Hamed Eskandarloo

Sol-Gel Low-temperature Synthesis of Stable Anatase-type TiO2 Nanoparticles Under Different Conditions and its Photocatalytic Activity

In this work, TiO2 nanoparticles in anatase phase was prepared by sol‐gel low temperature method from titanium tetra‐isopropoxide (TTIP) as titanium precursor in the presence of acetic acid (AcOH). The effects of synthesis parameters such as AcOH and water ratios, sol formation time, synthesis and calcination temperature on the photocatalytic activity of TiO2 nanoparticles were evaluated. The resulting nanoparticles were characterized by X‐ray diffraction, UV–Vis reflectance spectroscopy, transmission electron microscopy and Brunauer–Emmett–Teller techniques. Photocatalytic activity of anatase TiO2 nanoparticles determined in the removal of C. I. Acid Red 27 (AR27) under UV light irradiation. Results indicate that with increasing AcOH/TTIP molar ratio from 1 to 10, sol formation time from 1 to 3 h and synthesis temperature from 0 to 25°C, increases crystallite size of synthesized nanoparticles. It was found that optimal conditions for low temperature preparation of anatase‐type TiO2 nanoparticles with high photocatalytic activity were as follows: TTIP:AcOH:water molar ratio 1:1:200, sol formation time 1 h, synthesis temperature 0°C and calcination temperature 450°C.

Minimization of electrical energy consumption in the photocatalytic reduction of Cr(VI) by using immobilized Mg, Ag co-impregnated TiO2 nanoparticles

Magnesium and silver co-impregnated TiO2 nanoparticles were immobilized on a glass plate and used as a fixed-bed system for photocatalytic reduction of Cr(VI) to the less harmful Cr(III). Response surface methodology as a statistical technique was employed for optimizing the preparation conditions of Mg–Ag/TiO2, focusing on minimization of electrical energy consumption as the most important factor in selecting a wastewater treatment technology. Results showed that maximum photocatalytic reduction (84.44%), with minimum electrical energy consumption (30.31 kW h per m3 per order) were achieved at the optimized preparation conditions: Mg content of 0.82 wt%, Ag content of 2.6 wt%, and calcination temperature of 495 °C, whereas at the same conditions, using pure TiO2, Mg/TiO2, and Ag/TiO2 samples lead to 21.17%, 32.59%, and 63.61% photocatalytic reduction rates, and 232.1, 152.03, and 71.42 kW h per m3 per order electrical energy consumptions, respectively. The optimized Mg, Ag co-impregnated TiO2 nanoparticles were characterized by using XRD, SEM, TEM, DRS, EDX, and PL techniques. The considerable PL quenching in the co-impregnated TiO2 with optimized metals content suggests that the co-impregnation of Mg and Ag onto TiO2 could effectively inhibit the recombination probability of photogenerated electrons–holes pairs. Co-impregnation of Mg and Ag metals, and optimization of preparation conditions provides a synergistic effect in enhancement of the TiO2 activity and effective minimization of the electrical energy consumption and treatment cost.

Ultrasonic-assisted degradation of phenazopyridine with a combination of Sm-doped ZnO nanoparticles and inorganic oxidants

Pure and samarium doped ZnO nanoparticles were synthesized by a sonochemical method and characterized by TEM, SEM, EDX, XRD, Pl, and DRS techniques. The average crystallite size of pure and Sm-doped ZnO nanoparticles was about 20 nm. The sonocatalytic activity of pure and Sm-doped ZnO nanoparticles was considered toward degradation of phenazopyridine as a model organic contaminant. The Sm-doped ZnO nanoparticles with Sm concentration of 0.4 mol% indicated a higher sonocatalytic activity (59%) than the pure ZnO (51%) and other Sm-doped ZnO nanoparticles. It was believed that Sm(3+) ion with optimal concentration (0.4 mol%) can act as superficial trapping for electrons in the conduction band of ZnO and delayed the recombination of charge carriers. The influence of the nature and concentration of various oxidants, including periodate, hydrogen peroxide, peroxymonosulfate, and peroxydisulfate on the sonocatalytic activity of Sm-doped ZnO nanoparticles was studied. The influence of the oxidants concentration (0.2-1.4 g L(-1)) on the degradation rate was established by the 3D response surface and the 2D contour plots. The results demonstrated that the utilizing of oxidants in combination with Sm-doped ZnO resulting in rapid removal of contaminant, which can be referable to a dual role of oxidants; (i) scavenging the generated electrons in the conduction band of ZnO and (ii) creating highly reactive radical species under ultrasonic irradiation. It was found that the Sm-doped ZnO and periodate combination is the most efficient catalytic system under ultrasonic irradiation.

