carbon (TOC) analysis and measurement of nitrite and nitrate as final degradation products.

Topics: Carbon; Kinetics; Nanoparticles; Nitrates; Nitrites; Nitrophenols; Oxidation-Reduction; Titanium; Water Pollutants, Chemical; Water Pollution; Water Purification

Photocatalytic degradation of 4-nitrophenol was investigated using Fe-doped (1, 3, 5 and 8 wt.% Fe) TiO(2) catalysts under UV light irradiation in aqueous dispersions in the presence of H(2)O(2). Photocatalysts with the lowest Fe content (1%) showed a considerably better behavior with respect to the unloaded TiO(2) and the catalysts with higher Fe contents. Photocatalytic degradation was studied under different conditions such as amounts of 1% Fe-TiO(2) catalyst, H(2)O(2) dose and initial pH of 4-NP solution. The results indicated that about 67.53% total organic carbon of a solution containing 20 mg L(-1) 4-NP was removed at pH 6.17 by using 4.9 mM of H(2)O(2) and 0.4 g L(-1) of the catalyst in a 2-L batch photo-reactor, the complete degradation of 4-NP occurring after 60 min. It was also observed that catalytic behavior could be reproduced in consecutive experiments without a considerable decrease of the UV/Fe-TiO(2)/H(2)O(2) process efficiency.

Topics: Catalysis; Hydrogen Peroxide; Iron; Nitrophenols; Photolysis; Titanium; Ultraviolet Rays

p-Nitrophenol (PNP) is a difficultly decomposed organic pollutant under solar light in the absence of strong oxidants. This study shows that under artificial solar light PNP can be effectively degraded by a Cu(2)O/TiO(2) p-n junction network which is fabricated by anodizing Cu(0) particles-loaded TiO(2) nanotubes (NTs). The network is composed of p-type Cu(2)O nanowires on the top surface and Cu(2)O nanoparticles on the inner walls of the n-type TiO(2) NT arrays. The Cu(2)O/TiO(2) network shows much higher degradation rate (1.97 μg/min cm(2)) than the unmodified TiO(2) NTs (0.85 μg/min cm(2)). The enhanced photocatalytic acitivity can be attributed to the extended absorption in the visible resulting from the Cu(2)O nanowire networks and the effective separation of photogenerated carriers driven by the photoinduced potential difference generated at the Cu(2)O/TiO(2) p-n junction interface.

Topics: Catalysis; Chromatography, High Pressure Liquid; Copper; Environmental Pollutants; Gas Chromatography-Mass Spectrometry; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; Nanowires; Nitrophenols; Photochemistry; Spectrophotometry, Ultraviolet; Titanium

Nitration reactions of aromatic compounds are commonly involved in different industrial processes for pharmaceutical, pesticide or military uses. For many years, most of the manufacturing sites used lagooning systems to treat their process effluents. In view of a photocatalytic degradation assay, the wastewater of a lagoon was investigated by using HPLC coupled with mass spectrometry. The wastewater was highly concentrated in RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and two herbicides Dinoterb (2-tert-butyl-4,6-dinitrophenol) and Dinoseb (2-sec-butyl-4,6-dinitrophenol). First of all, an analytical method using solid-phase extraction (SPE) combined with HPLC ESI MS/MS was put in work for identification and titration of RDX, HMX and the two dinitrophenols in a complex natural matrix. Then, the UV/TiO2 treatment was investigated for pollutants removal. Dinitrophenolic compounds were significantly degraded after a 8-h-exposition of the wastewater/TiO2 suspension, whereas RDX and HMX were poorly affected.

