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Kinetics Of CompetitiveOzonation Of Some PhenolicCompounds Present InWastewater From FoodProcessing IndustriesF.J. Beltrán , J.F. García-Araya , F.J. Rivas , P.Álvarez & E. Rodrígueza Departamento de Ingeniería Química yEnergética. Universidad de Extremadura ,06071 Badajoz, SpainPublished online: 07 Apr 2008.

To cite this article: F.J. Beltrán , J.F. García-Araya , F.J. Rivas , P. Álvarez& E. Rodríguez (2000) Kinetics Of Competitive Ozonation Of Some PhenolicCompounds Present In Wastewater From Food Processing Industries, Ozone:Science & Engineering: The Journal of the International Ozone Association, 22:2,167-183, DOI: 10.1080/01919510008547218

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OZONE SCIENCE & ENGINEERING 0191-9512/00 $3.00+ .00Vol. 22, pp. 167-183 International Ozone AssociationPrinted in the U.S.A. Copyright © 2000

Kinetics Of Competitive Ozonation Of Some Phenolic

Compounds Present In Wastewater From Food

Processing Industries

F.J. Beltran, J.F. Garcia-Araya, F.J. Rivas, P. Alvarez and E. Rodriguez

Departamento de Ingenieria Quimica y Energetica. Universidad de Extremadura.06071 Badajoz. Spain

Received for Review: 26 October 1998Accepted for Publication: 12 May 1999

Abstract

Ozonation of four phenolic compounds found in wastewater effluentsfrom food manufacturing processes: Gallic (G-Ac) and p-hydroxybenzoic(pHB-Ac) acids, (+)-catechin ((+)-Cat) and tyrosol (Ty), has been carriedout in ultrapure water. The results showed that the direct reaction betweenozone and the organic compound seems to be the exclusive way ofphenolic compounds elimination. A kinetic study of these reactions wascompleted by using a high concentration of phenolic substances (up to 3 gL"1 total phenolic content) to simulate typical amounts of thesecompounds found in real wastewater. By means of a competitive method,rate constants of the direct reaction with ozone were determined atdifferent pH. The following reactivity was found depending on pH: pHB-Ac < Ty < G-Ac < (+)-Cat in acidic conditions, pHB-Ac « Ty < G-Ac <(+)-Cat in neutral conditions and pHB-Ac « Ty for basic conditions.Finally, validation of the calculated rate constants was completed bychecking the kinetic regime in which competitive reactions weredeveloped.

Introduction

Food manufacturing processes are industries of paramount importance in the economyof the South regions of Mediterranean countries. Although these industries do notbelong to the field of chemical or petrochemical groups, the wastewater they release

167

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168 F. J. Beltran et al.

constitutes a growing environmental problem difficult to eliminate. Thus,manufacturing processes of olives, tomatoes, raisins, etc., generate a large amount ofeffluent streams with a high organic content, especially phenolic type compounds(Garcia et al., 1989; Janer del Valle, 1980; Lopez and Ovelleiro, 1978; Rambaud andBontoux, 1974).

Biological treatment of these effluents seems to be a suitable method for purificationthough the presence of phenolic inhibitors makes the direct application of thistechnology inappropriate. For instance, phenol is a nutrient for bacteria as long as it isin the range of 80-100 ppm and, therefore, it is suitable for biological treatment,however, at slightly higher concentrations, above 200 ppm, phenol behaves as abactericide (Pruden and Le, 1976).

Use of ozone to reduce the level of phenolic compounds in food processingwastewater appears as an interesting technology due to the high reactivity of thesetypes of organics with ozone, especially at high pH (Hoigne, 1982). In addition toreducing organic matter content of wastewater, the use of ozone increases thebiodegradability of the treated wastewater (Beltran et al., 1997). In this sense, ozonemight be used as a pre-treatment step for biological digestion of contaminated effluentstreams. Until the present moment, the variety of works on phenol ozonation alreadypublished deal with low concentrations of phenolic compounds, far away from typicalamounts found in real wastewater. In addition, extrapolation of kinetics of modelcompounds at low concentration is not always possible (Gauducheau et al., 1986).

In this work, kinetics of the ozonation of four phenolic substances found at relativelyhigh concentration in food manufacturing industries are studied using a competitivemethod. The model compounds chosen in this work were gallic acid (G-Ac), p-hydroxybenzoic acid (pHB-Ac), tyrosol (Ty) and (+)-catechin ((+)-Cat) (see Figure 1for structures).

