A large amount of Reactive red 198 (RR198) is released yearly into the environment. RR198 is toxic for human and aquatic creatures; therefore, it should be removed from wastewater before releasing into the environment. In this study, the nano ZnO-Nd -photo-catalyst for the first time was synthesized by the combustion method. First, the physical characteristics of the generated nano photocatalyst were evaluated using FESEM, XRD, Bandgap calculation, and FTIR analysis. Then, the ZnO-Nd nano-photocatalyst was suspended into the contaminated water with RR198 dye in a falling-film photocatalytic reactor. The effects of parameters such as the amount of H2O2, catalyst dose, pH, and initial concentration of dye were investigated during the experiments. Finally, the decolorization process with the falling-film photocatalytic reactor was optimized using response surface methodology (RSM). The physical characteristics showed that the average particle size of the synthesized ZnO-Nd was 40 nm. Doping ZnO with Nd reduced the photocatalyst energy bandgap by 14%. The results indicated that the optimum amount of catalyst dose and pH level was 0.1 g/L and 5, respectively. The simultaneous usage of H2O2 and ZnO-Nd with an H2O2/dye ratio of two increased dye removal performance by 90%. The results demonstrated that the developed equations can be applied to predict the performance of the falling-film photoreactor. This study showed that using the nano ZnO-Nd photocatalyst in a falling-film photocatalytic reactor under optimum operating conditions is an appropriate way to remove RR198 from water.
This study investigated the effect of various parameters on the removal of Reactive Blue 203 dye from wastewater using ferrate(VI) oxidation process, ultraviolet radiation (UV) radiation and MgO nanoparticles under batch mode. Although several studies have been carried out on dye removal, there is no study on the removal of Reactive Blue 203 dye using ferrate(VI) oxidation process, UV radiation, and MgO nanoparticles. Therefore, the aim of this study is to investigate the effect of different factors including pH, temperature, contact time, the intensity of UV radiation and the concentration of MgO nanoparticles on Reactive Blue 203 dye removal using the above-mentioned methods. The results showed that the best pH values for dye removal using UV radiation, ferrate(VI), and MgO nanoparticles were 13, 1 and 13, respectively. The best temperature for Reactive Blue 203 dye removal using ferrate(VI) was 50°C. Hence, temperature variation had no significant effect on Reactive Blue 203 dye removal using UV irradiation and absorption by MgO nanoparticles. Based on the results, the best contact time was 15 minutes using UV radiation. The removal of Reactive Blue 203 dye using ferrate(VI) oxidation process was a quick reaction, and in a fraction of a second, the reactions were completed. The results showed that dye removal using MgO nanoparticles could be described by the Temkin isotherm. Therefore, the contact time was not considered as an effective parameter. In addition, the maximum dye removals were 95, 85 and 94% using UV irradiation, ferrate(VI) and MgO nanoparticles.
Background: Industrial dyes are toxic and carcinogenic, therefore, they should be removed from
wastewater. The aim of this study was to investigate the removal of acid orange 7 Dye from wastewater
using ultraviolet (UV) radiation, MgO nanoparticles, ultrasonic method alone and in combination with
each other.
Methods: The effects of some factors such as temperature, pH, hydraulic retention time (HRT), UV
power, and concentration of MgO nanoparticles on the removal of Acid Orange 7 dye from synthetic
wastewater using different methods were investigated. Also, adsorption isotherms for MgO nanoparticles
and kinetics for UV radiation were investigated.
Results: The optimum HRT was 55 minutes while the temperature was not effective in dye removal
using the ultrasonic method. Under optimum conditions for UV irradiation method (HRT = 70
minutes, UV power = 170 mW/cm2, and temperature = 10˚C), 58% of the dye was removed. However,
under optimum conditions for MgO nanoparticles method (HRT = 15 minutes, temperature = 20˚C,
and ratio of MgO nanoparticles to the initial dye concentration = 67.2), 82% of the dye was removed.
By combining these methods, the dye removal efficiency was significantly increased. The combination
of ultrasonic method and MgO nanoparticles had no significant effect on increasing the dye removal
efficiency from wastewater. It was revealed that dye removal using UV radiation can be described by
the first-order kinetics.
Conclusion: According to the results, UV radiation has a synergistic effect on the dye adsorption
process by MgO nanoparticles. Therefore, the combination of these methods can be effective for the
removal of dye from wastewater.
Introduction: Air pollution is a major problem in Isfahan, one of the major cities of Iran. A large number of jewelry making workshops are located in Isfahan, yet there is insufficient information about their pollutants emission rates. The aim of this study is to determine the emission factors of nitrogen oxides and volatile organic compounds (VOCs) in Isfahan’s jewelry making workshops.
Materials and methods: In the first step of this study, some jewelry making workshops were visited to find nitrogen oxides and VOCs emission sources. It was revealed that the only possible source of nitrogen oxides and VOCs in these workshops was use of the oxy fuel welding system used to melt gold. In the second step, a set of experiments was conducted to determine the emission factors of nitrogen oxides and VOCs while working with the oxy fuel welding system.
Results: The results of this study showed that the emission factor of nitrogen oxides in the oxy fuel welding system was 0.64 kg/kg consumed natural gas. It was also found that no VOCs were emitted while working with the oxy fuel welding system, since sufficient pure oxygen was produced in this system. Interview with managers of some jewelry making workshops showed that the average natural gas consumption in each workshop was 22 kg. Therefore, each jewelry making workshop in Isfahan emitted nearly 14.08 kg of nitrogen oxide per month.
Conclusion: It is revealed that in 2018, 81100.8 kg nitrogen oxides were emitted from jewelry making workshops into Isfahan’s atmosphere.
The main objective of this study was to compare the removal efficiency of nutrients using Lactuca sativa, Medicago sativa and Phragmites australis in subsurface flow constructed wetlands with horizontal flow. In order to test water quality, fabricated reactors designed and the plants cultivated in the soil while their root were inside the wastewater. A long time study carried out from spring till end of autumn (9 months) in order to evaluate the difference in removal rate based on the seasonal changes. The highest removal rate was during summer which followed by spring and autumn. Thus, the effect of plants on the removal efficiency of organic matter (COD, BOD), TSS and nutrient (P and TN) appeared to be dependent on the seasonal growth. Phragmites australis the most sensitive species in order the removal of nutrient from wastewater.
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