Advances in Chemical Engineering and Science, 2011, 1, 20-25
doi:10.4236/aces.2011.11004 Published Online January 2011 (http://www.SciRP.org/journal/aces)
Hydrothermal Synthesis and Characterization of a Novel
Zirconium Oxide and Its Application as an Ion Exchanger
Mamdouh M. Abou-Mesalam
Chemistry Department, Faculty of Science, Al-Baha University, Kingdom Saudi Arabia
Nuclear Fuel Technology Department, Hot Labs. Centre, At omic Energy Authority, Cairo, Egypt
Received December 25, 2010; revised January 10, 2011; accepted J a nu ary 15, 2011
Abstract
A novel hydrothermal zirconium oxide (ZrO2) ion exchange material was successfully synthesized by
hydrothermal technique. The material has been characterized using different tools such as thermal analysis
(DTA-TGA), FT-IR and X-ray diffraction studies. The results show that the prepared ZrO2 is pure and with a
unique shape and it belongs to the hexagonal system. Chemical resistively of the material for various media
such as, water, acids and bases have been assessed. The capacity of ZrO2 ion exchanger for Na+, Cu2+, Ni2+
and Zn2+ ions at natural pH has been determined. The effect of heating treatment for ZrO2 on ion exchange
capacity was studied. The sorption/ion exchange behaviour of Cu2+, Ni2+ and Zn2+ ions towards ZrO2 in dif-
ferent pH media has been investigated. The distribution coefficients and separation factors were determined.
Finally, Freundlich isotherms for Cu2+, Zn2+ and Ni2+ ions on hydrothermal ZrO2 ion exchanger were inves-
tigated and the Freundlich isotherm constants were conduced.
Keywords: Hydrothermal Synthesis, Zirconium Oxide, Ion Exchanger
1. Introduction
The methods for the synthesis of metal oxide ion ex-
change material mainly include chemical deposition,
sol-gel process, chemical vapor decomposition, gas-
phase reaction and hydrothermal synthesis. Among these
methods, hydrothermal method is a promising method
for synthesizing ideal CdO material with special mor-
phology via a simple, fast, low cost, low temperature,
high yield and scalable process [1]. Additional, high-
crystallized powders with narrow grain size-distribution
and high purity without heat treatment at high tempera-
ture are the advantages of hydrothermal technique [2-5].
Literature show many publications [6-9] on metal oxide
ion exchangers such as ZnO and TiO2 that have been
used extensively as photocatalyst due to their high
photocatalytic activity, non-toxic nature, inexpensive,
excellent chemical and mechanical stability. ZnO can be
also a suitable alternative to TiO2 because it is lower cost
and has the similar band gap energy around 3.2 eV. In
addition, ZnO shows better performance compared to
TiO2 in the degradation of several organic contaminants
in both acidic and basic medium, which has stimulated
many researchers to further explore the properties of
ZnO in many photocatalytic reactions [6-8]. As we know,
the shape, crystalline structure, and size of semiconduc-
tors are important elements in determining their physical
and chemical properties [9]. On the other hand, recent
literature indicates few works carried out on ZrO2 as ion
exchange materials. Additional, inorganic ion exchange
materials have found extensive applications in analytical
and industrial chemistry and played a vital role in the
treatment of environmental pollutants. Ion exchange ma-
terials with higher selectivities are continuously being
investigated [1 0,11].
Hopefully, the results of this work might provide a
promising data for the synthesis and characterization of
ZrO2 as inorganic ion exchange material and its applica-
tions for the removal of some toxic elements from haz-
ardous wastewater.
2. Experimental
2.1. Hydrothermal Preparation of ZrO2 Ion
Exchanger
Zirconium oxide (ZrO2) inorganic ion exchange material
was synthesized hydrothermally by the reaction of