Experimental

Experiments were carried out in a 1 L glass semi batch jacketed reactor equipped witha porous plate (40 nm porous diameter) situated at the bottom. Agitation was providedby means of bubbling 50 L h1 of an ozone-oxygen mixture. Water from a thermostaticbath was circulated through the reactor jacket to ensure a constant temperature insidethe reactor (20°C). During experiments, samples were withdrawn regularly from thereactor for analysis. Details of the experimental set-up can be found elsewhere(Beltran etal , 1995).

Organics used in this work were purchased from Sigma and used without furtherpurification. Aqueous solutions of phenolic compounds were prepared in high puritywater (Milli-Q MilliPore system) buffered with ortho-phosphoric acid and sodiumhydroxide. The ionic strength was 0.1 M in all cases. Ozone was produced in alaboratory ozonator from pure oxygen.

The ozone content of the gas leaving the reactor was measured iodometrically(Kolthoff and Belcher, 1957) while the dissolved ozone in the liquid phase was

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 169

analysed by the indigo method (Bader and Hoigne, 1981). Organics were analysed byhigh performance liquid chromatography. A 150 x 4 mm ID Nova-Pack C-18 (60 A)WATERS column was used. Flow rate of the mobile phase, acetonitrile-water (10/90w ) , was 1 mL min"1. The HPLC apparatus comprised an automatic sample injector, ahigh pressure pump, a tuneable absorption detector and a data base station integrator,all supplied by Hewlett-Packard (series 1100). Wavelength detector was set at 254 nm.

COOH COOH

oOH

p-Hydroxybenzoic Acid

CH2CH2OH

oTyrosol

OH

(+) Catechin

Figure 1. Molecular structure of phenol-type compounds investigated.

Results And Discussion

Ozonation of organics in water is a complex technology involving mass transferprocesses and a variety of possible chemical reactions, e.g. direct reactions betweenthe ozone molecule and the organics and radical reactions between hydroxyl radicalsand organics. In this latter case, radicals are produced through the ozone moleculedecomposition catalysed mainly by the hydroxyl ion (Staehelin and Hoigne, 1985).Because of the presence of the hydroxyl group attached to the aromatic ring, reactionswith electrophilic reagents like ozone are markedly favoured. Therefore, at pH < 12,the radical route of degradation of phenolic compounds may be neglected and thesesubstances are degraded exclusively by direct reaction with ozone. To corroborate this,a series of ozonation experiments with the phenolic compounds studied in the presenceand absence of a well-known hydroxyl radical scavenger (tert-butyl alcohol, t-BuOH)were carried out by varying the pH of the solution from 2 to 12. Ozonationexperiments of gallic acid and (+)-catechin were not completed at pH 12 due todecomposition of these substances at this pH (Tulyathan et al., 1989; Jensen and

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170 F. J. Beltr£n et al.

Pedersen, 1983). In all cases, oxidation rates in the presence (0.05 M) and absence oft-BuOH were similar. This confirmed that radical reactions in ozonation of the phenol-type substances studied can be discarded. Dissolved ozone concentrations in theaqueous solutions with and without the use of radical scavengers were comparable.Regarding the ozone effluent leaving the reactor, in the majority of cases the absenceof t-BuOH implied a higher concentration of ozone in the gas outlet stream. As anexample, Figures 2a and 2b show the aqueous normalised remaining concentration of(+)-catechin and that of dissolved ozone, respectively, with time during the ozonationof (+)-catechin at pH = 2. In Figure 3 it can be observed the results obtained from theozonation of pHB-Ac at different pH.

(a)

(b)

Figure 2. Ozonation of (+)-catechin. Effect of free radicals scavengers. Conditions:293 K; pH 2; ozone partial pressure =137 Pa; gas flowrate = 50 L h'1; initial organicconcentration = 10° M, a) Evolution of (+)-catechin normalised remainingconcentration with time, b) Evolution of dissolved ozone concentration with time. DO.OMt-BuOH, O 0.05Mt-BuOH.

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 171

1.0 G

30

Figure 3. Ozonation of p-hydroxybenzoic acid. Evolution of the normalisedremaining concentration with time. Effect of free radicals scavengers atdifferent pH. Conditions: 293 K; ozone partial pressure =137 Pa; gas flowrate= 50 L h"1; initial organic concentration = 10"3 M. • 0.0 M t-BuOH (pH = 2),• 0.05 M t-BuOH (pH = 2), A 0.0 M t-BuOH (pH = 7), A 0.05 M t-BuOH (pH= 7), • 0.0 M t-BuOH (pH = 12), O 0.05 M t-BuOH (pH = 12).

