Radiolysis and ozonolysis of a landfill leachate

Franco Cataldo • Giancarlo Angelini

Received: 2 January 2012 / Published online: 18 March 2012

� Akademiai Kiado, Budapest, Hungary 2012

Abstract A landfill leachate sample was radiolyzed with

c-rays at 12.5, 25, 50, 100, 200 and 400 kGy. The radio-

lyzed solutions were studied by UV–VIS–NIR spectros-

copy to measure the color change, by chemical oxygen

demand (COD) analysis to check the degree of minerali-

zation of the soluble organic matter present in the leachate

and by FT–IR spectroscopy of the humic substance of the

leachate. The results have shown that the humic substance

present in the landfill leachate is extremely refractory to

radiolysis: even at 400 kGy it was detected and recovered

only with minor changes. It is shown that the radiolysis

followed by ozonolysis is able to cause important

improvements of the leachate color and important reduc-

tion on the COD. However, the results in terms of

bleaching and COD abatement after radiolysis and ozon-

olysis of the leachate can be achieved directly by a simple

exhaustive ozonolysis of the leachate. The structural

changes occurring in the humic substances and in the

humic acids present in the leachate after radiolysis and

ozonolysis were analyzed by FT–IR spectroscopy.

Keywords Landfill leachate � Humic substances �Humic acids � Fulvic acids � Radiolysis � Ozonolysis �COD reduction

Introduction

Humic substances (HS) are organic macromolecules of

complex structure derived from the chemical and biological

decomposition of plants, animals and microorganisms in

soil. HS are the main constituents of humus, of sediments and

of peat and in can be extracted from certain types of coal. A

number of books and reviews deal with the formation, the

structure and the biochemical function of the HS in the

environment [1–7]. According to the isolation method the

HS can be separated into three fractions the true humic acid

(HA), fulvic acid (FA) and humin (HU). The key difference

in these three fractions are in solubility and molecular

weight. HA is soluble in basic solutions and is characterized

by an higher molecular weight than FA which, in its turn,

because of its lower molecular weight and richness in

functional group is soluble in water at any pH. Finally, HU is

instead the insoluble fraction of HS and although basically

has the structure of HA, it has a higher molecular weight and

also a high degree of crosslinks that make this macromole-

cule insoluble [1–9]. The chemical structure of HS is very

complex so that it cannot be represented by a single molec-

ular structure as in the case of normal molecules. Therefore

HS, and in particular HA, which is the predominant fraction

of HS, is represented by molecular models which may rep-

resent the average structure. In Scheme 1 are reported three

molecular models for the representation of HA [3–5, 7] while

for FA a chemical model is reported in Scheme 2 [6].

Another aspect emphasized by all authors when they talk

about the HA chemical structure regards its ability to form

supramolecular complexes with sugars, proteins and other

biochemically active molecules [1–8] other than the ability

to trap water molecules. Another feature of HA and FA

regards the ability of these macromolecules to bind metal

ions and to favor the mobility of such ions [1–8].

F. Cataldo � G. Angelini

CNR–Istituto di Metodologie Chimiche, Area della Ricerca

di Montelibretti, Via Salaria Km 29,300, 00016,

Monterotondo Scalo, Rome, Italy

F. Cataldo (&)

Soc Lupi Chemical Research srl, Via Casilina 1636/A,

00133 Rome, Italy

e-mail: franco.cataldo@fastwebnet.it

123

J Radioanal Nucl Chem (2012) 293:141–148

DOI 10.1007/s10967-012-1729-7

HA and FA are naturally occurring in small amounts in

groundwater and even in municipal tap water. The for-

mation of trichloromethane occurs just as a consequence of

the chlorine attack and degradation of the HA and FA

during the disinfection. However, the HS occurs in very

high to high concentration also in the liquor produced by

the rain which passes through the municipal landfill. Such

liquor is known as landfill leachate and is characterized by

an extremely high level of soluble organic matter other

than the presence of various electrolytes and cations

including transition metal cations [10, 11].