Topics: 2,4-Dinitrophenol; Aniline Compounds; Azocines; Catalysis; Chromatography, High Pressure Liquid; Dinitrophenols; Industrial Waste; Nitrobenzenes; Nitrophenols; Photolysis; Solid Phase Extraction; Spectrometry, Mass, Electrospray Ionization; Titanium; Triazines; Ultraviolet Rays; Water Pollutants, Chemical

This research focused on immersion method synthesis of visible light active salicylic acid (SA)-modified TiO2 nanotube array electrode and its photoelectrocatalytic (PEC) activity. The SA-modified TiO2 nanotube array electrode was synthesized by immersing in SA solution with an anodized TiO2 nanotube array electrode. Scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), UV-vis diffuse reflectance spectrum (DRS), and Surface photovoltage (SPV) were used to characterize this electrode. It was found that SA-modified TiO2 nanotube array electrode absorbed well into visible region and exhibited enhanced visible light PEC activity on the degradation of p-nitrophenol (PNP). The degradation efficiencies increased from 63 to 100% under UV light, and 79-100% under visible light (lambda>400 nm), compared with TiO2 nanotube array electrode. The enhanced PEC activity of SA-modified TiO2 nanotube array electrode was attributed to the amount of surface hydroxyl groups introduced by SA-modification and the extension of absorption wavelength range.

Topics: Catalysis; Electrochemical Techniques; Electrodes; Light; Nanotubes; Nitrophenols; Photolysis; Salicylic Acid; Titanium

We report on a novel amperometric biosensor for detecting phenolic compounds based on the co-immobilization of horseradish-peroxidase (HRP) and methylene blue (MB) with chitosan on Au-modified TiO2 nanotube arrays. The titania nanotube arrays were directly grown on a Ti substrate using anodic oxidation first; a gold thin film was then coated onto the TiO2 nanotubes by an argon plasma technique. The morphology and composition of the fabricated Au-modified TiO2 nanotube arrays were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. The effect of pH, applied electrode potential and the concentration of H(2)O(2) on the sensitivity of the biosensor have been systemically investigated. The performance of the proposed biosensor was tested using seven different phenolic compounds, showing very high sensitivity; in particular, the linearity of the biosensor for the detection of 3-nitrophenol was observed from 3 x 10(-7) to 1.2 x 10(-4)M with a detection limit of 9 x 10(-8)M (based on the S/N=3).

Topics: Biosensing Techniques; Chitosan; Electrochemical Techniques; Horseradish Peroxidase; Hydrogen Peroxide; Hydrogen-Ion Concentration; Methylene Blue; Nanotubes; Nitrophenols; Titanium

This study was aimed at elucidating the role of adsorbed Fe(II) on minerals in the reductive transformation of 2-nitrophenol (2-NP) by using electrochemical methods. The studies of Fe(ll) adsorption and 2-NP reduction kinetics showed that the identity of minerals such as gamma-Al2O3 and TiO and the solution pH were crucial factors to determine the Fe(ll) adsorption behavior and to influence the rate constant (k) of 2-NP reduction. Furthermore, two electrochemical methods, cyclic voltammetry (CV) and electrochemical impedance spectrometry (EIS), were applied to characterize the Fe(II) reactivity with both the mineral-coated and mineral-free electrodes. The electrochemical evidence confirmed that the peak oxidation potential (Ep) of complex Fe(II) can be significantly affected by the solution pH;the enhanced reductive transformation of 2-NP can be related to the reduced Ep of surface-complex Fe(II) and the reduced charge transfer resistance (R(CT)) of the Fe(III)/Fe(II) couple. All these relationships were studied quantitatively. At pH 6.7, the measured Ep and R(CT) decreased in the order TiO2/GC < gamma-Al2O3/ GC < GC (Ep, 0.140 < 0.190 < 0.242 V; R(CT), 0.30 < 0.41 < 0.78 komega), while the 2-NP reduction on different minerals were in the order TiO2 > gamma-Al2O3 > nonmineral (k x 10-2, 7.91 > 0.64 > 0.077 min(-l)).

