Optimized photocatalytic degradation of Alcian Blue 8 GX in the presence of TiO2 suspensions

The photocatalytic degradation of Alcian Blue 8 GX, a cationic copper phthalocyanine dye, has been investigated in aqueous suspensions containing the commercial catalyst TiO(2) P-25. The photodegradation of the organic molecule follows approximately a pseudo-first kinetic order, according to the Langmuir-Hinshelwood model. The effect of catalyst concentration, pH of the initial solution and the H(2)O(2) concentration upon the reaction rate was ascertained. It was shown that the photocatalytic degradation reaction can be mathematically described as a function of parameters such as pH, H(2)O(2) concentration and irradiation time, being modeled by the use of the response surface methodology. Optimized values for oxidizing agent, concentration, pH and UV exposure time for the studied system were determined.     

Photocatalytic degradation of indigo carmine in aqueous solution by TiO2-coated non-woven fibres

The photocatalytic degradation of indigo carmine has been investigated in aqueous solutions using TiO2 coated non-woven fibres as photocatalyst. The experiments were carried out to investigate the factors influencing the photocatalytic degradation, such as the previous adsorption in the dark, initial concentration of dye solution, temperature, and pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favoured by a high concentration of solution in respect to Langmuir-Hinshelwood model. The degradation rate was pH and temperature dependent with a high degradation rate at high temperature.     

Solar assisted photocatalytic and photochemical degradation of Reactive Black 5

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

Studies on photodegradation of two commercial dyes in aqueous phase using different photocatalysts

The present study involves the photocatalytic degradation of Methyl Orange (MO) and Rhodamine 6G (R6G), employing heterogeneous photocatalytic process. Photocatalytic activity of various semiconductors such as titanium dioxide (TiO(2)), zinc oxide (ZnO), stannic oxide (SnO(2)), zinc sulphide (ZnS) and cadmium sulphide (CdS) has been investigated. An attempt has been made to study the effect of process parameters viz., amount of catalyst, concentration of dye and pH on photocatalytic degradation of MO and R6G. The experiments were carried out by irradiating the aqueous solutions of dyes containing photocatalysts with UV and solar light. The rate of decolorization was estimated from residual concentration spectrophotometrically. Similar experiments were carried out by varying pH (2-10), amount of catalyst (0.25-2.0g/l) and initial concentration of dye (5-200mg/l). The experimental results indicated that the maximum decolorization (more than 90%) of dyes occurred with ZnO catalyst and at basic pH and the maximum adsorption of MO was noticed at pH 4 and of R6G at pH 10. The percentage reduction of MO and R6G was estimated under UV/solar system and it was found that COD reduction takes place at a faster rate under solar light as compared to UV light. In case of R6G, highest decolorizing efficiency was achieved with lower dose of catalyst (0.5g/l) than MO (1g/l) under similar conditions. The performance of photocatalytic system employing ZnO/solar light was observed to be better than ZnO/UV system.     

Photocatalytic degradation of Remazol Red F3B using ZnO catalyst

The photocatalytic degradation of aqueous solution of a commercial azo-reactive textile dye, Remazol Red F3B, has been investigated in a batch slurry reactor, in the presence of ZnO catalyst using two different UV light sources emitting at 254 nm and 365 nm. The effects of various process variables on degradation performance of the process have been investigated. The results showed that decolourization and total organic carbon (TOC) removal are both affected in the same manner by the solution pH in the pH range 6-10, showing maxima at pH 7 and pH 10. They are inversely related to the dye concentration, they increase in power-law with the light intensity. Decolourization is faster with 365 nm UV. TOC removal is not affected by UV wavelength in the initial period up to 20 min, after which it progresses faster under 365 nm UV radiation. These results indicate that the UV wavelength influences especially the degradation rate of the intermediate products generated during the initial period of the photocatalytic process. Finally, catalyst loading affects both efficiencies in the same trend, which are maximized at about 2 g/l catalyst loading.     

