Application of TiO2/perlite photocatalysis for degradation of ammonia in wastewater

The purpose of this study was removal of ammonia by a new photocatalytic process from synthetic wastewater under UV irradiation. TiO₂ was used as the photocatalyst and immobilized on perlite granules as a supporter. The prepared catalysts were characterized by SEM and FTIR analysis showed that TiO₂/perlite catalyst has mesoporous structures and uniform coating of TiO₂ on support. Also, the optimum efficiency of photocatalytical degradation of ammonia was obtained at pH 11 for UV intensity irradiation with 125 W lamp. About 68% degradation of ammonia in wastewater was achieved after 180 min of irradiation by using the optimized reaction conditions.     

Photoelectrocatalytic degradation of phenol using a TiO<Subscript>2</Subscript>/Ni thin-film electrode

As a new type of photoelectrode, TiO₂/Ni thin-film electrode was prepared by dip-coating technique. The structural and surface morphology of electrode was examined by X-ray diffraction (XRD) and scanning electron microscope (SEM). Effects of initial phenol concentration, pH value, number of film layers, voltage of electrical bias applied, variation of inorganic salt type and types of dissolved gas on the photoelectrocatalytic (PEC) degradation of phenol using ultraviolet (UV) illuminated TiO₂/Ni thin-film electrode were investigated. The mechanism of PEC degradation of phenol was also studied by analyzing reaction intermediates.     

铈掺杂纳米二氧化钛可见光光催化降解苯酚性能

采用Ce（NO3）3掺杂改性后的纳米TiO2粉末作为光催化剂（Ce-TiO2）,研究了Ce-TiO2在可见光条件下光催化降解苯酚的过程,考察了Ce掺杂量、焙烧温度、焙烧时间、pH值以及催化剂用量等因素对苯酚溶液光催化降解过程的影响。结果表明：可见光照射下,当Ce掺杂量为1.00%、焙烧温度为700℃、焙烧时间为3 h、反应溶液pH值为5、催化剂投加量为1.0 g/L时,苯酚的去除率达到最佳,为35.8%。     

High-throughput screening of transition metal-doped TiO<Subscript>2</Subscript> in photodecomposition of phenol under visible light

A catalyst library consisting of 20 catalysts with different metal and weight fraction-doped TiO₂ was prepared at one time for discovering the novel metal-doped TiO₂ photocatalyst, which is active under visible light irradiation. Combinatorial microbeam XRD and UV-vis spectrometer were used for analysis of crystal structure and photoactivity of 20 catalysts in the library, respectively. Photodecomposition of phenol was chosen as a probe reaction. The library preparation, XRD characterization and reaction test for 20 catalysts were completed within 48 hours. Among the catalysts in the library, 1.5 wt% Co/TiO₂ showed the best activity for phenol degradation. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Visible light-irradiated degradation of alachlor on Fe-TiO<Subscript>2</Subscript> with assistance of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

0.1 Fe/Ti mole ratio of Fe-TiO₂ catalysts were synthesized via solvothermal method and calcined at various temperatures: 300, 400, and 500 °C. The calcined catalysts were characterized by XRD, N₂-adsorption-desorption, UV-DRS, XRF, and Zeta potential and tested for photocatalytic degradation of alachlor under visible light. The calcined catalysts consisted only of anatase phase. The BET specific surface area decreased with the calcination temperatures. The doping Fe ion induced a red shift of absorption capacity from UV to the visible region. The Fe-TiO₂ calcined at 400 °C showed the highest photocatalytic activity on degradation of alachlor with assistance of 30 mM H₂O₂ at pH 3 under visible light irradiation. The degradation fitted well with Langmuir-Hinshelwood model that gave adsorption coefficient and the reaction rate constant of 0.683 L mg⁻¹ and 0.136 mg/L·min, respectively.     

UV and solar light photocatalytic removal of organic contaminants in municipal wastewater

This study investigated UV and solar photocatalysis of organic pollutants in municipal wastewater using metal-ion (Ag, Cu and Fe) doped TiO₂ photocatalysts. The effects of pH and catalyst dosage on photocatalytic performance were determined. The best performance was obtained using 0.5 g/L catalyst concentration and pH 6, and the treated water met specific requirements of the drinking water quality standards (phenol ≤10 μg/L) and wastewater effluents for discharge chemical oxygen demand (COD) levels (<30 mg/L). The photocatalysts were effective under both UV and visible light, thereby overcoming the limitation of TiO₂ which is only effective under UV light.     

