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Journal of Hazardous Materials 229–230 (2012) 258–264
Contents lists available at SciVerse ScienceDirect
Journal of Hazardous Materials
journal homepage: www.elsevier.com/locate/jhazmat
Combustion of isopropyl alcohol using a green manufactured CuFe2 O4
Yao-Jen Tu a,∗ , Chien-Kuei Chang b , Chen-Feng You a,∗
a
b
Earth Dynamic System Research Center, National Cheng-Kung University, No. 1, University Road, Tainan City 701, Taiwan, ROC
Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, No. 415, Chien Kung Road, Kaohsiung 807, Taiwan, ROC
h i g h l i g h t s
g r a p h i c a l
a b s t r a c t
A green method for manufacturing
CuFe2 O4 was developed from industrial Cu sludge.
The green manufactured CuFe2 O4
was effective for combustion of isopropyl alcohol.
96-h decay test shows the catalyst
has a good thermal stability and
durability.
Magnetic property may solve the catalyst recovery problem in fluidized
system.
This work achieved the goal of clean
production and sustainable development.
a r t i c l e
i n f o
Article history:
Received 17 February 2012
Received in revised form 2 May 2012
Accepted 30 May 2012
Available online 5 June 2012
Keywords:
Industrial Cu sludge
CuFe2 O4
Catalytic combustion
Isopropyl alcohol
Volatile organic compounds
a b s t r a c t
A green method for manufacturing CuFe2 O4 from industrial Cu sludge was successfully developed by
a combination of acid leaching, chemical exchange and ferrite process. The CuFe2 O4 was applied for
combustion of volatile organic compounds (VOCs) derived from isopropyl alcohol (IPA). The results show
that IPA was reacted to form intermediate acetone and CO2 at the temperature range of 110–170 ◦ C.
When the temperature was increased to 180 ◦ C, IPA can be 100% converted into CO2 . The 96-h decay
tests indicated that the catalyst has a good thermal stability and durability under the conditions of gas
hourly space velocity 30,000 h−1 , oxygen content 21%, IPA inlet concentration 2000 ppm, and reaction
temperature 180 ◦ C. The results demonstrate great potential that our manufactured CuFe2 O4 catalyst can
be used in combustion IPA streams to eliminate the emission of IPA.
Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved.
1. Introduction
Volatile organic compounds (VOCs) are defined as organic compounds with high vapor pressure that are easily vaporized under
ambient temperature and pressure conditions [1]. The World
Health Organization (WHO) definition of VOCs includes all organic
compounds or substances that are made up predominantly carbon
∗ Corresponding authors. Fax: +886 6 2758682.
E-mail addresses: [email protected] (Y.-J. Tu), [email protected]
(C.-F. You).
and hydrogen with boiling temperatures in the range of 50–260 ◦ C,
excluding pesticides [2]. Goldstein and Galbally (2009) reported
that anthropogenic sources emit about 142 tera-grams carbon per
year in the form of VOCs [3]. The huge VOCs emission generated
from industrial processes, such as aliphatic, aromatic, isopropyl
alcohol, benzene and toluene, are considered as severe air pollutants because of their high toxicity to ecological system and
carcinogenicity to human health [4,5].
Isopropyl alcohol (IPA), so called 2-propanol (dimethyl
carbinol), is commonly used as solvent and reactant in the chemical industries. With the toxicity to central nervous system, eyes,
nose, throat, and lung [6,7], it is classified nowadays among the
0304-3894/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jhazmat.2012.05.100
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Y.-J. Tu et al. / Journal of Hazardous Materials 229–230 (2012) 258–264
most hazardous atmospheric pollutants. IPA is also used in drying
baths for electroplating [8] and in cleaning items in the production
of thin film transistor (TFT)-liquidcrystal display, ion chromatography, and photonics industries [9]. From these drying and cleaning
procedures, IPA raises concerns of VOCs.
The catalytic combustion, due to its versatile for low concentrations organic emission, is one of the most popular techniques to
treat the harmful VOCs [9]. The precious metals, such as Pt, Pd, Rh,
Au, and V2 O5 , are always the most critical points for the activation
center of catalysts and are the most commonly used metals in the
environmental industry. Nevertheless, the high cost of these precious metals makes the catalysts less economic competition in the
market. An alternative approach for reducing the catalysts cost is
to use a common and cheap metal.