Topics: Adsorption; Aluminum Oxide; Electric Impedance; Electrochemistry; Electrodes; Environment; Hydrogen-Ion Concentration; Iron; Kinetics; Minerals; Models, Chemical; Nitrophenols; Oxidation-Reduction; Surface Properties; Titanium

Here we report an a novel approach, the marriage of photocatalytic degradation and electrochemical oxidation, to wastewater remediation based on the use of bifunctional electrodes. To illustrate this innovative technique, TiO2/Ti/ Ta2O5-IrO2 bifunctional electrodes were prepared using a facile thermal decomposition technique and employed in this study. The TiO2 photocatalyst was coated on one side of the Ti substrate, while the Ta2O5-IrO2 electrocatalytic thin film was coated on the other side. The fabricated bifunctional electrodes were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The performance of the bifunctional electrodes was tested using both 4-nitrophenol (4-NPh) and 2-nitrophenol (2-NPh) as model pollutants. Our study demonstrates that the prepared bifunctional electrodes exhibit high efficiency for both 4-NPh and 2-NPh degradation. In the degradation of 4-NPh a rate constant of 1.06 x 10(-2) min(-1) was created and a rate constant of 1.93 x 10(-2) min(-1) was produced for 2-NPh by the combination of the photochemical and electrochemical oxidation on the novel bifunctional electrodes, quadruple the rate constant created by the individual photochemical and photoelectrochemical methods. The innovative approach described in this study provides a very promising and energy efficient environmentally friendly technology for water purification and waste effluent treatment.

Topics: Catalysis; Electrochemistry; Electrodes; Microscopy, Electron, Scanning; Nitrophenols; Photochemistry; Platinum; Time Factors; Titanium; Waste Disposal, Fluid; Water Pollutants; Water Purification

Heterogeneous photocatalysis on metal oxide semiconductor particles is an advanced oxidation technology (AOT), which has been effective means of removing organic pollutants from water streams as it utilizes ultraviolet light with semiconductors acting as photocatalyst and leads to complete mineralization of pollutants to environmentally harmless compounds. In the present investigation, the photo-catalyzed degradation studies of p-Nitrophenol (PNP) were carried out in laboratory scale immersion well UV photo-reactor using semiconductor photo-catalyst TiO2 in suspension. For this purpose, low pressure 12 W mercury lamp was used and the effect of (i) time of irradiation, (ii) dose of TiO2, (iii) initial concentration of PNP and (iv) the addition of H2O2 to the system was studied to arrive at optimum process parameters for the complete degradation and decolorization of PNP. Simple UV irradiation could not achieve significant degradation of PNP. But UV+aeration+TiO2+ H2O2 combination achieved almost complete degradation of PNP. The spectrophotometric analysis showed that the rate of degradation of PNP was very fast in initial two hours and the maximum degradation was achieved in 5 hours. The degradation was found to increase in the order UV < UV + aeration < UV + aeration + TiO2 < UV + aeration + TiO2+ H2O2, and the degradation was found to be almost 100% for UV + aeration + TiO2 + H2O2, 91% for UV + aeration + TiO2, 43% for UV + aeration and only 26% for UV irradiation.

Topics: Catalysis; Nitrophenols; Oxidation-Reduction; Photochemistry; Titanium; Ultraviolet Rays; Water; Water Pollutants, Chemical; Water Purification

Aqueous 4-nitrophenol solutions containing TiO2 or Al2O3 nanoparticles were irradiated with electron beam. 4-Nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO2 or Al2O3 (2 g l(-1)) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO2 or Al2O3 nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO2 or Al2O3 during irradiation is just due to adsorption.

Topics: Adsorption; Aluminum Oxide; Chromatography, High Pressure Liquid; Electrons; Nanoparticles; Nitrophenols; Radiation, Ionizing; Titanium; Water Pollutants, Chemical; Water Pollution