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

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

Laser induced photocatalytic degradation of hazardous dye (Safranin-O) using self synthesized nanocrystalline WO3

The photocatalytic degradation of Safranin-O (known as Basic Red 2) in water using locally synthesized nanocrystalline WO(3) as a photocatalyst was investigated under UV laser irradiation. The photo-oxidation removal of the dye was monitored by UV-vis spectrophotometer. The blank experiments for either laser irradiated only Safranin-O solution or the suspension containing WO(3) and Safranin-O in the dark showed that both laser illumination and the photocatalyst were essential for the removal of Safranin-O. The effect of experimental parameters including laser energy, catalyst loading, solution pH and the initial dye concentration on photocatalytic degradation of Basic Red 2 were also investigated. Results indicate that the rate of reaction is strongly influenced by the adsorption of an azo dye into the surface of the photocatalyst materials and suggests an optimum catalyst loading and dye concentration for the degradation reaction. It was investigated that the adsorption of the dye decreases at higher alkaline pH because both catalyst and substrate are negatively charged, developing repulsive forces between them. Kinetic data obtained reveals that the rate of the reaction obeys the first-order kinetics.     

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

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

Photocatalytic degradation of C.I. Direct Red 23 in aqueous solutions under UV irradiation using SrTiO3/CeO2 composite as the catalyst

The photocatalytic degradation of C.I. Direct Red 23 (4BS) in aqueous solutions under UV irradiation was investigated with SrTiO3/CeO2 composite as the catalyst. The SrTiO3/CeO2 powders had more photocatalytic activity for decolorization of 4BS than that of pure SrTiO3 powder under UV irradiation. The effects of catalytic dose, pH value, initial concentration of dye, irradiation intensity as well as scavenger KI were ascertained, and the optimum conditions for maximum degradation were determined. Under the irradiation of a 250 W mercury lamp, the best catalytic dose was 1.5 g/L and the best pH was 12.0. Light intensity exhibited a significant positive effect on the efficiency of decolorization, whereas the initial dye concentration showed a significant negative effect. Under the conditions of a catalytic dose of 1.5 g/L, pH of 12.0, initial dye concentration of 100mg/L, light intensity of 250 W, and air flow rate of 0.15 m3/h, complete decolorization, as determined by UV-visible analysis, was achieved in 60 min, corresponding to a reduction in chemical oxygen demand (COD) of 69% after a 240 min reaction. A tentative degradation pathway based on the sensitization mechanism of photocatalysis is proposed.     

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

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

Sonochemical degradation of Basic Blue 41 dye assisted by nanoTiO2 and H2O2

The sonolysis of Basic Blue 41 dye in aqueous solution was performed at 35 kHz using ultrasonic power of 160 W and aqueous temperature of 25+1 degrees C within 180 min. The TiO2 nanoparticles were used as a catalyst to assist the sonication process. The effect of experimental parameters such as pH, H2O2 concentration and initial dye concentration on the reaction were investigated. It was recognized that in lower pH values the dye removal rate decreased. However, dye removal increased via increase in H2O2 concentration and lowering the initial dye concentration. All intermediate compounds were detected by integrated gas chromatography-mass spectrometry (GC/MS) and also ion chromatograph (IC). During the decolorization, all nitrogen atoms and aromatic groups of Basic Blue 41 were converted to urea, nitrate, formic acid, acetic acid and oxalic acid, etc. Kinetic studies revealed that the degradation process followed pseudo-first order mechanism with the correlation coefficient (R2) of 0.9918 under experimental conditions. The results showed that power ultrasound can be regarded as an appropriate tool for degradation of azo dyes to non-toxic end products.     