Due to the rapidity of the chemical reaction in this heterogeneous system, it isprobable that the kinetic regime was, in the majority of cases, fast with the reactiondeveloped in the film layer region. It is also highly probable that secondary productsconsume ozone. Taking this into account, determination of rate constants is notsuitable by direct kinetic methods derived from absorption theories applied to anirreversible gas-liquid reaction. Therefore, a competitive kinetic method was used bysimultaneous ozonation of one of the phenolic compounds (M) studied and anotherreference compound (R) that presents a similar reactivity towards ozone. However, thecompetitive kinetic method is applicable for rate constant acquisition provided that atany given time the concentrations of the substances to be ozonated are constant withinthe liquid film (Gurol and Nekouinaini, 1984). Figure 4 shows the different suitablecases which can be found, depending on the relative rates of mass transfer andchemical reaction for a gas-liquid heterogeneous reaction, where this condition isapplicable. From Figure 4 it can be observed that the kinetic regimes slow, diffusionaland fast pseudofirst order are suitable regimes for rate data determination since theconcentration of the ozonated substance (phenolic compounds in this work) does notchange with the position in the film layer. The moderate regime is also a possible casebut it could be used only when the concentrations of the phenolic compounds in thebulk of the liquid (CMo) and in the interface (C*M) are similar, though this is not alwaysthe case. CMo and C'M may be considered comparable if the following conditions aresatisfied:

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172 F. J. Beltrdn et al.

Diffuslonal regime

Ha < 0.3

LIQUID PHASE LIQUID PHASE

Moderate regime

0.3 < Ha < 3

Figure 4. Kinetic regimes in heterogeneous gas-liquid reactions. Conditions ofsuitability for rate constant determination.

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 173

Ha < 0.3 for slow and diffusional reactions [1]3 < Ha < E( / 2 for fast pseudofirst order reactions [2]

Ha and Ej representing the relative importance of the chemical and physical steps in agas-liquid reaction like:

^Products [3]

being defined as the dimensionless numbers of Hatta and instantaneous reaction factor,respectively:

Ha = v ° ' [4]

Ei = Z p D c C " ' + 1 &

where D o and DM are the diffusivities of ozone and the phenolic compound M, zM is

the stoichiometric ratio of their direct reaction, kM the rate constant of this reaction,referred to ozone disappearance and kL the individual liquid phase mass transfercoefficient.

In the kinetic method that follows a second order kinetics (first order for each reagent,ozone and M or R) was considered. Therefore, the disappearance rates of the phenoliccompound (M) and the substance taken as reference (R) are given by the followingequations:

d C M -k" .c .Cn reiM w M O* L J

j . 1*1 kj M \J$

= zR.k" .CR.CO t [7]dCR

where Q^ , CM and CR are the concentrations of ozone, phenolic (M) and reference (R)

compounds, respectively, at any point in the bulk of the liquid, k"M and k"R are thereaction rate constants for the direct ozone reactions with M and R, respectively, andzM and zR the corresponding stoichiometric coefficients, measured as ozone moleconsumed per compound mol consumed. These coefficients, zM and zR defined askM/k"M and kR/k"R , respectively, were obtained following a procedure already reported(Sotelo et al., 1990), except for the cases of ozone reactions with resorcinol and phenolthat were taken from previous works (Li et al., 1979; Sotelo et al., 1990). In these twocases, z is 2, while for the reactions between ozone and compounds used in this workcalculated z values were 1 for gallic acid and (+)-catechin, 1.5 for p-hydroxybenzoicacid and 0.75 for tyrosol. In most of cases, the reference compounds (R) in the kineticstudy were resorcinol and phenol. Rate constants, kR, of the reactions of ozone withphenol and resorcinol are given in Table I. In some cases, however, p-hydroxybenzoicacid also played this role, once the rate constant of its reaction with ozone was known.

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174 F. J. Beltran et al.