Ultrasonic-assisted sol–gel synthesis of samarium, cerium co-doped TiO2 nanoparticles with enhanced sonocatalytic efficiency

In this work, pure TiO2 and samarium, cerium mono-doped and co-doped TiO2 catalysts were synthesized by an ultrasonic-assisted sol-gel method and their sonocatalytic efficiency studied toward removal of Methyl Orange as a model organic pollutant from the textile industry. The relationship of structure and sonocatalytic performance of catalysts was established by using various techniques, such as XRD, TEM, SEM, EDX, DRS, and PL. A comparison on the removal efficiency of sonolysis alone and sonocatalytic processes was performed. The results showed that the samarium, cerium co-doped TiO2 catalyst with narrower band gap energy and smaller particle size leads to a rapid removal of pollutant. It was believed that Sm(3+) and Ce(4+) ions can serve as superficial trapping for electrons at conduction band of TiO2 and prolonged the lifetime of electron-hole pairs. Finally, the effect of synthesis and operational variables on the sonocatalytic activity of co-doped TiO2 catalyst was studied and optimized using response surface methodology as a statistical technique. The results showed that the maximum removal efficiency (96.33%) was achieved at the optimum conditions: samarium content of 0.6 wt%, cerium content of 0.82 wt%, initial pollutant concentration of 4.31 mg L(-1), catalyst dosage of 0.84 mg L(-1), ultrasonic irradiation power of 700 W, and irradiation time of 50 min.

Ultrasonic-assisted synthesis of Ce doped cubic–hexagonal ZnTiO3 with highly efficient sonocatalytic activity

Ce doped ZnTiO3 as a novel catalyst with highly efficient and stable sonocatalytic activity was synthesized via an ultrasound-assisted sol-gel method using non-ionic surfactant Pluronic F127 as structure directing agent. Synthesized samples were characterized by using various techniques, such as XRD, TEM, SEM, EDX, ​XRF, BET, DRS, and PL, and their sonocatalytic activity studied toward degradation of p-Nitrophenol as a model organic compound. The synthesized mesoporous Ce/ZnTiO3 had mixed cubic-hexagonal phase with large surface area (118.2 m(2) g(-1)) and narrow pore size distribution (4.9 nm). The effects of cerium concentration, calcination temperature, and calcination time on the structure and the sonocatalytic activity of Ce/ZnTiO3 were studied in detail. XRD results were suggested that the relation between the phase structure and the catalytic activity is considerable. Significant decrease in band-gap and PL intensity was observed with increasing the cerium concentration in the ZnTiO3. It became clear that the Ce/ZnTiO3 (0.81 mol%) shows high sonocatalytic activity compared with pure ZnTiO3 and other Ce/ZnTiO3 samples as well as commercial TiO2-P25. The possible mechanism for the enhanced sonocatalytic activity of Ce/ZnTiO3 was discussed in details. The electrical energy consumption was also considered during sonocatalytic experiments.

Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts

In this study, the photocatalytic efficiency of anatase‐type TiO2 nanoparticles synthesized using the sol–gel low‐temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV–light‐assisted photo and NaBH4‐assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed‐bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH‐modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH‐modified Cu/TiO2 nanoparticles.