Copper ferrite (CuFe2 O4 ), with the spinel structure, has a cubic
close-packed arrangement of the oxygen ions with Cu2+ and Fe3+
ions at two different crystallographic sites [10]. It is a relatively
cheap catalyst for replacing those of precious metal catalysts. Our
previous work showed that hydrothermal synthesized manganese
ferrite (MnFe2 O4 ) could convert IPA into CO2 at space velocity of
24,000 h−1 , oxygen content 21%, 1700 ppm IPA, and at reaction
temperature of 200 ◦ C [11]. Although copper ferrite has superior
catalytic activity [12–14], its effect on the thermal decomposition
of IPA has not yet been reported.
Several methods were reported to manufacture copper ferrite,
include co-precipitation [15], auto-combustion [16], and sol–gel
method [17]. If these catalysts can be obtained from industrial
sludge, the operation price could be further reduced.
Printed circuit board, denoted by PCB, is one of the most essential components for almost all electronic products. The amount of
waste sludge generated from PCB industry is rather substantial due
to its high demand in market. Our previous work has successfully
recycled copper powder from PCB industry by a combination of
acid leaching, chemical exchange, and ferrite process [18]. Under
the optimal conditions, almost 95% copper powder could be recycled. Furthermore, the ferrite process conducted can meet not only
the supernatant but also the sludge to the environmental rules.
The sludge generated from the ferrite process hence is regarded as
a general industrial waste due to its high stability. If the sludge does
not have other utility, it can be buried in a landfill.
We attempt to resource this sludge as a catalyst in this study
and apply to the combustion feasibility of VOCs derived from IPA.
The ultimate goal is to reach a clean production and sustainable
development, by transforming hazardous waste into valuable byproducts and to reduce the amount of waste and treatment costs.
2. Materials and methods
2.1. CuFe2 O4 catalyst preparation
The CuFe2 O4 catalyst was manufactured from a PCB industry
according to our previous procedures by combining acid leach,
chemical exchange, and ferrite process [18]. Briefly, acid leaching
was conducted using 500 g industrial sludge and 10 L dilute sulfuric
acid was added for extracting heavy metals. The controlled factors
include the concentration of sulfuric acid (0.5 N, 1 N, 2 N), leaching
temperature (25 ◦ C, 40 ◦ C, 50 ◦ C), and reaction time (10 min, 20 min,
40 min, 60 min, 90 min). The optimal acid leaching conditions were
found at 1 N sulfuric acid, temperature 50 ◦ C and last for 60 min.
In the chemical exchange, Fe powder was used as the sacrificed
metal to substitute Cu2+ in the liquid. The dosage of Fe powder (Fe/Cu molar ratio 1.0, 2.0, 5.0), reaction temperature (25 ◦ C,
40 ◦ C, 50 ◦ C), pH value (1.0, 2.0, 3.0) and agitation speed (200 rpm,
300 rpm, 400 rpm) were controlling factors in the experiments. The
optimal conditions in the chemical exchange experiments were
Acid leaching
reactor
259
Ferrite process
reactor
Chemical exchange
reactor
7
7
7
8
8
8
pH
ORP
1
2
5
9
Flow rate meter
4
9
1. pH controller
2. ORP controller
3. Temp. controller
4. Flow rate meter
5. Air inlet
3
Temperature
9
6
6. Air compressor
7. Agitation controller
8. Agitator
9. Sampler
Fig. 1. Batch reaction system of acid leaching, chemical exchange and ferrite process.
summarized as followed: Fe powder dosage Fe/Cu 5.0, pH 2.0, reaction temperature 50 ◦ C and agitation speed 200 rpm.
At the final stage, ferrite process was performed to ensure the
quality of supernatant and sludge for the EPA regulation. Parameters include the dosage of FeSO4 (Fe/Cu molar ratio = 10.0), reaction
temperature (80 ◦ C), pH value (9.0) and air supply rate (3.0 L/min/L
wastewater) were evaluated. The sludge generated from ferrite
process was then used as a catalyst for testing its combustion performance in VOCs derived from IPA.
Fig. 1 shows the batch reaction system for acid leaching, chemical exchange, and ferrite process applied in this study. It is made of
stainless steel where the diameter and length of the acid leaching
tank was 30 cm and 45 cm, respectively. A mixer with a rotation
speed of 200–1200 rpm was installed in the tank. The structure
of the chemical exchange tank is the same as the leaching tank.
