Photocatalytic activity of NiO nanoparticles under the different wavelengths
Ahadzadeh-Namin Kobra1, Fakhri-Mirzanagh Sheida1, Azizian-Kalandaragh Yashar1,2
1Department of Engineering Sciences, Faculty of Advanced Technologies, Sabalan University of Advanced Technologies (SUAT), Namin, Iran, [email protected]
2Department of Physics, University of Mohaghegh Ardabili, Ardabil, Iran
Abstract- In this research, NiO nanoparticles have been prepared by microwave-assisted method and the prepared product was annealed at 1000°C. The photocatalytic properties of this nanostructures were investigated under different light wavelengths in both
Ultraviolet and visible region. XRD pattern and UV-Visible spectrum exhibit that NiO nanoparticles have been produced purely and percent of degradation of Methylene blue (MB) in depended on light wavelength, which means, in low wavelengths degradation efficiency were imported.
Keywords: Degradation, Microwaves, NiO, Wavelengths
1. Introduction
Nanomaterials have expanded rapidly in the world and as soon as the magic application of them were identified and used in industrial and life. With expansion use of fossil fuels, wide-spreading research has been done to develop renewable energy technologies that make solar energy more important. Water is considered to be one of the vital human sources, that with the growth of population, water pollution, natural disasters and various other factors of natural resources. This has given rise to increasing concern among people in various provinces. The existence of any life depends on the water.
Usually, developing countries consume 22 % of the water resources[1] in industrial processes, resulting in industrial wastewater entering into a natural cycle of many toxic and non-degradable pollutants. Today, with the expansion of water recovery as well as the purification of that treated wastewater, it can be turned into a reuse cycle for various uses. The use of refined sewage is a convenient and affordable option for supplying the water needed in various industries, which will save existing water resources and prevent water loss and environmental pollution. This is exactly where the nanoscale material is needed, in Recent decades, destroy the pollutant of water by nanoscale materials has been proven [2].
One of the pollutant materials in the water is organic dyes, this material enters the water from Textile industrial. Nano oxide materials can remove this pollutant from water by own photocatalytic activity. Oxide nanoparticles were considered for high-density materials [3]. Many metal oxide nanoparticles used in photocatalysis action such as TiO2[4], ZnO[5], SnO2[6] and etc. In among of this materials NiO nanoparticles is unique material and have wide applications. NiO used in various fields such as catalysis, gas sensors, battery cathodes, heterogeneous catalytic materials and magnetic materials [7]
and was prepared by sol-gel, surfactant-mediated synthesis, thermal decomposition, polymer-matrix assisted synthesis and spray-pyrolysis methods [8]. nickel oxide (NiO) is p-type oxides that highly active material with wide band gap (3.6eV to 4.0 eV) and used widely in catalysis applications [9] that in combining by other oxide material can removed the organic dye under the visible light [10].
photocatalytic activities of materials in depended to light irradiation, in the other words, it depended to the wavelength of light [2] and in the meantime, OH radicals is an important element to photocatalytic degradation in various materials. [11].
In this work, by synthesis NiO nanoparticles by microwaves, photocatalytic activity has been investigated. XRD and UV_Visible analyzed and study the photoactinic activity under different radiation lamp and results reported.
2. Experimental
2.1 Preparation method
In this research has been used microwave method to produce NiO so that 0.2M from Nickel chloride.6H2O (NiCl2, KBR) dissolved in 40ml distilled water and stirred 30min, then 0.5M Na2S.3H2O (LOBA Chemie) added to solution drop by drop until pH of the solution be 7. Then by adding the 0.5M NaOH (Merk), reserved pH=14, then solution placed in Microwave device (SAMSUNG) for 15min by Power=180. This material washed 5 times by water and dry in Oven for 48hours. Then annealed in 1000 ͦ centigrade. The green powder was obtained.
2.2 Photocatalytic experimental method
To study the photocatalytic activity of NiO, at first 0.1g of NiO dispersed in 100ml of Methylene Blue (MB) 10ppm, and a spot under light and
temperature circulator. The dark time was 30min
and light time was 5min for the study of the degradation of MB. This research done on the two conditions, once under SMD lamp by Visible wavelength and latter, under the Mercury- Vapour lamp by UV-Visible wavelength.
3. Results and discussion 1.1 XRD (X-Ray diffraction)
XRD pattern of preparation NiO has been shown in fig 1. It has been observed that NiO was prepared without impurity and crystalline plates placed at the desired angle [12].
Here, the Debye-Scherrer relationship is used to calculate the average grain size of the ZnTiO3 nanoparticles [15]:
𝐷 = 𝑘𝜆
𝛽 cos 𝜃 (1)
In this regard D is the average grain size, k=0.9 for nanoparticles, λ=0.154 nm is the X-ray wavelength, β is half the peak width (FWHM) and θ is the peak angle. The average size of the NiO nanoparticles was approximately less than 25.6 nm.
Fig 1. XRD pattern of prepared NiO 4. UV-Visible spectrum
The optical properties of prepared nanostructures were investigated by UV-Vis absorption spectroscopy, as shown in Fig.2 NiO nanostructures have a strong peak centered at around 355 nm (3.55 eV), and weak shoulders around 219 nm. The optical band gap of NiO has been shown in fig 2 where that is about 4 eV [13].
Fig 2. Absorbance spectrum of NiO
5. Photocatalytic activity
In this work 0.1g of prepared NiO dispersed in 100ml of MB 10ppm and placed under UV- Visible
light. Photocatalytic diagram (fig 3) shows that MB degraded from water. In the next section, this solution placed under the SMD (Visible) light (fig 4) and this is understood that NiO cannot degrade the MB. Since the band gap of NiO is depended to the preparation method and it means that NiO under the Visible irradiation cannot degradation the MB although band gap of it is narrow. Photodegradation percent diagram has been shown in fig 5 and calculated by[14]:
Degradation Efficiency = (1 −𝐴𝑡
𝐴0) × 100 (2)
Where A0 and At are the absorbances of MB before and after the degradation process.
Fig 3.: Absorption spectra of MB and NiO catalyst solution the presence of UV light
Fig 4. Absorption spectra of MB and NiO catalyst solution the presence of UV light
Fig 5. Photodegradation percent diagram of NiO under the UV and Visible light 6. Conclusion
In this paper, NiO nanoparticles were prepared by microwaves method for investigation the photocatalytic activity. XRD pattern and UV-Visible spectrum exhibit that NiO was prepared purely. So that, by comparing the photocatalytic activity of NiO nanostructures to degrade MB from water under the two lamps, it was found that nanostructures underwent Visible light degradation at very low levels of about 20%, while the Uv light could destroy methylene blue The duration of 80 minutes is about 90%. As a result, the Uv light is a good option in investigating the photocatalytic activity of NiO nanoparticles from methylene blue degradation from water.
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