Photocatalytic removal of C.I. Basic Red 46 on immobilized TiO2 nanoparticles: artificial neural network modelling

Response surface methodology and artificial neural network for remediation of acid orange 7 using TiO2-P25: optimization and modeling approach

The primary responsibility for continuously discharging toxic organic pollutants into water bodies and open environments is the increase in industrial and agricultural activities. Developing economical and suitable methods to continuously remove organic pollutants from wastewater is highly essential. The aim of the present research was to apply response surface methodology (RSM) and artificial neural networks (ANNs) for optimization and modeling of photocatalytic degradation of acid orange 7 (AO7) by commercial TiO2-P25 nanoparticles (TNPs). Dose of TNPs, pH, and AO7 concentration were selected as investigated parameters. RSM results reveal the reflective rate of AO7 removal of ~ 94.974% was obtained at pH 7.599, TNP dose of 0.748 g/L, and AO7 concentration of 28.483 mg/L. The resulting quadratic model is satisfactory with the highest coefficient of determination (R2) between the predicted and experimental data (R2 = 0.98 and adjusted R2 = 0.954). On the other hand, ANNs were successfully employed for modeling of AO7 degradation process. The proposed ANN model was absolutely fitted with experimental results producing the highest R2. Furthermore, root mean square error (RMSE), mean average deviation (MAD), absolute average relative error (AARE), and mean square error (MSE) were examined more to compare the predictive capabilities of ANN and RSM models. The experimental data was well fitted into pseudo-first-order and pseudo-second-order kinetics with more accuracy. Thermodynamic parameters, namely enthalpy, entropy, Gibbs' free energy, and activation energy, were also evaluated to suggest the nature of the degradation process. The increase of temperature was analyzed to be more suitable for the fast removal of AO7 over TNPs. Graphical abstract.

Degradation of 1,2-dichloroethane by photocatalysis using immobilized PAni-TiO2 nano-photocatalyst

1,2-Dichloroethane is one of the most hazardous environmental pollutants in wastewaters. It is mainly used to produce vinyl chloride monomer, the major precursor for PVC production. It is determined to be a probable human carcinogen and has been listed as a priority pollutant by the United States Environmental Protection Agency. Due to high chemical stability and low biodegradability of 1,2-dichloroethane, heterogeneous photocatalysis was used for degradation of this chlorinated hydrocarbon. PAni-TiO₂ nanocomposite was synthesized by in situ deposition oxidative polymerization method and immobilized on glass beads by a modified dip coating and heat attachment method. The characteristics of synthesized PAni-TiO₂ nanoparticles were confirmed using the results of morphology tests including Fourier-transform infrared spectra, X-ray diffraction patterns, particle size analysis, UV-Visible spectrophotometer, scanning electron microscope, and energy-dispersive X-ray spectroscopy. The performance of photocatalytic degradation of 1,2-dichloroethane using synthesized PAni-TiO₂ nanocomposite in a designed and constructed pilot scale packed bed recirculating photocatalytic reactor under xenon light irradiation was investigated. The response surface methodology based on the central composite design was used to evaluate and optimize the effect of 1,2-dichloroethane concentration, residence time, pH, and coating mass as independent variables on the photocatalytic degradation of 1,2-dichloroethane as the response function. Results showed that actual and predicted results were well fitted with R² of 0.9870, adjusted R² of 0.9718, and predicted R² of 0.9422. The optimum conditions for 1,2-dichloroethane photocatalytic degradation were the 1,2-dichloroethane concentration of 250 mg/L, the residence time of 240 min, pH of 5, and coating mass of 0.5 mg/cm², which resulted in 88.84% photocatalytic degradation. Kinetic of the photocatalytic degradation at optimal condition follows the Langmuir-Hinshelwood first-order reaction with k = 0.0095 min^-1 with R² = 0.9455. Complete photocatalytic degradation of 1,2-DCE was achieved after 360 min.

