WATER POLLUTION CONTROL RESEARCH SERIES • 17020 EC I 11/71
FEASIBILITY STUDIES OF APPLICATIONS
OF
CATALYTIC OXIDATION IN WASTEWATER
U.S. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation's waters. They provide a central source of
information on the research, development and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts with Federal,
State, and local agencies, research institutions, and
industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, D.C. 20^60.
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FEASIBILITY STUDIES OP
APPLICATIONS OP CATALYTIC OXIDATION
IN WASTEWATER
SOUTHERN ILLINOIS UNIVERSITY
Carbondale, Illinois
for the
Environmental Protection Agency
Project # 17020 ECI
Contract # 14-12-572
November, 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 75 cents
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EPA Review Notice
Tills report has been reivewed by the Environmental Protection
and approved for publication. Approval does not sipjiify
tnat tne contents necessarily reflect the views and policies
of tne Environmental Protection Agency, nor does mention of
trade names or corrmercial products constitute endorsement or
recommendation for use.
11
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ABSTRACT
Wastewaters show 78% decrease in Chemical Oxygen Demand
(COD) and 96% decrease in Oxygen Demand Index (ODI) during
two hours insonation in the presence of activated Raney-Nickel
catalyst and air. In addition, sonocatalytic oxidation com-
pletely eliminates coliform organisms. The substitution of
air by ozone-oxygen mixture can result in COD reductions of
901. Significantly, treatment with activated Raney-Nickel
and ozone, without insonation; i.e., catalytic ozonation; is
nearly as effective. This process can remove 85% of the COD
and 60% of the TOC from secondary treatment effluents in two
hours under favorable conditions.
Ozonation of aqueous phenol solutions in the presence of
activated Raney-Nickel and ultrasound (sonocatalytic ozonation)
results in the reduction of phenol concentration, COD, and TOC;
the greatest decrease is in phenol concentration, the next
greatest is in COD, and the least is in TOC.
Aqueous solutions of Orthochloronitrobenzene (OCNB) react
only in the presence of ultrasound and aluminum, or activated
Raney-Nickel (sonocatalysis) at room temperature. In this
reaction, reduction products appear initially, but eventually
these products, and OCNB, are eliminated from the solution.
This report was submitted in fulfillment of Project Number
17020 ECI, Contract 14-12-572, under the sponsorship of the
Water Quality Office, Environmental Protection Agency.
111
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CONTENTS
PAGE
Conclusions 1
Recommendations 3
Introduction 5
Literature Review 6
Research Plan 7
Experimental 8
A. Apparatus 8
B. Analytical Procedures 8
C. Experimental Procedures 13
Results and Discussions 14
A. Wastewater Experiments 14
B. Phenol Experiments 36
C. Orthochloronitrobenzene Experiments 58
Acknowledgment 65
List of References 67
List of Publications 69
List of Personnel in the Project 71
Glossary 73
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FIGURES
PAGE
1. Experimental Equipment Schematic 9
2. Comparison of COD Values Using Standard
Method and Technicon COD Analyzer 11
3. lodometric Ozone Analysis Apparatus 12
4. Wet and Dry Weight Ratio of Activated
Raney-Nickel in Water 15
5. COD Reduction Using Ultrasonic Energy 17
6. Experimental Data Demonstrating the
Sonocatalytic Effect 18
7. Reduction in COD and ODI by Sonocatalysis
Using V205 19
8. Reduction in COD and ODI by Sonocatalysis
Using Activated Raney-Nickel 20
9. Coliform Reduction by Sonocatalysis Using
V2°5 22
10. COD Reduction by Ozonation, Catalytic
Ozonation and Sonocatalytic Ozonation 27
11. ODI Reduction by Ozonation, Catalytic
Ozonation and Sonocatalytic Ozonation 28
12. COD Reduction by Sonocatalytic Ozonation:
Effect of Catalyst Dose 29
13. COD Reduction by Sono-ozonation and
Sonocatalytic Ozonation: Influence of
Initial COD 30
14. COD Reduction by Catalytic Ozonation:
Effect of Agitation 33
15. COD Reduction by Catalytic Ozonation:
Effect of Catalyst Dose 34
16. TOC Removal by Catalytic Ozonation 37
vi
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17. Sonocatalytic Oxidation of Phenol 38
18. Phenol Conversion by Different Oxidative
Treatments 40
19. Catalytic Ozonation of Phenol: Effect
of Catalyst Dose 42
20. Comparison of Phenol Conversion by
Oxidative Processes: Effect of
Catalyst Dose 43
21. Conversion of Phenol and COD Removal by
Ozonation: Effect of Catalysis by Activated
Raney-Nickel 46
22. Conversion of Phenol and COD Removal by
Sono-oxidation: Effect of Catalysis by
Activated Raney-Nickel. 47
23. Conversion of Phenol and COD Removal by
Sono-ozonation: Effect of Catalysis by
Activated Raney-Nickel 48
24. Comparison of COD Removal from Aqueous
Phenol Solution by Different Types of
Treatment 49
25. TOC Removal in Aqueous Phenol Solution 50
26. UV Spectra, Sono-ozonation of Phenol
(Reference: Water) 52
27. UV Spectra, Sono-ozonation of Phenol
(Reference: Phenol) 53
28. UV Spectra of Synthetic Mixture and
Reaction Products 54
29. UV Spectra for Different Types of
Treatment 55
30. Thin Layer Chromatograms 56
31. Structures of Intermediate Products in
OCNB Experiments 61
vti
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TABLES
PAGE
1. A Summary of the Effect of Sonocatalysis
on Wastewaters 21
2. Coliform Versus Time with Ultrasound and
Different Catalysts 23
3. Comparison of Experimental Data of
Sonocatalytic Oxidation and Batch Carbon
Adsorption 24
4. Catalytic Oxidation of Wastewater by
Boiling 26
5. Ozone Concentration in Gas Feed Mixtures 32
6. Ozone Utilization during Ozonation of
Wastewater 35
7. Milligrams Ozone Decomposed and Used in
2-Hour Reaction 44
viii
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CONCLUSIONS
1. Sonocatalytic oxidation of wastewaters occurs at room
temperature. Insonation, activated Raney-Nickel catalyst,
and air flow can remove 78% of the COD, 96% of the ODI, and
100% of coliform organisms in treated wastewaters. As a
catalyst, activated Raney-Nickel is stable under ultrasonic
irradiation.
2. The replacement of air by ozone-oxygen mixtures (sono-
catalytic ozonation) improves the sonocatalytic process.
3. At higher concentrations of ozone, the combination of
activated Raney-Nickel and ozone (catalytic ozonation) destroys
85% of the COD and 60% of the TOG in treated wastewaters in two
hours under favorable conditions. Catalytic ozonation, as an
innovative method for advanced waste treatment, is a significant
contribution of this project.
4. There is a sonocatalytic effect observed in the oxidation
of aqueous solutions of phenol and orthochloronitrobenzene (OCNB).
Sonocatalysis occurs at an optimum dose of catalyst, and greater
amounts of catalyst interfere with insonation.
5. Sonocatalytic ozonation of phenol results in a rapid decrease
of phenol concentration, a less rapid decrease in COD, and still
less rapid decrease in TOC. Phenol appears to be converted in
steps to intermediates at higher oxidation states, and is con-
verted, slowly, to carbon dioxide and water. The oxygenated inter-
mediate species identified on the mechanistic pathway are catechol,
hydroquinone, pyrogallol, and others.
6. Although neither catalytic oxidation nor sono-oxidation of
OCNB occurs at room temperature, the combination of sonocatalytic
oxidation does occur which can remove all traces of the compound
from aqueous solution. It is possible that insonation dislodges
the protective oxide coating from aluminum, exposing fresh metal
which is then available for catalytic action.
7. Of the ozone fed into the reaction system, 401 to 75% is
consumed during the course of catalytic ozonation and sonocataly-
tic ozonation.
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RECOMMENDATIONS
1. Continue the study of catalytic ozonation as an advanced
waste treatment process.
2. Develop a continuous flow reactor for evaluating catalytic
ozonation for COD and TOG removal from waste waters.
3. Evaluate ozone consumption and the possibility of ozone
recycling.
4. Continue to search for new catalysts comparable to activated
Raney-Nickel, investigating catalyst life and regeneration pro-
cedures .
5. Continue the study of catalysts and various energy sources
to evaluate their synergistic effect.
6. Continue the mechanistic study of catalytic processes with
synthetic wastes with the aim of improving the processes with
wastewaters.
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INTRODUCTION
Water pollution has become one of the major problems
facing this nation and innovative methods are needed to solve
it. Therefore, we decided to embark on a systematic investi-
gation of catalytic oxidation as an advanced wastewater treat-
ment method. Heterogeneous catalytic oxidation is a logical
starting point because of the economic advantage in using
atmospheric oxygen, and the known capacity of various substances
to catalyze the oxidation reaction. Recently, we discovered a
synergistic effect between certain catalysts and ultrasound
(sonocatalysis). Since waste waters are very dilute solutions
of pollutants, and since reactions are usually slow at low
concentrations, it seemed appropriate to determine whether
sonocatalytic oxidation could increase reaction rates enough
to be feasible for wastewater treatment. Aside from a consid-
eration of reaction rates, there was evidence that sonocatalysis
could destroy pollutants which neither catalytic oxidation, nor
ultrasound, could accomplish alone. The objective of this
research, therefore, is to investigate the feasibility of using
catalytic and sonocatalytic processes for advanced wastewater
treatment.