The soluble organic matter in a landfill leachate was

analyzed by some scientists [12–16] and the analytical data

show that indeed such a matter is very similar to the soil

HS, HA and FA [12–16]. However the landfill leachate

water is heavily polluted since the chemical oxygen

demand (COD) is extremely high when the leachate is

young and acidic, for instance values as high as 40,000

mg/L were reported [16] but drops to 5,000 mg/L when the

methanogenic fermentation starts and the pH becomes

Scheme 1 Humic acid

chemical structure models from

top to bottom according to

Flaig, Stavenson and Stein [5]

Scheme 2 Structural model of FA [6]

142 F. Cataldo, G. Angelini

123

slightly basic and stabilizes at later stages, when the landfill

is several years old at COD values of 1,000 mg/L or less

[16]. In addition to HA and FA the landfill leachate con-

tains a series of volatile fatty acids (formic, acetic, propi-

onic, n-butyric, iso-butyric, valeric, iso-valeric and

n-caproic acid) and is very rich in ammonium ion and free

ammonia [16]. Concerning the HA, the elemental compo-

sition of an average mature leachate is about C = 57.1 %,

H = 7.0 %, O = 30.2 %, N = 5.7 % and S in trace

amounts. HA is characterized by a H/C = 1.48,

O/C = 0.40 and N/C = 0.09 and appears richer in carbon

content than aquatic and terrestrial natural HA [15, 16]. On

the other side the FA from an average mature leachate

shows an elemental analysis C = 53.6 %, H = 6.7 %,

O = 33.8 %, N = 2.5 % and S = 3.4 %. FA is charac-

terized by a H/C = 1.49, O/C = 0.47 and N/C = 0.04,

again higher carbon content than aquatic and terrestrial

natural FA with an important presence of S which instead

is not present in natural FA [15, 16]. From the elemental

analysis and the spectroscopic analysis it was concluded

that the HS from landfill has lower aromatic structure

content than natural HS but the aromaticity increases with

the landfilling age [15, 16]. Other feature of the HS from

landfill leachate regards the fact that FA fraction is more

abundant than the HA fraction while the opposite is true in

natural HS [15]. Furthermore, the molecular weight of the

HS from the leachate is about 2,600 Da for the HA and

about 2,000 Da for the FA while in natural HS both HA

and FA have usually much higher molecular weight [15].

The purification of the water containing landfill leachate

represents a real challenge. For example, the use of ozone

alone permits the COD abatement of only 25–30 % [11, 17]

and to achieve a breakthrough it is necessary for example

to combine the active carbon treatment of the leachate with

the ozonolysis [11]. Since radiation processing has been

proposed in several occasions in the wastewater treatment

[18–22], we have dedicated this paper to the effects of cradiation on the treatment of a medium age leachate.

Experimental

Materials and equipment

Landfill leachate sample was obtained from a landfill located

in the central Italy. The landfill site is 6–7 years old. Refer-

ence HA sample was obtained from Aldrich. Synthetic

humic acid-like samples were prepared as described in a

previous work [23]. The COD was measured by the bichro-

mate methodology according to the ISO 1,5705 standard test.

The UV–VIS–NIR spectra of the leachate sample

before and after radiolysis and/or ozonolysis were recorded

on a Shimadzu UV2450 spectrophotometer without any

dilution. The FT–IR spectra of the leachate samples were

recorded on an IR300 spectrometer from Thermo-Electron.

The samples of leachate in pristine form, after radiolysis or

after ozonolysis were transferred into a Petri dish and

evaporated to dryness at 55 �C. The dried residues were

collected and utilized to prepare the KBr pellets to record

the infrared spectra in transmittance mode.

Irradiation of the landfill leachate samples

The landfill leachate used in this study was characterized

for its pH, COD and other parameters (see the results and

discussion section). A sample of the leachate was then

stored as reference for further studies and analysis while

other samples of the same leachate were transferred in a

series of vials having a volume of 50 mL each. The vials

filled with the leachate were closed in presence of air with

a screw cap and irradiated with a 60Co c-ray source at the

CNR–IMC facility using a dose rate of 1 KGy/h. A total of

6 vials were irradiated respectively to a total dose of 12.5,

25, 50, 100, 200 and 400 kGy. After the irradiation the

samples were opened to measure the pH, the COD and

other parameters like the absorption curve in the UV–VIS–

NIR in comparison to the pristine reference leachate sam-

ple. Surprising all the leachate samples after any radiation

dose administered were collected quite unaltered (see for

details the results and discussion section).

After drying of the leachate samples in a Petri dish, also

the FT–IR spectra of the residue was recorded.