Nanocellulose/TiO2 composites: preparation, characterization and application in the photocatalytic degradation of a potential endocrine disruptor, mefenamic acid, in aqueous media

Nanocellulose (NC)-supported TiO2 nanoparticles, termed NCTs, were prepared by an ultrasonic impregnation method. The as-synthesized NCTs were thoroughly characterized and studied for the photodegradation of mefenamic acid (MEF), an anthranilic acid derivative drug. The adsorption potential of NCTs increased with TiO2 loading and 10 wt% TiO2 NCT showed the highest sorption potential. Adsorption kinetics of MEF onto NC and NCTs indicated that the equilibrium was reached within 50 min. A pseudo-second-order model clearly represented the experimental kinetic data and demonstrated that the MEF sorption was mainly chemisorption. Equilibrium sorption analysis indicated that the adsorption followed the Langmuir model with a monolayer sorption capacity of 22.43 mg g-1 for 10 wt% TiO2 NCT. The photocatalytic degradation rates of NCTs were identical with respect to their adsorption capacities, and the apparent rate constant (kapp) values indicated that the amount of TiO2 in NCTs played a vital role in the degradation of MEF. Furthermore, 10 wt% TiO2 NCT showed excellent catalytic activity and reusability even after five cycles of photodegradation.

Immobilized TiO2 on glass spheres applied to heterogeneous photocatalysis: photoactivity, leaching and regeneration process

Heterogeneous photocatalysis using titanium dioxide as catalyst is an attractive advanced oxidation process due to its high chemical stability, good performance and low cost. When immobilized in a supporting material, additional benefits are achieved in the treatment. The purpose of this study was to develop a simple protocol for impregnation of TiO₂-P25 on borosilicate glass spheres and evaluate its efficiency in the photocatalytic degradation using an oxidizable substrate (methylene blue), in a Compound Parabolic Concentrator (CPC) reactor. The assays were conducted at lab-scale using radiation, which simulated the solar spectrum. TiO₂ leaching from the glass and the catalyst regeneration were both demonstrated. A very low leaching ratio (0.03%) was observed after 24 h of treatment, suggesting that deposition of TiO₂ resulted in good adhesion and stability of the photocatalyst on the surface of borosilicate. This deposition was successfully achieved after calcination of the photocatalyst at 400 °C (TiO₂-400 °C). The TiO₂ film was immobilized on glass spheres and the powder was characterized by scanning electron microscopy (SEM), X-ray diffraction and BET. This characterization suggested that thermal treatment did not introduce substantial changes in the measured microstructural characteristics of the photocatalyst. The immobilized photocatalyst degraded more than 96% of the MB in up to 90 min of reaction. The photocatalytic activity decreased after four photocatalytic cycles, but it was recovered by the removal of contaminants adsorbed on the active sites after washing in water under UV-Vis irradiation. Based on these results, the TiO₂-400 °C coated on glass spheres is potentially a very attractive option for removal of persistent contaminants present in the environment.

Treatment of artificial wastewater containing two azo textile dyes by vertical-flow constructed wetlands

The release of untreated dye textile wastewater into receiving streams is unacceptable not only for aesthetic reasons and its negative impacts on aquatic life but also because numerous dyes are toxic and carcinogenic to humans. Strategies, as of now, used for treating textile wastewaters have technical and economical restrictions. The greater part of the physico-chemical methods, which are used to treat this kind of wastewater, are costly, produce large amounts of sludge and are wasteful concerning some soluble dyes. In contrast, biological treatments such as constructed wetlands are cheaper than the traditional methods, environmental friendly and do not produce large amounts of sludge. Synthetic wastewater containing Acid Blue 113 (AB113) and Basic Red 46 (BR46) has been added to laboratory-scale vertical-flow construction wetland systems, which have been planted with Phragmites australis (Cav.) Trin. ex Steud. (common reed). The concentrations 7 and 208 mg/l were applied for each dye at the hydraulic contact times of 48 and 96 h. Concerning the low concentrations of BR46 and AB113, the unplanted wetlands are associated with significant (ρ < 0.05) reduction performances, if compared with planted wetlands concerning the removal of dyes. For the high concentrations of AB113, BR46 and a mixture of both of them, wetlands with long contact times were significantly (ρ < 0.05) better than wetlands that had short contact times in terms of dye, colour and chemical oxygen demand reductions. Regarding nitrate nitrogen (NO₃-N), the reduction percentage rates of AB113, BR46 and a mixture dye of both of them were between 85 and 100%. For low and high inflow dye concentrations, best removals were generally recorded for spring and summer, respectively.

