American Journal of Anal yt ical Chemistry, 2011, 2, 206-211
doi:10.4236/ajac.2011.22024 Published Online May 2011 (http://www.SciRP.org/journal/ajac)
A Comparative Investigation of Lead Sulfate and Lead
Oxide Sulfate Study of Morphology and Thermal
Decomposition
Seyed Ali Akbar Sajadi
Sharif University of Technology, Institute of Water & Energy, Tehran, Iran
Received November 30, 2010; revised March 3, 2011; accepted March 20, 2011
Abstract
The compound lead oxide sulfate PbSO4.PbO was prepared in our laboratory. The Thermal behavior of
PbSO4 was studied using techniques of Thermogravimetry under air atmosphere from 25 to 1200˚C. The
identity of both compounds was confirmed by XRD technique. Results obtained using both techniques sup-
port same decomposition stages for this compound. The electron microscopic investigations are made by
SEM and TEM. The compound is characterized by XRD and the purity was determined by analytical Meth-
ods. Also a series of thermogravimetric analysis is made and the ideal condition is determined to convert this
compound to pure lead oxide.
Keywords: Lead Oxide Sulfate, Lead Sulfate, XRD, Thermal Analysis, Thermogravimetry, TGA
1. Introduction
Lead compounds are used in different industries world-
wide due to their chemical and physical characteristics
[1-6]. One of the most important characteristics of the
lead is its reactions with acids and bases as well as with
air, which are well-known as oxidation. In consequence
of these kinds of reactions compounds like “lead (II)
oxide, lead (IV) oxide, sulfate, lead carbonate, lead ni-
trate as well as alkaline lead acetate” have been produced.
Some are the end product of a desired process but most
of them are undesired byproducts and are known as dis-
turb compounds [8,9].
Lead (IV) oxide is one of the most important com-
pounds used in lead-acid batteries, which are produced
daily all over the world [5,7].
The goal of this work was to investigate the morphol-
ogy and crystal size of PbSO4. PbO and study of thermal
properties of lead sulfate in different temperature condi-
tions. Pure lead (II) oxide has been reported to be the
final product of thermal decomposition process of num-
ber of different lead compounds [10-12]. The Morphol-
ogy of these compounds was also reported [13-15].
2. Experimental
2.1. Materials and Equipment
Lead oxide sulfate was prepared in this laboratory as
described in this paper. Alkaline lead (II) acetate pur-
chased from Fluka (Art. No.: 15317). H2NSO3H amido
sulfonic acid purchased from Merck (Art. No.: 10010
30250).
TGA: Thermogravimeter, Mettler TG50, coupled with
a TA processor.
XRD: X-Ray diffractometer D 5000, Siemens, Kristal-
loflex.
SEM: scanning electron microscope SEM (REM-
JEOL-JSM-840).
TEM: transmission electron microscope (EM-Hitachi,
H-600).
2.2. Preparation of Lead Oxide Sulfate
PbSO4·PbO
2.0284 g alkaline lead (II) acetate was added to 10 ml
H2NSO3H solution (0.3236 g solved in H2O). It was
produced a clear solution. This solution was transferred

S. A. A. SAJADI207
in a quartz ampoule. The ampoule was then sealed care-
fully. This was heated in a sealed tube furnace at 130 for
about 20 hours and then 4 hours at 140. The ampoule
was cooled to room temperature. From solution is formed
needle-shaped crystals (about 0.5 mm long). To clean the
product it was filtered and several times washed with
water and alcohol. Afterwards was dried in a desiccator
over silica gel at 25˚C.
2.3. X-Ray Diffraction of PbSO4 and Lead Oxide
Sulfate PbSO4
.PbO
The lead oxide sulfate sample was prepared for X-ray
using Bedacryl and exposed with CuKα1 radiation for
two hours. Figure 1 shows the XRD diagram of the com-
pound PbSO4.PbO.
2.4. Electron Micrographs Investigations of
PbSO4 and PbSO4
.PbO
The morphologic investigations of lead oxide sulfate and
lead sulfate that is the goal of this work, were accom-
plished by an electron microscope SEM(REM-JEOL-
JSM-840). The preparation of the samples consisted of
coating of the surface with gold steam during 2 to 4 min-
utes (Figures 3 and 4).
The second series of electron microscopic investiga-
tion with TEM equipment were accomplished (EM-Hi-
tachi, H-600). The sample was prepared as follows. The
white powdery sample was coated first with a thin coal
film. This film was then treated with HF acid from the
surface and investigated in the TEM equipment. The
applied enlargement was 20000× (Figure 5).
2.5. TGA Analysis of Lead Sulfate PbSO4
8.197 mg of PbSO4 were weighted in a standard con-
tainer from corundum. This sample was heated (5˚C/min)
from 25 to 1200˚C under air atmosphere (15 ml/min)
(Figure 6).
3. Results and Discussion
3.1. X-Ray Diffraction of PbSO4 and Lead Oxide
Sulfate PbSO4
.PbO
The both Figures 1 & 2 show the experimental XRD
results of both above mentioned compounds. These re-
sults correspond to standard diagrams (ASTM: 36-1461
and 33-1486).
3.2. Electron Micrographs Investigations of
PbSO4 and PbSO4
.PbO
As indicated from Figure 3, crystals are round and hex-
agonal with a diameter of 1 to 10 µm, the reasonable
enlargement in SEM photographs was 3000 times. They
are arranged well next to each other and form large
round crystals. Figure 4 shows the SEM photographs of
PbSO4.PbO. As we can see large crystals was formed in
the form of long and laminar texture. These crystals have
a length of ca. 300 µm and a diameter of about 20 µm.
The reasonable enlargement in SEM photographs was 200
times. In addition to the large crystals can be seen even
small crystals, which have a diameter of about 5 µm.
Figure 5 shows TEM photographs of PbSO4.PbO. The
crystals are somewhat larger, they form also small
Figure 1. XRD diagram of PbSO4.

