Photocatalytic conversion of benzene to phenol using modified TiO2 and polyoxometalates

The application of photocatalytic reactions to organic synthesis has attracted interests in view of the development of environmentally benign synthetic processes. This study investigated the effects of various parameters (electron acceptor, surface modification, and the combination of photocatalysts) on the direct synthesis of phenol from benzene using photocatalytic oxidation processes. The OH radicals generated on UV-illuminated TiO₂ photocatalyst directly hydroxylate benzene to produce phenol, hydroquinone, and catechol. The addition of Fe³⁺, H₂O₂, or Fe³⁺ + H₂O₂ highly enhanced the phenol production yield and selectivity in TiO₂ suspension. Surface modifications of TiO₂ had significant influence on the phenol synthetic reaction. Depositing Pt nanoparticles on TiO₂ (Pt/TiO₂) markedly enhanced the yield and selectivity. Surface fluorination of TiO₂ (F-TiO₂) increased the phenol yield two-fold because of the enhanced production of mobile (free) OH radicals on F-TiO₂. Polyoxometalate (POM) in phenol synthesis played the dual role both as a homogeneous photocatalyst and as a reversible electron acceptor in TiO₂ suspension. POM alone was as efficient as TiO₂ alone in the phenol production. In particular, the addition of POM to the TiO₂ suspension increased the phenol yield from 2.6% to 11% (the highest yield obtained in this study). Reaction mechanisms for each photocatalytic system were discussed in relation to the phenol synthesis.     

Photodegradation of chloroacetic acids over bare and silver-deposited TiO2: Identification of species attacking model compounds, a mechanistic approach

Photocatalytic degradation of chloroacetic acids (ClAAs) over various bare and silver-deposited Degussa P25 TiO₂ particles was studied. Adsorption measurements carried out using TiO₂ photocatalysts of different origin demonstrated significant dependence of the adsorption efficiency on the nature of semiconductor particles and on the number of chlorine atoms of the substrate. Irradiation of the reaction mixtures containing monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA), respectively, over P25 titania were performed under anaerobic and aerobic conditions. The progress of photocatalysis was followed by measuring the substrate concentration, the total organic carbon content (TOC) and the concentration of the chloride ion in the liquid phase of reaction mixtures. Opposite trends in the photodecomposition rate of the substrates were obtained for aerobic v_MCA≈v_DCA>v_TCA and for anaerobic experiments v_TCA>v_DCA>v_MCA, respectively. The evolved CO₂ was also measured under aerobic photodecomposition of DCA. Important role of hydroxyl radicals in the photomineralization of mono- and dichloroacetic acid was confirmed by using coumarin (COU) as a hydroxyl radical scavenger and oxalic acid as an efficient scavenger for holes. Silver deposition onto the TiO₂ surface enhanced the efficiency of the semiconductor by a factor of 4 for the photooxidation of TCA and by a factor of 1.4 for DCA and MCA.     

A New Mechanism of the Selective Photodegradation of Antibiotics in the Catalytic System Containing TiO2 and the Inorganic Cations

The mechanism of sulfisoxazole (SFF) selective removal by photocatalysis in the presence of titanium (IV) oxide (TiO₂) and iron (III) chloride (FeCl₃) was explained and the kinetics and degradation pathways of SFF and other antibiotics were compared. The effects of selected inorganic ions, oxygen conditions, pH, sorption processes and formation of coordination compounds on the photocatalytic process in the presence of TiO₂ were also determined. The Fe³⁺ compounds added to the irradiated sulfonamide (SN) solution underwent surface sorption on TiO₂ particles and act as acceptors of excited electrons. Most likely, the SFF degradation is also intensified by organic radicals or cation organic radicals. These radicals can be initially generated by reaction with electron holes, hydroxyl radicals and as a result of electron transfer mediated by iron ions and then participate in propagation processes. The high sensitivity of SFF to decomposition caused by organic radicals is associated with the steric effect and the high bond polarity of the amide substituent.     