Laser-induced removal of a dye C.I. Acid Red 87 using n-type WO3 semiconductor catalyst

Water contamination by organic substances such as dyes is of great concern worldwide due to their utilization in many industrial processes and environmental concerns. To cater the needs for waste water treatment polluted with organic dyes, laser-induced photocatalytic process was investigated for removal of a dye derivative namely Acid Red 87 using n-type WO₃ semiconductor catalyst. The degradation was investigated in aqueous suspensions of tungsten oxide under different experimental conditions using laser instead of conventional UV lamp as an irradiation source. The degradation process was monitored by measuring the change in dye concentration as a function of laser irradiation time by employing UV spectroscopic analysis. The degradation of dye was studied by varying different parameters such as laser energy, reaction pH, substrate concentration, catalyst concentration, and in the presence of electron acceptors such as hydrogen peroxide (H₂O₂), and potassium bromate (KBrO₃). The degradation rates were found to be strongly dependent on all the above-mentioned parameters. Our experimental results revealed that the dye degradation process was very fast (within few minutes) under laser irradiation as compared to conventional setups using broad spectral lamps (hours or days) and this laser-induced photocatalytic degradation method could be an effective means to eliminate the pollutants present in liquid phase. The experience gained through this study could be beneficial for treatment of waste water contaminated with organic dyes and other organic pollutants.     

纳米TiO2/硅藻土复合材料光催化降解作用研究

以硅藻土为载体, 四氯化钛为前驱体, 采用水解沉淀法制备了纳米TiO₂/硅藻土复合材料。结合XRD、SEM、氮气吸脱附等表征手段, 探究了复合材料对罗丹明B的光催化性能, 对影响复合材料光催化性能的因素进行了研究。结果表明: 锐钛矿型纳米TiO₂以团聚体和分散状负载于硅藻土表面。催化剂用量、染料溶液pH、无机离子、光照强度等因素都会在不同程度上影响TiO₂/硅藻土复合材料的光催化性能。在染料初始浓度为10 mg/L, 催化剂用量1.0 g/L, 紫外光强度为300 W, 光照60 min的条件下, 罗丹明B光催化降解率达到99.8%。     

Modeling electrowinning process in an expanded bed electrode

In this paper, the photocatalytic degradation of methamidophos, an organophosphorous pesticide, was investigated in aqueous solution by using TiO(2) as a photocatalyst. The degradation was studied under different conditions such as the amount of the photocatalyst, illumination time, pH of the system, reaction temperature, initial concentration, electron acceptors, metal ions and presence of anions. The results showed that the photocatalytic degradation of methamidophos was strongly influenced by these parameters. The best conditions for the photocatalytic degradation of methamidophos were obtained. The optimum amount of the photocatalyst used is 12.0g/L. The photodegradation efficiency of methamidophos increases with the increase of the illumination time. Alkaline media are favorable for the photocatalytic degradation of methamidophos. The degradation efficiency is enhanced by increasing reaction temperature, and the photodegradation efficiency decreases with the increase in the initial concentration of methamidophos. The photodegradation efficiency of methamidophos is accelerated by adding a small amount of H(2)O(2), K(2)S(2)O(8), KBrO(3), Fe(3+) or Cu(2+). There are no obvious effects on the reactions with the addition of a small amount of Na(+), K(+), Mg(2+), Ca(2+), Zn(2+), Co(2+) and Ni(2+) or adding trace amount of SO(4)(2-), Cl(-), Br(-). The possible roles of the additives on the reactions and the possible mechanisms of effect were also discussed.     