Table I. Rate constants (kj) of ozone-resorcinol and ozone-phenol reactions used inthis work

PH

2

6.3

9

Ozone-resorcinol reaction"

105

Ozone-phenol reaction11

1.3xlO3

3.5xlO5

1.6xlO8

'Taken from Sotelo et al. (1991). Taken from Hoigne and Bader (1983). Units areinM's1

Ozone concentration in equations [6] and [7] can be removed by dividing bothexpressions:

CM zR .kR .<[8]

After integration of eq.[8] the following equation is obtained:

where• k

[9]

[10]

Equation [9] was applied to a series of competitive ozonation experiments (see TableII) aimed at determining k"M. Consequently, a plot of the left hand side of equation [9]versus the natural logarithm of the normalised remaining concentration of thereference compound should give a straight line whose slope is £• From this slope,known the values of k"R, zM and zK, k"M can be calculated. As an example, Figure 5ashows the variation of the normalised concentration of resorcinol and gallic acid withtime obtained from the competitive ozonation of both substances (run 3 in Table II).Figure 5b shows a plot of Ln(CM/CMo) versus Ln(CR/CRo) for the aforementionedexperiment. From Figure 5b, it can be observed that experimental points follow astraight line, corroborating the suitability of equation [9]. Table III shows the rateconstant values obtained from experiments of competitive ozonation presented inTable II. Competitive ozonations were carried out at reactor inlet ozone partialpressures much higher than those applied to ozonation of single compounds (seeconditions in captions of Figures 2 and 3 and Table II) since the consumption of ozonewas expected to be higher. Once the values of k"M were known, the kinetic regime was

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 175

checked using equations [4] and [5] to confirm the validity of the method used. Sinceperfect mixing was assumed for both the gas and water phases COj* was calculated

from the outlet ozone partial pressure by applying Henry's law. The Henry constantwas obtained from Sotelo et al. (1989) work while the value of kL = 3.7x10"* ms"' wasdetermined by applying the equation of Calderbank for bubble contactors, with bubblediameter higher than 2 mm (Froment and Bischoff, 1979). The value of DOj (1.76x10"9 m V ) was calculated from the equation of Johnson and Davis (1996). Diffusivities ofthe organic compounds in water were obtained using the equation of Wilke and Chang(Reid et al., 1977) (see Table IV). In some experiments (runs 5, 6, 7, 9, 11 and 12)effluent ozone from the reactor was not detected and, hence, data of Ej were estimated

from values of Co * determined from the reactor inlet ozone partial pressure. It is

evident that in these particular cases the estimated values of E/2 resulted smaller thanthe actual ones (see equation [5]) which represents the most difficult conditions for afast pseudofirst order kinetic regime to develop (see condition [2]). Notice that forkinetic studies, values of E( are only necessary when the Hatta number is higher than 3,that is, for fast or instantaneous kinetic regimes of absorption (Danckwerts, 1970).

Figure 5. Competitive ozonation of gallic acid and resorcinol. Conditions: 293 K; pH2; ozone partial pressure = 483.Pa; gas flowrate = 50 L h'1; initial organicconcentrations a) Evolution of the normalised remaining concentration withtime. : D 2.5 103 M resorcinol, O 2.5 10"3 M gallic acid, b) Application ofEquation [9].

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176 F. J. Beltran et al.

Table II. Experimental conditions for competitive ozonation reactions'

RUN#

1

2

3

4

5

6

7

8

9

10

11

12

Ozonated compounds

Rb.pHB-Ac

G-AcRb

TyG-Ac

Rc

(+)-CatRc

Rb

pHB-AcRb

pHB-Ac(+)-CatG-Ac

Rd

Ty(+)-CatG-Ac

Rd

Ty(+)-CatG-Ac

Rd

Ty(+)-CatG-Ac

Rd

Ty(+)-CatG-Ac

Rd

Ty(+)-CatG-Ac

Rd

Ty

C o x l 0 \ M

20202.52202.52.50.110102010101.55.47.23.61.55.47.23.61.55.47.23.61.55.47.23.61.55.47.23.60.752.73.61.8

P0 3. Pa

461

450

483

483

486

486

486

1063

1571

504

504

483

PH

2.0

2.0

2.0

2.0

6.3

9.6

6.3

6.3

6.3

2.0

9.0

6.3

'Co = Initial compound concentration, P03 = Ozone partial pressure at the reactor inlet.'Reference compound was phenol. 'Reference compound was resorcinol. dReferencecompound was p-hydroxybenzoic acid.