ICA and ANN Modeling for Photocatalytic Removal of Pollution in Wastewater

This paper discusses the elimination of Colour Index Acid Yellow 23 (C.I. AY23) using the ultraviolet (UV)/Ag-TiO2 process. To anticipate the photocatalytic elimination of AY23 with the existence of Ag-TiO2 nanoparticles processed under desired circumstances, two computational techniques, namely artificial neural network (ANN) and imperialist competitive algorithm (ICA) modeling are developed. A sum of 100 datasets are used to establish the models, wherein the introductory concentration of dye, UV light intensity, initial dosage of nano Ag-TiO2, and irradiation time are the four parameters expressed in the form of input variables. Additionally, the elimination of AY23 is considered in the form of the output variable. Out of the 100 datasets, 80 are utilized in order to train the models. The remaining 20 that were not included in the training are used in order to test the models. The comparison of the predicted outcomes extracted from the suggested models and the data obtained from the experimental analysis validates that the performance of the ANN scheme is comparatively sophisticated when compared with the ICA scheme.

Sonocatalytic performance of Er-doped ZnO for degradation of a textile dye

Pure and erbium (Er)-doped ZnO samples were synthesized through a sonochemical method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. The synthesized samples were used as a catalyst for the sonocatalytic decolorization of Reactive Orange 29 (RO29) as a model organic pollutant. The decolorization efficiency was 63%, 68%, 88%, and 75% for undoped, 2%, 4%, and 6% Er-doped ZnO, respectively. The effect of different experimental parameters including catalyst content, dye concentration and ultrasound power was investigated on the sonocatalytic decolorization of RO29. Among several radical scavengers (i.e. chloride, carbonate and sulfate anions and t-butanol), the chloride anion showed the most inhibitive effect on the sonocatalysis performance. Improvement of the sonocatalytic process by K2S2O8 and H2O2 enhancers was also studied. The reusability of the synthesized sonocatalyst was evaluated in several consecutive runs, and a decline of only 4% was observed in the process performance after five runs. The intermediates produced during the degradation of RO29 were identified by GC-MS analysis.

Mathematical Kinetic Modelling and Representing Design Equation for a Packed Photoreactor with Immobilised TiO2-P25 Nanoparticles on Glass Beads in the Removal of C.I. Acid Orange 7

In this work, a design equation was presented for a batch-recirculated photoreactor composed of a packed bed reactor (PBR) with immobilised TiO2-P25 nanoparticle thin films on glass beads, and a continuous-flow stirred tank (CFST). The photoreactor was studied in order to remove C.I. Acid Orange 7 (AO7), a monoazo anionic dye from textile industry, by means of UV/TiO2 process. The effect of different operational parameters such as the initial concentration of contaminant, the volume of solution in CFST, the volumetric flow rate of liquid, and the power of light source in the removal efficiency were examined. A rate equation for the removal of AO7 is obtained by mathematical kinetic modelling. The results of reaction kinetic analysis indicate the conformity of removal kinetics with Langmuir-Hinshelwood model (kL-H = 0.74 mg L-1 min-1, Kads = 0.081 mg-1 L). The represented design equation obtained from mathematical kinetic modelling can properly predict the removal rate constant of the contaminant under different operational conditions (R2 = 0.963). Thus the calculated and experimental results are in good agreement with each other.

Bio-inspired route for the synthesis of spherical shaped MgO:Fe(3+) nanoparticles: Structural, photoluminescence and photocatalytic investigation

MgO:Fe(3+) (0.1-5 mol%) nanoparticles (NPs) were synthesized via eco-friendly, inexpensive and simple low temperature solution combustion route using Aloe vera gel as fuel. The final products were characterized by SEM, TEM and HRTEM. PXRD data and Rietveld analysis revealed the formation of cubic system. The influence of Fe(3+) ion concentration on the structure morphology, UV absorption, PL emission and photocatalytic activity of MgO:Fe(3+) NPs were investigated. The yellow emission with CIE chromaticity coordinates (0.44, 0.52) and average correlated color temperature value was found to be 3540 K which corresponds to warm light of NPs. The control of Fe(3+) on MgO matrix influences the photocatalytic decolorization of methylene blue (MB) under UV light. The enhanced photocatalytic activity of MgO:Fe(3+) (4 mol%) was attributed to dopant concentration, effective crystallite size, textural properties, decreased band gap and capability for reducing the electron-hole pair recombination. Further, the trends of inhibitory effect in the presence of different radical scavengers were explored. These findings open up new avenues for the exploration of Fe-doped MgO in eco-friendly water applications and in the process of display devices.