Different Effects of Fluoride Surface Modification on the Photocatalytic Oxidation of Phenol in Anatase and Rutile TiO2 Suspensions

The effect of calcination temperature on the photocatalytic degradation of phenol with aqueous suspensions of synthetic anatase and rutile TiO₂ under UV light irradiation (λ > 320 nm), was studied in the absence and presence of NaF. The presence of fluoride accelerates the degradation of phenol in anatase TiO₂, with this positive effect increasing at first, before declining with increasing calcined temperature. A negative effect of fluoride was observed for all the rutile TiO₂ suspensions. The selectivity of catechol increased in the presence of fluoride in both anatase and rutile TiO₂ suspensions.     

Photocatalytic degradation of methylene blue and acetaldehyde by TiO<Subscript>2</Subscript>/glaze coated porous red clay tile

Nanosized TiO₂ sol synthesized by sol-gel method was successfully coated on the porous red clay tile (PRC tile) with micrometer sized pores. PRC tile was first coated with a low-firing glaze (glaze-coated PRC tile) and then TiO₂ sol was coated on the glaze layer. A low-fired glaze was prepared at various blending ratios with frit and feldspar, and a blending ratio glazed at 700 °C was selected as an optimum condition. Then TiO₂ sol synthesized from TTIP was dip-coated on the glazed layer (TiO₂/glaze-coated PRC tile), and it was calcined again at 500 °C. Here, these optimum calcination temperatures were selected to derive a strong bonding by a partial sintering between TiO₂ sol particles and glaze layer. Photocatalytic activity on the TiO₂/glaze-coated PRC tile was evaluated by the extent of photocatalytic degradation of methylene blue and acetaldehyde. Methylene blue with the high concentration of 150 mg/l on the surface of TiO₂/glaze-coated PRC tile was almost photodegraded within 5 hours under the condition of average UV intensity of 0.275 mW/cm₂, while no photodegradation reaction of methylene blue occurred on the glaze-coated PRC tile without TiO₂. Another photocatalytic activity was also evaluated by measuring the extent of photocatalytic degradation of gaseous acetaldehyde. The photodegradation efficiency in TiO₂/glaze-coated PRC tile showed about 77% photocatalytic degradation of acetaldehyde from 45,480 mg/l to 10,536 mg/l after the UV irradiation of 14 hours, but only about 16% in the case of the glaze-coated PRC tile.     

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.     

CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> catalyst prepared by physical mixing for NH<Subscript>3</Subscript> selective catalytic reduction: Evidence about the migration of sulfates from TiO<Subscript>2</Subscript> to CeO<Subscript>2</Subscript> via simple calcination

A mechanical mixture of CeO₂ and TiO₂ powder with a small amount of sulfate was applied for the selective catalytic reduction (SCR) of NO with NH₃. After calcination at 500 oC, the mixed sample showed significantly enhanced activity and selectivity compared to the uncalcined one and, moreover, demonstrated even higher activity than the conventional V₂O₅/TiO₂ catalyst above 300 °C. Combined characterization results revealed that the main active sites were newly formed sulfate species on CeO₂, the number of which increased with calcination. Temperatureresolved DRIFT spectra provided convincing evidence about the migration of sulfate species from TiO₂ to CeO₂, as confirmed from the shift of v(S=O) band as a result of the mechanical mixing and the subsequent calcination.     

Photoelectrocatalytic activity of bi-layer TiO<Subscript>2</Subscript>/WO<Subscript>3</Subscript> coatings for the degradation of 4-chlorophenol: effect of morphology and catalyst loading

WO₃ and bi-layer WO₃/TiO₂ coatings of different catalyst loadings were electrosynthesized on stainless steel 304 (SS) substrates from acidic aqueous solutions by single-step and consecutive steps potentiostatic cathodic deposition. The resulting WO₃/SS and TiO₂/WO₃/SS photoelectrodes were screened for their photoresponse under ultraviolet (UV) and visible light illumination by photovoltammetry and photoamperometry in sulphate solutions, in the absence and presence of 4-chlorophenol (4-CP). They were also evaluated for bulk photo-oxidation of 4-CP under constant potential, in the voltage range determined on the basis of the photovoltammetric tests. The optimal weight ratio between TiO₂ and WO₃ was also established, ensuring the best performance of these photoelectrodes for the photooxidation of 4-CP under UV and visible light irradiation.     