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 177

For experiments in which more than two phenol compounds were ozonated (runs 7-12), the Hatta number was always higher than 3 and smaller than E/2 , therefore, theywere considered to be in the fast pseudofirst order regime. Table V shows the valuesof Ha, E/2 and kinetic regimes for the rest of runs. From Table V, it can be observedthat with the exception of the experiments completed at pH = 6.5 with phenol (R) andp-hydroxybenzoic acid (M) (run 5), and at pH 2 in ozone reactions with p-hydroxybenzoic acid and phenol (runs 1 and 2, respectively), the rest of ozonationsdeveloped in the moderate regime. As has already been pointed out, the competitivemethod used in this work can also hold in the moderate regime provided the interfaceand bulk concentrations of the compounds to be oxidized (included the referenceorganic) are practically similar. From Table V it can be seen that in the experimentscarried out within the moderate regime, only two substances were ozonated. Thisimplies that the equations proposed by Onda et al., (1970) can be applied. Theseauthors studied the kinetics of a system in which a gas while being absorbed in a liquidundergoes two reactions in parallel:

ZMO3 + b

O,+R\ ^ > Products

^ > Product[11]

[12]

Table III. Rate constants derived from the application of competitive ozonation kinetics(Eq.[91).

Compound

PHB-Ac

PHB-Ac

PHB-Ac

G-Ac

G-Ac

G-Ac

G-Ac

G-Ac

(+)-Cat

(+)-Cat

(+)-Cat

(+)-Cat

(+)-Cat

Ty

Ty

Ty

Ty

Ty

Ty

Run

1

5

6

3

7

8

9

12

4

7

8

9

12

2

7

8

9

12

11

pH

2.0

6.3

9.0

2.0

6.3

6.3

6.3

6.3

2.0

6.3

6.3

6.3

6.3

2.0

6.3

6.3

6.3

6.3

9.0

Intercept

-0.0023

0.0079

0.0176

0.0347

-0.0013

0.0112

-0.0207

0.0251

0.0587

0.0467

0.0123

-0.0440

0.0168

0.0126

-0.0001

-0.0127

-0.0156

-0.0215

-0.0450

0.301

1.009

0.826

1.944

2.869

2.668

2.582

2.450

10.580

5.715

5.200

7.965

5.855

4.445

1.199

0.977

1.183

1.101

1.059

k"Mxl0-5,M's-'

0.002

1.78

644

0.97

5.10

4.75

4.60

4.36

5.30

10.2

9.25

14.2

10.4

0.03

2.13

1.73

2.11

1.96

683

kMxl0-5,

M-'s-1

0.003

2.67

966

0.97

5.10

4.75

4.60

4.36

5.30

10.2

9.25

14.2

10.4

0.022

1.60

1.30

1.58

1.47

512

Notice that kM = zMk"M

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178 F. J. Beltran et al.

Table IV. Aqueous difrusivity values of phenol compounds studied

Compound

Gallic acid

p-hydroxybenzoic acid

Tyrosol

(+)-Catechin

Phenol

Resorcinol

Molal volume*, cm3mol''

157

142

155

277

103

111

Difrusivityxl0l0,m2s"' b

7.1

7.6

7.2

5.1

9.2

8.8

'From Le Bas method. bFrom Wilke and-Chang equation (Reid et al., 1977)

Table V. Hatta, instantaneous reaction factor numbers and kinetic regime forcompetitive ozonations with two compounds

RUN

1

2

3

4

5

PH

2.0

2.0

2.0

2.0

6.3

Ozonatedcompounds

pHB-Ac (M)

Phenol (R)

Ty(M)

Phenol (R)

G-Ac (M)

Resorcinol (R)

(+)-Cat (M)

Resorcinol(R)

pHB-Ac (M)

Phenol (R)

Hatta

0.2

0.4

0.7

0.2

1.7

1.7

0.8

3.5

8.1

6.6

E/2

2395

3667

792

220

375

880

0.813

109

167

128

Kinetic regime.

Slow

Moderate

Moderate

Slow

Moderate

Moderate

Moderate

Fast pseudofirst order

Fast pseudofirst order

Fast pseudofirst order

Then, the chemical rate of ozone disappearance can be written as follows:

where: "~rM =

[13]

[14]

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 179

—ZR

[15]

The rate of ozone absorption for this system can be expressed either by equation [16]or by equation [17] (Onda et al., 1970):

N O j = k L a C o / 1 - — -

where:

"Mo.