Simulated solar UV/TiO(2) photocatalysis was efficient to detoxify a mixture of 100 mgphenoll(-1) and 50 mgp-nitrophenol (PNP) l(-1) and allow the subsequent biodegradation of the remaining pollutants and their photocatalytic products under photosynthetic aeration with Chlorella vulgaris. Photocatalytic degradation of phenol and PNP was well described by pseudo-first order kinetics (r(2)>0.98) with removal rate constants of 1.9x10(-4) and 2.8x10(-4)min(-1), respectively, when the pollutants were provided together and 5.7x10(-4) and 9.7x10(-4)min(-1), respectively, when they were provided individually. Photocatalytic pre-treatment of the mixture during 60 h removed 50+/-1% and 62+/-2% of the phenol and PNP initially present but only 11+/-3% of the initial COD. Hydroquinone, nitrate and catechol were identified as PNP photocatalytic products and catechol and hydroquinone as phenol photocatalytic products. Subsequent biological treatment of the pre-treated samples removed the remaining contaminants and their photocatalytic products as well as 81-83% of the initial COD, allowing complete detoxification of the mixture to C. vulgaris. Similar detoxification efficiencies were recorded after biological treatment of the irradiated mixture with activated sludge microflora or with an acclimated consortia composed of a phenol-degrading Alcaligenes sp. and a PNP-degrading Arthrobacter sp., although the acclimated strains biodegraded the remaining pollutants faster. Biological treatment of the non-irradiated mixture was inefficient due to C. vulgaris inhibition.

Topics: Alcaligenes; Arthrobacter; Catalysis; Chlorella vulgaris; Chlorophyll; Lepidium sativum; Nitrophenols; Phenol; Photosynthesis; Plant Stems; Titanium; Ultraviolet Rays; Waste Disposal, Fluid; Water Pollutants, Chemical

In the present study an attempt is made efficiently to degrade USEPA listed 4-chloro-2-nitrophenol (4C-2-NP), widely available in bulk drug and pesticide wastes using various advanced oxidation processes (AOPs). A comparative assessment using various AOPs (UV, H(2)O(2,) UV/H(2)O(2), Fenton, UV/Fenton and UV/TiO(2)) was attempted after initial optimization studies, viz., varying pH, peroxide concentration, iron concentration, and TiO(2) loading. The degradation of the study compound was estimated using chemical oxygen demand (COD) reduction and compound reduction using spectrophotometric methods and further validated with high performance liquid chromatography (HPLC). The degradation trends followed the order: UV/Fenton > UV/TiO(2) > UV/H(2)O(2) > Fenton > H(2)O(2) > UV(.) It can be inferred from the studies that UV/Fenton was the most effective in partial mineralization of 4C-2-NP. However, lower costs were obtained with H(2)O(2). Kinetic constants were evaluated using first order equations to determine the rate constant K.

Topics: Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Hydrogen Peroxide; Hydrogen-Ion Concentration; Iron; Kinetics; Nitrophenols; Oxidants, Photochemical; Oxidation-Reduction; Oxygen; Peroxides; Spectrophotometry; Titanium; Ultraviolet Rays; Water Purification

The efficiency of photocatalytic reactions was limited by the wide band-gap of TiO(2) and the high degree of electron-hole recombination inherent in photocatalytic process, as well as by the limited adsorption capability of photocatalysts. In order to increase the overall efficiency, the surface of nanometer size TiO(2) was simply and fast modified by chemical adsorption in saturated solution of salicylic acid. A stable, light yellow surface complex was formed quickly, which has obvious absorption in the region from 320 to 420 nm. Through surface modification, the adsorption efficiency of 4-nitrophenol by TiO(2) was enhanced from 42 to 84%. The photocatalytic efficiency was tested on the degradation of 4-nitrophenol. The influences of catalyst and its dosage, pH value, and 4-nitrophenol concentration on the degradation were investigated. Under such photodegradation conditions as initial pH 4.0, 4-nitrophenol 5 mg l(-1), catalyst 100 mg, and irradiation time 160 min with 160 W high-pressure mercury lamp, the degradation efficiency of 4-nitrophenol by TiO(2) was increased from 39.5 to 79.3% after surface modification, and furthermore, the degradation efficiency could be enhanced to 91.1% if the concentration of 4-nitrophenol was not more than 1 mg l(-1). Compared with the pure TiO(2), surface modification led not only to improve the surface coverage of 4-nitrophenol, but also to increase the light utilization. Both of these factors were crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of aromatic pollutants.