Photocatalytic degradation of imidacloprid pesticide in aqueous solution by TiO2 nanoparticles immobilized on the glass plate

The purpose of this study is to appraise the photocatalytic degradation of imidacloprid pesticide in an aqueous solution. To this end, imidacloprid was degraded using TiO₂ nanoparticles immobilized on a glass plate under UV light illumination. The effects of operational parameters (initial concentration of imidacloprid, pH, and light intensity) on the activity of TiO₂ nanophotocatalyst and the kinetics of the reaction were investigated. The results indicated that TiO₂ had impressive photocatalytic proficiency in the presence of UV-C light irradiation for the removal of imidacloprid from the aqueous solution. The highest efficiency for the removal of imidacloprid (R%?=?90.24) was obtained in the initial concentration of 20?mg?L^?1 imidacloprid, pH?=?5, and light intensity of 17?W?m^?2 after 180?min. The results of the mineralization studies represented a subtractive trend of total organic carbon (TOC) and an increase in the mineralization products during the reaction time.     

Preparation and characterization of a novel activated carbon‐supported N‐doped visible light response photocatalyst (TiO2−xNy/AC)

A photocatalyst, TiO_2?xN_y/AC (activated carbon (AC) supported N‐doped TiO₂), highly active in both the Vis and UV range, was prepared by calcination of the TiO₂ precursor prepared by acid‐catalyzed hydrolysis in an ammonia atmosphere. The powders were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, X‐ray diffraction, N₂ adsorption, Fourier transform infrared spectroscopy and phenol degradation. The doped N in the TiO₂ crystal lattice creates an electron‐occupied intra‐band gap allowing electron‐hole pair generation under Vis irradiation (500–560 nm). The TiO_2?xN_y/AC exhibited high levels of activity and the same activity trends for phenol degradation under both Vis and UV irradiation: TiO_2?xN_y/AC calcined at 500 °C for 4 h exhibited the highest activity. The band‐gap level newly formed by doped N can act as a center for the photo‐generated holes and is beneficial for the UV activity enhancement. The performance of the prepared TiO_2?xN_y/AC photocatalyst revealed its practical potential in the field of solar photocatalytic degradation of aqueous contaminants. Copyright © 2007 Society of Chemical Industry     

Enhanced photocatalytic activity of TiO2/SiO2 by the influence of Cu-doping under reducing calcination atmosphere

Cu-doped titania photocatalyst supported on silica beads (Cu-TiO₂/SiO₂) were prepared under different Cu-ion concentration and under different calcination atmosphere. The properties and performance of Cu-TiO₂/SiO₂ were compared with undoped TiO₂/SiO₂ photocatalyst. The effect of Cu-doping and calcination atmosphere on photocatalytic degradation of phenol under both black light and visible light irradiation were investigated, where in both cases the degradation rate of phenol by Cu-doped catalyst prepared under reducing calcination atmosphere was found to be higher than the undoped catalyst or Cu-doped catalyst prepared under air atmosphere. This may be attributed to increase in visible light absorption and lengthening of photogenerated electron–hole pair recombination time. The photocatalytic beads were characterized by X-ray diffraction (XRD), UV-Vis absorption spectroscopy and SEM/EDAX analysis.     

Modeling and optimization of photocatalytic/photoassisted-electro-Fenton like degradation of phenol using a neural network coupled with genetic algorithm

Oxidation of phenol in aqueous media using supported TiO₂ nanoparticles coupled with photoelectro-Fenton-like process using Mn²⁺ cations as catalyst of electro-Fenton reaction was studied. The influence of the basic operational parameters such as initial pH of the solution, applied current, initial Mn²⁺ concentration, initial phenol concentration and kind of ultraviolet (UV) light on the oxidizing efficiency of phenol was studied. An artificial neural network (ANN) model was coupled with genetic algorithm to predict phenol oxidizing efficiency and to find an optimal condition for maximum phenol removal. The findings indicated that ANN provided reasonable predictive performance (R² = 0.949).     

Efficient photocatalytic removal of aqueous Cr(VI) by N-F-Al tri-doped TiO<Subscript>2</Subscript>

As chromium is a common heavy metal contaminant in water, we have prepared N-F-Al tri-doped TiO₂ catalyst for Cr(VI) removal under visible light. The sample was prepared via a sol-gel method and was characterized by XRD, BET, UV-vis DRS, XPS and SEM techniques. In the photocatalytic experiments, effects of Al/Ti ratio, F/Ti ratio, calcination temperature and different dopants were investigated. The optimum Al/Ti molar ratio, F/Ti ratio and calcination temperature proved to be 0.01, 0.1 and 500 °C, respectively, which is in accordance with the characterization analysis. Catalysts prepared under this condition showed a high photoactivity for Cr(VI) removal in water.     