Degradation of antidepressant drug fluoxetine in aqueous media by ozone/H2O2 system: process optimization using central composite design

The main objective of this work is the modelling and optimization of antidepressant drug fluoxetine degradation in aqueous solution by ozone/H2O2 process using central composite design. The operational parameters were ozone concentration, initial hydrogen peroxide concentration, reaction time and initial fluoxetine concentration. A good agreement between the predicted values of fluoxetine removal and experimental results were observed (R2=0.976 and Adj-R2=0.955). Pareto analysis indicated that all selected factors and some interactions were effective on the removal efficiency. It was found that the reaction time is the most effective parameter in the ozone/H2O2 process. The maximum removal efficiency (86.14%) was achieved at ozone concentration of 30 mg L(-1), initial H2O2 concentration of 0.02 mM, reaction time of 20 min and initial fluoxetine concentration of 50 mg L(-1) as the optimum conditions.

Bio-inspired synthesis of Y2O3: Eu(3+) red nanophosphor for eco-friendly photocatalysis

We report the synthesis of Y2O3: Eu(3+) (1-11 mol%) nanoparticles (NPs) with different morphologies via eco-friendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies of Y2O3: Eu(3+) NPs were characterized by PXRD, SEM, TEM, HRTEM, UV-Visible and PL techniques. The PXRD data and Rietveld analysis confirms the formation of single phase Y2O3 with cubic crystal structure. The influence of Eu(3+) ion concentration on the morphology, UV-Visible absorption, PL emission and photocatalytic activity of Y2O3: Eu(3+) nanostructures were investigated. Y2O3: Eu(3+) NPs exhibit intense red emission with CIE chromaticity coordinates (0.50, 0.47) and correlated color temperature values at different excitation ranges from 1868 to 2600 K. The control of Eu(3+) ion on Y2O3 matrix influences the photocatalytic decolorization of methylene blue (MB) as a model compound was evaluated under UVA light. Enhanced photocatalytic activity of conical shaped Y2O3: Eu(3+) (1 mol%) was attributed to dopant concentration, crystallite size, textural properties and capability of reducing the electron-hole pair recombination. The trend of inhibitory effect in the presence of different radical scavengers followed the order SO4(2-)>Cl(-)>C2H5OH>HCO3(-)>CO3(2-). These findings show great promise of Y2O3: Eu(3+) NPs as a red phosphor in warm white LEDs as well as eco-friendly heterogeneous photocatalysis.

Artificial neural network modeling of photocatalytic removal of a disperse dye using synthesized of ZnO nanoparticles on montmorillonite

In this study, the photocatalytic ability of ZnO/Montmorilonite (ZnO/MMT) nanocomposite under UV-A, UV-B and UV-C radiation was investigated. ZnO nanoparticles were synthesized on the surface of MMT and used as photocatalyst in decolorization of Disperse Red 54 (DR54) solution. Synthesized nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) techniques and nitrogen adsorption/desorption isotherms curves. The average width of synthesized ZnO particles is in the range of 30-45 nm. Effect of UV light regions, initial dye concentration, initial dosage of nanocomposite, and reusability of catalyst was studied on decolorization efficiency. The highest decolorization efficiency was achieved under UV-C radiation. A three-layered feed forward back propagation artificial neural network model was developed to predict the photocatalysis of DR54 under UV-C radiation. According to ANN model the ZnO/MMT dosage with a relative importance of 49.21% is the most influential parameter in the photocatalytic decolorization process.

Predicting the optimum compositions of a parenteral nanoemulsion system loaded with azithromycin antibiotic utilizing the artificial neural network model

For the purpose of brain delivery via intravenous administration, the formulation of an azithromycin-loaded nanoemulsion system was optimized utilizing the artificial neural network (ANN) as a multivariate statistical technique.

Removal of organic dyes by UV/H2O2 process: modelling and optimization

The effects of different operational parameters on the decolorization of a dye solution containing C.I. Acid Blue 92 (AB92) or C.I. Acid Black 1 (AB1) by the UV/H2O2 process were optimized using response surface methodology (RSM). The reaction time, dye and H2O2 initial concentrations and distance of the UV lamp from the solution were chosen as input variables. The removal process was performed according to a central composite design. Predicted results by the proposed models were in good agreement with experimental values (R2 = 0.942 and 0.957 for AB92 and AB1, respectively). The optimum points were located by graphical response surfaces and contour plots. The removal process of the dyes was compared and the efficiency difference justified by considering the chemical structure of the dyes. Additionally, the electrical energy consumption and the related treatment costs were estimated employing the figure-of-merit electrical energy per order (E(EO)).