The experimental approach consisted of four parts:
(1) Sonocatalytic oxidation (ultrasound + catalyst +
environmental oxygen) as a treatment process for
wastewater and for representative compounds.
(2) Sonocatalytic ozonation (ultrasound + catalyst +
ozone) as a treatment process for wastewater and
for representative compounds.
(3) Catalytic ozonation (catalyst + ozone) as a treat-
ment process for wastewaters and for representative
compounds .
(4) Mechanistic studies of sonocatalysis in synthetic
wastes.
To evaluate the effectiveness of these processes for wastewater
treatment, it is desirable to use the effluent from a sewage treat-
ment plant for experimentation. This furnishes a direct means to
test and compare the efficiency of the process with the existing
one. On the other hand, constituents of waste waters cannot be
held constant and assays are not available for making detailed
analyses. It is not possible to interpret the data accurately
for a kinetic study. Therefore, a synthetic waste or a represen-
tative compound should be used in order to investigate the mecha-
nism of catalytic reactions, and to determine their interactions
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with ultrasonic energy. Both phenol and orthochloronitrobenzene
(OCXB) are important and common aromatic compounds in industrial
wastes. OCNB is difficult to remove by biological processes.
Therefore, the choice of these two compounds for a mechanistic
study would be of both practical and theoretical value -
LITERATURE REVIEW
Weissler (16) did an extensive study on the iodine clock
reaction under ultrasonic irradiation at high frequency (400
KHz and 1000 KHz). It was found that the reaction rates were
influenced by the variation of sound intensity, duration of
exposure, and the presence of a particular gas.
Chen and Kalback (2) studied the effect of sonic vibrations
on the hydrolysis of methyl acetate using a low frequency (23
KHz) generator. They found that the reaction rate increases
with an increase of ultrasonic intensity. However, Fogler and
Barnes (7) studied the optimum ultrasonic power of the same
reaction at 27.5 KHz and concluded that the rate of reaction
does not increase indefinitely with increasing intensity.
Instead, it reaches some optimum value after which any further
increase in power input only decreases the reaction rate.
Polotskii (13) reported the action of ultrasonic irradiation
at high frequency on certain aqueous solutions produced both
nitrate and nitrite compounds. Fitzgerald (6) conducted a
series of experiments on insonation of distilled water saturated
with various gases to produce hydrogen peroxide in aqueous environ-
ment .
Lur'e (11) did an extensive study on the oxidation of
potassium iodide and aqueous phenol solutions in an ultrasonic
field at high frequency (800 KHz). He found that the oxidation
reaction in an ultrasonic field is due to ionization of water
molecules and the formation of reactive free radicals. These
radicals may enter into the benzene ring and decompose the phenol
molecules.
The ultrasonic cleavage of certain heterocyclic and aromatic
rings to produce acetylene has been reported by Zechmeister and
his collaborators (17,18). A similar result has also been observed
by Currell and Zechmeister (4) in the ultrasonic treatment of
aqueous solutions of cyclohexanol.
Jellinek and Whitte (8) conducted a series of experiments
on the degradation of long chain molecules by ultrasonic waves.
The)' reported that ultrasonic degradation of long chain molecules
in solution under ordinary conditions is intimately connected with
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the collapse of small cavities. During such a collapse, velocity
and pressure gradients are generated in the neighborhood of the
cavity.
Heterogeneous catalysts, both metals and metal oxides, have
been used (4) in the catalytic oxidation of carbon monoxide,
sulfur dioxide, ammonia, methanol and hydrocarbons such as ali
phatic, aromatic and heterocyclic compounds at elevated tempera-
tures. No information is known in the literature for catalytic
oxidation in aqueous solution at ambient temperatures except the
previous work by Chen, Chang and Smith (3).
Ozone has been used for many years in various European
cities for the purification of water (15). The city of Phila-
delphia in Pennsylvania has used this method (1). Ozone is
generally reported to be very effective for disinfection and to
decrease odors, tastes, and organic matter of waters.
Ozone is about 13 times more soluble in water than oxygen.
The solubility of pure ozone is reported to be between 0.57
and 0.8 g/1 at 20°C. At saturation, an aqueous solution in
contact with oxygen containing 2 wt. percent ozone will contain
about 11 mg/1 ozone and 40 mg/1 oxygen (9,10).
Processes have been developed for the destruction of oxidi
zable waste in industrial waters. For example, ozone has been
shown to be effective in destroying phenols (12) and cyanides
(14). Aromatic compounds are oxidized with formation of ozonides
and eventual decomposition of the ring structure.
RESEARCH PLAN
The research plan of the present project includes the follo-
wing considerations:
1. Set up a reaction system which can be used to evaluate
sonocatalytic oxidation, sonocatalytic ozonation and catalytic
ozonation processes for wastewater treatment.
2. Evaluate the performance of each process using the
effluents from Carbondale sewage plants, and pure solutions
of phenol and OCNB.
3. Investigate the significance of parameters of the pro-
cesses such as ultrasonic intensity, amount of catalyst,
reaction time, gas flow rate, ozone consumption, initial
pollutant content in the waste waters, and the stability
of the catalysts.
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4. Obtain kinetic information with wastewaters as well as
with synthetic wastes.
5. Study the mechanisms involved in sonocatalysis.
EXPERIMENTAL
A. Apparatus
The experimental equipment is shown schematically in Figure
1. A thin-walled, flat bottomed pyrex tube (2.25 in. x 16 in.)
was used as a reaction vessel. Inside the vessel, two 2-mm I.D.
glass tubes extending from the upper part of the vessel to the
bottom allowed for sparging gas into the solutions. A condenser
was connected to the top of the vessel by 60/50 and 24/40 joints
for condensing the mist produced by ultrasonic vibrations. The
vessel was immersed in a constant temperature jacket.
A section of plexiglass tubing, 6-inches O.D. by 12-inches
long, was used as a constant temperature jacket. Constant tem-
perature water was circulating into the jacket through a 1/4
inch water tap 1 inch from the bottom of the jacket and drained
out by gravity through a 1/2-inch water tap located 2 inches
from the top of the jacket. The temperature of circulating water
was maintained within ±0.5°C of the predetermined temperature.
The 800 KHz Macrosonic submersible piezoceramic transducer
with a surface area of 1.5 square inches was mounted at the
center of the bottom of the jacket. A Macrosonics Model 180-VF
high frequency generator supplied power to the transducer.
A scale was attached on the front wall of the jacket to
ensure accurate placement of the reaction vessel one inch above
the transducer surface. The same reaction vessel was used through-
out this research to eliminate the effect of wall thickness.
For studies of catalytic processes, the same reaction system
was used. Instead of using ultrasonic irradiation to homogenize
the reaction mixture, a magnetic stirrer was used for agitation.
Two ozonators were used to generate ozone. A Welsbach Model
T23 ozonator produces about 68 mg ozone per hour at 1.15 mg/1.
The other one, Welsbach Model T408, generates about 10 g ozone per
hour at about 33 mg/1.
B. Analytical Procedures
1. Chemical Oxygen Demand (COD) - The standard dichromate
procedure is given in Reference (19). In all analyses, 50-ml
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VENT
GAS
WATER
GENERATOR
DRY ICE
CONDENSER
L
\
WIRE
GAS
WATER
REACTION
VESSEL
COOLING
JACKET
RING STAND
-TRANSDUCER
Figure 1: Experimental Equipment Schematic
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aliquots were used. Silver sulfate and mercuric sulfate were
added to each sample to catalyze organic oxidation and prevent
chloride interference, respectively. According to Standard
Methods, the accuracy of the COD test for most organic compounds
in waste waters is on the order of 95 to 1001 of the theoretical.
Due to the time required to conduct the wet analysis, a Technicon
Auto-Analyzer was later used to determine COD in samples. The
results from the Technicon Analyzer were very satisfactory. A
comparison of experimental data from these methods is shown in
Figure 2.
2. Oxygen Demand Index (ODI) Model Dr. Colorimeters
from Hach Chemical Company (Ames, Iowa) is used to analyze ODI.
The procedure is given in Reference (20) . The Oxygen Demand
Index is a rapid chemical test which gives an approximate of the
normal five day Biochemical Oxygen Demand (BOD).
3. Coliform Analysis Sabro Coliform Analyzer from
General Ionics Corporation (Bridgeville, Pennsylvania) was used
to determine coliform organisms.
4. Total Organic Carbon (TOC) The total amount of organic
carbon in the reaction samples was determined by a Beckman Model
915 Total Carbon Analyzer.
5. Gas Chromotography The phenol concentration in the
samples was determined by gas chromotographic analysis. A 5' x
1/8" OV-17 column (51 methyl-phenyl-silicone on 80/100 mesh
chromosorb W) was used in a Varian Aerograph Model 1520C Gas
Chromotograph. The Gas Chromotograph has a flame ionization
detector with nitrogen as the carrier gas. The temperature con-
ditions were: Column 150°C, injector 190°C and detector 210°C.
