Efficacy of Cr-doped ZnO nanoparticles in removal of reactive black 5 dye from aqueous solutions in presence of solar radiation

Background and purpose: Dyes from textile industry are amongst the major pollutants of the environment that are harmful for both human health and the environment. Azo dyes constitute the largest and the most important class of commercial dyes, accounting for 50 of all commercial dyes. This study investigated the efficacy of Cr-doped ZnO nanoparticles in removal of reactive black 5 (RB5) dye from aquatic solutions in presence of solar radiation. Materials and methods: An experimental laboratory study was done by designing the surface-answer test. Cr-doped ZnO nanoparticles were synthesized using co-precipitation method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization of the nanoparticles prepared. Effects of parameters such as pH, nanoparticle dosage, initial RB5 concentration, and contact time on the removal efficiency of RB5 were studied. The remaining concentration of RB5 was analyzed by UV/VIS spectrophotometer at a wavelength of 597 nm. Finally, the statistical analysis of the model was conducted by ANOVA. Results: Results showed that removal efficiency increased by increasing nanoparticle dosage and contact time. Also, we found that removal efficiency decreased by increasing the initial dye concentration and pH. The optimum condition for dye removal was obtained at pH 4, nanoparticle dosage of 1.75 g/L, initial dye content of 112.5 mg/L, and 75 min contact time. In this condition the efficiency removal and desirability were 75.41 and of 0.905, respectively. Conclusion: Removal of textile dyes was found to be quick and effective when using Cr-doped ZnO nanoparticles. Also, designing and performing the experiment (in low frequency) can help in optimizing the efficiency removal of pollutant from aqueous media. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Levels and health risk assessments of particulate matters (PM 2.5 and PM 10 ) in indoor/outdoor air of waterpipe cafés in Tehran, Iran

To determine the concentration of particulate matters (PM 2.5 and PM 10 ), 36 samples were collected from indoor/outdoor air of hookah cafés (HS), cigarette cafés (CS), both hookah and cigarette (HCS), and no-smoking building (NS) in Tehran City from December 2017 to March 2018. The mean ± SD of PM 10 concentration in the indoor air of the cafés in terms of HS, CS, HCS, and NS sites has been 702.35, 220.20, 1156.60, and 60.12 μg/m 3 , while for PM 2.5 , the values have been 271.92, 111.80, 619.10, and 22.25 μg/m 3 , respectively. It was also found that the PM concentration inside the cafés was higher during weekend session (with a higher number of active smokers), than during the weekday sessions. Moreover, the PM levels in the indoor air of the cafés were considerably higher than those of the outdoors (p < 0.05). Based on path analysis, the number of �active smokers� had the highest influence on production of PM inside the cafés, followed by the tobacco type. Finally, the mean excess lifetime cancer risk (ELCR) for PM 2.5 in the indoor air of cafés was observed in the range of 0.64 � 10 �5 �14.98 � 10 �5 . Also, the mean of hazard quotient (HQ) for PM2.5 and PM 10 was calculated in range of 0.82�18.4 and 0.16�3.28, respectively, which corresponds to an unacceptably high risk for human health. The PM levels in the indoor air of smoking cafés in Tehran are significantly high, such that it can cause serious risks for the health of both the customers and personnel. Thus, it is necessary that suitable controlling strategies be adopted for this public health threat. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature

Turbulence Modeling of Wall Jets using the Algebraic Structure Based Model

Report PRE-2628. The Algebraic Structure Based Model (ASBM) of Langer and Reynolds (2003) provides an innovative approach for modeling the turbulent stresses, while incorporating information on the structure of turbulence and providing closure for Reynolds-averaged Navier-Stokes equations. The normal turbulent stresses, for which the ASBM has shown superior results, are difficult to replicate using the conventional Boussinesq hypothesis that forms the backbone of common eddy-viscosity models. The results for mean velocities and diagonal turbulent stresses, and the computational cost are kept at an acceptable level to allow the model to compete effectively with common eddy-viscosity models. In this work, the ASBM has been applied to two new validation cases; the plain wall jet of Eriksson et al. (1998) and the slot impinging jet of Zhe and Modi (2001). Encouraging results are obtained for the normal turbulent stresses, while the mean velocities and turbulent shear stress are comparable to the v2f eddy-viscosity model of Lien and Durbin (1996). Also drawbacks of the ASBM are pointed out that emerge from the fact that the model is algebraic and hence relies only on local flow properties.Energy TechnologyProcess and EnergyMechanical, Maritime and Materials Engineerin