In the ferrite process tank, diameter and length was 23 cm and
40 cm, respectively and had installed a temperature controller, an
air supplier, and a pH controller.
The manufactured catalyst was collected using a magnetic separation method by Nd–Fe–B magnet whose shape was in 4 cm length,
2 cm wide, and 1 cm thickness. The product was then washed with
de-ionized water several times until the pH of the solution reached
around 7. The solids were then dried at 50 ◦ C for 24 h in an oven
and stored for further tests.
2.2. Catalyst characterization
Scanning electron microscopy (JSM-6330, Japan) was used to
study the morphology and microstructure of the manufactured catalyst. X-ray powder diffraction (XRD) was performed to determine
the crystalline structure of CuFe2 O4 on Bruker D8-Advance diffractometer with Cu-K␣ radiation ( = 0.15406 nm). The catalyst was
scanned from 10◦ to 80◦ (2) with a scanning rate 0.5◦ min−1 and
a step size 0.02◦ ·Superconducting Quantum Interference Device
(MPMS-XL7, Quantum Design, USA) was commissioned to reveal
the saturation magnetization of the sludge generated from the
FP. BET surface area (m2 g−1 ), pore volume (cm3 g−1 ), and average pore size (Å) were determined by ASAP 2010 surface analyzer
(Micromeritics Co., USA).
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Fig. 2. A schematic diagram of the catalytic incineration procedures.
2.3. IPA catalytic combustion system
To understand the IPA combustion performance, various parameters including the blank test, the IPA inlet concentration, the space
velocity, and the oxygen content were investigated.
Fig. 2 illustrates the experimental apparatus, which includes an
IPA feeding system, a catalytic reaction system, a product sampling
and analysis system. The IPA feeding system use herein included
IPA, nitrogen, and air gases, which were delivered to the reaction
system through individual stainless steel pipes. The gases were filtered using a filter (GFIMS 100, SGE) to eliminate moisture and
impurities that may damage to the flow meter. Additionally, the
mass flow meter was used to control the flow rate precisely. The
gases were uniformly mixed in a chamber before entered the reaction system.
A catalytic reaction system was set up to heat a catalytic reaction
tube inside a furnace. The reaction tube was made of quartz, with
a length of 30 cm and a diameter of 2.54 cm; a quartz spacer was
placed in the center of the tube to support the catalysts. Before the
catalysts were installed, a layer of glass wool and 5 g glass sand were
introduced to prevent the catalysts from being removed and clogging the pores of the catalytic bed to cause any pressure drop. The
catalysts were screened to ensure they were uniform in size before
they were packed. After they had been packed, a layer of glass sand
was placed above the catalysts to ensure that the gases entered the
catalytic bed uniformly, to prevent turbulence on the catalytic bed.
A K-type thermocouple was placed above the catalytic bed to measure the temperature inside the tube. Additionally, a temperature
controller was installed to control heating in the furnace.
As the mixed gases passed the catalytic reaction system, they
reacted and then were collected in the sampling bags before being
injected into a gas chromatograph (GC) for IPA concentration analyses using a flame ionization detector. A flue gas analyzer (IMR
2000) and GC/thermal conductivity detector (GC-14A TCD system,
Shimadzu) were used to monitor oxygen (O2 ) content and measure
the amount of carbon dioxide (CO2 ) produced.
3. Results and discussion
3.1. The properties of PCB industrial sludge
The important properties of PCB industrial sludge used here is
its abundance in copper. More detailed information on this sludge
material can be referred to our previous work [18]. Briefly, the
sludge contains 60% water and has an average pH of 7.05. Six
heavy metals, including Cu, Pb, Cd, Zn, Ni, and Cr, were less than
105 mg kg−1 (dry base) except Cu 158,000 mg kg−1 (dry base). This
means about 15.8% Cu in the sludge, indicating its high recycle
value.
3.2. Manufacturing of CuFe2 O4 catalyst
As mentioned in Section 2.1, 500 g of the industrial sludge was
acid leaching with 10 L dilute sulfuric acid to extract copper from
solids. Fe powder was used as sacrificed metal to substitute Cu2+
in the liquid during chemical exchange. To further ensure that
supernatant would qualify to fulfill the effluent standards, ferrite
process was performed after the chemical exchange. A green lowcost catalyst copper ferrite (CuFe2 O4 ) was then manufactured after
the ferrite process. The corresponding reactions of acid leaching,
chemical exchange, and ferrite process are described as Eq. (1)–(3),
respectively.