Effect of surface hydroxyl groups of pure TiO2 and modified TiO2 on the photocatalytic oxidation of aqueous cyanide

It is still debatable whether the photocatalytic oxidation of cyanide proceeds via hydroxyl radicals or by photogenerated holes. We synthesized pure TiO₂ catalysts via sol-gel process. In order to elucidate the oxidation pathway of cyanide, we used hydroxyl radical scavengers and controlled the concentration of surface hydroxyl group on the catalysts adopting fluoride-exchange. The degree of fluoride-exchange of TiO₂ catalysts was independent of the pH of suspension. We also adopted a polyoxometalate, tungstophosphoric acid (TPA, H₃PW₁₂O₄₀) which is well known for high charge transfer ability and hydrolytic stability. TPA-modified TiO₂ catalysts were prepared with sol-gel technique to overcome the high solubility of TPA in water. As another attempt for the insoluble TPA, proton of TPA supported on TiO₂ catalysts was replaced by cesium ion to form Cs-TPA/TiO₂ catalysts. Both attempts were successful in immobilizing TPA on TiO₂ catalysts. Commercially available TiO₂ catalysts such as P25 from Degussa AG were also used as catalysts. XRD analysis revealed that pure TiO₂ and TPA-modified TiO₂ catalysts prepared by sol-gel process were composed of well-developed anatase crystalline structure. In the presence of hydroxyl radical scavengers, the photoactivity of TPA-modified TiO₂ catalysts was retarded much less than that of pure TiO₂ catalysts. The concentration of surface hydroxyl group was effectively suppressed by the fluoride-exchange causing the decrease of the activity of the catalysts. In the case of fluoride-exchanged catalysts, the drop in activity was obvious for the pure TiO₂ catalysts in the presence of iodide as a hydroxyl radical scavenger suggesting that indirect oxidation via hydroxyl radicals was the preferential reaction pathway. For the TPA-modified TiO₂ catalysts, meanwhile, the diminution was such a small extent suggesting that direct oxidation by photogenerated holes was the main reaction pathway. The activity arising from TPA in the catalysts was due to the Keggin structured anion (PW₁₂O ₄₀ ^3- ) which acted as an electron relay with the aid of dissolved oxygen in the reaction system. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Electrochemically assisted photocatalytic degradation of oxalic acid on particulate TiO2 film in a batch mode plate photoreactor

Electrochemically assisted photocatalytic degradation of oxalic acid was studied in a batch mode plate photoreactor composed of particulate TiO₂ film immobilized on Ti metal plate (Ti/TiO₂ electrode) and Pt wires immersed in a flowing film of aqueous solution (Pt counter electrode). The degradation rate of oxalic acid was followed as a function of the potential of the Ti/TiO₂ electrode, the oxygen concentration and the light intensity. The presence of oxalic acid caused an increase in the measured photocurrent by one order of magnitude which is due to its reaction with photogenerated holes. The degradation rate increased with increasing potential up to 0.5 V vs SCE, then the increase was more gradual. Electrochemically assisted photocatalytic degradation of oxalic acid also proceeded in the absence of oxygen. The photogenerated electrons caused hydrogen evolution (low oxygen concentration) or predominantely oxygen reduction (high oxygen concentration) on the Pt counter electrode.     

Photocatalytic mineralization of phenol catalyzed by pure and mixed phase hydrothermal titanium dioxide

The photocatalytic mineralization of phenol catalyzed by pure (anatase, rutile) and mixed phase hydrothermal TiO₂ was studied in aqueous solution employing different oxidative agents, H₂O₂ and O₂. In the case of H₂O₂, rutile particles, having large dimensions and high aspect ratio (size: 30–70 nm × 150–350 nm), display the highest catalytic activity due to their low tendency to recombine electrons and holes generated by UV irradiation. By using water dissolved gaseous O₂, the catalytic TiO₂ activity generally decreases and rutile displays the lowest efficacy. In fact, oxygen preferentially chemisorbs at the surface of the nanosized particles of anatase (5–15 nm) and acts as effective electron scavenger, inhibiting the electron-hole recombination. The number of electron and hole traps (Ti³⁺, O₂⁻ and O⁻) and the rate of formation of the short-lived hydroxyl radicals OH under UV irradiation, were evaluated by electron paramagnetic resonance (EPR). A correlation was suggested among the amount of the charge carrier centers, the rate of formation of OH radicals and the catalyst photoactivity. This confirms that the photocatalytic properties depend on the possibility that electrons and holes separately interact with the oxidative agents at the TiO₂ surface, inducing the formation of OH radicals.     