Sample size for injection was usually 1.5 yl.
6. Thin Layer Chromotography (TLC) In attempting to
determine the reaction products, thin layer Chromotography was
used. For the thin layer material, a 2:3 mixture of Silica Gel
HF 254 + 366 and Silical Gel G was used. The developing sol
vents were mixtures of cyclohexane and ethyl acetate in different
ratios. Some IR, NMR and Mass-Spectra were run on the compounds
separated on TLC.
7. UV Spectrophotometry For the identification of com-
pounds formed during treatment, some spectra were run on a Beckman
UV Spectrophotometer Model DB.
8. Determination of Ozone Concentration The equipment
for the absorption of ozone for measurement is shown in Figure 3.
The ozone-oxygen mixtures from the outlet of the ozonator were
passed through a fritted-glass sparger in a gas absorber containing
10
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120 ._
100 -
^80 -
§
,60
CO
03
a)
g
40
20
O Standard Method
A Technicon COD Analyzer
20
40
60
80
100
120
Standard Solution COD (mg/1)
Figure 2: Comparison of COD Values Using Standard
Method and Technicon COD Analyzer
11
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0.
t-0
Absorber
Wet Test Meter
Porous Plate
Figure 3: lodometric Ozone Analysis Apparatus
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400 ml of 2% KI solution. The volume of gas was measured by a
wet test meter. Ten ml of 10% sulfuric acid and 10 ml of starch
indicator were added to KI solution after absorption, and the
iodine produced was titrated with standard 0.1 N thiosulfate
solution. The ozone concentration (C) is calculated according
to the following equation:
(Normality of Na2S2C>3) (Volume of Na2S203) (24)
C = __ . _
(Corrected sample volume in liters)
C = Concentration of ozone in mg/1.
The amount of dissolved ozone used in reaction and decomposed
in the reaction solutions was determined by sparging the feed
gas mixture into waste waters and measuring the difference in
ozone concentration between theinlet gas and the effluent gas (21) .
9. Ultrasonic Intensity Measurement - To determine the
ultrasonic intensity applied to the reaction mixture, 350 and 3250
milliliters of water were placed in the reaction vessel and in
the cooling jacket, respectively. Ultrasound of a known level was
applied to the stationary water for a measured period of time.
The temperature change of the water in both the reaction vessel
and in the cooling jacket was measured.
From the temperature rise, the power input was evaluated for
each ultrasonic intensity level.
C. Experimental Procedures
In the wastewater experiments, effluent samples from the
Carbondale city sewage treatment plant were used. Secondary
effluent from an activated sludge process was stabilized in a
refrigerator for three to five days, and the solid precipitants
filtered out before the experiments were conducted.
In all of the experiments, 350 ml of reaction mixture
(waste waters or synthetic waste), with or without catalyst, was
charged into the reactor (Figure 1). Compressed air or ozone-
oxygen mixture was sparged into the reaction mixture slowly
through a rotameter.
In a typical sonocatalytic experimental run, the reactor
vessel was placed in the cooling jacket and the bottom of the
reactor was carefully adjusted to a distance of one inch above
the transducer surface. After proper adjustment, a known amount
of reaction mixture and catalyst were put into the reactor, and
the ultrasonic generator was then switched on.
Aliquots of the reactor mixture were withdrawn at different
time intervals for analysis. The samples with catalysts in them
were centrifuged and filtered to obtain clear solutions before
13
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the analysis was performed.
Activated Raney-Nickel from Davison Division of W. R.
Grace and Company [South Pittsburg, Tennessee) was stored in
water. A series of experiments were conducted by weighing the
wet and dry Raney-Nickel; the data are shown in Figure 4. From
the plot, the dry weight of the activated Raney-Nickel can be
estimated.
In the experiments without ultrasonic irradiation, a magnetic
stirrer was used to agitate the reaction mixture. All other
experimental procedures were identical to those of the sonocata-
lytic ones.
RESULTS AND DISCUSSION
The results and discussions of this report are divided into
three parts. They are:
A. Wastewater Experiments
B. Phenol Experiments
C. Orthochloronitrobenzene Experiments
In the wastewater experiments, the effort was concentrated
on investigating the feasibility of different processes for
advanced waste treatment. Their performances were evaluted at
various operating conditions. The results were empirical in
nature.
In the phenol study, both empirical and kinetic information
were obtained. An attempt was made to investigate the mechanisms
involved in the sonocatalytic processes.
The work on Orthochloronitrobenzene was primarily a mecha-
nistic investigation. Some experiments were also performed to
show the feasibility of eliminating the compound from waste
waters.
A. Wastewater Experiments
Three sets of experiments were conducted for wastewater:
sonocatalytic oxidation, sonocatalytic ozonation and catalytic
ozonation.
1. Sonocatalytic Oxidation
In the sonocatalytic oxidation work, 350 ml of waste-
water was used, and the experimental procedure, previously
described, was followed.
14
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1000 i—
800
60
e 600
60
•H
0)
55
400
200
200 400
600
800
1000
Wet Weight (mg)
Figure 4;
Wet and Dry Weight Ratio of Activated
Raney-Nickel in Water
15
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Figure 5 shows COD reduction in wastewaters by ultra-
sonic energy at two levels of ultrasonic intensities. It
can be seen that at a frequency of 800 KHz, the rate of COD
removal increased due to irradiation with ultrasonic energy.
However, increasing the energy level above 18.2 watts/cm^
did not improve significantly the COD removal rate.
Experimental results shown in Figure 6 are a demonstra-
tion of the sonocatalytic effect. Using a reaction mixture
containing twenty milligrams of Mn02 catalyst in 350 ml of
wastewater, sonocatalytic oxidation is more effective for
COD reduction than either catalysis or ultrasonic irradiation
alone. The effect of the sonocatalytic reaction is greater
than the additive effects, and a synergistic behavior is
observed.
Figures 7 and 8 show the reduction in the COD and ODI
in wastewater by sonocatalytic oxidation using V^Os and
activated Raney-Nickel, respectively. It appears that both
catalysts can effectively destroy the pollutants in waste-
water. However, the V205 catalyst is not physically stable
under ultrasonic treatment; the catalyst is solubilized and
the wastewater becomes yellow during the course of sono-reac-
tion. On the other hand, activated Raney-Nickel catalysts
were very stable during ultrasonic irradiation. No breakage
of the catalyst was observed, and the color of the wastewater
remained clear. A summary of the experimental results using
various catalysts is listed in Table 1. Of the wide assortment
of catalysts used, activated Raney-Nickel catalyst was most
effective for the removal of COD and ODI from wastewater.
It is shown in Figure 9 that substantial reduction in
coliform organisms can be obtained by sonocatalytic oxida-
tion using VoO^ as catalyst. However, it was concluded from
similar studies using other catalysts, and ultrasound alone,
that essentially complete kills can also be achieved by ultra-
sonic radiation alone (Table 2).
It was interesting to compare sonocatalytic oxidation
with the well-known carbon adsorption process. T.M. Granular
activated carbon from Calgon Corporation was used for experi
mentation. The experimental data are shown in Table 3. It
can be seen that sonocatalytic oxidation with activated
Raney-Nickel catalyst is compared favorably with batch carbon
adsorption.
As one of the possible explanations for the sonocatalytic
effect, it was thought that ultrasonic energy generates heat
on the surface of the solid catalysts, and that the high sur-
face temperature would promote the reaction. If this were
true, then a similar effect could be obtained simply by
boiling the reaction mixture with the catalyst at high temperature
16
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120 i-
100 -
Intensity (watts/cm^)
O
A 18.2
D 33.3
Insonation Time (hr)
Figure 5: COD Reduction Using Ultrasonic Energy:
Effect of Ultrasonic Intensity at 800 KHz and 25.5°C
17
-------
120 |-
100
80
bO,n
060
§
u
40
20
20 mg. Mn02 Catalyst
Ultrasound + 20 mg Mn02
J I L
10 20 30 40 50 60
Reaction Time (min)
Figure 6: Experimental Data Demonstrating the
Sonocatalytic Effect
18
-------
120 r-
100
COD
GDI
123
Reaction Time (hrs)
Figure 7: Reduction in COD and ODI by Sonocatalysis Using
19
-------
120 i-
100 T-
oo
6
60 I—
40 h-
20 I—
Figure 8:
A COD
n
0.5 1 1.5
Reaction Time (hrs)
Reduction in COD and ODI by Sonocatalysis
Using Activated Raney-Nickel
20
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TABLE 1: A SUMMARY OF THE EFFECT OF SONOCATALYSIS ON WASTEWATER
Amt. (mg/
350 ml of
Wastewater)
Ultrasonic
Energy
(watts/cm^)
% COD
Reduction
in 2 Hours
% GDI
Reduction
in 2 Hours
Stability of
Catalysis Under
Ultrasonic
Ni Supported
on Kieselguhr
MoOg Supported
on Alumina
ZnO Supported
on Alumina
Activated Raney
Nickel
V205
Pt. Black
A1203
Fe03
Silica Gel
Silica Gel
Mn02*
Mn02*
None*
500
500
500
1000
20
20
20
20
500
500
20
20
0
33.3
33.3
33.3
33.3
33.3
33.3
33.3
33.3
33.3
0
33.3
0
33.3
40%
491
39.5%
78%
42%
48%
35%
7%
63%
38%
50%*
9%
18%
48%
56%
33%
96%
45%
47%
52%
20%
68%
30%
Stable
Stable
Stable
Stable
Soluble in Water
Stable
Became Colloidal
Became Colloidal
Particals Broken Up
Stable
Became Colloidal
Stable
^Experimental Data at One Hour
-------
30,000 k
25,000 -
80 100
Reaction Time (min)
Figure 9: Coliform Reduction by Sonocatalysis Using
22
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TABLE 2: Coliform versus time with different catalysts
(20 mg in 350 ml waste waters), at 25.5°C,
ultrasonic treatment intensity 33.3 watts/cm^,
air flow.