Preparation of TiO2 nanoparticles by the sol–gel method under different pH conditions and modeling of photocatalytic activity by artificial neural network

In this study, TiO2 nanoparticles were prepared by the sol–gel method under different pH conditions and the structural properties of TiO2 nanoparticles were obtained by X-ray diffraction and transmission electron microscopy. The photocatalytic activity of TiO2 nanoparticles was studied in the removal of C.I. Acid Red 27 (AR27) under UV light. The desired gelation pH for photocatalytic removal of AR27 was obtained at pH 5. At this pH, the predominant crystal phase of TiO2 is anatase and its crystallite size is smaller than at other gelation pHs. The artificial neural network (ANN) technique was applied to model and predict the photocatalytic activity of TiO2 nanoparticles prepared at the desired gelation pH. Four effective operational parameters were inserted as the inputs of the network and reaction rate constants (kap) were introduced as the outputs of the network. The results showed that the predicted data from the designed ANN model are in good agreement with the experimental data with a correlation coefficient (R2) of 0.9852 and mean square error of 0.00242. The designed ANN provides a reliable method for modeling the photocatalytic activity of TiO2 nanoparticles under different operational conditions. Furthermore, the relative importance of each operational parameter was calculated based on the connection weights of the ANN model. The initial dosage of TiO2 nanoparticles was the most significant parameter in the photocatalytic removal of AR27, followed by the UV-light intensity and initial AR27 concentration.

Fabrication of an inexpensive and high efficiency microphotoreactor using CO2 laser technique for photocatalytic water treatment applications

In this study, a micro-photoreactor with catalyst-immobilized micro-channels was designed and fabricated using CO2 laser as a simple and inexpensive technique. The micro-photoreactor is composed of an array of micro-channels, a quartz plate, and an array of UV-LEDs. The micro-channels with the dimension of 400 µm width, 50 µm depth, and 80 cm length were inscribed on a flat plate of poly(methyl methacrylate) (PMMA). The illuminated specific surface area for the designed micro-reactor was calculated to be 25000 m–1. To examine the performance of miniaturized photoreactor, the photocatalytic degradation of 4-Nitrophenol as a refractory pollutant was investigated. The effects of operational variables on the performance of micro-photoreactor were studied. Higher photocatalytic degradation is obtained for low flow rates, high light intensities, long micro-channels lengths, and low inlet concentrations. Also, the performance of micro-photoreactor was examined in the presence of different types of TiO2 catalysts with an average particle size between 5 and 27 nm (such as P25, PC500, Merck, and UV100) and textile dyes with different chemical structures (such as Acid Orange 7, Acid Violet 19, Basic Red 46, Methyl Orange, and Malachite Green). Finally, the reusability of miniaturized photoreactor was evaluated and the results showed satisfactory stability and reusability for the designed micro-reactor in the photocatalytic degradation of organic pollutants.

Application of artificial neural network (ANN) for modeling of dyes decolorization by Sn/Zn-TiO2 nanoparticles

This study examined the implementation of artificial neural network (ANN) for the prediction and modeling of methylene blue (MB) and methyl orange (MO) dyes decolorization in aqueous solution using Sn/Zn-TiO2 nanoparticles prepared by sol–gel method. Operational parameters such as amount of catalyst, concentration of dye, reaction time, and temperature of solution were employed as inputs to the network and dye decolorization efficiency was the output of the network. ANN predicted results are in good agreement with the experimental results data with a correlation coefficient (R2) of 0.9839 and 0.9887 for MB and MO dyes, respectively. The sensitivity analysis investigated that studied parameters have different effect on dyes decolorization. For both dyes, reaction time is the most influential parameter and the temperature of solution is the less influential variable in the removal efficiency of both dyes. The results indicated that neural network modeling could effectively predict and model the photocatalyt...

Optimization of UV/inorganic oxidants system efficiency for photooxidative removal of an azo textile dye

AbstractIn this paper, photooxidative removal of C.I. Basic Red 46 (BR46) as a model organic pollutant was investigated in the presence of UV/inorganic oxidants system. The aim of this study was to evaluate the efficiency of hybrid oxidant system including inorganic oxidant species such as persulfate (), peroxymonosulfate (), periodate (), bromate (), and chlorate () under UV-C light irradiation. The effect of various inorganic oxidants concentration in different reaction times was predicted and optimized in the photooxidation process using response surface methodology. It was found that the concentration of inorganic oxidants significantly affected the removal rate of BR46. Modeling results showed that the predicted values of removal efficiency were found to be in good agreement with the experimental results with a correlation coefficient (R2) of 0.9462. Optimization results showed that maximum removal efficiency (95.51%) was achieved at the optimum oxidants concentration: of 118 mg L−1, of 24 mg L−1, of...