Liquid phase deposition of mesoporous TiO2/DNA hybrid film: Characterization and photoelectrochemical investigation

A photoelectroactive TiO₂/DNA hybrid film was synthesized via the liquid phase deposition (LPD) process. Scanning electron microscopic (SEM) characterization showed that the compact TiO₂ film was changed to a mesoporous structure when DNA was present in the deposition solution, which might be the result of TiO₂ particles growing along the backbones of the double-helical structure of DNA molecules. Although UV absorption spectra and cyclic voltammograms indicated that the deposited TiO₂ on the substrate surface was decreased in the presence of DNA, an enhanced photocurrent response was observed. The electrochemical impedance and cyclic voltammetric measurements using K₃[Fe(CN)₆] as a redox probe suggested that the mesoporous film provided a relatively more efficient electron transfer interface, which could improve the photoelectron transfer rate from the semiconducting film to the electrode and reduce the recombination of photoelectrons and holes. This results in an enhanced photocurrent. Even after long-term and continuous UV irradiation, the mesoporous film exhibited a promoted photoelectrochemical response. The promoted photoelectrocatalytic degradation of methylene blue was obtained on the TiO₂/DNA composite film, which is consistent with the enhanced photocurrent, and this demonstrates that DNA behaved as a useful biomaterial for the synthesis of a photoelectroactive hybrid film with improved performance.     

Effect of the microwave-assisted hydrothermal synthesis conditions on the photocatalytic properties of BiNbO4 and silver nanocomposites

Developing new photocatalysts based on metal oxide semiconductors for dye degradation under sunlight irradiation is an expanding area of research. These studies mainly focus on efficiency enhancement by controlling the morphology and crystalline structures, lowering the bandgap energy, and adding co-catalysts. Here we describe the microwave-assisted hydrothermal synthesis of bismuth niobate nanostructures (BiNbO₄) and its decoration with silver nanoparticles through an in situ microwave-assisted reflux synthesis. The resultant catalyst was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance, zeta power and electrochemistry. Furthermore, the photocatalytic activity was evaluated by quantifying hydroxyl and superoxide radicals generated by holes and electrons photogenerated on the catalyst surface, respectively, and through the degradation of Rhodamine B. The studies revealed that the crystalline structure strongly depends on the irradiation conditions, forming a mixture of triclinic and orthorhombic BiNbO₄. Also, the decoration method results in the formation of metallic Ag, AgO and Ag₂O. As a result, the catalyst formed by BiNbO₄ synthesized at 150 °C and 550 W irradiation power, decorated with silver nanoparticles, showed the highest photocatalytic activity (32.6%).     

Efficient photocatalytic degradation of organic dyes over titanium dioxide coating upconversion luminescence agent under visible and sunlight irradiation

In order to use the sunlight efficiently, a new titanium dioxide (TiO₂) photocatalyst with high catalytic activity under visible light irradiation was prepared with sol–gel technique. In this work, an upconversion luminescence agent, crystallized Er³⁺:Y₃Al₅O₁₂, was synthesized and its characters were determined. It is found that this crystallized Er³⁺:Y₃Al₅O₁₂ can emit three upconversion fluorescent peaks below 387 nm under the excitation of 488 nm visible light. Hence, this upconversion luminescence agent could transform visible light into ultraviolet light, which could satisfy the genuine requirement of TiO₂ photocatalyst. Additionally, the upconverison mechanisms were also discussed. Meanwhile, the prepared TiO₂ photocatalysts coating upconversion luminescence agent were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic activity of prepared TiO₂ powder was tested through the degradation of congo red in aqueous solution as a model compound under visible and sunlight irradiation. To affirm the complete mineralization, the ion chromatography and total organic carbon (TOC) were used to observe the mineralized anions and organic residues. The experimental results proved that the prepared TiO₂ photocatalyst coating crystallized Er³⁺:Y₃Al₅O₁₂ behaved much higher photocatalytic activity under visible light and sunlight irradiation, and was able to decompose the congo red in aqueous solution efficiently. Therefore, this method may be envisaged as a novel technology for treating dyes wastewater using solar energy, especially for textile industries in developing countries.     