Cu-sludge(s) + H2 SO4(aq) → Cu2+ (aq) + sludge(s)
(1)
Fe0 (s) + Cu2+ (aq) → Fe2+ (aq) + Cu0 (s)
(2)
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Fig. 3. Effect of temperature on IPA conversion in blank test. Test conditions: inlet
concentration = 2000 ppm, GHSV = 30,000 h−1 , O2 = 21%. The relative error of the
three times replicates in all points were below 2%.
261
Fig. 4. Effect of temperature on IPA conversion at different oxygen content. Test
conditions: inlet concentration = 2000 ppm, GHSV = 30,000 h−1 . The relative error of
the three times replicates in all points were below 2%.
3.3.3. Effect of space velocity
Gas hourly space velocity (GHSV) is defined as reactant gas flow
rate/reactor volume. The formula can be expressed as Eq. (4).
Cu2+ (aq) + 2Fe2+ (aq) + 6OH− (aq) + 1/2O2(aq) → CuFe2 O4(s) + 3H2 O
(3)
3.3. IPA catalytic combustion
3.3.1. Blank test
To determine if the thermal decomposition of IPA was significant at the selected reaction conditions, a blank test in atmosphere
was conducted from 30 ◦ C to 500 ◦ C. No catalyst was added to the
reactor in this experiment. The glass wool, with same volume catalyst, was put on the reactive bed to represent catalyst. The effect of
temperature on IPA conversion in the blank test was demonstrated
in Fig. 3. It shows that only 12% IPA could be converted at 200 ◦ C
without catalyst. Even when combustion temperature was raised
to 500 ◦ C, only 75% conversion of IPA was completed. This implies
that the decomposition of IPA is associated with much energy consumption when no catalyst used. On the other hand, the lowest
temperature required for IPA combustion was rather different in
the presence or absence of CuFe2 O4 . If no CuFe2 O4 , the IPA combustion started at about 120 ◦ C, which is much higher than in the case
of CuFe2 O4 presence. This is consistent with the MnFe2 O4 catalyst
on IPA combustion [11].
3.3.2. Effect of oxygen content
T50 , the temperature needed to attain 50% IPA conversion, of
the three investigated oxygen content ranges (10%, 15%, and 21%)
was 140, 120, and 110 ◦ C, respectively. It shows that the conversion
of IPA increases with oxygen content (Fig. 4). On the other hand,
the oxygen content influenced strongly the conversion at 150 ◦ C.
The IPA conversion increases 26% at oxygen content of 21% compared with at 10%. Nevertheless, the conversion was independent
of oxygen content when the temperature exceeded 180 ◦ C. Similar
observations were reported in literatures [11,19]. It is suggestive
that the amount of oxygen demanded in the IPA catalytic combustion should be exceeded the theoretical oxygen. Apparently,
the contacting opportunities between the IPA and oxygen were
increasing at high oxygen content and thus promoting conversion
[11].
GHSV (h−1 ) =
Q (m3 h−1 )
V (m3 )
(4)
where Q is the reactant gas flow rate (m3 h−1 ) and V is the reactor
volume (m3 ). In other words, GHSV is the inverse of time, indicating a lower GHSV corresponds to a longer retention time. Increasing
the retention time will enhance the extent of reaction. Hence, the
conversion rises as the space velocity decreases [20]. The relationship between the IPA conversion and the GHSV was demonstrated
in Fig. 5. The results indicate that a smaller conversion is associated
with a larger GHSV at a given temperature. At 150 ◦ C, the IPA conversion was 98% under GHSV 8000 h−1 . However, it fells to 85% and
67% when GHSV increased to 15,000 h−1 and 30,000 h−1 , respectively. The conversion decreases generally as the GHSV increased,
but the GHSV only slightly affected the conversion when temperature exceeded 180 ◦ C.
Fig. 5. The relationship between temperature and IPA conversion under different
GHSV conditions. Test conditions: inlet concentration = 2000 ppm, O2 = 21%. The relative error of the three times replicates in all points were below 2%.
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Fig. 6. The relationship between temperature and IPA conversion at different inlet
concentrations. Test conditions: GHSV = 30,000 h−1 , O2 = 21%. The relative error of
the three times replicates in all points were below 2%.
