preparation of nano-tio2 in inverse microemulsion system with tioso4 as raw material
TRANSCRIPT
Preparation of Nano-TiO2 in inverse Microemulsion system
with TiOSO4 as raw material
Xingxin JIA 1,a, Wenyuan GAO 1,2,b , Meihong Niu 3,c 1.Department of Material Science and Engineering,Dalian Polytechnic University, Dalian 116034,
China
2. Liaoning Province Key Laboratory of Advanced Material and Material Modification, Dalian 116034,
China
3.Department of Environmental and Light Chemical Engineering,Dalian Polytechnic University,
Dalian 116034, China
Keywords: microemulsions; nano meter; titanium dioxide; anatase.
Abstract. The nanosized TiO2 was prepared by microemulsion process in the system of
cyclohexane/[Span80 combine with Tween40]/water with TiOSO4 as raw material. The synthesis
process of the powder was investigated by differential thermal analysis (DTA), X-ray diffraction
(XRD) and laser particle size analysis (LPSA). The results showes that TiO2 with the average size of
19.5nm and narrow size distribution was prepared under these conditions of Span80 of 8g and
Tween40 of 2g as the emulsifier, water/oil mass ratio of 1/4, amount of TiOSO4 of 10mL with the
consistency of 0.8mol/L, calcination temperature of 480 ˚C for 20min.
Introduction
Nano TiO2 has been widely used in solar cells, waste water treatment, cosmetics and paints and
various other areas because of its good corrosion resistance, chemical stability, high photocatalytic
activity, high whiteness and advantages such as cheap, non-toxic, no second pollution [1]. Preparation
of anatase nano TiO2 with the better performance of photocatalytic degradation[2] has become the
focus of the research due to the urgency of the problems of sewage treatment. Therefore, it has been
pursued the main objective to obtain high-performance anatase nano TiO2 from cheap raw materials
and simple preparation methods in recent years.
In this work, nano TiO2 with small particle size and narrow particle size distribution was
prepared in micro-emulsion composed of cyclohexane/ [Span 80 combined with Tween40]/water, the
non-ionic surfactant synergistic effect of Span80 and Tween40[3] which could increase the stability
of emulsion was made full use of. As the raw material of reaction, TiOSO4 was non-toxic and cheap
[4]. Surfactants, Span80 and Tween40 were food additives, as solvent, cyclohexane could be
recycled. The preparation method had the advantages of safe, low toxicity, pollution-free, simple
process and gentle reactionconditions.
Experiment
Reagents. Titanyl sulfate and cyclohexane used in the experiment both were AR, surfactants such as
Span80 and Tween40 were industrial supplies, laboratory water was deionized water.
Preparation of nano-titanium dioxide powder. Span80 and Tween40 were added into 50g
cyclohexane, mixed them evenly for 30min. Then divided the mixture into two copies of the same
volume, 10mL ammonia of 3 mol/L was added in one par, made of the stable emulsion A; Another
was added to 10mL TiOSO4 solution, mixing evenly, obtained emulsion B. Under the condition of
strongly mixing, emulsion A was added to emulsion B by 3mL/min by drops, stirring for 1h, the white
translucent emulsion was obtained.
Applied Mechanics and Materials Vols. 174-177 (2012) pp 747-750Online available since 2012/May/14 at www.scientific.net© (2012) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMM.174-177.747
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Precipitation was obtained by centrifuging it for 15min with a centrifugal speed of 4500r/min.
The precipitate was washed in deionized water for three times and then dried for 2h under 60˚C.
Grounded it to powder, put it into muffle furnace and calcined it, then the product was obtained.
Characterization. Calcination temperature system for preparation of anatase nano TiO2 was
determined by DTA. Crystalline form was examined by XRD. The particle size and distribution were
determined by LPSA.
Results and Discussion
Determination of the mass ratio of surfactants and calcination temperature.
The choice of surfactants. The particle size of TiO2 was directly impacted by the stability of the
emulsion system[5], while the surfactant was the key to stable emulsion. Mixture of Span80 and
Tween40 was used as the surfactant by calculating the surfactant hydrophilic-lipophilic balance
(HLB) value, based on the synergies of surfactants [6]. The micellar sizes in the emulsion as mass
ratios of Span80: Tween40 of 9:1, 8:2 and 7:3 were examined while other factors remain unchanged.
Results were shown in Table1.
The average particle size of micelles was small, but the distribution was wide when the ratio was
9:1. The reason was that lack of the amount of Tween40, whose hydrophilic was better, resulting in
the water core coated not solid. When it was 7:3,average particle size of micellar was large and
distribution was wide, due to inadequate amount of the Span80 with better lipophilic, resulting in
surfactant water nuclear was not formed completely covered. So, the best ratio was 8:2.
Table 1 Micella sizes with different mixture ratios of Span80 and Tween40
m(Span80):m(Tween40 9:1 8:2 7:3
average particle size[nm] 14.8 17.6 90.2
particle size distribution[nm] 5~200 15~30 55~300
Determination of calcination temperature. TiO2 precursor was prepared under the conditions
of mixture of Span80 and Tween40 of 10g with the mass ratio of 8:2, TiOSO4 of 10mL with the
concentration of 0.8mol/L, ammonia of 10mL with the concentration of 3mol/L. It was examined by
DTA after dried, and the result was shown in Figure1. There was an endothermic peak at 135˚C ,
which resulted from the demyelination of free water, bound water and residual organic solvent
evaporation. There was a wide exothermic peak at 296˚C , which was caused by degradation of
residual solvents and surfactants organic matter. There was a sharp and large exothermic peak at
474˚C , and no obvious peak appeared behind it, showed that the crystal of TiO2 changed from
amorphous to anatase at 474˚C .