Ozonolysis of the landfill leachate samples

The ozonolysis of landfill leachate was studied following the

batch reaction approach already applied in the ozonolysis of

certain terpenes [24] and in another leachate ozonolysis

study [11]. The standard procedure adopted involves the use

of 25 mL of landfill leachate in 500 mL round bottomed

flask equipped with gas inlet and outlet valves. The flask was

evacuated with the aid of an aspirator and charged with an

O3/O2 mixture with 5 % O3 content by weight corresponding

to about 50 mg ozone. The leachate was hand shaken with

ozone for 1 min. The change of color of the leachate from

brown-turbid to yellow was immediate. The mixture was left

to react for 15 min and hand shaken from time to time. Then,

the flask was again evacuated and filled with other 50 mg of

ozone. It was hand-shaken for 1 min and the leachate color

turned from yellow to very light yellow and the solution

appeared transparent. The above procedure was adopted

both for the reference pristine leachate and also for each of

the radiolyzed samples at 12.5, 25, 50, 100, 200 and

400 kGy. Thus, after radiolysis 50 % the mentioned samples

were subjected also to ozonolysis while the other 50 % was

characterized directly for reference.

Radiolysis and ozonolysis 143

123

Results and discussion

Irradiation of the landfill leachate samples: color

changes and UV–VIS–NIR absorption curves

As reported in the experimental section, 6 samples of

landfill leachate were radiolyzed in closed flasks in pres-

ence of air respectively at 12.5, 25, 50, 100, 200 and

400 kGy. With great surprise, at the end of the irradiation

all samples showed visually the brown color they had

before the irradiation. Even the samples with the higher

radiation dose appeared brown.

For a more quantitative analysis of the color change all

the samples were analyzed by the electronic absorption

spectroscopy. Figure 1 shows the UV–VIS–NIR absorption

curve of the irradiated samples against the reference pris-

tine leachate sample. The reference leachate sample shows

a cut off at about 362 nm and a tail of higher light

absorption between 450 and 1,100 nm which could be due

also to the light scattering caused by the suspended parti-

cles. The radiolysis of the leachate samples causes a small

blue shift of the cut off to 354 nm with the exception of the

sample irradiated at 400 kGy whose cut off is slightly

higher than that of the reference sample (i.e. 368 vs.

362 nm). Only the absorption tail of the radiolyzed samples

between 450 and 1,100 nm shows a significant reduction in

intensity. Thus, the irradiation is not decisive in the color

improvement of the leachate since the cut off of the

absorption curve of the radiolyzed samples remains almost

the same as the pristine leachate sample. A slight

improvement in the appearance of the radiolyzed samples

regards their absorption tail above 450 nm which show less

light absorption and this could be attributed to less light

scattering due to suspended particles. For comparison, in

Fig. 1 is reported also the absorption curve of a leachate

ozonized but not radiolyzed [24]. The cut off of the

absorption curve in this sample occurs at 317 nm against

the 362 nm of the pristine untreated sample. Such a blue

shift of 45 nm and the disappearance of the long absorption

tail in the VIS–NIR in the case of the ozonized leachate

sample causes a complete bleaching of the leachate which

appears pale yellow in color and transparent [24]. From

these data it is evident that the ozonolysis is by far more

effective than radiolysis in the improvement of the color

and the appearance of the leachate.

In Fig. 2 are shown the absorption curves of the pristine

leachate and the radiolyzed leachate samples after dilution

1:10 with distilled water. In these conditions the distinction

between the pristine and the irradiated samples appears

much less evident. Again, the sample treated with 400 kGy

appears even worse in light absorption that the reference

sample while all the other radiolyzed samples are practi-

cally identical to the pristine reference leachate. The latter

shows two shoulders in the absorption curve located at 276

and 321 nm which are less evident in the radiolyzed

samples.

Another aspect to be reported here, is the typical smell

of the leachate due to a series of volatile organic com-

pounds included also a series of fatty acids we have

mentioned in the introduction and free ammonia [16]. The

smell of the leachate samples remained almost unchanged

up to 50 KGy. Only the sample irradiated to 100 kGy and

those at higher radiation dose showed a distinctive bitu-

minous smell. Just for comparison, the ozonolysis of the

leachate involves the complete deodorization together with

the decoloration.

Radiolysis and ozonolysis of the leachate samples:

chemical analysis by COD

The effects of radiolysis on the HS present in the landfill

leachate can be measured by the COD which is a mea-

surement of the amount of oxygen needed to destroy

completely the dissolved organic matter in polluted water.