CATALYST
Mn02
PtOo
£
Ag20
V2°5
V205
no
ULTRASOUND
yes
yes
yes
yes
no
yes
COLIFORM
(ORIGINAL)
31500
22300
20600
28800
20100
26200
COLIFORM
(4 hr)
0
0
0
0
3900
0
23
-------
TABLE 3: Comparison of the experimental data of sonocatalytic oxidation
with activated granular carbon adsorption on reduction of GDI
in waste waters (initial ODI concentration 25 ppm).
N. Item
AMOUNT \
70 mg
200 mg
500 mg
1000 mg
ONE HOUR
RANEY- NICKEL
WITH ULTRASONIC
TREATMENT
23
21
18
10
ACTIVATED
GRANULAR CARBON
22
22
19
15
TWO HOURS
RANEY- NICKEL
WITH ULTRASONIC
TREATMENT
20
18
13
0
ACTIVATED
GRANULAR CARBON
20
16
13
9
-------
To test this hypothesis for wastewater samples, three
experiments were conducted. The experimental data are given
in Table 4. It can be seen that heat generated by boiling
effects negligible changes in COD and ODI.
2. Sonocatalytic Ozonation
After it was determined from the sonocatalytic oxida-
tion experiments that activated Raney-Nickel was the most
suitable catalyst from the standpoint of stability and
effectiveness, an attempt was made to improve treatment
efficiency by using ozone-oxygen mixture as the gas flow.
A set of experiments were conducted to investigate the
ozonation of wastewater under the following conditions:
a. Ozonation alone
b. Ozonation and activated Raney-Nickel catalysis
c. Ozonation and ultrasonic irradiation
d. Ozonation, catalysis, and ultrasonic irradiation.
A Welsbach Ozonator Model T23 was used initially to
generate ozone. The rate of ozone generated was very small;
only 68 mg per hour.
The effectiveness of each method of treatment in reduc-
ing the COD, and ODI, of wastewater is shown in Figures 10
and 11, respectively. The results indicate that sonocata-
lytic ozonation (condition d., above) gives the best perfor-
mance. The fact that the effectiveness of ozone oxidation
can be improved by catalysis suggests the possibility of a
new process which can find application in waste treatment.
Even greater efficiencies could be realized, by optimization
techniques.
The effect of various doses of activated Raney-Nickel
catalyst on sonocatalytic ozonation is presented in Figure
12. It is shown that large increases in the catalyst dose
results in only a minimal increase in the rate of COD removal
in wastewater, within the range investigated.
The effect of initial concentration of COD in waste-
waters on the rate of COD removal at 25.5°C and 33.3 watts/cm2
is presented in Figure 13. Wastewater samples with a lower
COD value were obtained by passing the effluent from the
secondary treatment plant through a carbon adsorption column.
In this way, the COD of the effluent was reduced from an
initial value of 100 mg/l to 42 mg/1 and 12 mg/1. Each sample
was treated under identical experimental conditions. As seen
in Figure 13, the greatest COD removal is obtained when the
initial COD is highest. Also, after 2 hours reaction time,
the greatest COD remains in the sample which had the greatest
initial COD. In other words, the final COD is directly
25
-------
TABLE 4: Catalytic Oxidation of Wastewater by Boiling
S3
CT>
\ Item
Time \
Initial
concen-
tration
Two hour
boiling
Raney
Nickel
500 mg
74
68
COD
Raney
Nickel
500 mg
Zeolite
500 mg
74
70
Zeolite
500 mg
74
71
ODI
Raney
Nickel
500 mg
26
22
Raney
Nickel
500 mg
Zeolite
500 mg
26
25
Zeolite
500 mg
26
25
-------
§
Ozone
Ozone & Nickel
X Ozone & Ultrasound
O Ozone, Nickel & Ultrasound
Figure 10:
0.5 1
Reaction Time (hr)
COD Reduction by Ozonation, Catalytic Ozonation,
and Sonocatalytic Ozonation
27
-------
40 —
30
H
P
O
20
10
A Ozone
d Ozone & Nickel
X Ozone & Ultrasound
O Ozone, Nickel & Ultrasound
0.5 1
Reaction Time (hr)
1.5
Figure 11:
ODI Reduction by Ozonation, Catalytic Ozonation,
and Sonocatalytic Ozonation
28
-------
Catalyst Dose
D 285 mg/1
A 1425 mg/1
2850 mg/1
Figure 12:
0.5 1
Reaction Time (hr)
COD Reduction by Sonocatalytic Ozonation:
Effect of Catalyst Dose
29
-------
120 h
100
Q
O
40
20
— Sono-ozonation
Sonocatalytic
Ozonation
80 -
60 _
0.5
1.5
Figure 13:
Reaction Time (hr)
COD Reduction by Sono-ozonation and Sonocatalytic
Ozonation: Influence of Initial COD
30
-------
related to initial COD; the percent removal being about
the same for each of the three samples (about 75%).
3. Catalytic Ozonation
The experimental results for COD removal by catalyzed
ozonation reactions (Figure 10) indicated that catalytic
ozonation (as well as sonocatalytic ozonation) could be a
potential treatment process for wastewater. Catalytic ozona-
tion will be further considered in this section.
In previous experiments, the ozonator used produced only
a small amount of ozone (about 68 mg of ozone per hour at
1.15 mg/1 of ozone). Since further experimentation of this
process seemed desirable, a new ozonator of greater capa-
city was purchased. The ozone concentrations in the gaseous
mixtures at different flow rates from this generator were
determined by the iodometric method. The data are shown
in Table 5. It can be seen that about ten grams of ozone
per hour at 33.0 mg/1 were generated by this ozonator.
(This is compared to 68 mg of ozone per hour generated by
the previously used ozonator.)
Figure 14 shows data from four experiments in catalytic
ozonation. In two of those experiments, agitation in the
reaction mixture was accomplished by ozone bubbling alone.
A magnetic stirrer was used to agitate the reaction mixture
in the two other experiments. The results indicated that
the type of agitation dLd effect the oxidation rate and,
therefore, a magnetic stirrer.was used in subsequent runs.
Experimental results for catalytic ozonation using
samples at different initial COD levels and different amounts
of catalyst are presented in Figure 15. It is seen that with-
in the catalyst range studied, the rate of COD removal is
increased with an increase in the amount of catalyst used; and
that a lower COD results when the initial COD is lower. The
removal of up to 85% of the COD from strong effluents, and up
to 80% from a better quality sample suggests that catalytic
ozonation could be applied under a variety of circumstances
in wastewater treatment.
In order to determine the amount of ozone consumed during
the catalytic ozonation process, the concentration of ozone
in the gas mixture was measured at the inlet and the outlet
of the reaction system. The data in Table 6 indicate that
greater agitation; i.e., mixing versus simple bubbling;
results in greater amounts of ozone used in reaction, which
agrees with the COD data shown previously in Figure 14. High-
shear mixing would, no doubt, result in increased rates of
ozone utilization and increased rates of COD removals.
31
-------
TABLE 5: Ozone Concentration in Gas Feed Mixtures
SAMPLE
1
2
3
GAS FLOW
RATE
(1/min)
0.4
0.5
0.6
NazS203
TITRATED
(ml)
21.2
30.55
35.78
GAS FEED
ACCUMULATED
IN WET TEST
METER
(liter)
1.4736
2.237
2.577
DENSITY OF *
OZONE-OXYGEN
MIXTURE
AT 70°F,6 psig
(mg/1)
995
995
995
CONCEN-
TRATION
OF OZONE
(mg/1)
34.55
32.77
33.320
WEIGHT I OF
OZONE IN
OZONE-
OXYGEN
MIXTURE (%)
3.47
3.29
3.34
* Data from Welsbach Corporation
-------
100
Without Agitation
With Agitation
o
Figure 14:
0.5 1 1.5
Reaction Time (hr)
COD Reduction by Catalytic Ozonation:
Effect of Agitation
33
-------
100 Jc-
60 L
U)
Q
O
U
40
20 h-
Figure 15
£ No Catalyst
D 1430 mg/1 R-N
O 2860 mg/1 R-N
0.5 1 1.5 2
Reaction Time (hr)
COD Reduction by Catalytic Ozonation
Effect of Catalyst Dose
34
-------
TABLE 6: Ozone Utilization During Ozonation of Wastewater
SAMPLE
Ozonation w/o
Agitation
Ozonation Wit!