NOj =kLaCOj*

M2 =

[16]

[17]

[18]

For these equations, the values of the interface concentration of M and R (C'M and C'R)might be estimated admitting that the profiles of the dimensionless concentrationsCM/CMo and CR/CRo are suitable for being expressed as quadratic functions of thedimensionless distance (w) from any point of the stationary film layer to the gas-liquidinterface as equations [19] and [20] below:

/ | W 2 + CM1

"Mo

where:

'"Mo ^

XW = 5 T

R O

"Mo C.

[19]

[20]

[21]

In equation [21], x is the distance from the gas-liquid interface and 8, represents thethickness of the film layer in the liquid phase. In addition, conservative equations of Mand R are expressed as follows:

d 2 r"M _ .

1 dx2

d2CT 2 [23]

dividing equations [22] and [23]:

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180 F. J. Beltran et al.

DM n kR CR d2(CM/CM o)DM

Dr dw2 D03 dw2 [24]

substituting equations[19] and [20] in eq.[24] and integrating the resulting equationwithin the following limits:

and

'Mo

CM0 CM O

and

and

' M _ *-M [25]

[26]

expression [27] is deduced:

CR =C R O

6 zR DR k, ^ CMo

! i 5 zM DM k2

6 zR DR k,

j C

c

, CM

Mo

[27]

where once C'M is known, C'R can be estimated. In this study, C'M and C'R werecalculated by means of a trial and error method with equations [16], [17] and [27]using experimental data (CMo, CRo and COj ) and calculated kinetic parameters (kM, kR,DM» DR. ZM and ZR)- In all cases the interface concentration was practically equal to theconcentration in the bulk of the liquid, with deviations less than 1%. Therefore it canbe assumed for the experiments developed in the moderate regime that theconcentrations of M and R are constant and the rate constants found are, consequently,validated. Table VI shows, as an example, the values of CM, CR, C'M and C*R and thedeviation percentage between them for run 3.

Conclusions

The ozonation of gallic and p-hydroxybenzoic acids, (+)-catechin and tyrosol, presentin wastewater of numerous food processing industries like olive and tomatotransformation factories, wine and wine byproducts production, etc., appears as afeasible complementary technology to biological oxidation, which applied alone is anon-viable technology taking into account the high concentration of these organics inwastewater effluents.

Ozonation of these four phenol-type compounds is carried out through direct reactionswith ozone, the contribution of the indirect way (with hydroxyl radicals) beingnegligible. The compounds studied showed the following order of reactivity towardsozone, depending on pH:

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 181

pHB-Ac < Ty < G-Ac < (+)-Cat (acid pH)pHB-Ac « Ty < G-Ac < (+)-Cat (neutral pH)

pHB-Ac » Ty (basic pH)

At the conditions here applied, the kinetic regime of ozone absorption varied betweenmoderate and fast pseudo first order. Rate constants of the direct reactions ozone-compound were determined at different pH from a competitive kinetic method. Amodified method of Onda et al. (1970), based on the film theory, was used to checkthe similarity between the concentrations of the phenol-type compounds studied at thebulk of water and at the gas-water interface in cases of moderate kinetic regime forozone absorption. For the conditions applied in this work, values of theseconcentrations resulted in a diference of less than 1% for both the reference andphenol-type substance when working in the moderate regime, validating, thus, thecalculated reaction rate constants.

Table VI. concentrations of gallic acid (M) and resorcinol (R) in bulk waterand at the gas-water interface during their competitive ozonation

CM X 103

2.500

2.090

1.817

1.596

1.351

1.033

0.671

0.507

0.061

C\, x 103

2.495

2.086

1.813

1.592

1.348

1.030

0.668

0.503

0.060

% deviation

0.20

0.19

0.22

0.25

0.22

0.29

0.45

0.79

0.98

CR x 103

2.500

1.251

2.058

1.943

1.777

1.540

1.240

1.102

0.612

C'B x 103

2.496

2.246

2.054

1.939

1.773

1.536

1.234

1.094

0.606

% deviation

0.17

0.19

0.20

0.19

0.22

0.22

0.44

0.76

0.90

Acknowledgement

The authors thank the C.I.C.Y.T. of Spain for the economic support (Research grantAMB97/339).

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Ozonation of Phenolic Compounds in Wastewater from Food Processing 183

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Key Words

Ozone; Competitive Ozonation Kinetics; Gallic Acid; p-Hydroxybenzoic Acid; (+)-Catechin; Tyrosol; Film Theory; Food Processing; Wastewater; Industrial Wastewater;Phenolic Compounds;

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