UDC 678.01:544.77
New method polyol synthesis of nanoscale nickel under microwave
activation
Shishlova Y.K1.,Khrustalev D.P2.Naboko E.P1.
1 Karaganda
State Technical University, 100027, Karaganda, Mira B., No 56, undergraduate,
tel. +7 (7212)56-59-35, e-mail: [email protected]
2
Karagandy state medical university, 100027, Karaganda, Gogol street, 4, professor, tel. +7
(7212)51-34-79, e-mail: [email protected]
3 Karaganda State Technical University, 100027, Karaganda, Mira B., No 56 Cand.
Eng.,ass/professor, tel. +7 (7212)56-59-35, e-mail: [email protected]
Summary: Nanodimensional nickel is the demanded material which
found the application in the most various fields of science, technique, the
industry. The research falls into the fields of creation of a new way of receiving
nanodimensional nickel in the conditions of microwave activation. The
developed way of receiving nanodimensional nickel differs in the fact that all
processes of formation of nanodimensional nickel are carried out in the water
and glyceric environment, flow past in the conditions of microwave activation
and completely come to the end within 10-20 minutes.
Key words: nanotechnology, nanodimensional nickel, polyol synthesis,
microwave activation
Introduction
The methods of polyol synthesis differing diversity in the choice of the
particular reactants consist of strictly defined reagent groups solvent (typically
polyhydric alcohols), nanoparticle stabilizer (e.g., polyvinylpyrrolidone), heavy
metal acetate, acidity regulator (sodium hydroxide), a reducing agent (e.g.
hydrazine). In some methods, the formation of the nanoparticles is effected by
convection heating, and it takes two hours or more, in other under microwave
irradiation, and it takes about 10-15 minutes. It should be emphasized that in all
the examples media described authors solvent was either pure polyol
(ethyleneglycol [1], glycerin [2], propylene glycol [3], polyethylene glycol [4],
or a mixture of a polyhydric alcohol with a high boiling polar, aprotic solvent
(e.g. ethylene-dimethylformamide [5]).
The aim of the study is to develop a highly efficient technology for
synthesizing nano-sized nickel, meeting the requirements of "Green Chemistry"
concept.
Experimental part
1. Synthesis of nanoscale nickel in an aqueous medium the glycerol (2:1).
The multimode microwave reactor was placed Erlenmeyer flask containing 250
ml of 0.0375 g of nickel formate dissolved in a mixture of 5 ml of glycerol and
10 ml of water. Erlenmeyer flask connected to a high performance reflux. The
reaction mixture was irradiated for 15 minutes by microwave. Power 360 W
irradiation. The color of the solution changes from green to light gray. Test with
dimethylglyoxime does not give a positive response to the presence of ions Ni2+
[6]. A micrograph of the synthesized particles is shown in Figure 1.
2. Synthesis of nanoscale nickel in an aqueous glycerol medium (1:1). The
multimode microwave reactor was placed Erlenmeyer flask containing 250 ml
of a nickel formate 0.0375 g dissolved in 7.5 ml of glycerol, and 7.5 ml of water.
Erlenmeyer flask connected to a high performance reflux. The reaction mixture
was irradiated for 11 minutes by microwave. Power 600 W irradiation. The
color of the solution changes from green to dark gray. Test with
dimethylglyoxime does not give a positive response to the presence of ions Ni2+
[6]. A micrograph of the synthesized particles is shown in Figure 2.
3. Synthesis of nanoscale nickel in glycerol medium (control). The
multimode microwave reactor was placed Erlenmeyer flask containing 250 ml
of 0.0375 g of nickel formate dissolved in 15 ml of glycerol. Erlenmeyer flask
connected to a high performance reflux. The reaction mixture was irradiated for
10 minutes by microwave. Power 600 W irradiation. The color of the solution
changes from green to dark gray. Test with dimethylglyoxime does not give a
positive response to the presence of ions Ni2+ [6]. A micrograph of the
synthesized particles is shown in Figure 3.
Results and discussion
One of the most popular methods for producing nanosize particles and
heavy metals, particularly nickel, polyol synthesis is described in detail in the
books [7,8].