Agitation
Catalytic
Ozonation
With
Agitation
OZONE
CONCENTRATION
IN GAS FEED
Cmg/1)
32.77
32.77
32.77
OZONE
CONCENTRATION
IN GAS OUTLET
(mg/1)
25.30
20.927
17.049
OZONE
CONSUMPTION
Cmg/1)
7.47
11.843
15.721
WEIGHT PERCENT
OF OZONE
CONSUMED
(%)
22.8
36.2
48
00
Oi
-------
Toward the end of the period of this project, some
experiments were conducted to determine if simple oxygena-
tion or complete conversion to carbon dioxide, as measured
by changes in TOC, resulted from catalytic ozonation. Using
a wastewater having an initial TOC of 50 mg/1, 45% of the
TOC was removed in 2 hours at a catalyst dose of 143 mg/1,
and 60% of the TOC was removed at a catalyst dose of 14300
mg/1 (Figure 16).
4. Conclusions of Waste Water Experiments
Summarizing all the experimental results in wastewaters,
the following conclusions can be drawn:
(a) Ultrasound alone has a significant effect on the
oxidation of wastewater when air is used as the feed gas.
Sonocatalysis exhibits a synergistic effect; i.e., the
results of sonocatalytic oxidation are better than the
combined effects of sono-oxidation and catalytic oxi
dation.
(b) Activated Raney-Nickel was found to be a good
catalyst for sonocatalytic oxidation (ultrasound, acti-
vated Raney-Nickel and air). A reduction in COD of 78%
and ODI of 96% was obtained in two hours of treatment.
Furthermore, this catalyst is stable under ultrasonic
irradiation.
(c) At low catalyst concentration and low ozone doses,
there is only a slight synergetic effect in sonocatalytic
ozonation (ultrasound, activated Raney-Nickel and ozone).
Sonocatalytic ozonation, however, can remove COD and ODI
in wastewater.
(d) The unique combination of activated Raney-Nickel
and ozone/oxygen mixtures could be a potentially effec-
tive treatment process for wastewater. Depending on the
initial COD of the waste, and the concentration of cata-
lyst, a 40% to 85% reduction in COD and a 60% reduction
in TOC have been achieved for wastewater.
(e) Bacteriological examination indicates that the
water samples after different treatments are free of
coliform organisms.
B. Phenol Experiments
1. Different Types of Treatment
Ke have reported previously (3) that addition of a cata-
lyst in the sono-oxidation of aqueous phenol retards the
reaction rate. These results are reproduced in Figure 17.
The reason for this inhibition was attributed to the fact that
36
-------
50
40 -
30 -
bo
S
o
H
20 -
10 -
0.5
O Ozone Alone
Q 143 mg/1 R-N
A 14300 mg/1 R-N
1.5
Reaction Time (hr)
Figure 16: TOC Removal by Catalytic Ozonation
37
-------
500
400
tc
E
^
PL,
300
C
O
200
rt
-------
there is no catalytic oxidation of phenol at room tempera-
ture. In certain situations, therefore, solid catalysts
in the solution actually interfere with ultrasonic waves
transmitted from the generator and reduce the effect of
ultrasonic irradiation.
Figure 18 shows the experimental data of various types
of treatment for phenol solutions. In all the experiments,
200 ml of 0.00532M aqueous phenol solution (500 mg per liter)
were used. Analyses were performed mainly by gas chromato-
graphy. Treatment time was three hours and samples were
withdrawn every half hour. The results are summarized in
the following:
(a) The phenol solution was dosed with 160 mg of acti-
vated Raney-Nickel and stirred with a magnetic stirrer.
No change in 1he phenol concentration was observed.
(b) About 65 mg ozone per hour (1.15 mg per liter)
were bubbled through the phenol solution. The treat-
ment caused a 31% decrease in phenol concentration in
three hours.
(c) The phenol solution was irradiated by ultrasound.
An almost linear decrease of the phenol concentration of
60% occurred in three hours.
(d) A combined treatment of ultrasonic irradiation and
ozone bubbling showed a decrease in phenol of 91%.
(e) 160 mg of activated Raney-Nickel in the phenol
solution irradiated with ultrasound causes no appreciable
change in comparison with the ultrasonic irradiation
alone (60% decrease) .
(f) 160 mg of activated Raney-Nickel together with ozone
bubbling effects the phenol decrease considerably, 68%
compared with 31% ozone bubbling alone.
(g) The lowest phenol concentration after three hours'
treatment was reached by a combination of ultrasonic
irradiation, ozone bubbling and 160 mg of activated
Raney-Nickel. The decrease was 95%.
From the experimental data, two important points are
revealed. First, it verifies the previous results that cata-
lyst actually inhibits the sono-oxidation. However, catalysts
promote the sono-ozonation process because the ozonation of
phenol is promoted by catalysts. Secondly, catalytic ozona-
tion alone effectively oxidizes phenol without insonation.
39
-------
500
Ultrasound +
Ozone + 160 mg Raney-Nickel -
400
Ultrasound + Ozone
oo
0
o
-H
CD
O
u
S
0)
.c
P-I
300
200
100
160 mg Act. Raney-Nickel
D
Ozone + 160 mg
Raney-Nickel
Ultrasound + 160 mg
Raney-Nlckel
Figure 18:
1 2
Reaction Time (hrs)
Phenol Conversion by Different
Oxidative Treatments
40
-------
2. Variation of the Amount of Catalyst
A set of experiments were conducted to study the effect
of the variation of the amount of activated Raney-Nickel in
the different types of treatment. The results are summarized
as follows:
(a) Different amounts of activated Raney-Nickel in
aqueous phenol solutions were agitated with a magnetic
stirrer; no conversion of phenol was observed in any case.
(b) Aqueous phenol containing different amounts of acti-
vated Raney-Nickel under ultrasonic irradiation did not
show significant differences in comparison with the
results without a catalyst.
(c) An increase in the amount of catalyst during ozona-
tion, however, causes an increase in the amount of phenol
converted. The results are shown in Figures 19 and 20.
(d) These phenomena of maximum catalyst dose for cataly-
tic sono-oxidation and optimum catalyst dose for sono-
catalytic ozonation are clearly observed in Figure 20.
Increasing the amount of catalyst during sono-ozonation
increases phenol conversion to a maximum, but further
increases in a catalyst decrease phenol conversion
because of interference with insonation. (Figure 20)
In all cases, sonocatalytic ozonation is better than
either catalytic ozonation or sonocatalytic oxidation. As is
seen, when the amount of catalyst in the aqueous solution ex-
ceeds the optimum level, a decrease in rate of conversion
results.
3. Ozone Consumption
For both process application and mechanistic study, it was
of interest to evalute how much ozone is consumed in different
types of treatment. A set of experiments were performed in
which ozone concentrations at the inlet and outlet of the reac-
tion system were determined by iodometric methods at different
times. The experimental results for a two-hour reaction
period are shown in Table 7. As expected from prior results,
the use of insonation and catalyst resulted in the greatest
utilization of ozone. Parallel conclusions on phenol conver-
sions and ozone consumption can be drawn for both the sono-
ozonation and catalytic ozone processes. In comparing ozone
utilization by aqueous phenol solution to utilization by dis-
tilled water under similar experimental conditions, it appears
that a significant amount of ozone is used in the oxidation
of phenol. Furthermore, both ultrasound and catalyst have the
41
-------
500
400 _
300 -
o
u
0)
ex,
200 -
100
Figure 19:
Reaction Time (hrs)
Catalytic Ozonation of Phenol
Effect of Catalvst Dose
42
-------
500
Ultrasound + Ozone + RaNi
Ultrasound + RaNi
100
0
200 400
mg of Activated Raney-Nickel Catalyst
600
Figure 20: Comparison of Phenol Conversion with Variation of
the Amount of Catalyst (Three Hours Treatment)
43
-------
TABLE 7
Milligrams Ozone Decomposed and Used in 2-Hour Reaction
SAMPLE
Treatment
Ozonation
Catalytic Ozonation
Sono-ozonation
Sonocatalytic Ozonation
Distilled
Water
8
10
13
23
200 mg/1
Phenol Solution
41
76
96
120
Ozone produced in 2 hours: 145 mg
Catalyst: 200 mg activated Raney-Nickel/200 ml
44
-------
ability to either absorb or decompose ozone according to
the experimental data of distilled water. Therefore, resi-
dual ozone in the solutions is small.