Structural, photophysical and photocatalytic properties of novel Bi2AlVO7

Bi(2)AlVO(7) was prepared by solid-state reaction technique for the first time and the structural and photocatalytic properties of Bi(2)AlVO(7) and Bi(2)InTaO(7) were investigated. The results showed that Bi(2)AlVO(7) crystallized in the tetragonal crystal system with space group I4/mmm. In addition, the band gaps of Bi(2)AlVO(7) and Bi(2)InTaO(7) were estimated to be about 2.06 and 2.81 eV. The photocatalytic degradation of aqueous methylene blue (MB) dye with Bi(2)AlVO(7) or Bi(2)InTaO(7) as catalyst was investigated under visible light irradiation. Bi(2)AlVO(7) showed higher photocatalytic activity compared with Bi(2)InTaO(7) for photocatalytic degradation of MB under visible light irradiation. Complete removal of aqueous MB dye was realized after visible light irradiation for 160 min with Bi(2)AlVO(7) as the photocatalyst. The reduction of the total organic carbon (TOC) and the formation of inorganic products, SO(4)(2-) and NO(3)(-) revealed the continuous mineralization of aqueous MB dye during the photocatalytic process. The possible photocatalytic degradation pathway of aqueous MB dye was revealed under visible light irradiation.     

Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst

The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH₀ 7, 90 °C using 0.6 ml H₂O₂/350 ml solution and 1 g/l catalyst was 97% (in 4 h), 100% (in 45 min) and 58% (in 4 h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH₀ 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH₀ 7 was taken as operating pH due to almost comparable removals as of pH₀ 2 and no leaching of Fe ions.     

Photocatalytic degradation of carbofuran using semiconductor oxides

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

Heterogeneous photocatalytic degradation of p-toluenesulfonic acid using concentrated solar radiation in slurry photoreactor

In this work, the photocatalytic degradation (PCD) of p-toluenesulfonic acid (p-TSA) in batch reactor using concentrated solar radiation was investigated. The effect of the various operating parameters such as initial concentration of substrate, catalyst loading, solution pH and types of ions on photocatalytic degradation has been studied in a batch reactor to derive the optimum conditions. The rate of photocatalytic degradation was found to be maximum at the self pH (pH 3.34) of p-TSA. It was also observed that in the presence of anions and cations, the rate of PCD decreases drastically. The kinetics of photocatalytic degradation of p-TSA was studied. The PCD of p-TSA was also carried at these optimized conditions in a bench scale slurry bubble column reactor using concentrated solar radiation.     

Photodegradation of acetaminophen in TiO(2) suspended solution

This study investigated the photocatalytic degradation of acetaminophen (APAP) in TiO(2) suspended solution under a 250 W metal halide lamp. The influence of some parameters on the degradation of acetaminophen was studied and described in details, such as initial APAP concentration, initial pH value and TiO(2) dosage. After 100 min irradiation, about 95% of APAP is decomposed in the 1.0 g L(-1) TiO(2) aqueous solution with an initial concentration of 100 micromol L(-1). The effect of adsorption at three different pH values has also been analyzed and it has been conducted that pH 3.5, at which APAP was readily adsorbed also degraded at a faster rate. Reaction rate at pH 6.9 and pH 9.5 was 2.84 and 2.96 microM min(-1), respectively. Direct hole (h(+)) oxidation and ipso-substitution was found to be the main initial step for APAP degradation. Main reaction intermediates and products were identified by GC/MS analysis. The mechanism of acetaminophen photocatalytic degradation in TiO(2) suspended solution was studied not only experimentally but also theoretically by calculating the frontier electron density of APAP. The results obtained indicated that TiO(2) photocatalytic degradation is a highly effective way to remove APAP from wastewater and drinking water without any generation of more toxic products.     

Visible light-activated cadmium-doped ZnO nanostructured photocatalyst for the treatment of methylene blue dye

An attempt was made to prepare Cd-doped ZnO photocatalyst for visible light assisted degradation of a textile dye (methylene blue, MB) in aqueous solutions by a traditional sol–gel process. The as-prepared nanoparticles were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy, and photoluminescence spectra techniques. The results showed that the Cd-doped ZnO possess the single-phase hexagonal wurtzite structure. The photocatalytic activity of the nanoparticles under visible light was investigated by measuring the photodegradation of MB in aqueous dispersion. The effects of key operation parameters such as initial dye concentration, catalyst loading as well as initial pH value on the decolorization extents were investigated. The results indicate that the decolorization of the organic molecule followed a pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Under the optimum operation conditions, approximately 85.0% dye removal was achieved within 3.5 h.