3.3.4. Effect of IPA inlet concentration
The catalytic combustion method has become the most popular
technique, mainly because of its economical for organic emissions
<5000 ppm [9]. Generally speaking, the concentration of catalytic
incineration was in accordance with 1/4 lower explosive limit
(LEL) of target pollutant (LEL = 2.02% (V/V) for IPA). The safety IPA
combustion concentration, therefore, must be controlled at below
5000 ppm. The VOC inlet concentration will theoretically affect the
conversion efficiency. Thus three IPA inlet concentrations (500,
1000, and 2000 ppm) were selected to understand their combustion
conversions. The relationships between temperature and IPA conversion at different inlet concentrations under GHSV = 30,000 h−1
and oxygen content = 21% were shown in Fig. 6. The IPA conversion increases apparently with decreasing inlet concentrations. It
seems that the differences of T50 at three IPA inlet concentrations
(500, 1000, and 2000 ppm) were rather small at 105, 110, and 115 ◦ C
(Fig. 6). In addition, the IPA conversion could achieve 100, 97, and
89% at the IPA concentrations of 500, 1000, and 2000 ppm at 170 ◦ C.
However, the concentrations became irrelevant when the temperature reached at 180 ◦ C, the conversions were all near 100%.
3.3.5. Catalytic combustion production
Selection of the catalytic material for various organic pollutants
decomposition has been the subject of many literature studies. The
reactants and catalysts typically control the products of catalytic
reaction. It is known that primary alcohol can be oxidized to aldehyde and secondary alcohol can be oxidized to acetone [21]. Eqs. (5)
and (6) specify the oxidation of IPA (secondary alcohol) to acetone
and the complete oxidation of IPA to CO2 , respectively.
C3 H7 OH + 1/2O2 → CH3 COCH3 + H2 O
(5)
C3 H7 OH + 9/2O2 → 3CO2 + 4H2 O
(6)
The catalytic combustion products associated with the investigated
temperatures show in Fig. 7. Detailed results of IPA conversions are
summarized in the Supplementary Information (Table S1). These
results indicate that CO2 was the final product when IPA reacted
with CuFe2 O4 catalyst at temperature over 190 ◦ C. It is evident that
the percentage of IPA conversion is proportional to the production
of CO2 . IPA was reacted to form intermediate acetone and CO2 at
the temperature range of 110–170 ◦ C, where the amount of acetone
decreased when temperature increased. IPA was 100% converted
Fig. 7. Catalytic combustion productions associated with various investigated
temperatures. Test conditions: inlet concentration = 2000 ppm, GHSV = 30000 h−1 ,
O2 = 21%. The relative error of the three times replicates in all points were below 2%.
into CO2 when the temperature increased to 190 ◦ C. Compared
with results in our previous study [11], this green manufactured
catalyst CuFe2 O4 shows better performance than the synthesized
MnFe2 O4 on IPA combustion, supporting the potential application
of CuFe2 O4 . In addition, Lou and Chang (2006) reported that only
few metals, such as Cu and Mn, could not adsorb CO2 , showing that
Cu and Mn is favorable for the CO2 desorption from the surface of
catalyst [22]. Thus CuFe2 O4 and MnFe2 O4 have better performances
in converting CO to CO2 . The final product in this study is also CO2 ,
indicating that desorption of CO2 plays an important role in IPA
combustion process, and further indicates the CuFe2 O4 generated
from PCB industry performs well in IPA combustion.
3.4. Characterization of the catalyst CuFe2 O4
The BET properties of surface area, pore volume, and average pore size of the fresh and used catalyst were summarized in
Table 1. They showed no much difference and reflect stable thermal
property of the CuFe2 O4 . Its crystalline appearance indicates that
powder of catalyst aggregated by numerous of fine particles (Fig. 8).
The SEM photo shows primary particle sizes ranged from tens to
110 nm. The average pore diameter (18.57 Å) measured was caused
by intervals of numerous random stacked particles. The measured
surface area (69.06 m2 g−1 ) and the pore volume (0.11 cm3 g−1 ) are
far lower than normal porous materials, demonstrating the surface
area of this catalyst is attributed to the outside surface.