M. M. A. Mesala m 21
equi-concentrations (5%) solutions of zirconium oxy-
chloride (ZrOCl2) and NH4OH with volumetric ration 2:1
under magnetic stirring. After mixing, the reaction mix-
ture was further stirred for 60 min under constant stirring
rate at room temperature to ensure all of the reagents
react completely. Subsequently, the mixture was trans-
ferred to a Teflon-lined stainless steel autoclave which
were sealed and maintained at 130  1˚C for 24 h, and
then it was natural cooled at room temperature. After
hydrothermal reaction, the resulting solid products were
filtered and washed with deionized water for several
times in order to remove Cl- ions. Finally, the solid ZrO2
ion exchanger was dried in drying oven at 70  1˚C for
overnight, and then ground, sieved and stored at room
temperature.
2.2. Characterization of Prepared ZrO2 Ion
Exchanger
FTIR spectrum of ZrO2 ion exchange material was car-
ried out using FTIR Spectrometer; BOMEN, MB-series
and the measurements were carried out using KBr disc
method technique. X-ray diffraction pattern of ZrO2 ion
exchange material was carried out using SHIMADZO
X-ray diffractometer, XD-D1, with a nickel filter and a
Cu-K radiation. Differential thermal and Thermogra-
vimetric analyses for ZrO2 was carried out using a
SHIMADZU (DTA-TG) thermal analyzer obtained from
Shimadzu Kyoto “Japan”. The sample was measured for
ambient temperature up to 850˚C with heating rate of 5
deg./min. The surface area values of ZrO2 were meas-
ured using BET-technique as an adsorption phenomenon
of nitrogen gas on the powder surface at 77 K.
2.3. Chemical Resistively of ZrO2 Ion Exchanger
The chemical resistively of the ZrO2 in various media
H2O, HNO3, HCl, NaOH and KOH was studied by tak-
ing 0.5 mg of sample in 50 ml of the particular medium
and allowing it to stand for 24 h. The percent of solubil-
ity was calculated and summarized in Table 1.
2.4. Sorption Studies:
Capacity of ZrO2 for Na+, Cu2+, Ni2+ and
Zn2+ Ions:
The capacity of ZrO2 ion exchanger for Na+, Cu2+, Ni2+
and Zn2+ ions (in nitrate from) was carried out by equi-
librium batch technique. 0.1 g of ion exchanger was
equilibrated with 10 ml of 50 ppm of Na+, Cu2+, Ni2+ and
Zn2+ ion solutions (natural pH) in a shaker thermostat at
25  1˚C. The capacity value was calculated by the fol-
lowing formula;
%Vm.mmol g
100 o
Uptake
Capacity C (1)
where % uptake is the percent uptake of metal ions equal




100
ofo
CCC , and Co, Cf is the initial and final
concentration of the ions in solution, V is the solution
volume and m is the sorbent mass.
The effect of heating temperature treatment of ion ex-
changer on ion exchange capacity of ZrO2 ion exchanger
for Na+, Cu2+, Ni2+ and Zn2+ ions was studied by pre-
treatment of 1 g portion of the material at different heat-
ing temperature for 4 h at temperatures between 50˚C
and 600˚C in a muffle furnace. Then the capacity was
carried out as described previously.
2.5. Effect of pH Medium on Sorption Behaviour
of ZrO2 Ion Exchanger:
Effect of pH medium on the sorption behaviour of vari-
ous metal ions Cu2+, Ni2+ and Zn2+ (in nitrate from) on
ZrO2 ion exchanger was investigated. A series of metal
solutions was prepared with concentrations equal 50 ppm
at different pH adjusted using nitric acid from pH (1) to
(5). The experiment was carried out by equilibration of
0.1 g of ion exchanger with 10 ml of metal ion solution.
The mixture shaken for 3 h in shaker thermostat at 25 
1˚C. Then the solutions were separated and the metal ion
concentrations were determined using the supernatant
liquid by atomic absorption spectrometer. The sorption
percent, distribution coefficients and separation factors
were determined using the following expressio ns;
100
oe
o
CC
Sorption PercentC


(2)

oe
de
CC
Distribution coefficient KVmmlg
C

 (3)
 

Ad
Bd
K
B
Separ ati on factor a
K
A
 (4)
Where;
Kd(A) is the distribution coefficient of (A) ion,
Kd(B) is the distribution coefficient of (B) ion,
Co is the initial concentration of metal ion,
Ce is the final concentration of metal ion,
V is the solution volume,
m is the mass of ion exchanger.
2.6. Sorption Isotherm
For adsorption iso therms for Cu2+, Ni2+ and Zn2+ ions on
ZrO2 ion exchanger were investigated, 10 ml metal ion
solution of different metal ion concentrations varied from
2  10-2 M to 5  10-4 M were equilibrated for a sp ecific