The pristine leachate sample had a COD of 5,165 mg/L

but, as shown in Fig. 3, the COD does not change after

Fig. 1 Landfill leachate (neat)

absorption curves in the UV–

VIS–NIR. The violet curve with

higher absorption between 400

and 1,100 nm is due to the

reference pristine leachate. The

red curve with the minimal

absorption between 450 and

1,100 nm is due to ozonized

leachate. The intermediate

curves between these two

extremes are due to the

radiolyzed leachate samples.

(Color figure online)

144 F. Cataldo, G. Angelini

123

radiolysis remaining above 5,000 mg/L at any radiation

dose used. Only at 400 kGy the COD goes slightly below

the threshold of 5,000 mg/L but remains extremely high.

These results demonstrate that the radiolysis is not able to

cause the mineralization of the soluble organic matter (HA,

FA) present in heavily polluted water coming from a

landfill leachate. The COD data are completely in line with

the electronic absorption spectra discussed in the previous

section where it was shown the absence of significant

effects of radiolysis on the color of the HA and FA dis-

solved in the leachate. For comparison, it is worth men-

tioning that the exhaustive ozonolysis of a leachate causes

a COD abatement of 25–30 % [17, 24]. Indeed, the COD of

the pristine leachate at 5,165 mg/L drops to 3,720 mg/L

after ozonolysis confirming that ozone is more effective

agent than radiation in the degradation of HS and HA/FA.

However, as pointed out in our previous work [24] and in

literature [17, 25], HS in general and HA and FA in par-

ticular are considered highly resistant to ozonolysis and the

COD drop of 25–30 % after ozonolysis of a landfill

leachate is not considered at all a sufficient step for the

complete mineralization of the HS [24, 25]. Indeed ozone

is an effective agent in the treatment and potabilization of

lightly polluted groundwater with a COD\20 mg/L but is

not resolutive with heavy polluted waters like the landfill

leachate. Similarly, also water radiolysis using c-rays or

electron beam was proposed and tested in the treatment and

disinfection of lightly polluted water [18–22] but radiolysis

alone, was already recognized not effective in the treatment

of water containing high levels of HS and HA so that it has

been proposed a process of radiolysis and simultaneous

ozonolysis followed by chlorination to get rid of the sol-

uble humic matter present in heavily polluted water [18].

The last process gives clear idea on the resistance to

mineralization offered by the HS and HA because of their

aromatic nature of the main units as shown in Scheme 1.

Furthermore, the hydroxyl radical attack which is effective

on simple aromatic substrates [20–22] cannot be as effec-

tive with HA because these molecules are already poly-

hydroxylated [26, 27]. Other complications which occur

during the radiolysis of a leachate regard the presence

of carbonate ions, ammonia ions and several transition

Fig. 2 Landfill leachate (after

dilution with distilled water

1:10) absorption curves in the

UV–VIS–NIR. The green curvewith higher absorption between

260 and 450 nm is due to the

leachate radiolyzed at 400 KGy.

The thick red curve is due to the

reference pristine leachate and

shows two shoulders at about

276 and 321 nm; it is

overlapped to the other landfill

leachate samples radiolyzed at

different doses comprised

between 12.5 and 200 kGy.

(Color figure online)

Fig. 3 COD (in mg/L) of the

leachate. From left to right are

reported the COD values of the

pristine leachate and the

leachate samples irradiated from

12.5 to 400 kGy. The changes

are minimal

Radiolysis and ozonolysis 145

123

metals [11] which may inhibit the degradation reactions

expected by the hydrated electron and by the hydroxyl

radical. Only in this way it is explainable the failure of the

leachate radiolysis process.

In order to verify the hypothesis that the radiolysis of the

leachate may enhance its further degradability with ozone,

the leachate samples radiolyzed at 12.5, 25 and 400 kGy

were subjected to exhaustive ozonolysis as reported in the

experimental section. The results were as follows:

