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In this study, Ag-ZnO nanophotocatalyst has been synthesized through microemulsion technique and the effect of silver modification on ZnO nanorods has been evaluated. The photocatalytic activity of nanocatalyst was examined by degradation of Acid Yellow 23 (AY23) as a model of mono azo dye under UV illumination. Ag-ZnO catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS) and diffuse reflectance spectroscopy (DRS) analysis. The degradation of AY23 was studied under different operational parameters. Results show that the photocatalytic reaction followed the pseudo-first-order kinetic. The highest photocatalytic degradation of 20 mg/L AY23 dye solution under UV irradiation (light intensity = 50 W/m2 , [Ag-ZnO]0 = 400 mg/L with 2 wt% Ag doped ZnO, calcined at 450 °C) was about 93.3% during 30 minutes of reaction that shows an enhancement in comparison to pure ZnO which was 65.48%. [ABSTRACT FROM AUTHOR]

The synthesis of silver doped nano-particulate titanium dioxide (Ag/TiO2) using a microemulsion method and an investigation of its photocatalytic activity for the degradation of Acid Red 27 in distilled water under UV-irradiation is reported. The prepared Ag/TiO2 is characterized using transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The size of the Ag nanoparticles is around 5–15 nm, with almost uniform distribution on the TiO2 particles. The efficiency of the photocatalytic process is evaluated to establish the optimum conditions, found to be at 2 wt% of Ag loading on TiO2, catalyst dosage of 400 mg L−1, and calcination temperature of 300°C. Complete decolorization of the dye solution on Ag/TiO2 was observed in 20 min of UV irradiation in the optimum conditions. [ABSTRACT FROM AUTHOR]

The photocatalytic activity of silver-doped ZnO was tested by photocatalytic degradation of C.I. Acid Red 88 (AR88) as a model contaminant from monoazo textile dyes. Silver-doped ZnO was prepared by photodeposition (PD) method. Results show that silver-doped ZnO is more efficient than undoped ZnO at photocatalytic degradation of AR88. The PD method parameters such as irradiation time, calcination temperature and silver content of doping were effective on the photoactivity of silver-doped ZnO. Silver content had an optimum value of 0.5% for achieving high photocatalytic activity. In the real wastewater from a textile-dyeing factory color removal with pure and silver-doped ZnO after 18 min of irradiation were 45 and 90%, respectively. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles with different average diameter of particles (8, 18 and 27 nm) and different crystal structure (anatase and rutile) were used for degradation of C.I. Acid Red 88 (AR88) as a model compound. The degree of degradation of AR88 by TiO2 nanoparticles under irradiation of UV-light (254nm) with TiO2-UV100 (8 nm diameter and 100% anatase) is lower than TiO2-Merck (27 nm diameter and 95% anatase). TiO2-P25 with structure of anatase and rutile (80:20) combination shows higher photoactivity than other samples such as TiO2-UV100 and TiO2-Merck. Kinetics of removal of AR88 with all of nanosized-TiO2 particles is pseudo-first-order. The apparent reaction rate constant (kap) for removal of AR88 in the presence of different nanosized-TiO2 particles decreases with increasing of AR88 initial concentration. For TiO2-P25 and TiO2-UV100 a linear relation and for TiO2-Merck a nonlinear relation between kap and light intensity were obtained. [ABSTRACT FROM AUTHOR]

In this study, to investigate the application of heterogeneous photocatalysis in the removal of organic contaminants from aqueous media a novel tubular continuous-flow photoreactor with supported TiO2-P25 on glass plates was designed and constructed. The photoreactor comprises six quartz tubes and a UV lamp which was placed in the center of the quartz tubes. 4-nitrophenol (4-NP) as a most refractory pollutant was chosen as a probe pollutant to examine the photoreactor efficiency for environmental cleaning applications. Results of experiments show that the removal efficiency of 4-NP in this photoreactor is a function of photoreactor length, gas and liquid flow rates and 4-NP initial concentration. Kinetics analysis indicates that degradation of 4-NP in continuous-mode can be modeled with the Langmuir-Hinshelwood (L-H) model (kL-H = 1.5 mg L-1 min-1, Kads = 0.11 mg-1 L). A design equation was obtained with a combination of L-H modified equation and tubular reactor design equation. This equation can be used for estimation of 4-NP concentration in different photoreactor lengths under various operational parameters. Mineralization study was followed through total organic carbon (TOC) analysis and measurement of nitrite and nitrate as final degradation products. [ABSTRACT FROM AUTHOR]

Abstract: The effect of heat attachment method parameters such as: sonication time, dosage of catalyst, immobilization temperature and type of solvent were investigated for enhancement of photocatalytic activity of immobilized ZnO nanoparticles on glass plate. Photocatalytic activity of immobilized ZnO was tested in the removal of C.I. Acid Red 88 (AR88) as a model contaminant from textile industry. Results indicated that sonication time, dosage of catalyst and immobilization temperature were very effective on photocatalytic activity of immobilized ZnO on glass plate and using ethanol instead of water at preparation of immobilized ZnO did not show any considerable effect. In another step, the effect of operational parameters such as light intensity and initial concentration of AR88 on the removal of AR88 were investigated with immobilized ZnO on glass plate. Results indicated that removal rate decreased with increasing initial concentration of AR88 but increased with increasing UV light intensity. [Copyright &y& Elsevier]