4. Analysis of Chemical Oxygen Demand
In the previous experiments, analyses of phenol were
performed by gas chromatography, which shows only the de-
crease in the phenol concentration. Since it is desirable
to get information about the oxidation state of the compounds
formed, a Technicon AutoAnalyzer was used to determine Chemi-
cal Oxygen Demand (COD). For this reason, another set of
experiments was performed starting with a 40 ppm phenol solu-
tion and treating it for seven hours by different oxidation
processes. The following treatments were compared to each
other: ozonation versus catalytic ozonation; sono-oxidation
versus sonocatalytic oxidation; and sono-ozonation versus
sonocatalytic ozonation. The results are shown in Figures
21, 22 and 23 respectively. In every case, the average
oxidation state of the reaction mixture gets higher with
increasing time of treatment. This is represented by a
decrease in the chemical oxygen demand (COD). However,
whereas phenol is no longer detected after 2 1/2 hours, the
COD values decrease rather slowly. Apparently, the rate of
phenol conversion to catechol and resorcinol is greater than
the rates of subsequent steps leading to higher oxidation
states. Nevertheless, in the case of sonocatalytic ozona-
tion, the decrease in COD to 12% after seven hours of treat-
ment is considerable, while catalytic ozonation alone reduces
COD to 35%.
In Figure 24, the COD removed is plotted against time
for different types of treatment of aqueous phenol solutions
at 500 ppm. Sonocatalytic ozonation (ultrasound, activated
Raney-Nickel and ozone) is the best combination for removing
COD. Both catalytic ozonation and sono-ozonation are superior
to ozonation alone.
A Beckman Model 915 Total Carbon Analyzer was used to
determine whether the carbon contents of the aqueous phenol
solution has been changed during treatment by ozonation and
catalytic ozonation. Data indicated that the TOG was reduced
very slowly. This would indicate that while most of the phenol
in solution is converted into compounds of higher oxidation
states, only a small part is converted to carbon dioxide
during treatment. These results are shown in Figure 25 and
should be compared to Figure 24.
5. Determination of the Reaction Products
a. Analysis by UV - Spectrophotometry
Since the gas chromatograph method was used primarily
for phenol determinations and since the method does
not supply information about the reaction products
(beside the phenol peak, no other peaks were observed),
45
-------
100
80
60 -
rt
e
40
20 -
Ozone
Ozone + Catalyst
Figure 21:
L 2 3 4 5 6 7
Reaction Time (hr)
Conversion of Phenol and COD Removal by Ozonation
Effect of Catalysis by Activated Raney-Nickel
46
-------
100
80
00
g
240
-------
100
80
— Ultrasound + Ozone
— Ultrasound + Ozone +
Catalyst
Figure 23:
Reaction Time (hrs)
Conversion of Phenol and COD Removal by
Sono-ozonation: Effect of Catalysis by
Activated Raney-Nickel
48
-------
400
Ultrasound + Ozone + RaNi-
300
200
o
E
0
Q
O
U
100
Ozone V RaNi
Ultrasound + Ozone
Reaction Time (hrs)
Figure 24: Comparison of COD Removal from Aqueous Phenol
Solutions by Different Types of Treatment
49
-------
100
Ul
o
60
ti
n)
I 90
o
o
H
4-1
C
0)
u
M
0)
80
T" Sono-oxidation
O Ozonation
D Sonocatalytic Oxidation
• Catalytic Ozonation
I
I
I
Figure 25
234!
Reaction Time (hrs)
TOC Removal in Aqueous Phenol Solution
-------
an ultraviolet-spectrophotometer was used to analyze
samples. Phenol in water exhibits an absorption band
at about 270 mm. This band corresponds to the weak
260 mm band of benzene, which is the forbidden transi-
tion to a homopolar excited state. The substituted
auxochrome OH, which is a polar group containing
unshared electrons, shifts the band to longer wave-
lengths and also intensifies it. Figure 26 shows UV
spectra obtained after different times of sono-ozona-
tion. It is seen that the vibrationa-1 structure of the
270 mm band disappears. This is generally the case
when the substituent is a polar group, and a polar
solvent like water is used. However, the increasing
background in the UV spectra makes a quantitative
analysis almost impossible. On the other hand, this
background points to the formation of one or more
new compounds. In Figure 27, the spectra of treated
solutions are compared, to that of the starting material,
and new absorption bands at about 280 and 230 mm can be
seen. Figure 28 shows that a mixture of hydroquinone
and catechol in aqueous phenol solution furnishes a
similar spectrum. It is assumed, therefore, that both
hydroquinone and catechol are formed. Figure 29 shows
the spectra of reaction products after six hours of
different treatments. Considering spectrum "d" in this
plot, it seems that the intermediates, catechol, resor-
cinol and others, have disappeared under the more power-
ful treatment (sonocatalytic ozonation). This obser-
vation is in agreement with the observation that ini-
tially, the solution becomes yellow but after a longer
time, it becomes colorless again. In contrast, some
hydroquinone and catechol are left in the solution
under either ozonation or catalytic ozonation.
b. Analysis by Thin Layer Chromatography (TLC)
Thin layer chromatography was used to acquire more infor-
mation about the reaction products (see C. orthochloro-
nitrobenzene for description of the Techniques). The
time of treatment was varied in a set of experiments
with a 500 mg/1 aqueous phenol solution (100 mg phenol
in 200 ml H20) treated by ultrasound, ozone, and acti-
vated Raney-Nieke 1. After a given reaction time, the
reaction mixtures were extracted with ether, most of
the ether was vaporized, and the concentrated extracts
were put on a thin layer plate. Subsequent to ether
extraction, the reaction mixtures were freezedried and
the residues were dissolved in acetone, The acetone
solutions were concentrated and put on a thin layer
plate (chromatograph e). The distribution of ether
extractable compounds on the TLC plate is shown in Fig-
ure 30. After one hour of sonocatalytic ozonation, an
additional less polar product can be observed at the top
51
-------
200
240 -
280 -
320 -
20 40 60
Transmission (Reference: Water)
80
100
Figure 26: UV Spectra, Sono-ozonation of Phenol Solution
a: starting material; b: after 1/4 hr-, c: 1/2 hr:
d: 3/4 hr-, e: 1 hr-, f: 1 1/2 hr-, g: 2 hrs-, h: 2
1/2 hrs-, i: 3 1/2 hrs treatment.
-------
200
Ul
240
280
320
0
80
100
20 40 60
Transmission (Reference: Phenol)
Figure 27: UV Spectra, Sono-ozonation of Phenol Solution
-------
280 r
Figure 28:
240
280
320
0
80
20 40 60
Transmission (Reference: Phenol)
UV Spectra of Synthetic Mixture and Reaction Products
a: Hydroquinone, b: Catechol, c: Hydroquinone
and Catechol, d: Aqueous Phenol solution after
1/2 hour treatment with U.S. + 0
100
-------
200 r-
240 -
m
280
320
20 40 60 80
Transmission (Reference: Water)
Figure 29: UV Spectra of Reaction Products
100
for Different Types of Treatment of Aqueous Phenol Solution
a: 03, b: 03 + 0.5 gr Ni, c: 03 + U.S., d: 03, U.S.,and
0.5 gr Ni using a more powerful U.S. generator)
-------
W)
O
CO
©
d)
e)
Figure 30: Thin Layer Chromatograms
(a): starting material; b)c)d): concentrated ether
extract of solutions treated for b) 1 hour, c) 3
hours, d) 5 hours', e) solid residue dissolved in
acetone.
56
-------
of the thin layer plate (chromatogram c). This com-
pound is the only one which remains after a treatment
of five hours (chromatogram d). Only the lower part
of the chromatograph b remains.
In order to get enough material for infrared and
mass spectrometric analyses, sonocatalytic ozonations
of aqueous phenol solutions of higher concentrations
(1 g or 3 g phenol in 200 ml H20) were conducted for
longer periods (16 hours, 20 hours).
The compounds formed in several runs were combined,
and extracted with ether. The ether extract was concen-
trated and thrice separated by preparative TLC. These
relatively pure materials were analyzed by mass spectro-
metry. In the spectra of the less polar compounds, the
masses 108 (quinone) and 110 (hydroxybenzenes) appear,
as well as mass 127 (protonized pyrogallol). The most
polar compound, which remains at the starting point on
the TLC plate, shows a main peak at m/e = 98 in its mass
spectrum. This could be the molecular peak of 2-cyclo-
hexene-1-ol or cyclohexanone- However, this would mean
that a reduction of phenol occurs in the reaction. Al-
though reduction of orthochloronitrobenzene occurs (see
Section C), it seems rather unlikely here. While all
spectra contained several impurities, along with small
amounts of solvent used for separation on TLC, the
spectra show positive evidence of the presence of com-
pounds like catechol, hydroquinone, and resourcinol, as
well as quinoneand pyrogallol, in the reaction mixture.
After ether extraction, the remaining aqueous solu-
tion was freezedried and the solid residue treated with
diazomethane. If the residue is an acid, the correspon-
ding methyl ester should be formed. IR and NMR spectra
of the reaction product show evidence of esters, although
it was not possible to evaluate the spectra quantitatively
6. Conclusions of Phenol Experiments
a. Phenol in aqueous solution does not react with oxy-
gen (air) under the influence of catalysts. On the other
hand, phenol is oxidized by air and ultrasonic irradiation.