Sample of pristine leachate ozonized ? COD = 3,720

mg/L with a COD abatement of only 28 % the original

value of 5,165 mg/L

Sample 12.5 kGy ozonized ? COD = 4,225 mg/L

with a COD abatement of only 18 % the original value

of 5,165 mg/L

Sample 25 kGy ozonized ? COD = 4,280 mg/L with a

COD abatement of only 17.1 % the original value of

5,165 mg/L

Sample 400 kGy ozonized ? COD = 3,835 mg/L with

a COD abatement of only 25.7 % the original value of

5,165 mg/L

The data show that the COD abatement was the best

with the direct ozonolysis of the landfill leachate without

the previous radiolysis treatment. Instead, the previous

radiation processing of the leachate leads to a more

‘‘refractory’’ or recalcitrant behavior to ozonolysis. The

interpretation of these results can be achieved considering

that the few radiolysis studies of HA in water have shown

that crosslinking and coagulation of the HA molecules may

occur reducing the number of sites reactive with ozone [18,

26–30]. Furthermore the radiolysis of HA leads also to

chemiluminescence which was interpreted as a conse-

quence of radiolytic oxidation [28–30].

Radiolysis and ozonolysis of the leachate samples:

other chemical analysis and FT–IR spectroscopy

The iron content in the 400 kGy radiolyzed leachate was

found at 11.7 mg/L against 12.9 mg/L of the pristine

sample. No changes also in the chloride content which was

found at a concentration of 2,430 mg/L in the 400 kGy

sample and whose concentration in the pristine leachate

was 2,550 mg/L. Also the pH of the leachate remained

unchanged at about 8.0 at any radiation dose employed.

Only the ammonium concentration was found halved from

115 mg/L of the pristine solution to 65 mg/L at 400 kGy.

The ammonium ion can be reduced to hydroxylamine by

the hydroxyl radical.

In Fig. 4 are reported the FTIR spectra of the pristine

landfill leachate and the leachate samples radiolyzed at

400 kGy and radiolyzed and ozonized. For reference are

reported also the FTIR of a standard HA and synthetic HA

prepared according to Ref. [23]. There is an abundant lit-

erature on the interpretation of the infrared spectra of HS

and HA from sediments [3, 4, 7, 31, 32] and from leachate

624

656 709

833

871

1016

1051 1145

1411

1699 3388

169-37 Humic acid from landfill leachate 400 kGy+O3

1

Abs

621

656 706

836 869

927

1022

1048

1081

1414 1573

1670

2923

2965 3400

169-37 Humic Acids from leachate after 400 kGy dried

0.0

0.5

1.0

Abs

621 659

880 927

1019

1048

1075 1299

1411 1567

1673

2929

2970 3406

169-37 Humic acid from landfill leachate reference

0

1

2

Abs

432

471 536

692 795

913 945

1007

1031 1101 1381

1587 1702

2847

2917 3388 3617

3688

Humic acid Aldrich standard dried

0.0

0.2

0.4

Abs

488 621

689 804 854 1104 1319 1361

1417

1608 1658

3188

3406

58-12 HQ+BQ(NH3)

0.5

Abs

500 1000 1500 2000 2000 3000

Wavenumbers (cm-1)

Fig. 4 FT–IR spectra in KBr.

From bottom to top: reference

synthetic HA synthesized

according to [23]; standard HA

from Aldrich; HA from landfill

leachate (reference, pristine);

HA from leachate radiolized at

400 kGy; HA from leachate

radiolyzed at 400 kGy and

ozonized

146 F. Cataldo, G. Angelini

123

[15, 16], we have used these data in the following dis-

cussion of the infrared spectra shown in Fig. 4.

The infrared spectrum of HS/HA from pristine leachate

(Fig. 4) is characterized by three strong absorption bands at

3,400 cm-1 due to OH groups, 1,567 cm-1 assigned to

aromatic C=C stretching and amide band due to presence

of peptides and proteins, and 1,414 cm-1 due to carbox-

ylate groups, bending of phenolic C–O bond and, again to

aromatic vibrations. The strong band at 1,567 cm-1 shows

also a shoulder at 1,673 cm-1 which is due to ketonic and

carboxylic groups conjugated with double bonds. The

presence of aliphatic moieties in the HS/HA from pristine

leachate is indicated by the mC–H bands at 2,970 and

2,929 cm-1. Other spectral features of HS/HA from pris-

tine leachate regards a series of bands at 1,075, 1,048 and

1,019 cm-1 due to C–O bending and, finally, the aromatic

nature of the HS/HA is further confirmed by the aromatic

C–H bending at 880 cm-1. Thus, the infrared spectrum of

HS/HA from pristine leachate is consistent with the model

chemical structures shown in Scheme 1. Furthermore,

Fig. 4 show also a comparison between the infrared spec-

trum of HS/HA from pristine leachate and a standard HA

sample from sediments obtained from Aldrich. The spectral

similarities are striking especially for the three main

absorption bands mentioned above. Spectral differences in

the region between 900 and 1,100 cm-1 can be attributed

to a different content of silica and silicates, being richer in

these mineral fractions the standard HA from sediments.