Photocatalytic mineralisation of organic compounds: a comparison of flame-made TiO2 catalysts

A comparative photocatalytic analysis was carried out on TiO₂ made in a Flame Spray Pyrolysis (FSP) process and flame-made Degussa P25. Both have similar crystallinity, phase composition, phase segregation and a non-porous surface. Hence comparison was made based on their difference in specific surface area, organic adsorption and the amount of OH• generated upon illumination. The photocatalytic activity tests were carried out using the following series of organic compounds: sucrose, glucose, fructose, maleic acid, glyoxylic acid, oxalic acid, isobutyric acid, phenol and methanol. FSP-made TiO₂ outperformed P25 for saccharides mineralisation, while for phenol and methanol mineralisation P25 was better than FSP-made TiO₂. Similar mineralisation rates were observed for both FSP-made and P25 TiO₂ for the mineralisation of carboxylic acids. This shows that the relative performance of the photocatalysts depends on the type of organic compounds to be degraded. The high surface area and possibly a more efficient interfacial charge transfer of FSP-made TiO₂ provided an efficient pathway for saccharides mineralisation. As for phenol and methanol, the mineralisation rates were higher when using P25 due to the greater amount of OH• radicals generated by this photocatalyst. The fast mineralisation rates of carboxylic acids made degradation of these organic compounds to be less affected by the TiO₂ photocatalyst properties and conditions tested in this work.     

Photocatalysts for reagentless disinfection on the basis of titanium dioxide films modified by silver nanoparticles

Using the test cultures of Pseudomonas fluorescens and Lactococcus lactis bacteria, photoinduced pathophysiological properties of film titanium dioxide photocatalysts modified by silver nanoparticles are investigated. It is shown that the deposition of silver leads to an increase in the adsorption of microorganisms from the solution and to a rise in the efficiency of photogeneration of hydroxyl radicals and superoxide ions, which provides the attainment of a high level of antimicrobial activity. In particular, the survival rate of P. fluorescens eubacteria under the UV irradiation in contact with the TiO₂/Ag catalyst decreases by a factor of more than 70 compared with irradiation in the absence of the photocatalyst. The developed photocatalysts allow the manifold increase in the efficiency of the disinfection of aqueous media with the use of ultraviolet.     

Photocatalytic and photoelectrochemical performance of crystallized titanium dioxide sol with neodymium ion modification

Titanium dioxide was modified with neodymium metal ion by a wet‐chemical coprecipitation–peptization technique under low temperature to produce crystallized sol catalyst (Nd³⁺? TiO₂). Crystal structure was characterized by X‐ray diffraction measurement. Sol particle size was studied by means of particle size distribution measurement. Surface hydroxyl groups were determined using Fourier transform infrared spectroscopy. Photocatalytic reactivity of sol photocatalysts was investigated under ultraviolet and visible light irradiation. Photodegradation and photomineralization under ultraviolet and visible light excitation were studied in the TiO₂ and Nd³⁺? TiO₂ hydrosol reaction system. A photocurrent–time spectrum was also applied to characterize the electron‐transferring efficiency in the process of self‐sensitization and dye‐sensitization photocatalysis reactions. As an application approach of sol catalyst, Nd³⁺? TiO₂ sol was coated on a diffusing optical fibers bundle and the photocatalytic reaction was investigated in the immobilization fiber reactor. Copyright © 2005 Society of Chemical Industry     

TiO2-graphene nanocomposite for electrochemical sensing of adenine and guanine

TiO₂-graphene nanocomposite was prepared by hydrolysis of titanium isopropoxide in colloidal suspension of graphene oxide and in situ hydrothermal treatment. It provides an efficient and facile approach to yield nanocomposite with TiO₂ nanoparticles uniformly embedded on graphene substrate. The electrochemical behavior of adenine and guanine at the TiO₂-graphene nanocomposite modified glassy carbon electrode was investigated. The results show that the incorporation of TiO₂ nanoparticles with graphene significantly improved the electrocatalytic activity and voltammetric response towards these species comparing with that at the graphene film. The TiO₂-graphene based electrochemical sensor exhibits wide linear range of 0.5–200 μM with detection limit of 0.10 and 0.15 μM for adenine and guanine detection, respectively. The excellent performance of this electrochemical sensor can be attributed to the high adsorptivity and conductivity of TiO₂-graphene nanocomposite, which provides an efficient microenvironment for electrochemical reaction of these purine bases.     

