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In this study, La and Mg doped, and co-doped ZnO nanoparticles were prepared using the sol-gel method. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and N2 physisorption techniques. The XRD results indicated that the prepared nanoparticles can be well adopted by the hexagonal wurtzite structure crystal and there are no second impurity peaks. Studies of the FESEM, EDX and TEM have shown that the samples have uniform spherical-like morphology with a homogenous distribution. The incorporation of La and Mg into the ZnO lattice had no effect on the morphology of the nanoparticles, but a reduction in the size of the grains (≈ 14 nm to ≈ 7 nm) was observed due to the insertion of these ions. The results of N2 physisorption indicated that there was an increase in BET surface area and pore volume for doped and co-doped samples. The results of DRS showed an increase in band gap energy and a blue shift at the absorption edge for doped and co-doped samples. The photocatalytic activity of the prepared catalysts was evaluated in the removal of RhB under UVA irradiation. The results showed that Mg5%-La5%/ZnO had the highest photoactivity (91.18 %) among all samples. [ABSTRACT FROM AUTHOR]

In this study, TiO2 nanowires (TNWs) were synthesized through hydrothermal method and were characterized using X‐Ray diffraction (XRD), transmission electron microscopy (TEM) and BET techniques. Monoclinic TiO2 (B) is the dominant phase of TNWs up to 600°C which is completely transformed into a highly crystalline anatase phase at 800°C. The photocatalytic activity of TNWs, prepared at various calcination temperatures, was investigated in the removal of Rhodamine B as an organic model pollutant. The results indicated that the photocatalytic activity of TNWs, prepared at 800°C calcination temperature, was better than that of other samples and even TiO2–P25 nanoparticles. [ABSTRACT FROM AUTHOR]

In this article, response surface methodology (RSM) was used to obtain optimum conditions for removal of p-nitrophenol (PNP) by UV/H2O2 process using spinning disk photoreactor (SDP). For this purpose, the effect of five independent variables, the initial concentration of PNP, the initial concentration of H2O2, pH, solution volume, and irradiation time on the PNP removal percent, was investigated. Central composite design, one of the response surface techniques used for process optimization. The results showed a good agreement between the RSM predicted and experimental data with "R2" and "Adjusted R2" of 0.9692 and 0.9480, respectively. In addition, "Predicted R2" of 0.8909 is in reasonable agreement with "Adjusted R2" of 0.9488. At optimal conditions, that is, PNP concentration of 20.78 mg L−1, H2O2 concentration of 1355.83 mg L−1, solution volume of 566.08 mL, irradiation time of 12.30 min, and pH of 4.59 the removal percent predicted by RSM is 100% which has good correspondence with its experimental value (98.67%). [ABSTRACT FROM AUTHOR]

In this study, Mg-doped ZnO nanoparticles with 2% Mg content were synthesized by sol-gel method. The structure and morphology of the nanoparticles were characterized by TEM, BET and UV-Vis absorbance techniques. From TEM image, it was found out that the nanoparticles had uniform size and uniform distribution. BET analysis revealed that in comparison with pure ZnO, Mg 2%/ZnO nanoparticles had a higher specific surface area. Based on UV-Vis absorbance analysis, Mg 2%/ZnO nanoparticles shifted to a lower wavelength (blue-shift), showing a high photocatalytic activity under UV light irradiation. The central composite design under the response surface methodology (RSM) was used for optimization of the photocatalytic removal of Rhodamine B (RhB) with Mg 2%/ZnO nanoparticles. The results showed that there was a good agreement between the predicted data from RSM and the experimental data with a correlation coefficient of 0.9354. The determined optimum values for removal of RhB were as follows: Mg 2%/ZnO nanoparticles dosage of 500 mg L-1, initial RhB concentration of 6 mg L-1, the irradiation time of 6 min, and pH = 8. In order to get more information about photocatalytic activity of the prepared Mg 2%/ZnO nanoparticles, a comparison was made between the photocatalytic activity in this study and that reported by other researchers. The results revealed the synthesized Mg 2%/ZnO nanoparticles had considerable photocatalytic activity. [ABSTRACT FROM AUTHOR]