However, catalysts interfere with sono-oxidation.
b. Phenol reacts with ozone slowly, but activated Raney-
Nickel catalyzes the reaction. Application of activated
Raney-Nickel, ozone, and ultrasound gives the best per-
formance under the same operating conditions.
c. By measuring changes in phenol concentration, COD,
and the TOG of the reaction mixtures, it was found that
the rate of phenol disappearance is nuch faster than the
rate of TOG removal. Apparently, phenol is converted
sequentially to more and more highly oxidized compounds,
57
-------
while only a small portion is actually converted to
co2.
d. Intermediate products in the reaction mixture are
identified as catechol, hydroquinone, quinone aid pyro-
gallol; compounds which are more highly oxidized than
phenol. However, these compounds also disappear during
sono-catalytic ozonation showing that even more highly
oxidized compounds are formed.
e. Both catalytic, and sonocatalytic, ozonation would
apply as treatment processes for phenol wastes.
•
C. Orthochloronitrobenzene (OCNB) Experiments
1. Reaction Mixtures
Reaction mixtures consisted of 200 ml distilled water,
5 grams of freshly sublimed OCNB, and 5 grams of aluminum
powder or 2 grams of activated Raney-Nickel catalyst. The
gas was oxygen, air, or ozone/oxygen mixtures. Since much
more OCNB was present than was required for saturation,
solid substrate was present in the reaction mixture and
tended to sublime and become entrained in the gases. The
amount collected in the trap depended on the duration of
sparging, the flow rate of gases, and the initial concen-
tration of OCNB. For example, after six hours insonation
and air sparging, 0.30 grams of OCNB was recovered in the
cold trap. This does not occur, however, if only a satura-
ted solution (approx. 2 x 10'3M) of substrate is used.
Some experiments were run with a saturated solution of
OCNB in water. To 200 ml of this solution was added 2 grams
of either aluminum powder or activated Raney-Nickel. The
sample was irradiated with ultrasound at 800 KHz and sparged
with an ozone/oxygen mixture for 24 hours. At the end of
the reaction time, neither OCNB, nor any products, could be
detected by thin layer chromatography in the reaction mixture.
Since the starting material is easily detected in an identical
experiment in the absence of catalyst, it must be concluded
that the sonocatalytic reactions ultimately destroy OCNB.
2. Isolation and Identification of Products
After insonation for 6 hours, the reaction mixture is
filtered to remove catalyst and solid OCNB. The yellow
aqueous solution of intermediates, products, and unreacted
OCNB, is separated by ether extraction into two fractions.
Several products can be seen upon thin layer chromatographic
analysis of reaction mixtures. The ether extract, after
concentration and TLC analysis (silica gel and 60/40 cyclo-
hexane/ethyl acetate solvent) separates into three major
58
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components (A, B, and C) plus OCNB. The aqueous portion,
upon being concentrated by freeze drying, consists of a
dark brown tacky material. It is highly polar; not being
eluted from a TLC plate under the conditions given above.
A test for aluminum is faintly positive when the aqueous
portion (about 200 ml) is concentrated to 0.5 ml; however,
no positive test is obtained with the unconcentrated reac-
tion mixture. Qualitatively, it appears that bubbling
ozone/oxygen through the reaction mixture slightly increases
the reaction rate. On the other hand, when nitrogen is the
sparging gas, the same types of products' are obtained, but
more slowly. While the isolations were made from the alumi-
num-catalyzed reactions, active Raney-Nickel, compared to
aluminum, appears to give lower yields and slightly different
products.
Although no products are found in the absence of ultra-
sound at room temperature in 48 hours, reaction does occur
in boiling water. After 100 hours of refluxing OCNB, water,
aluminum powder and air and then isolating the organic materials,
a TLC separation is obtained which is similar to the separa-
tion obtained from the sonocatalytic reaction mixture. The
major difference is that compound A is the main product, and
little of the dark brown, tacky, material is formed. In the
refluxing experiment, copious quantities of Al(OH)j are formed,
which is in contrast to insonation at room temperature. Under
similar reflux conditions, activated Raney-Nickel also pro-
duces products; however, some new products are formed.
By repeating sonocatalysis of OCNB several times, and
combining the reaction mixtures, it was possible to amass
sufficient material to isolate each of the three major compo-
nents; A, B, and C. Actually, the dark brown, tacky, mate-
rial was the major product but was not resolvable by our
procedures.
3. Isolation and Identification of Compound B
Compound B was separated from the combined ether extracts
from ten runs (5 gms OCNB, 5 gms Al°, 200 ml HoO, air, 6 hours
reaction). The combined extract was eluted through a silica
gel column (50 gm) with petroleum ether, then with 10% ethyl
ether in petroleum ether, and finally with 20% ethyl ether
in petroleum ether. In the first fraction, compound B elutes
along with small amounts of other products and some OCNB, but
in later fractions, only OCNB elutes. Products not eluted
with the ethyl ether-petroleum ether mixtures are eluted with
methanol. Repeated preparatory TLC (8" x 8" plate of mixture
of Silica gel G and Silica gel HP 254 + 366 in 3/2 ratio
developed with a 1/1 mixture of cyclohexane and ethyl acetate)
of combined ether extracts yields a mixture of compound B
59
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contaminated with OCNB. Final elution with a 60/40 mixture
of cyclohexane/ethyl acetate separates compound B from OCNB.
Further purification of B by sublimation at 140°C and
1 mm Hg gives an orange yellow solid. Infrared analysis in
Nujol shows absorption bands at 1610, 1580, 1370, 1340, 1250,
1055, 1025, and 750 cm'1- The mass spectrum (10 volts) shows
weak parent peaks at m/e of 270/268/266 and major fragments
at 254/252/250, 233/231, 141/139, 113/111, and 38/36. An
elemental analysis results in the following elemental distri-
bution: %C: 56.00, %H: 2.99, IN: 10.79, and %C1: 25.14.
Based on these analyses, compound B is postulated to be 2,2'-
dichloroazoxybenzene (Figure 31).
4. Isolation and Identification of Compound C
Since compounds A and C have similar retentions on TLC
analysis, they are easily separated from B and OCNB, but
not easily from each other. First, the ether extract was
concentrated andirost of the OCNB was removed by sublimation
at 50°C and 1 mm Hg. The residue was separated by repeated
preparative TLC (8" x 8" plate of silica gel B/silica gel
HF 254 in 3/2 ratio developed with a 60/40 ethyl acetate/
cyclohexane mixture). Combinations of several TLC separa-
tions yielded compound C which was further purified twice
by sublimation at 138°C and 1 mm Hg to a yellow solid (20 mg
from 10 gm starting OCNB). Infrared analysis of compound C
shows major adsorption at 3290, 3380, 1500, 1270, 1200, 1040,
and 910 cm"1. The mass spectrum (10 volts) shows major peaks
at m/e of 143/145, 141 and 44; and minor peaks at 113, 80,
78, 58 and 36/38. Elemental analysis of compound C results
in the following: C: 50.51%, H: 4.32%, N: 9.07%; and by
difference (because insufficient sample was sent for analysis)
0: 11.24% and Cl: 24.89%. We believe Compound C is ortho-
chlorophenylhydroxylamine (Figure 31).
5. Isolation and Identification of Compound A
Compound A was isolated in the same manner as C except
with more difficulty because of its lower concentration.
Purification by double sublimation at 140°C and 1 mm Hg
yielded a dark red solid. Compound A apparently decomposes
or oxidizes on standing because all the analytical data
indicated that compound A was a mixture; e.g., mass spectral
analysis changed with time, and elemental analysis showed
C: 66.71, H: 4.40, H: 11.41, Cl: 2.85, 0: 14.63. Different
isolations of compound A, however, always exhibited a mass
spectrum peak at m/e 212 and we believe this to be the
parent peak. A possible structure is shown in Figure 31.
This compound of that structure would exhibit m/e 212 and
the elemental analysis would be that of a mixture which
would be approximately 90% compound A and 10% compound C.
60
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Compound Structure
A 0=Q=N-N=Q=0
(suggested)
D 2,2'-dichloroazoxy-
benzene
Orthochlorophenyl-
hydroxylamine
Figure 31: Structures of Intermediate Products
in OCNB Experiments
61
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6. Comparison with Known Zinc Reductions
It is well known that the zinc reductions of nitro-
aromatics yield a variety of compounds as shown in the
chart below:
Zn-NH4CL/H20
PhN02-
50-55°C
dextrose - NaOH
100°C
Zn(2 moles)-NaOH/CH3OH/H20
_>PhNHOH (55%)
(phenyIhydroxy1amine)
o-
_>PhN+=NPh (80%)
(azoxybenaene)
reflux
Zn(3 moles) NaOH/CH3OH
Sn(or Fe) - HC1
(85%)
(azobenzene)
PhNH-NHPh (88%)
-> (hydroazobenzene)
_ PhNH2
>(aniline)
Since Compounds B and C are reduction products of the OCNB,
it is clear that reduction as well as oxidation is occurring.
7. The Flaking Oxide Theory
Aluminum is a very reactive metal. However, unless its
protective oxide coating is destroyed, aluminum is passive
towards many substances. It seems probable in our experi-
ments that insonation causes the oxide layer to flake off
and expose the bare aluminum metal. Hydrogen is formed upon
contact with water and a catalytic hydrogenation proceeds
on the aluminum surface. Support for this comes from the
fact that essentially the same products are formed on acti-
vated Raney-Nickel, which contains several percent aluminum.