Regarding the mechanism of the polyol metal recovery of heavy metals
from their salts is no single opinion. It is believed that due to the air under the
influence of oxygen and heavy metal salts, hydroxyl groups oxidized to the
aldehyde, those in turn reduced to the free metal ions state, finally oxidizing the
aldehyde group to a carboxylic acid.
This means that the glycols and polyglycols in the synthesis of nanosized
metal particles and spent for reuse requires regeneration, that refers to
significant disadvantages of this method.
Common disadvantages polyol synthesis method of nanoparticles
necessary to include the use of 100% of the polyol, as a medium for the reaction.
Polyethylene glycol and polypropylene glycol, of course, very effective medium
for nanoscale nickel, but they are expensive and oxidized polyglycols before
reusing them to regenerate, which is very expensive.
Ethylene glycol is poisonous. Its use as a solvent and reactant is not
recommended because of the high toxicity and water solubility [9]. Propylene
glycol, owing to the good solubility in water, on the one hand and a high boiling
point on the other, can not be called environmentally friendly solvent [9]. Thus,
the existing methods for the synthesis of polyol violate paragraphs 2,5,7 concept
of "green chemistry", and the process of producing nano-sized nickel does not
meet the criteria of ecological purity. [10]
Objective research - the development of environmentally friendly, method
of obtaining nano nickel, by partial replacement of the polyol (in which he plays
both the role and the solvent and reagent) to a mixture of water and glycerol,
where the water will act as a solvent, and glycerol - reagent and cosolvent with
the functions of the particles of the stabilizer.
It should be noted that prolonged heating of the nickel formate aqueous
solution in conditions of both microwave and thermal heating by any change
does not, which eliminates nickel recovery by hydrothermal mechanism.
Nanoscale particles of nickel were successfully synthesized by reduction
of nickel formate in an aqueous-glycerol medium under microwave irradiation
for 10-20 minutes. The duration of reaction was determined by the concentration
of glycerol in the solution, which ranged from 25 to 50%. The glycerol
concentration was higher, the faster and more efficient process proceeded.
Glycerin in this process is a reducing agent and stabilizer cosolvent
nanoparticles.
The formation of nano-sized nickel from nickel formate is carried out in
the bath-type reactor.
Figures 1 and 2 show the nickel particles synthesized in an aqueous
glycerol mixture at a ratio (by volume) of water and glycerol 2: 1 and 1: 1.
Nickel particle sizes are in the range 293- 616 nanometers and up to and from
the first experiment and to 332-567 nanometers. To compare the efficiency of
the method we performed a restore of nickel formate in pure, not diluted with
water glycerin. Surprisingly, nickel recovery in pure glycerol occurs with the
same intensity as the 50% aqueous glycerol solution and is completed within 10
minutes. Nickel recovery in 33% strength glycerol solution flows 1.5 times
longer and completed in 15 minutes. When the volume ratio of water and
glycerol 3: 1 reduction process slow and inefficient, and further diluting glycerol
is not effective.
Figure 3 shows the result in the recovery of nickel formate glycerol
medium. As can be seen from the photomicrographs, the nickel particle size
greater than pure glycerine in water-glycerol mixtures.
Picture 1 - The shape and dimensions of the nickel particles, synthesized in
example 1 (raster scanning microscope TESCAN)
Figure 2 - The shape and dimensions of the nickel particles synthesized
under Example 2 (a raster scanning microscope TESCAN)
Figure 3 - The shape and dimensions of the nickel particles synthesized in
the conditions of Example 3 (a raster scanning microscope TESCAN)
Conclusion
1. It is found that for the synthesis of the polyol from a corresponding
nanoscale nickel formate under microwave activation instead of 100% glycerol
is possible with the same efficiency to use its aqueous solutions.
2. Recommended volumetric ratio of glycerol to water and the reaction of
the polyol reduction of nickel of 1: 1-2: 1.
3. The use of microwave activation reduces the time of synthesis of
nanosized nickel 4-8 hours to 10-20 minutes.
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