M. M. A. Mesala m 22
period of time (3 h) with 0.1 g of exchanger. After 3 h
(time sufficient to attain equilibrium) the supernatant
liquid was removed immediately and the metal ion con-
centration evaluated by atomic absorption spectrometer.
The experiments were carried out in shaker thermostat at
25  1˚C. The equilibrium concentration (Ceq.) and amount
uptake (W) were calculated in mmol/g as follows;
o
WUptake CVmmmolg (5)

1o Uptake C 
eq
C (6)
Plot of C against C/W and/or log Ceq. against log W/m
were performed to obtain the required isotherm.
3. Results and Discussions
Chemical resistively of ZrO2 ion exchange material was
checked in different media such as H2O, HNO3, HCl,
NaOH and KOH. The data represented in Table 1 indi-
cated that ZrO2 is very stable in water and stable in acid
medium, maximum tolerable limits being 2 N HNO3 and
2 N HCl, and it is not stable in base medium, maximum
tolerable limits being 1 N NaOH and 0.5 N KOH. This
means that ZnO2 ion exchange material is chemically
stable in acid medium and hence can be used for analyti-
cally import ant separat i ons.
The FTIR adsorption analysis of the synthesized ZrO2
ion exchanger is represented in Figure 1. Figure 1
shows a broad transmittance peak in the range of
3600-2500 and ~1640 cm-1, which could be assigned to
the stretching and the bending modes of water molecules
adsorbed on ZrO2 sample [12,13]. The transmittance
peak in the range of 500-45 0 cm-1 may be related to Zr-O
bond [12,13].
X-ray diffraction pattern of ZrO2 ion exchang er is rep-
resented in Figure 2. This figure manifested that the syn-
thesized ZrO2 had a crystalline structure and the ma-
Table 1. Chemical resistively of ZrO2 ion exchange material
for H2O, acid and base media at 25  1˚C (standard error
0.01 %).
Me-
dium
Concen-
tration,
M
%
Solu-
bility Medium Concen-
tration,
M
%
Solu-
bility
H2O -- -- 0.1 --
0.1 0.12 0.5 0.25
0.5 0.19 1.0 1.52
1.0 0.25 2.0 3.50
2.0 1.70 4.0 5.40
4.0 2.50
NaOH
6.0 25.25
HNO3
6.0 13.0 0.1 0.15
0.1 -- 0.5 2.5
0.5 0.12 1.0 15.52
1.0 0.22 2.0 18.50
2.0 1.20 4.0 20.23
4.0 2.80
KOH
6.0 26.22
HCl
6.0 4.90
Figure 1. Infrared spectrum of ZrO2 ion ex chang er at 25  1˚C.
Figure 2. X-ray diffraction pattern of ZrO2 ion exchanger
at 25  1˚C.
terial is present in one phase Figure 2. According to
Joint Committee for Powder Standard Diffraction
(JCPSD) the peaks well matched with these peaks of the
hexagonal cards that means ZrO2 was belong to hexago-
nal system.
Differential thermal and Thermogravimetric analyses
for ZrO2 is represented in Figure 3. Figure 3 indicated
two endothermic peaks at 92 and 380˚C that may be re-
lated to dehydration of free water and interstitial water,
respectively. From TG curve we found that the weight
firstly is high related to loss of water, then there are
gradually stable in the curve during the heating process.
These data confirm the thermal stability of ZrO2 com-
pared to other organic and inorganic ion exchanger. Also,
these data indicates the suitability of application of ZrO2
at higher temperatures.
The surface area value of ZrO2 was found to be 33.44
m2/g as determined by the BET adsorption of nitrogen
gas.
Preliminary studies for the time required for equilib-
rium of the studied cations on ZrO2 ion exchange mate-
rial was carried out and the results indicated the equilib-
rium was attained within 3 h.
Wavenumber (cm-1)