Indeed, the synthetic HA shown in Fig. 4, being by defi-

nition free from any mineral contaminations, displays an

infrared spectrum similar to that of HS/HA from pristine

leachate especially in the 900–1,100 cm-1 spectral region.

Based on the previous results on UV–VIS–NIR mea-

surements and COD measurements, it is no more a surprise

that the infrared spectrum of HS/HA from radiolyzed

leachate at 400 kGy is practically identical to that of the HS/

HA from pristine leachate (see Fig. 4). No significant

changes can be observed with the exclusion of the increase in

the intensity of the shoulder at 1,670 cm-1 (with respect to

the band at 1,570 cm-1) which indicates an increase of

oxidation and of carbonyl and carboxyl groups. This fact is

consistent with the analysis made by Goraczko and colleague

[29, 30] showing that the radiolysis of HA solutions causes

an increase of the oxygen content of the macromolecule and

a consequent reduction of the carbon content. The ozonolysis

of the radiolyzed leachate causes a strong increase in the

intensity of the infrared band at 1,670 cm-1 with the a

broadening of the band so that it displays also a shoulder at

about 1,700 cm-1 (Fig. 4). These changes are completely in

line with a profound oxidation of the HS/HA from leachate

caused by the ozonolysis and the consequent increase in the

ketone and carboxylic groups in the macromolecule. Fur-

thermore, after the ozonolysis the aliphatic bands at 2,970

and 2,929 cm-1 are completely reduced to two extremely

weak bands. This important observation suggests that the

ozone attack toward the HS/HA from leachate is essentially

directed towards the aliphatic bridges connecting the aro-

matic units and toward the aliphatic side bridges in general.

Of course these implies that the ethylenic double bonds

which are selectively and specifically attacked by ozone are

located in these aliphatic bridges and side chains. A conse-

quence of this selective oxidation by ozone is that the

ozonized HS/HA from leachate must have lower molecular

weight than the pristine HS from leachate and, additionally

must have also a higher aromatic content which survive the

oxidation and may represent the ‘‘refractory’’ nuclei which

are recalcitrant to oxidation and degradation. This view is

completely in line with the behavior toward oxidation of the

common HS from sediments whose structure is similar to

that of the HS present in the landfill leachate.

Conclusions

Landfill leachate disposal and treatment is a serious con-

temporary environmental problem. In the present work we

have studied the effects of high energy radiation on the

decomposition of the soluble organic matter present in the

leachate at different radiation doses. With great surprise we

have found that radiolysis of the leachate even at 400 kGy

leads to marginal improvements in its brown color and no

significant abatement of the COD. This means that the

mineralization of the soluble organic matter caused by the

radiolysis is negligible. Only the subsequent ozonolysis of

the radiolyzed leachate samples leads to significant color

improvements and a COD abatement of the 26 %. How-

ever, is it shown that the same COD abatement can be

achieved by direct exhaustive ozonolysis of the leachate

sample without the need of a previous radiation treatment.

Furthermore, by a simple ozonolysis also the color of the

leachate becomes pale yellow and transparent from the

original brown and turbid aspect.

By FT–IR spectroscopy it is shown that the radiation

resistance of the HS from leachate derives not only from

their very complex chemical structure (which may imply

some steric hindrance in certain chemical reactions) but

also from the fact that the HA macromolecule is made by

polyhydroxylated aromatic units which appear particularly

resistant to radiolysis. Moreover, the crude landfill leachate

contains a plethora of cations and anions including transi-

tion metal cations, carbonate and nitrite anions and

ammonia/ammonium ions which may interfere significantly

with the radiolysis of the soluble organic matter present in

the leachate. This can be a further justification of the dis-

appointing results of the effects of high energy radiation on

the degradation of the HS/HA present in the leachate.

Radiolysis and ozonolysis 147

123

Instead, by FT–IR is its shows that the ozonolysis is

directed exclusively toward the ethylenic double bonds of

the aliphatic bridges connecting the aromatic units of the

humic acids or toward the side chains and therefore it

results more successful in the oxidation and degradation of

the HS of the leachate.

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