Preparation of TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> hollow spheres and their activity in methylene blue photodecomposition

PSA [poly-(styrene-methyl acrylic acid)] latex particle has been taken into account as template material in SiO₂ hollow spheres preparation. TiO₂-doped SiO₂ hollow spheres were obtained by using the appropriate amount of Ti(SO₄)₂ solution on SiO₂ hollow spheres. The photodecomposition of the MB (methylene blue) was evaluated on these TiO₂-doped SiO₂ hollow spheres under UV light irradiation. The catalyst samples were characterized by XRD, UV-DRS, SEM and BET. A TiO₂-doped SiO₂ hollow sphere has shown higher surface area in comparison with pure TiO₂ hollow spheres. The 40 wt% TiO₂-doped SiO₂ hollow sphere has been found as the most active catalyst compared with the others in the process of photodecomposition of MB (methylene blue). The BET surface area of this sample was found to be 377.6 m²g⁻¹. The photodegradation rate of MB using the TiO₂-doped SiO₂ catalyst was much higher than that of pure TiO₂ hollow spheres.     

Photocatalytic degradation of trichloroethylene over TiO<Subscript>2</Subscript>/SiO2 in an annulus fluidized bed reactor

The effects of superficial gas velocity (Ug), wavelength and intensity of ultraviolet (UV) light, oxygen and H₂O concentration on the photocatalytic degradation of TCE (Trichloroethylene) over TiO₂/SiO₂ catalyst have been determined in an annulus fluidized bed photoreactor. The key factor in determining the performance of the annulus fluidized bed photoreactor is found to be an optimum superficial gas velocity (Ug) that provides the optimum UV lighttransmit through the proper size of bubbles in the photoreactor. The degradation efficiency of TCE increases with light intensity but decreases with wavelength of the UV light and H₂O concentration in the fluidized bed of TiO₂/silica-gel photocatalyst. The optimum concentration of O₂ for TCE degradation is found to be approximately 10%. The annulus fluidized bed photoreactor is an effective tool for high TCE degradation with efficient utilization of photon energy. This paper is dedicated to Professor Dong Sup Doh on the occasion of his retirement from Korea University.     

Hydrodynamics,mass transfer,and photocatalytic phenol selective oxidation reaction kinetics in a fixed TiO2 microreactor

Photocatalytic phenol dissociation was studied in a microreactor, with a TiO₂ layer immobilized on the reactor inner walls. Experiments were conducted for various residence times, initial concentrations, pH values, and UV light irradiation intensities. The intermediates and products (catechol, hydroquinone, and resorcinol) were quantitatively investigated to determine the predominant reaction pathways for the investigated anatase catalyst. A three‐dimensional mathematical model was used to simulate the heterogeneous photocatalysis reaction conditions with Langmuir–Hinshelwood mechanism, considering the adsorption/desorption thermodynamic equilibria, and for kinetic parameter estimation via regression analysis. The effectiveness factor, Thiele modulus, and the correction function were calculated to determine the pore diffusion effects. The value of pH had the dramatic effect of lowering the reaction rate due to the competitive adsorption of hydroxide ions and protons on the catalyst surface. A phenol conversion of 79.5% was achieved at the residence time of 7.22 min, but without total mineralization. © 2014 American Institute of Chemical Engineers AIChE J, 61: 572–581, 2015     

Anatase-Titania Templated by Nanofibrillated Cellulose and Photocatalytic Degradation for Methyl Orange

In this work, novel titania (TiO₂) nanoparticles were designed as a high performance photocatalyst. It was obtained by a simple method of dispersing nanofibrillated cellulose (NFC) onto the surface of titanium tetrachloride (TiCl₄), inducing crystallization and removing NFC templates. Under UV light irradiation, The TiO₂ nanoparticles displayed excellent photocatalytic activity for the decomposition of methyl orange solution. It was found that TiO₂ after calcination had a more efficiency than that before calcination. The optimum calcination temperature for the removal of NFC templates was 300?°C. Methyl orange solution had been remarkably degraded by TiO₂ nanoparticles when the mass ratio of TiCl₄ and NFC was 12:1. These results indicate that the TiO₂ nanopartilces can be easily applied in the field of wastewater treatment.