In this study, Ag/TiO2--P25 nanoparticles prepared via photodeposition method and its textural properties were characterized using X--ray diffraction (XRD), transmission electron microscopy (TEM), UV--vis diffuse reflectance spectroscopy (DRS), and N2 physisorption techniques. The cements modified with TiO2--P25 and Ag/TiO2--P25 nanoparticles were immobilized on tile plates, and their photocatalytic activity was evaluated versus the removal of Erioglaucine as the model organic pollutant. The Ag/TiO2--P25 modified cement showed the highest photocatalytic activity compared to TiO2--P25 modified cement due to the positive effect of silver in trapping photogenerated electrons at conduction band of TiO2. Also, the effect of operational variables such as initial Erioglaucine concentration, irradiation time, and UV--light intensity on the photocatalytic activity of Ag/TiO2--P25 modified cement was investigated and optimized using the Taguchi approach. The optimum operational conditions were found to be: initial Erioglaucine concentration of 5 mg L-1, irradiation time of 90 min and UV--light intensity of 55.9 W m-2. [ABSTRACT FROM AUTHOR]

The photooxidative removal of analgesic pharmaceutical compound phenazopyridine (PhP) from aqueous solutions by UV/H2O2 system with a re-circulated photoreactor was investigated. Response surface methodology (RSM) was employed to optimize the effect of operational parameters on the photooxidative removal efficiency. The investigated variables were: the initial PhP and H2O2 concentrations, irradiation time, volume of solution and pH. The analysis of variance (ANOVA) of quadratic model demonstrated that the described model was highly significant. The predicted values of the photooxidative removal efficiency were found to be in a fair agreement with experimental values (R2 = 0.9832, adjusted R2 = 0.9716). The model predicted that the optimal reaction conditions for a maximum removal of PhP (>98%) were: initial PhP concentration less than 23 mg L-1, initial concentration of H2O2 higher than 470 mg L-1, solution volume less than 500 mL, pH close to 2 and irradiation time longer than 6 min. [ABSTRACT FROM AUTHOR]

In this study, a horizontally rotating disc recirculated (HRDR) photoreactor equipped with two UV lamps (6 W) was designed and fabricated for photocatalytic removal of p-nitrophenol (PNP). Photocatalyst (TiO2) nanoparticles were immobilized onto a high-density polyethylene (HDPE) disc, and PNP containing solution was allowed to flow (flow rate of 310 mL min-1) in radial direction along the surface of the rotating disc illuminated with UV light. The efficiency of direct photolysis and photocatalysis and the effect of rotating speed on the removal of PNP were studied in the HRDR photoreactor. It was found that TiO2-P25 nanoparticles are needed for the effective removal of PNP and there was an optimum rotating speed (450 rpm) for the efficient performance of the HRDR photoreactor. Then effects of operational variables on the removal efficiency were optimized using response surface methodology. The results showed that the predicted values of removal efficiency are consistent with experimental results with an R2 of 0.9656. Optimization results showed that maximum removal percent (82.6%) was achieved in the HRDR photoreactor at the optimum operational conditions. Finally, the reusability of the HRDR photoreactor was evaluated and the results showed high reusability and stability without any significant decrease in the photocatalytic removal efficiency. [ABSTRACT FROM AUTHOR]

Hydrothermal method was used to synthesize TiO2 nanotubes (TNTs), which are considered as a novel adsorbent with high surface area and adsorption capacity. Different methods including X-ray diffraction (XRD), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) analysis were used to investigate and identify synthesized TNTs. The adsorption capacity of TNTs was investigated with regard to removing Basic Violet 2 (BV2) as a model organic pollutant from aqueous solution. The mean outer, inner diameter and thickness of the TNTs were found to be approximately 9, 4 and 2.5 nm, respectively. BET-BJH method was used for measuring specific surface area and pore volume of the TNTs which turned out to be 200.38 m2 g−1 and 0.44 cm3 g−1, respectively. The results of the study indicated synthesized TNTs may be considered as efficient and effective adsorbent for removing BV2 (75.63%) from aqueous solution. The impact of the operational variables, i.e. initial BV2 concentration (2-20 mg L−1), dosage of adsorbent (0.01-0.6 g), and pH (2-8) in relation to the adsorption capacity of BV2 onto TNTs were investigated. The experimental results of the study were meticulously taken into consideration for discussing and analyzing the adsorption isotherms and kinetics. It was found that the collected experimental data regarding the kinetic and isotherm examinations were compatible and well-matched with the pseudo-first order kinetic model and Langmuir isotherm model (R2 = 0.9634). [ABSTRACT FROM AUTHOR]