Topics: Adsorption; Catalysis; Hydrogen-Ion Concentration; Molecular Structure; Molecular Weight; Nanostructures; Nitrophenols; Oxidation-Reduction; Photochemistry; Salicylic Acid; Spectrum Analysis; Titanium

Nanometer size titanium dioxide modified with 3,5-dinitrosalicylic acid (3,5-DA) was prepared using chemical adsorption method. The influences of surface modification on the adsorption of p-nitrophenol (PNP) and the dispersion in solvent such as water, benzene and ethanol were studied. The 3,5-dinitrosalicylic acid is bonded to the surface hydroxyl from TiO2 nanoparticles, results in the formation of a stable, six-ring complex which color is buff. The 3, 5-DA-modified TiO2 nanoparticles have good dispersive capacity in water, benzene and ethanol. Under the optimum conditions such as pH value 3, adsorption time 10 min, the adsorption ratio of PNP by TiO2 is improved from 43% to 99.9% through surface modification. A new method could be used to remove directly 3 approximately 10mg/L PNP, and the residual concentrations is below the integrated wastewater discharge standard (GB 8978-1996).

Topics: Adsorption; Metal Nanoparticles; Nitrophenols; Salicylates; Titanium; Waste Disposal, Fluid

Photodegradation of pentachlorophenol (PCP) and p-nitrophenol (PNP) in soil was carried out in a designed rotary reactor, which can provide the soil particles with continually uniform irradiation, and on a series of thin soil layers. TiO2, as a kind of environmental friendly photocatalyst, was introduced to the soil to enhance the processes. Compared with that on the soil layers, photodegradation of PCP at initial concentration of 60 mg/kg was improved dramatically in the rotary reactor no matter whether TiO2 was added, with an increase of 3.0 times in the apparent first-order rate constants. The addition of 1 wt% TiO2 furthered the improvement by 1.4 times. Without addition of TiO2, PNP (initial concentration of 60 mg/kg) photodegradation rate in the rotary reactor was similar to that on the soil layers. When 1 wt% additional TiO2 was added, PNP photodegradation was enhanced obviously, and the enhancement in the rotary reactor was 2 times of that on the soil layers, which may be attributed to the higher frequency of the contact between PNP on soil particles and the photocatalyst. The effect of soil pH and initial concentrations of the target compounds on the photodegradation in the rotary reactor was investigated. The order of the degradation rate at different soil pH was relative to the aggregation of soil particles during mixing in the rotary reactor. Photodegradation of PCP and PNP at different initial concentrations showed that addition of TiO2 to enhance the photodegradation was more suitable for contaminated soil with higher concentration of PCP, while was effective for contaminated soil at each PNP concentration tested in our study.

Topics: Catalysis; Chromatography, High Pressure Liquid; Environmental Pollution; Hydrogen-Ion Concentration; Nitrophenols; Pentachlorophenol; Photolysis; Soil; Soil Pollutants; Titanium

The surface of nanometer size TiO(2) was simply and fast modified by chemical adsorption in saturated solution of 5-sulfosalicylic acid. After surface modification, a stable, yellow surface complex was formed quickly, the wavelength response range of TiO(2) was expanded, it has obvious absorption in the region from 320 to 450 nm; the adsorption efficiency of p-nitrophenol (PNP) by TiO(2) was enhanced from 42% to 84%. The photocatalytic activity was tested on the degradation of PNP. The influences of catalyst and its dosage, pH value, and PNP concentration on the degradation were investigated. On optimal photodegradation conditions, including initial pH 4.0, PNP 5 mg l(-1), catalyst 100 mg, irradiation time 120 min with 160 W high-pressure mercury lamp, the degradation efficiency of PNP was increased from 40% to 88% after surface modification. Surface modification led not only to an increase in the light utilization, but also improved the surface coverage of PNP in comparison with the pure TiO(2). Both of these factors are crucial for the photocatalytic activity of heterogeneous photocatalysis, especially for photodegradation of benzenoid pollutants.