Optimization of photocatalytic degradation of sulphonated diazo dye C.I. Reactive Green 19 using ceramic-coated TiO2 nanoparticles

Optimization of photocatalytic degradation of C.I. Reactive Green 19 (RG 19) under UV light irradiation using ceramic-coated TiO2 nanoparticles in a continuous circulation rectangular photoreactor was studied. The used catalyst was TiO2 Millennium PC-500 (crystallite mean size 8 nm) immobilized on ceramic plates. A central composite design was used for optimization of the UV/TiO2 process. Predicted values of decolorization efficiency were found to be in good agreement with experimental values (R2 = 0.97 and Adj-R2 = 0.91). Optimization results showed that maximum decolorization efficiency was achieved at the optimum conditions of: initial dye concentration 10 mg/L, UV light intensity 47.2 W/m2, flow rate 150 mL/min and reaction time 240 min. Photocatalytic mineralization of RG 19 was monitored by chemical oxygen demand (COD) decrease and changes in the UV-Vis spectrum.

Influence of operational parameters and kinetics analysis on the photocatalytic reduction of Cr(VI) by immobilized ZnO

In the present work the performance of immobilized ZnO on a glass plate with the heat attachment method has been described for photoreduction of Cr(VI) to the less harmful Cr(III) at different operational parameters. The photoreduction of Cr(VI) on the surface of the immobilized ZnO catalyst was studied as a function of the pH of solution, initial Cr(VI) concentration and ultraviolet (UV) light intensity. Results indicated that the reduction rate decreases with increasing initial concentration of Cr(VI) and initial pH of solution, whereas it increases with increasing UV light intensity. The photoreduction rate of Cr(VI) on the surface of the immobilized ZnO in the presence of O2 as mobile gas is more than Ar and N2. The reduction process of Cr(VI) by immobilized ZnO also could be done under visible light irradiation. Pseudo first-order kinetics were observed for the photoreduction of Cr(VI) at different operational conditions. With non-linear regression analysis a mathematical kinetics model was developed for the pseudo first-order constant (k(ap)) as a function of operational parameters.

Simulated-sunlight-activated photocatalysis of methylene blue using cerium-doped SiO2/TiO2 nanostructured fibers

Cerium-doped SiO2/TiO2 nanostructured fibers were fabricated by electrospinning technology. The prepared fibers were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Using the fibers as catalysts, photocatalytic degradation of Methylene Blue (MB) aqueous solution was carried out under simulated sunlight. The 0.2% Ce doping proved to be the optimal concentration for the doping of TiO2/SiO2, compared to other Ce-doped molar concentrations. The 0.2% Ce-doped SiO2/TiO2 fibers exhibited higher photocatalytic activity than industrial Degussa P25 and the samples doped with only Ce or SiO2. The reasons for improving the photocatalytic activity were also discussed. Several operational parameters were studied, which showed that the photocatalytic efficiency of MB was influenced by parameters such as the initial dye concentration, the initial pH, inorganic anions, and so on. In addition, the influences of an electron acceptor and a radical scavenger suggested that OH was the dominant photooxidant during the photocatalytic process. The reuse evaluation of the fibers indicated that their photocatalytic activity had good stability.

Synthesis of TiO2 nanoparticles in different thermal conditions and modeling its photocatalytic activity with artificial neural network

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.

Application of response surface methodology in the optimization of photocatalytic removal of environmental pollutants using nanocatalysts

Response surface methodology is a widely used technique for modelling and optimization of the photocatalytic treatment processes of water and wastewater. This methodology not only estimates linear, interaction and quadratic effects of the factors on the response, but also provides a prediction model for the response at the range of the variables studied and the optimum conditions to achieve the highest performance. The present paper reviews the results of application of this innovative methodology in modelling and optimization of the photocatalytic treatment processes. Different experimental designs including 3k factorial, Doehlert, Box-Behnken and central composite designs have been developed to describe the treatment processes of dyeing effluents, pharmaceutical agents and hazardous phenolic compounds. The results showed that response surface methodology can describe the behaviour of complex reaction systems, such as photocatalytic processes, in the range of experimental conditions adopted. Optimization based on response surface methodology can also estimate the conditions of the photocatalytic processes to achieve the highest performance.