In this study, ZnO nanoparticles with different Mg contents and calcination temperatures were synthesized by the sol–gel method. The photocatalytic activity of the synthesized nanoparticles was investigated in the photocatalytic degradation of Rhodamine B. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX)-mapping, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) techniques. The XRD results showed that the doped nanoparticles had the same crystal structure as the pure ZnO. The EDX and mapping findings indicated the existence of Mg in the doped sample. SEM and TEM analysis showed the spherical shape and uniform-size distribution of the nanoparticles. Based on DRS spectra, the band gap energy value of 2.0 wt% Mg doped ZnO was 3.26 eV, which was larger than the ZnO nanoparticles’ band gap energy. Using BET analysis, the surface areas of ZnO and 2.0 wt% Mg/ZnO were calculated to be 14.9 and 22.5 m2 g−1, respectively. The results of the photocatalytic activity indicated that Mg/ZnO was more active than pure ZnO photocatalyst due to its higher surface area and larger band gap energy. Maximum photocatalytic activity was achieved for Mg/ZnO nanoparticles with 2.0 wt% Mg and at the calcination temperature of 400°C. [ABSTRACT FROM PUBLISHER]

In this study, the photodegradation of cefazolin was investigated in the presence of suspended and immobilized TiO2on a glass plate. The effects of the operational parameters such as the catalyst dosage for the suspended system, the initial pH of the solution, the initial concentration of the cefazolin, and light intensity were examined and compared in both systems. Scanning electron microscopy and atomic force microscopy were used to determine the surface properties of the immobilized catalyst on glass. The favorable conditions obtained for the photodegradation of cefazolin were pH 5, light intensity = 17 W m−2, and [cefazolin]0 = 20 mg L−1in both the systems. Also, in the slurry system, the most suitable catalyst dosage was 400 mg L−1. The kinetic examination, following the pseudo-first-order reaction kinetics, was made based on the Langmuir–Hinshelwood model. [ABSTRACT FROM PUBLISHER]

In this study, removal efficiency of phenazopyridine (PhP) as a model pharmaceutical contaminant was investigated in a batch-recirculated photoreactor packed with immobilized TiO2-P25 nanoparticles on glass beads. Influence of various operational parameters such as irradiation time, initial concentration of PhP, volume of solution, volumetric flow rate, pH and power of light source was investigated. Results indicated that removal percentage increases with the rise of irradiation time, volumetric flow rate and power of light source but decreases with the rise of initial concentration of PhP and volume of solution. Highest removal percentage was obtained in the natural pH of PhP solution (pH= 5.9). Results of mineralization studies also showed a decreasing trend of total organic carbon (TOC) and producing mineralization products such as NO3-, NO 2-and NH 4-.Modeling of the process using artificial neural network showed that the most effective parameters in the degradation of PhP were volume of solution and power of light source. The packed bed photoreactor with TiO2-P25 nanoparticles coated onto glass beads in consecutive repeats have the proper ability for PhP degradation. Therefore, this system can be a promising alternative for the removal of recalcitrant organic pollutants such as PhP from aqueous solutions. [ABSTRACT FROM AUTHOR]

In the present study, Ag–TiO2-P25 nanoparticle was synthesized using photodeposition technique and Mg was impregnated onto the Ag–TiO2-P25 for the preparation of co-doped nanoparticles. The physicochemical properties were characterized by X-ray diffraction (XRD), specific surface area and porosity (Brunauer–Emmett–Teller (BET) and Barret–Joyner–Halender), transmission electron microscopy, diffuse reflectance spectroscopy (DRS), scanning electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy techniques. The BET surface area of the co-doped TiO2-P25 was larger than that of the monometallic catalysts and the XRD data showed anatase and rutile crystalline phases in catalysts, indicating that Ag and Mg co-doping did not influence the crystal patterns of TiO2-P25. Also, the DRS results indicated that the band gap of co-doped photocatalyst was smaller than that of the monometallic and undoped TiO2-P25 and there was a shift in the absorption band toward the visible light region. Additionally, the photocatalytic efficiency of the synthesized catalysts was evaluated by degradation of C.I. Acid Red 27 under visible light irradiation. The results showed that Ag-(1 wt%) and Mg-(0.25 wt%) co-doped TiO2-P25 had the highest photoactivity among all samples under visible light. The optimum calcination temperature and time were 350°C and 1 h, respectively. The results of the total organic carbon analysis indicated 66% mineralization of AR27 after 20 min of irradiation time. [ABSTRACT FROM AUTHOR]