Topics: Adsorption; Benzenesulfonates; Benzoic Acid; Catalysis; Nitrophenols; Particle Size; Photochemistry; Salicylates; Surface Properties; Titanium; Ultraviolet Rays; Water Pollutants, Chemical; Water Purification

Characterization of polycrystalline TiO(2) bare or porphyrin impregnated powders, used as photocatalysts for the degradation of 4-nitrophenol (4-NP) in aqueous suspension, was performed by time-resolved microwave conductivity (TRMC) measurements and electronic paramagnetic resonance (EPR) and X-ray photoelectron (XPS) spectroscopies. The presence of porphyrin sensitizers, as the metal-free or Cu [5,10,15,20-tetra (4-tert-butylphenyl)] porphyrin, impregnated onto the TiO(2) surface improved the photocatalytic activity of the bare TiO(2). TRMC measurements indicate that the number and lifetime of the photoinduced excess charge carriers increase in the presence of the macrocycles, and EPR and XPS spectroscopies support the mechanistic hypotheses based on the photoreactivity experiments.

Topics: Catalysis; Crystallization; Electric Conductivity; Microwaves; Molecular Structure; Nitrophenols; Photochemistry; Porphyrins; Spectrum Analysis; Time Factors; Titanium

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.

Topics: Anti-Infective Agents; Catalysis; Coloring Agents; Environmental Pollution; Incineration; Nanotechnology; Nitrophenols; Phenol; Photochemistry; Salicylic Acid; Semiconductors; Titanium

This article describes a method for treating aqueous 4-nitrophenol by mixing with TiO2-SnO2 coupled particles. The reactivity of single photocatalysis (TiO2 and SnO2 all as 1.2 g/L) is compared with that of mixing TiO2-SnO2 (0.6 g/L + 0.6 g/L) coupled particles. Aqueous 4-nitrophenol was treated by single photocatalysis or coupled semiconducting particles in a double-layer glass batch reactor using a 15W UV fluorescent tube at 25 degrees C and 300 rpm for mixing. The results demonstrated that pH and the concentration of TiO2 were the factors that most influenced the degradation characteristics, and that the system of TiO2-SnO2 coupled particles improved the efficiency of removal of refractory organic pollutants by 15%, by the inter-particle electron transfer (IPET) effect. The results showed that the degradation of aqueous 4-nitrophenol was 75% when coupled particles were used--better than the 60% obtained using single photocatalysis--with a reaction time of 120min.

Topics: Catalysis; Coloring Agents; Nitrophenols; Photochemistry; Semiconductors; Titanium; Water Purification

The formation of nitrophenols was studied as a consequence of ultra violet (UV) irradiation of aqueous solutions of phenol and nitrate in the range of pH 1-12. The study was performed both in homogeneous phase and in the presence of water-suspended TiO2. The effects of pH, dissolved oxygen and 2-propanol as .OH scavenger have been evaluated. A reaction mechanism is proposed, based on the experimental results.

Topics: Free Radical Scavengers; Hydrogen-Ion Concentration; Nitrates; Nitrophenols; Oxidants, Photochemical; Photochemistry; Titanium; Ultraviolet Rays; Water Pollutants, Chemical

Phenol photonitration and photonitrosation were studied both in homogeneous and in heterogeneous phase in the presence of TiO2 particles. The effect of pH as well as of the semiconductor particles on the kinetics and products of the reaction was observed. Formation of nitrophenols is enhanced at acidic pH, due to thermal processes initiated by nitrous acid, as well as in the presence of TiO2, due to the photocatalytic oxidation of nitrite.

Topics: Catalysis; Coloring Agents; Hydrogen-Ion Concentration; Kinetics; Nitrites; Nitrophenols; Oxidation-Reduction; Photochemistry; Semiconductors; Temperature; Titanium; Water Pollutants, Chemical