8. The Temperature Rise Theory
Although no products are found in the absence of ultra-
sound at room temperature, reaction does occur in boiling
water in 48 hours with both aluminum powder and activated
Raney-Nickel. When refluxing with aluminum, however, copious
quantities of Al(OH), are formed in contrast to the room
temperature sonocatalysis. While it may be possible that
insonation is causing a temperature rise at the aluminum
surface, the absence of AL(OH)3 during sonocatalysis mili-
tates against this position.
9. Conclusions of OCNB Experiments
Sonocatalysis of aqueous OCNB over aluminum powder or
62
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activated Raney-Nickel in the presence of air, oxygen or
ozone results initially in some reduction products but
eventually in oxidation products and the complete destruc-
tion of the compound. The effect of insonation may be to
clean the aluminum surface by dislodging the aluminum oxide,
The possibility exists that an increase in surface tempera-
ture occurs , but conditions are such that concomitant forma-
tion of Al(OH)is prevented.
63
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ACKNOWLEDGMENT
The authors wish to express their appreciation to Dr.
F. Patil and Dr. Konrad Seyffarth, Research Associates, for
their diligent efforts and valuable contributions to this
project, and to Mr. F. Y. Wound, a graduate student, for his
collections of experimental data.
The financial support by the Office of Water Quality,
Environmental Protection Agency, through Contract No.
14-12-572 is gratefully acknowledged. The EPA Project
officer for this contract was Francis L. Evans, III. We
appreciate the samples of Raney-Nickel furnished by the
Davison Division of W. R. Grace and Co.
65
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LIST OF REFERENCES
1. Bean, E.L., Advances in Ch.em. Ser., 21, 430 (1958).
2. Chen, J.W. and Kalback, W.M., I and EC Fundamentals, 6,
175 (1967) . ~
3. Chen, J.W., Chang, J.A. and Smith, G.V., "Sono-Oxidation
In Aqueous Solutions", Symposium Volume, "Sono
Chemical Engineering^" Chemical Engineering Progress,
in press.
4. Currell, D.L. and Zechmeister, L., J. Amer. Chem. Soc.,
80_, 205-208 (1958).
5. Dixon, J.K. and Longfield, J.E., "Catalysis", Vol. VII.,
p. 325, Reinhold, New York (1960).
6. Fitzgerald, M., Griffing V. and Sullivan, J.J., J. Chem.
Phys. , 2S_, 926 (1960) .
7. Fogler, H.S. and Barnes, D. , I and EC Fundamentals, 7_,
222 (1968) .
8. Jellinek, H.H.G. and Whitte, G., J. Polymer Sci. , 6_,
6, 757-766 (1951).
9. Kilpatrick, M.L., Herrick, C.C. and Kilpatrick, M. , "The
Decomposition of Ozone in Aqueous Solution", J. Am.
Chem. Soc., 78_, 1784 (1956).
10. Koppe, P. and Giebler, G., "Ozone Decomposition in Water,"
Chemical Abstracts, 65, 489d (1966).
11. Lur'e, Yu Yu, Russian J. Phys. Chem., 37_, No. 1, 1264 (1963)
12. Niegowski, S.J., IE 5 C, 4_5, 632 (1953).
13. Polotskii, I.G., Zhur. Obshch. Khim. , 17_, 649 (1947).
14. Selm, R.P., Advances in Chem. Ser., 20, (1957).
15. Torricelli, A., Advances in Chem. Ser. , 21, 454 (1958).
16. Weissler, Alfred, AIChE Symposia 47, 22 (1951).
17. Zechmeister, L. and Wallcave, L., J^ Amer. Chem. Soc., 77,
2953-2960 (1955).
67
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18. Zechmeister, L. and Magoon, E.F., J. Amer. Chem. Soc.^,
7B_, 2149-2150 (1956).
19. American Public Health Association, Standard Methods for
the Examination of Waste and Waste Watef^llth Ed.,
New York (1960).
20. Water and Waste Water Analysis Procedures, Hach Chemical
Co. , Ames, Iowa (1969) .
21. Basic Manual of Laboratory Ozonation Techniques, The
Welsbach Corporation, Philadelphia, Pa.(T970)•
68
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LIST OF PUBLICATIONS § PATENTS
1.
Chen, J.W., Chang, J.A. and Smith, G.V., Symposium
Series in Sono Chemical Engineering , Chemical
Engineering Progress, edited by Scott Fogler,
published
(1971).
y AIChE, New York, Vol. 67, 18-26
2.
3.
4.
5.
6.
"Sonocatalytic Processes in Advanced Waste Water
Treatment," F.Y. Wound, M.S. Thesis', Southern
Illinois University (1970).
"Sonocatalysis" by Gerard V. Smith, Juh W. Chen, F-
Patil and Y. Pavlou, to be submitted to J.
Catalysis .
"Sonocatalytic Reactions of Aqueous Orthochloronitro-
benzene with Air, Oxygen and Ozone over Aluminum
and Raney-Nickel During Ultrasonic Irradiation,"
by Gerard V. Smith, Juh W. Chen and F. Patil to be
submitted to J. Catalysis.
"Catalytic and Sonocatalytic Oxidation of Aqueous Phenol"
by Gerard V. Smith, Juh W. Chen and Konrad Seyffarth,
to be submitted to J. Catalysis.
"Catalytic and Sonocatalytic Oxidations of Waste Waters,"
by Juh W. Chen, Gerard V. Smith, Konrad Seyffarth
and J. Wound, to be submitted to Environmental Science
and Technology.
7. Patent disclosures are being made covering the following
concepts:
a) oxidations of organic compounds in aqueous solutions
using a catalyst and ozone.
b) oxidations of organic compounds in aqueous solutions
using a catalyst, ultrasound and oxygen or ozone.
c) oxidations and/or reductions of organic compounds
using aluminum or aluminum containing alloys such as
Raney-Nickel in aqueous solutions and irradiating
with ultrasound.
69
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LIST OF PERSONNEL IN THE PROJECT
Dr. Juh W. Chen, Professor and Chairman, Thermal and Environ-
mental Engineering, Coprincipal Investigator
Dr. Gerard V. Smith, Associate Professor of Chemistry, Coprinci-
pal Investigator
Dr. F. Patil, Research Associate
Dr. Konrad Seyffarth, Research Associate
Mr. Fu-Yii Wound, Research Assistant
71
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GLOSSARY
BOD Biochemical Oxygen Demand
Catalyst - An agent which promotes the rate of reaction
Catalytic Oxidation An oxidation process with catalyst and
air C°xygen)
COD - Chemical Oxygen Demand
OCNB Orthochloronitrobenzene
ODI - Oxygen Demand Index, approximately equal to BOD^.
Sonocatalysis - Catalysis under insonation
Sonocatalytic Oxidation - Catalytic oxidation under insonation
Sonocatalytic Ozonation - Catalytic ozonation under insonation
73
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
I, Report So,
4. Title
3. Accession No.
W
FEASIBILITY STUDIES OF APPLICATIONS OF
CATALYTIC OXIDATION IN WASTEWATER,
7. Author(s)
Chen, J. W., and Smith, G. V.
9. Organization
Southern Illinois University at Carbondale, 111.
12. Sponsoring Organization
15. Supplementary Notes
Final Contract Report, 67 p, 31 fig, 7 tab, 21 ref.
5. Report Date
6,
8, Performing Organization
Report No.
10. Project No.
EPA, WOO 17020 ECI 11/71
11. Contract/Grant No.
EPA, WQO 14-12-572
13. Type of Report md
Period Covered
16. Abstract
Wastewaters show 78% decrease in Chemical Oxygen Demand (COD) and 96% decrease in
Oxygen Demand Index (ODI) during two hours insonation in the presence of activated
Raney-Nickel catalyst and air. In addition, sonocatalytic oxidation completely
eliminates coliform organisms. The substitution of air by ozone-oxygen mixture can
result in COD reductions of 90%. Significantly, treatment with activated Raney-
Nickel and ozone, without insonation; i.e., catalytic ozonation; is nearly as
effective. This process can remove 85% of the COD and 60% of the TOG from secondary
treatment effluents in two hours under favorable conditions.
Ozonation of aqueous phenol solutions in the presence of activated Raney-Nickel and
ultrasound (sonocatalytic ozonation) results in the reduction in phenol concentra-
tion, COD, and TOG; the greatest decrease is in phenol concentration, the next
greatest is in COD, and the least is in TOC.
Aqueous solutions of Orthochloronitrobenzene (OCNB) react only in the presence of
ultrasound and aluminum, or activated Raney-Nickel (sonocatalysis) at room tempera-
ture. In this reaction, reduction products appear initially, but eventually these
products, and OCNB, are eliminated from the solution.
17 a. Descriptors
I7b. Identifiers
COD Removal, TOC Removal, Catalytic Oxidation of Organic Pollutants,
Catalytic Ozonation, Advanced Wastewater Treatment
* * *
Orthochloronitrobenzene, Phenol, Activated Raney-Nickel, Ultrasound
17c. CO WRR Field & Group 05D
18. Availability
19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
Abstractor Juh W. Chen
| institution southern Illinois University
WRSIC 102 (REV. JUNE 1971)
9J3.28I
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