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SYNTHESIS AND STUDY OF PHOTODEGRADATION PROCESSES OF NANOSTRUCTURED MATERIALS BASED ON ELEMENTS OF AII BVI GROUP
Nurbolat SH.T.
undergraduate Assembayeva A.R. undergraduate Kadir M.F. undergraduate Yskak M.T. bachelor Kalkozova ZH.
Candidate of Physical and Mathematical Sciences Al-Farabi Kazakh National University, Almaty, Kazakhstan
ABSTRACT
TiO2 and ZnO powders were prepared by hydrothermal synthesis of nanostructured materials. Their photo-catalytic activity and structure were examined. There were also compared the photocatalytic properties of the synthesized nanopowders and ready. photodegradation rate was measured for the organic compound TiO2 and ZnO - dye Rhodamine B. It was confirmed that originally not transparent solution of Rhodamine B becomes transparent as a result of irradiation for 3 hours. These changes can be seen from the change in absorbance spectra of constructing through the irradiation solution of Rhodamine B with the addition of TiO2 and ZnO powders.
Keywords: hydrothermal synthesis, photocatalysis, photodegradation, ultraviolet irradiation, organic dyes, optical density.
Introduction
In our days, one of the most debated topics is the pollution of water and its cleaning path. The most important pollutants of freshwater are a variety of chemical dyes [1].
The heterogeneous photocatalysis used as a cheap technology of water purification from heavy metals and organic impurities and various dyes. Using sunlight and ultraviolet radiation makes photocatalysis technology cheap, environmentally friendly, and are allowed to be available for use worldwide. Photocatalysis has been successfully used in many developing countries during bleaching and freshwater disinfection [2-4]. Use of ZnO and TiO2 as a catalyst in FC processes does not require sophisticated equipment and it is advantageous for the settlements without electricity [3,4].
ZnO and TiO2 An Bvi compounds belonging to the group have unique properties. Such properties of TiO2
as above the high strength, high ability for redox reactions, price affordability promote its use as a catalyst [5-7].
Reduction of ZnO nano particle size to the appropriate area of excitons leads to the appearance of defects at the quantum level and thus changing its photophysical and photochemical properties. For this reason, zinc oxide is attributed to a number of particularly promising photocatalysts [8-10].
Experimental part:
Synthesis of ZnO and TiO2 particles
In the synthesis of ZnO nanopowders hydrothermal synthesis we used next reagents: copper nitrate hexahydrate (Zn (NO3) 2 • 6H2O) and methenamine (C6H12N4). After weighing the desired amount of the reactants are dissolved separately in a sealed container with a magnetic stirrer. After dissolution, they are heated at a temperature of 90°C
The scientific heritage No 9 (9),2017 for 2 hours in the water. After cooling, the solution was precipitated, rinsed 2-3 times in distilled water and dried in an oven preheated to a temperature of 100
°C. By this method by varying the concentration of the reactants and the amount of water nanopowders we obtain the following:
Table 1
characteristics of synthesized ZnO powders
№ Amount of zinc Amount of Amount of Synthesis time , Synthesis tem-
nitrate, М water, ml methenamine, М hour perature,°C
2 0,15 100 0,15 2
4 0,25 200 0,25 2 90
6 0,35 200 0,35 2
Results and discussion
The study of the structural properties of the synthesized powders
In the course of the structure of the synthesized samples was investigated. Also, the sizes of zinc oxide powder were examined by a scanning electron microscope (SEM).
c) d)
The structures of ZnO which synthesized at a) purchased ZnO ;
b) 0,15M (Zn(NOs)r6H2O) and ( CH1N4)/100ml water;
c) 0,25M(Zn(N03)2• 6H2O) and ( CH1N4)/200ml water;
d) 0,35M (Zn(N03)26H20) and ( C6Hi2N4)/200ml water concentrations Figure 1 -SEM pictures of purchased and synthesized by hydrothermal synthesis at 90°C ZnO powders
In an experiment it was shown that by adding the reactants in 0.1 M available minimum size of the powders, and that at lower concentrations of the
reagents a synthesized powders dimensions also decrease. And their photocatalytic activity increases with decreasing size of the powders.
The electron microscope pictures of synthesized titanium dioxide were made on a scanning electron
microscope microscope Company, USA, 2008).
Quanta 200i 3D (FEI
а) purchased TiO2 powder
b) synthesized TiO2 powder
Figure 2 - SEMpictures of purchased and synthesized TiO2powders
Research of photocatalytic activity of zinc oxide and titanium oxide
To study the photocatalytic activity of ZnO and TiO2 powder was used a solution-dye rhodamine B. Research of photocatalytic activity was carried out on the installation shown in the figure. For the experiment we use a certain amount of dissolved in water rhodamine B. To explore the spectrometer Perkin Elmer Lambda-35 optical density of rhodamine B should not raise 3.5. To achieve this we dissolved 0.016 g of Rhodamine B in 1 liter of distilled water. In
this case, a solution of 112.5 ml was enough to complete the filling of dishes. This solution was poured into glassware, introducing top veiled xenon lamp quartz tube. Glassware with the solution is placed on a magnetic stirrer. The light comes on, and the solution is irradiated for a certain time. Every 10 minutes we take a solution of the sample in the dishes. The sample is poured into a quartz optical cell and we record its spectrum absorbance at Perkin Elmer Lambda-35 spectrometer. The spectra obtained are shown in the figure below.
Figure 3 - The change in optical density range of Rhodamine B as a function of exposure time
Conclusion
Was created an installation of the photodegradation processes of organic compounds, as well as during the operation were used research materials for installing the photocatalytic activity, also we used reactor for carrying out a hydrothermal synthesis at high pressure and temperature. Photodegradation rate was investigated TiO2 and ZnO on an example of an organic compound - Rhodamine B. It has been shown that the opaque solution by adding an organic dye Rhodamine B becomes clear after about 3 hours of exposure. These changes can be
seen from the absorbance spectrum changes depending on the irradiation time Rhodamine B solution with the addition of ZnO and TiO2 powders.
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