Photocatalytic Degradation of Organic Dyes by a High Efficient TiO2-Based Catalysts Under Solar Light Irradiation

In this work, the Er³⁺:YAlO₃/Fe-doped TiO₂ composite, a high efficient TiO₂-based photocatalyst, was synthesized by ultrasonic dispersion and liquid boil methods. Among which, the Er³⁺:YAlO₃ is a kind of upconversion luminescence agent, which was prepared by nitrate-citric acid method. It can emit ultraviolet light under visible light excitation. The Er³⁺:YAlO₃/Fe-doped TiO₂ composite was characterized by X-ray diffraction and UV–vis spectral techniques. The degradation of Acid Red B dye was used to evaluate the photocatalytic activity of the Er³⁺:YAlO₃/Fe-doped TiO₂ composite under solar light irradiation. It was found that the photocatalytic activity of Er³⁺:YAlO₃/Fe-doped TiO₂ composite was much higher than that for the similar system with only Fe-doped TiO₂. And the influencing factors, such as Er³⁺:YAlO₃ content, irradiation time, initial concentration of Acid Red B, addition amount of Er³⁺:YAlO₃/Fe-doped TiO₂ and NaCl, on the photocatalytic degradation were also investigated. The Er³⁺:YAlO₃ as upconversion luminescence agent can elevate the photocatalytic activity of Fe-doped TiO₂ powder. Moreover, the Fe²⁺ ion can restrain the recombination of photogenerated electrons and holes. Thus, this Er³⁺:YAlO₃/Fe-doped TiO₂ composite is a useful material for the detoxification of wastewater because it can efficiently utilize solar light by converting visible light into ultraviolet light.     

Enhanced Luminescence of Eu-Doped TiO2 Nanodots

Monodisperse and spherical Eu-doped TiO₂ nanodots were prepared on substrate by phase-separation-induced self-assembly. The average diameters of the nanodots can be 50 and 70 nm by changing the preparation condition. The calcined nanodots consist of an amorphous TiO₂ matrix with Eu³⁺ ions highly dispersed in it. The Eu-doped TiO₂ nanodots exhibit intense luminescence due to effective energy transfer from amorphous TiO₂ matrix to Eu³⁺ ions. The luminescence intensity is about 12.5 times of that of Eu-doped TiO₂ film and the luminescence lifetime can be as long as 960 μs.     

SnO2 nanoparticle embedded TiO2 nanofibers — Highly efficient photocatalyst for the degradation of rhodamine B

SnO₂ nanoparticle embedded TiO₂ nanofibers were fabricated by a simple electrospinning method. The relationship between the SnO₂/TiO₂ weight ratio and photocatalytic efficiency was investigated from the view point of Rhodamine B decomposition. In addition, electron microscopic analysis, energy dispersive analysis, X-ray diffraction analysis, and photoluminescence study demonstrated that SnO₂ nanoparticle was successfully embedded in TiO₂ nanofibers. TiO₂ nanofibers containing SnO₂ nanoparticle provided an enhanced interfacial region between TiO₂ and SnO₂. SnO₂ nanoparticles embedded TiO₂ nanofibers exhibited highly efficient photocatalytic activity under UV light irradiation due to high charge separation of electron–hole pairs.     

CeOx/TiO2-yFy nanocomposite: An efficient electron and oxygen tuning mechanism for photocatalytic inactivation of water-bloom algae

Eutrophication raises a widespread problem for rivers and lakes all over the world, which serves as a seedbed for uncontrollable growth of harmful algae. Here, we prepare CeO_x/TiO_2-yF_y nanocomposites by a facile sol-gel method to offer an efficient solution for inactivation of harmful algae such as Microcystis aeruginosa with visible light irradiation. The results show that the nanocomposites hold ideal CeO_x coupling and F doping forms when the calcination temperature is 550?°C (CeO_x/TiO_2-yF_y-550). The CeO_x/TiO_2-yF_y-550 nanocomposite exhibits a higher light absorption capacity and lower recombination efficiency for photogenerated carriers in comparison to the CeO_x/TiO_2-yF_y nanocomposite. Moreover, it exhibits an excellent photocatalytic inactivation efficiency of 100% following 4?h irradiation. We also find that the photosynthetic efficiency of algal cells reduces in the inactivation process, and the electron transport process in the photosynthetic system is inhibited, which are ascribed to the formation of hydroxyl radicals (·OH) and superoxide radical (·O₂^-). Such an efficient photocatalytic inactivation performance for the CeO_x/TiO_2-yF_y-550 can be attributed to the outstanding contribution of ·O₂^- resulting from the electron and oxygen tuning by CeO_x coupling and F doping.     