The XRD spectra of freshly made and used (thermally reacted)
catalysts were demonstrated in Fig. 9. The XRD pattern of the freshly
made catalyst presents the diffraction peaks at d-spacings of 4.790,
2.960, 2.517, 2.100, 1.613, 1.479, 1.272, 1.087, and 0.964 Å, which
matched well with the CuFe2 O4 (JCPDS file number 00-025-0283).
These results indicate the XRD pattern of the used catalyst did
Table 1
BET properties of the fresh and used catalyst.
Catalyst
Specific surface
area (m2 g−1 )
Pore volume
(cm3 g−1 )
Average pore
size (Å)
Fresh CuFe2 O4
Used CuFe2 O4 a
69.06
68. 83
0.11
0.10
18.57
18.84
Conditions of each cycle: temperature = 200 ◦ C; inlet concentration = 2000 ppm;
reacted time = 24 h.
a
The used CuFe2 O4 refers to the catalyst after 5th reused cycles.
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263
Fig. 8. SEM photo of the catalyst.
Fig. 10. The comparison of IPA conversion with time at different temperature during the 96 h-decay test. Test conditions: inlet concentration = 2000 ppm,
GHSV = 30,000 h−1 , O2 = 21%. The relative error of the three times replicates in all
points were below 2%.
Furthermore, the saturation magnetization of the catalyst was
determined to be 62.52 emu g−1 (Fig. S1). No remanence was
detected in the sample, confirming that this magnetic catalyst was
superparamagnetic. This magnetic catalyst can be collected using
a magnet in the experiments. When the external magnetic field
was removed, the materials could be well re-dispersed again. This
magnetic property has great potential for applying the catalyst to
catalytic combustion in fluidized bed system, solving the recovery
problems of relatively fine catalysts.
Fig. 9. The XRD spectra of the freshly made and used catalysts CuFe2 O4 . (Fresh catalyst means the catalyst just manufactured after acid leaching, chemical exchange,
and ferrite process. Used catalyst means after 24 h reaction under the conditions
of inlet concentration = 2000 ppm, GHSV = 30,000 h−1 , O2 = 21%. The relative error of
the three times replicates in all points were below 2%.).
not change to other crystalline phases, supporting that our manufactured CuFe2 O4 was stable after 24 h thermal reaction at inlet
concentration = 2000 ppm, GHSV = 30,000 h−1 and O2 = 21%.
3.5. Reusability of CuFe2 O4
Five combustion cycles were conducted to estimate the
reusability of the CuFe2 O4 catalyst for the IPA combustion. In each
cycle, the combustion temperature was started at room temperature to check the catalyst tolerance of temperature variation and
the same catalyst was reused without any treatment in subsequent
cycle. The results reveal that IPA combustion efficiency could attain
to 99% in all five cycles. There was almost no activity loss of CuFe2 O4
after the first cycle, then achieved a more stable state in the subsequent cycles. These results confirm that our green manufactured
catalyst CuFe2 O4 has a good tolerance to temperature variation and
has high potential to be reused for many cycles.
The 96-h catalyst decay experiment was conducted to understand the thermal stability and durability of the CuFe2 O4
thoroughly. The results of IPA conversions in the 96-h decay tests at
150, 175, and 200 ◦ C are compared (Fig. 10). These results show that
IPA conversion reduced slightly at the beginning of 24-h period. The
activity of CuFe2 O4 was stabilized 24 h later and reached a constant
equilibrium rate at each given temperatures during the 96-h decay
experiment.
4. Conclusion
A green manufactured catalyst CuFe2 O4 was successfully developed from industrial wastes sludge. The catalytic combustion
feasibility of VOC derived from IPA on this catalyst has been investigated in detail. The results reveal that the combustion of IPA using
catalyst CuFe2 O4 could be ignited at a rather low temperature. One
hundred percent conversion was achieved under the conditions
of GHSV 30,000 h−1 , oxygen content 21%, IPA inlet concentration
2000 ppm, and reaction temperature 180 ◦ C. The reaction temperature is the most important factor during the catalytic combustion
process. In this study, IPA could be completely converted into CO2
and H2 O at temperature >180 ◦ C whatever the conditions of GHSV
or inlet concentration. More importantly, the catalyst has a good
thermal stability and durability during 96-h decay test. The magnetism of this catalyst has great potential for studying catalytic
combustion in fluidized bed system and solving the recovery problems of relatively fine catalysts particles.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.jhazmat.2012.05.100.
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