Photo-assisted hetero-fenton decolorization of azo dye from contaminated water by Fe-Si mixed oxide nanocomposite

An aerogel of silica gel dopeyd with 2.86 wt% Fe was prepared by an alkoxide sol-gel method and using tetraethyl orthosilicate as a precursor material. The synthesized aerogel was calcined at 500 degress C to produce nanoparticle solids, and was characterized by XRD, FT-IR and SEM. The nanosized iron-silica gel mixed oxide was tested in the photooxidation of the azo dye Acid Red 14 (AR 14) using 30% aqueous hydrogen peroxide as oxidant and UV light. The 2.86 wt% Fe-loaded SiO2 showed very good efficiency in the decolorization of AR 14. The effects of various parameters including solution pH, catalyst, oxidant and initial dye concentrations on photodegradation were investigated and the optimum conditions were determined. The catalyst was resistant to leaching and could be recycled several times without appreciable loss of activity.

Enhanced photocatalytic degradation of C.I. Basic Violet 2 using TiO2-SiO2 composite nanoparticles

In this report, TiO(2) -SiO(2) composite nanoparticles were prepared by the thermal hydrolysis method using titanium tetrachloride and tetraethylorthosilicate as TiO(2) and SiO(2) precursors, respectively. The prepared nanoparticles were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption/desorption and UV-Vis diffuse reflectance spectroscopy (DRS). The results indicated that, in comparison with pure TiO(2), TiO(2)-SiO(2) composite nanoparticles had a higher thermal stability, which prevents phase transformation from anatase to rutile. In addition, the TiO(2)-SiO(2) nanoparticles had a higher specific surface area, larger pore volume, greater band gap energy and smaller crystallite size. Thus, the surface area of TiO(2)-40% SiO(2) composite nanoparticles was about 17 times higher than that of pure TiO(2) nanoparticles. The photocatalytic activity of TiO(2)-SiO(2) composite nanoparticles in the photodegradation of C.I. Basic Violet 2 was investigated. The photodegradation rate of Basic Violet 2 using TiO(2)-40% SiO(2) nanoparticles calcined at 600°C was much faster than that using pure TiO(2) and Degussa P25 TiO(2) by 10.9 and 4.3 times, respectively. The higher photoactivity of the TiO(2)-SiO(2) composite nanoparticles was attributed to their higher surface area, larger pore volume, greater band-gap energy and smaller crystallite size compared with pure TiO(2).

Thin wetted film cylindrical flow photo reactor for the degradation of Procion blue H-B dye over TiO2 and ZnO

A thin wetted film cylindrical flow reactor was fabricated for photocatalytic oxidation of Procion blue H-B dye in textile washwater with the suspensions of TiO2 and ZnO. The disappearance of colour and organic reduction were studied in terms of the removal of colour and chemical oxygen demand (COD). Operating parameters such as effect of pH, UV irradiation with and without catalyst, initial concentration of dye and effect of flow rate were studied and kinetics of Procion blue H-B dye has been studied over TiO2 and ZnO surfaces. Since adsorption is the prerequisite condition for decolorization/degradation of dye molecules in the presence of heterogeneous catalysis, the Langmuir and Freundlich isotherms were examined to verify the adsorption intensity. The results clearly demonstrated that, the optimum loading of the photocatalyst was found to be 300 and 400 mg/L of TiO2 and ZnO, respectively. The maximum COD reduction efficiency was 68% for TiO2 and 58% for ZnO. On the other hand, the colour removal efficiency was found to be 74% and 69%, respectively for TiO2- and ZnO-assisted systems under optimum conditions. Conclusively, these two semiconductors could degrade Procion blue H-B dye at different time intervals and both isotherms fit well.

Mineralization of C.I. Acid Red 14 azo dye by UV/Fe-ZSM5/H2O2, process

The zeolite Fe-ZSM5 was applied as a heterogeneous catalyst in the photo-Fenton process for mineralization of azo dye Acid Red 14 (AR14). Under optimal conditions (20 mM of H2O2 0.25 g L(-1) of catalyst and initial natural pH of the solution) 76% of total organic carbon (TOC) of a solution containing 40 mg L(-1) of the dye could be removed after 120 min in a 1.0 L tubular, closed-circulation batch photoreactor. Leaching tests and comparative experiments indicated that the application of the heterogeneous catalyst could increase the photo-Fenton process efficiency. A kinetic model was developed for this process and showed that the dye mineralization rate obeyed the pseudo-first order kinetic when the initial concentration of the dye was low. It was also observed that the catalytic behaviour of Fe-ZSM5 could be reproduced in consecutive experiments without a considerable drop in the process efficiency. Estimation of electrical energy consumption (EE/O) of the process as a function of mineralization efficiency revealed that the UV/Fe-ZSM5/H2O2 process not only increased the mineralization efficiency of the process, but also decreased the cost of electrical energy consumed by the process.