M. M. A. Mesala m 23
Figure 3. DTA and TG curves for ZrO2 ion exchanger.
The capacity of ZrO2 ion exchanger for Na+, Cu2+,
Ni2+ and Zn2+ ions was carried out by equilibrium batch
technique and the data was represented in Table 2. The
data in Table 2 shows that the selectivity sequence of
ZrO2 for the studied cations was fond to Na+  Cu2+ 
Zn2+  Ni2+. This sequence may be due to the generally
stronger electrostatic interactions of divalent cations
compared to mono valent ones. Also, this sequence is
parallel to the order of ionic radii and stated that the
studied cations are absorded in hydrated state [14].
The effect of heating temperature of ion exchanger on
ion exchange capacity was studied and the data repre-
sented in Table 2. The data indicated that as the heating
temperature of ZrO2 increased the capacity for Na+, Cu2+,
Ni2+ and Zn2+ ions decreased. This may be due to as the
heating temperature increased the loss of water content
of ZrO2 are increased as shown in DTA-TG curves
(Figure 3). This behaviour can be interpreted by the
heating effect. Since, in the early stage of the heating
only water molecules present in the cavity of the ex-
changer will be lost (cavity water), and by increasing the
heating temperature the water molecules present in the
structure will be lost during condensation (condensation
water) leading to shrinkage in the cavity and channels of
the exchanger at higher temperatures [14]. This shrink-
age in the structure leads to some strike difficulties and
decrease in the number of exchangeable active sites of
the exchanger.
Effect of pH on the sorption behaviour of various
metal ions Cu2+, Ni2+ and Zn2+ (in nitrate form) on ZrO2
ion exchanger was carried out at different pH and the
data are represented in Figure 4. The data indicated that
the sorption percent of Cu2+, Ni2+ and Zn2+ ions on ZrO2
are increased with increasing the pH of the medium.
The Kd values of Cu2+, Ni2+ and Zn2+ on ZrO2 ion ex-
changer as a f Figure 5. Non-linear relations between log
Kd and pH was observed.
When the simple ion exchange proceeds by the fol-
lowing reaction unction of pH of solution are represented
in
Table 2. Capacity of ZrO2 for Na+, Cu2+, Ni2+ and Zn2+ ions
at Natural pH , V/m = 100 ml/g and t = 25  1˚C.
Capacity, mmol/g
Cation At 50˚CAt 200˚C At 400˚C At 600˚C
Na+ 1.49 1.22 1.1 0.95
Cu2+ 1.33 1.30 1.15 1.03
Ni2+ 0.80 0.74 0.69 0.55
Zn2+ 0.95 0.88 0.80 0.65
12345
2
3
4
5
6
7
8
9
10
11
Cu2+
Zn2+
Ni2+
Figure 4. Effect of pH of the medium on the sorption per-
cent of Cu2+, Zn2+ and Ni2+ ions on ZrO2 ion exchanger at
25  1˚C.
nn
nH MMnH


 (7)
in sufficiently diluted solution, where activity coeffi-
cient may be neglected, the selectivity coefficient can be
defined by the following equation [15];
n
n
MHnn
MH
KHM










(8)
where n
M




 and H




 denote to the concentrations
of n
M

and
H

ions in the exchanger, respectively,
and n M




 and H




 are their concentrations in
solution. Since the Kd value is the ratio between the
metal ion concentration in the exchanger an d in the solu-
tion, then n
MHd n
H
KK
H






(9)
Or n
MHd n
H
KK
H






(10)
by taking the logarithm of the two sides
n
M
dH
logKlogKHnlog H

 


 (11)
p
H
Sorption Percent
Temp. oC

M. M. A. Mesala m 24
12345
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Cu2+
Zn2+
Ni2+
Figure 5. Log Kd of Cu2+, Zn2+ and Ni2+ ions versus pH of
medium on ZrO2 ion exchanger at 25  1˚C.
When n MH