Photocatalytic reactivity and diffusing OH radicals in the reaction medium containing TiO2 particles

The generation of OH radicals on UV-illuminated TiO₂ surface is mainly responsible for the photocatalytic oxidation of pollutants in various contaminated environmental media. Although the reactivity of OH radicals is largely limited within the surface region, the possibility of OH desorption and diffusion into the reaction medium has been often raised. This study provides several examples for the presence of diffusing OH radicals in aqueous solution and polymer matrix containing TiO₂ particles. The photocatalytic degradation rates of (CH₃)₄N⁺ in TiO₂ suspension were comparable between acidic and alkaline conditions, which could not be explained by a simple electrostatic surface charge model. From the present mechanistic study, it is suggested that the photocatalytic oxidation of (CH₃)₄N⁺ at acidic pH mainly proceeds through free OH radicals in the solution bulk, not on the surface of TiO₂. The diffusing OH radicals also played the role of main oxidants in the solid phase. The photolysis of TiO₂-embedded PVC composite films generated cavities around the imbedded TiO₂ particles and the development of cavity diameter continued even after the direct contact between the PVC and TiO₂ was prohibited. This implied that active oxygen species that were photogenerated on TiO₂ surface desorbed and diffused across a few micrometers to react with the polymer matrix.     

Facile synthesis of TiO<Subscript>2</Subscript>/ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocomposite by sol-gel auto combustion method for superior visible light photocatalytic efficiency

Photocatalytic composite materials having photon absorption capability in the range of visible light were synthesized by loading TiO₂ (5, 10, 15, and 20 wt%) on ferrite nanocomposites by sol-gel auto-combustion method. The synthesized nanocomposites were analyzed using X-ray diffraction, Transmission electron microscopy, diffuse reflectance spectroscopy and N₂ adsorption techniques. The generation of photo active hydroxyl radicals for all the synthesized composites was found higher under the irradiation of red LED (RLED irradiation) which was confirmed by degradation of rhodamine B dye under irradiation of RLED. Photocatalytic activity of the synthesized nanocomposites was also carried out under irradiation of ultraviolet (UVLED) and blue (BLED) light emitting diodes, which is comparatively less than for the reaction under red LED irradiation. The operational parameters like catalyst amount, pH and concentration of dye solution were studied and ESI-MS degradation pathway is proposed by analyzing the degraded samples.     

Photocatalytic activity of TiO2 supported on multi-walled carbon nanotubes under simulated solar irradiation

TiO₂ particles supported on multi-walled carbon nanotubes (MWCNTs) were prepared using a sol–gel method to investigate their photocatalytic activity under simulated solar irradiation for the degradation of methyl orange (MO) in aqueous solution. The prepared composites were analyzed using XRD, SEM, EDS and UV–vis absorption spectroscopy. The results of this study indicated that there was little difference in the shape and structure of MWCNTs/TiO₂ composite and pure TiO₂ particles. The composite exhibited enhanced absorption properties in the visible light range compared to pure TiO₂. The degradation of MO by MWCNTs/TiO₂ composite photocatalysts was investigated under irradiation with simulated solar light. The results of this study indicated that MWCNTs played a significant role in improving photocatalytic performance. Different amounts of MWCNTs had different effects on photodegradation efficiency, and the most efficient MO photodegradation was observed for a 2% MWCNT/TiO₂ mass ratio. Photocatalytic reaction kinetics were described using the Langmuir–Hinshelwood (L–H) model. The photocatalyst was reused for eight cycles, and it retained over 95.2% photocatalytic degradation efficiency. Possible decomposition mechanisms were also discussed. The results of this study indicated that photocatalytic reactions with TiO₂ particles supported on MWCNTs under simulated solar light irradiation are feasible and effective for degrading organic dye pollutants.