0 200 400 600 800 1000-50
0
50
100
150
200474℃
296℃DT
A
Temperature/℃
135℃
10 20 30 40 50 60 70
0
100
200
300
400
500
600
700
CP
S
2θ/°
Figure 1 Differential thermal curve of Titania precursor Figuer 2 X ray diffraction pattern
of TiO2 at 480˚C
748 Advanced Building Materials and Sustainable Architecture
Figure2 was contrasted with card 40-477 of the standard pattern library, there was the most
obvious diffraction peak at 25.36°, which should be attributed to the diffraction plane of (101) of
anatase TiO2, and the conclusion that the crystal formation of TiO2 was gotten.
Influence of the amount of surfactant on the particle size. The stability of emulsion, micellar
water pool sizes, which affect the particle size of titanium dioxide both were influenced directly by
the amount of surfactant [7]. The particle sizes of anatase nano TiO2 samples prepared with surfactant
of 5g, 10g and 15g while other parameters remain unchanged, the results as a, b, and c were shown in
Figure3.
When the surfactant amount was 5g, such as “a”, the particle size distribution was wider, and the
average particle size was larger. When it was 10g shown in “b”, nano TiO2 with narrow distribution
and average particle size of 19.5nm was prepared. When the surfactant amount increased to 15g,
although part of particles with smaller size generated, but the reunion of particles generated, and the
production was reduced. The reasons, insufficient amounts of surfactant resulted in water nuclear
particle size too large, then particle size of titania generated in water nuclear was large; the exchange
of components between nano-droplets was inhibited by the superfluous surfactant, and the results that
emulsion was too stable and not conducive to the formation of precipitation was caused in, while the
powders were easy to reunite when the emulsion coat washed away. Thus the optimal amount of
surface could be determined to be 10g.
a b c
Figure 3 Particle size distributions of TiO2 by different amounts of surfactant
Influence of mass ratio of water /oil on the particle size. Water/oil mass ratio directly affect the
stability of emulsion and water nuclear size [7]. Four different ratios of water/oil obtained by
changing the dosage of cyclohexane while water was 20g were tested: 1/2, 1/3, 1/4 and 1/5. The
results were shown in Table2. Emulsion was opaque when the mass ratio was large, which was
caused from the inadequate of oil phase, inadequate water nuclear dispersion and the reunion of
precipitation. Emulsion gradually became translucent after the mass ratiowas smaller than 1/4, but the
particle size changed little. But too small mass ratio would reduce the yield. So, the optimal mass ratio
of water/oil should to be 1/4 taking both the factors of preparation of powders with smaller sizes and
thrift of cyclohexane into consideration.
Table 2 The impact of water / oil ratios on the products
mass ratio of water /
oil
average particle size of
TiO /nm
emulsion
appearance 1/2 221.8 opaque
1/3 75.5 opaque
1/4 20.2 translucent
1/5 19.6 translucent
Influence of concentration of titanyl sulfate solution on particle size. Reactant concentration
had a direct impact on the particle size and the distribution. Particle sizes of titanium dioxide prepared
with five TiOSO4 concentrations were discussed in the work: 0.4mol/L, 0.6mol/L, 0.8mol/L,
1.0mol/L and 1.2mol/L. Trend of the average particle size was shown in Figure4.
Size distribution(s)
5 10 50 100 5001000 5000Diameter (nm)
10
20
% in c
las
s
Size distribution(s)
5 10 50100 5001000 5000Diameter (nm)
20
40
60
80
% in c
lass
Size distribution(s)
5 10 50100 5001000 5000Diameter (nm)
5
10
% in c
las
s
Applied Mechanics and Materials Vols. 174-177 749
0.4 0.6 0.8 1.0 1.20
20
40
60
80
100
120
140
160
Th
e av
erag
e par
ticl
e si
ze o
f T
iO2/n
m
The concentration of titanyl sulfate/mol*L-1
Figure 4 Particle Distributions with the different concentrations of reactant
When the TiOSO4 concentration was less than 0.8mol/L, the average particle size increased with
the increase of the concentration of TiOSO4, but changed little; the particle size increased rapidly with
the increase of the concentration of TiOSO4 while it was larger than 0.8mol/L. The reason was that the
reaction rate was too fast when the concentration of TiOSO4 e was too large, which led to particle
agglomeration. So, the titanyl sulfate concentration was determined to be 0.8 mol / L.
Conclusions
Several factors of the microemulsion system affecting the size distribution of TiO2 were discussed:
the amount of surfactant, mass ratio of water/oil, reactant concentration and calcination parameters.
Concluded that: precipitation of TiO2 precursor prepared under the conditions of mixture of Span80
and Tween40 with the mass ratio of 8:2 of 10g, mass ratio of water/oil of 1/4, TiOSO4 solution of
0.8mol/L of 10mL, and anatase nano TiO2 with average particle size of 19.5nm could be obtained by
calcining the precipitation of TiO2 precursor at 480˚C for 20min.
Acknowledgements
The authors gratefully thank Bureau of Municipal and Rural Construction of Dalian and The Key
Laboratory program of Liaoning Province institution of higher education (LS2010009) for the
financial supports
References
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[3] F.A.Deorsola,D.Vallauri: Powder Technology. Vol. 190(2009), p. 304.
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