and n MH




, the
magnitude n
MH
KH



is considered constant, thus
Equation (11) can be reduced to
d
logKC npH (1 2)
Which implies that a plot of log Kd versus pH should
be linear with a slope (n). Figure 5 shows the depend-
ency of log Kd values of Cu2+, Zn2+ and Ni2+ ions on pH
of the solution with non-ideality of the exchange reaction
for Cu2+, Zn2+ and Ni2+ ions on Zr O2 ion exchanger. The
non-ideality results may be due to the presence of other
mechanism beside the ion exchange mechanism such as
the physical adsorption between the metal ions and the
exchanger that could be related to the ionic potential of
the cations [15].
The distribution coefficients (Kd) and separation fac-
tors () for the mentioned cations in different pH me-
dium were calculated and tabulated in Table 3. The data
in Table 3 indicated that the distribution coefficients
have the affinity sequence Cu2+ > Zn2+ > Ni2+ for ZrO2.
This sequence supports the sorption of metal ions in hy-
drated state. The separation factors for the studied
cations were calculated and indicated that Cu2+ ion can
easily separated from Zn2+ and Ni2+ ions in waste water
solutions.
The nature of adsorption processes for Cu2+ , Zn2+ and
Ni2+ ions on ZrO2 were investigated by gradual increase
of the sorbate concentration and measuring the amount
sorbed at each equ ilibrium concentration. The freu ndlich
isotherm most widely used mathematical model, given
an empirical expression encompassing the surface het-
erogeneity and exponential distribution of active sites
and their energies was tested in the following form;
Table 3. Distribution coefficients and separation factors for
Cu2+, Zn2+and Ni2+ ions on ZrO2 in different pH media at 25
 1˚C.
pH of
medium Parameter Cu2+ Zn2+ Ni2+
Kd, ml/g 3.31 2.282.3
0.690.69
1
Separation factor,  1.01
Kd, ml/g 5.82 4.664.60
0.800.79
2
Separation factor,  1.00
Kd, ml/g 8.93 7.537.18
0.840.81
3 Separation factor,  0.95
Kd, ml/g 9.89 9.058.69
0.920.88
4 Separation factor,  0.96
Kd, ml/g 11.73 9.599.19
0.820.78
5 Separation factor,  0.96
1eq
logWmLogKnlog C

 (13)
where W: is the amount uptake, Ceq.: the equilibrium
concentration, m: mass of the ion exchanger, and, n and
K are the freundlich constants measure the adsorption
intensity and adsorption capacity of the sorbent, respec-
tively, and computed from the slope and intercept of the
linear relationship.
Plots of log W/m against log Ceq. linear relationships
were obtained for Cu2+, Zn2+ and Ni2+ ions on ZrO2 as
shown in Figure 6. The data in Figure 6 show the ap-
plicability of freundlich isotherm for Cu2+, Zn2+ an d Ni2+
ions on ZrO2 ions and all of these cations are physically
sorbed on ZrO2. The values of adsorption capacity (K)
and adsorption intensity (n) for Cu2+, Zn2+ and Ni2+ ions
on ZrO2 were computed from the linear relationships in
Figure 6 and tabulated in Table 4. As seen from Table 4
the numerical values of (0 < n < 1) suggest the surface of
the sorbent of heterogeneous type [16]. Also the numeri-
cal value of (n) is only reduced at lower equilibrium
concentrations. Freundlich sorption isotherm does not
predict any saturation of the solid surface thus envisages
infinite surface coverage mathe matically.
Similar results were also reported for the adsorption of
Table 4. Freundlich constants (n and K) for sorption of
Cu2+, Zn2+ and Ni2+ ions on ZrO2 at t = 25  1˚C.
Freundlich constants
Cations n K
Cu2+ 0.71 1.80  10-2
Zn2+ 0.67 7.76  10-3
Ni2+ 0.63 4.17  10-3
Log Kd
pH

M. M. A. Mesala m 25
-4.6 -4.4 -4.2 -4.0 -3.8 -3.6 -3.4 -3.2 -3.0 -2.8 -2.6
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Cu2+
Zn2+
Ni2+
Figure 6. Freundlich adsorption isotherms for Cu2+, Zn2+
and Ni2+ ions on ZrO2 ion exchanger at 25  1˚C.
Zn2+, Cu2+, Cd2+ and Ni2+ ions on poly acrylamide acrylic
acid impregnated with silico-titanate ion exchanger [17]
and UO22+ and Th4+ ions on titan ium antimonate [18].
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Log Ceq.
Log W/m