S. A. A. SAJADI 208
Figure 2. XRD diagram of PbSO4
.PbO.
Figure 3. SEM electron microscopic photograph of lead sulfate, enlargement is 3000×.
crystals. Individual particles look angular and hexagonal
and can be observed in small and larg of dimensions.
Apart from brocken crystals they are mainly arranged
crystals. The reasonable enlargement in TEM photo-
graphs was 20,000 times.
3.3. Thermal Investigations of Lead Sulfate
PbSO4
TGA-results:
TGA curve of thermal dcomposition of PbSO4 is e

S. A. A. SAJADI209
Figure 4. SEM electron microscopic photograph of PbSO4
.PbO, enlargement is 200×.
Figure 5. TEM electron microscopic photograph of PbSO4
.PbO, enlargement is 20000×.

S. A. A. SAJADI 210
shown in Figure 6. The curve shows the weight loss
(vertical axis) versus increase in temperature (horizontal
axis).
The results indicate thermal decomposition consists of
two subsequent stages in the temperature range of 880˚C
- 1200˚C and summarized in Table 1.
The first stage takes place between 886˚C - 1142˚C.
The regarding calculations of weight loss are reported.
The computed stoichiometry of decomposition prod-
ucts are in good agreement with experimental results
(quantitative and percent decrease in weight).
1) First & second points o TGA curve (25˚C - 886˚C)
A heating rate of 5˚C/min was chosen to determine the
real value of adsorbed quantity of water as well as find-
ing out more information on what is taking place in this
temperature range. The experiment was accomplished in
the air atmosphere with a constant gas flow of 15
ml/min.
In these two temperatures range i.e., points 1 & 2 we
consider no significant weight decrease. In other words it
takes place no reaction.
2) Third & fourth points of TGA curve (886˚C - 1200˚C)
In the temperature range of 886˚C - 1142˚C we con-
sider weight loss equal to about 89.19% starting material
and occur in the temperature range of 886 - 1142˚C. The
X-ray analysis of the product confirms presence of α- &
β-PbO. This was checked by spectrometric analysis and
the calculated brutto formula of PbO is reached.
We want to point out again that the pyrolysis of PbSO4
within the range 886˚C - 1142˚C in the air atmosphere
led to PbO, i.e. the reaction PbSO4 → PbO ran off com-
pletely with approximately 1100˚C. From the above TG
diagram it is evident that the pyrolysis reaction of PbSO4
in the range 886˚C - 1142˚C consists of two stages. The
final decomposition product is PbO.
Therefore, study of thermal Behavior of PbSO4, by
Thermogravimetry suggests four different stages as dis-
cussed above. At first the compound losses SO3 followed
Figure 6. TGA diagram of lead sulfate (PbSO4).
Table 1. Results from the thermal investigations of α-PbO2 in temperature range 25˚C - 1200˚C in air atmosphere.
Point No. Start temp.
[˚C]
End temp.
[˚C]
Weight decrease
[mg]
Weight decrease
[%]
1 25.0 240.7 ~0 ~0
2 25.0 886.7 ~0 ~0
3 25.0 1142.4 7.311 89.19
4 25.0 1199.6 7.539 91.97

S. A. A. SAJADI 211
by evaporation of PbO in the approximately temperature
range of 1100˚C to 1200˚C. We are not able to consider
these two phenomenons separately because these two
reactions overlap each other.
4. Conclusions
It was clearly stated that the final product consists only
of α- and β-PbO, which was a good result. The chemical
analysis showed no impurities. The thermal investiga-
tions of PbSO4 by TG method showed that under air at-
mosphere the compound decomposes to α- and β-PbO.
Since PbO does not contain impurities, one can reuse in
the industry. Lead sulfate can be converted to PbO in
industry which is an economical procedure.
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