Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
Research Article, Issue 3
Analytical Methods in Environmental Chemistry Journal
Journal home page: www.amecj.com/ir
AMECJ
Ultraviolet-activated sodium perborate process (UV/SPB) for
removing humic acid from water
Ahmed Jaber Ibrahim a,*
a Scientic Research Center, Al-Ayen University, ThiQar 64011, Iraq
ABSTRACT
Humic acid (HA) has a complex chemical composition and the ability
to chelate, adsorb, and exchange ions with organic and inorganic
contaminants in bodies of water, which worsens water quality and
poses a threat to human health and the environment. In this research,
an Ultraviolet-activated sodium perborate (UV/SPB) symbiotic
method (UV/SPB) was developed to eliminate humic acid in water.
The major synergistic and degradative processes of the humic acid
were investigated, as well as the impact of the starting humic acid
concentration, sodium perborate dose, and primary pH value on
the humic acid elimination. Results indicate that just 0.5 % and
1.5 % of humic acid were eliminated mostly by sole UV and sole
sodium perborate (SPB) methods, respectively. More effectively than
other methods, UV/SPB removed humic acid with an efciency of
88.83%. An experiment using free radicals to mask them revealed
that the primary catalyst for humic acid removal is the hydroxyl
radical generated by sodium perborate activation. The excitation-
emission matrix spectroscopy, Ultraviolet-visible absorption (UV-
Vis) spectrum, absorbance ratio values, specic Ultraviolet-visible
absorbance values (SUVA), and UV/SPB method performance
ndings demonstrated the UV/SPB method’s capability to degrade
and mineralize humic acid.
Keywords:
Absorption,
UV-vis spectrum,
Environment,
Contaminants,
Humic acid
ARTICLE INFO:
Received 3 June 2022
Revised form 9 Aug 2022
Accepted 28 Aug 2022
Available online 29 Sep 2022
*Corresponding Author: Ahmed Jaber Ibrahim
Email: ahmed.jibrahim@alayen.edu.iq
https://doi.org/10.24200/amecj.v5.i03.191
1. Introduction
Humic acid, a non-regular macromolecular
polymer formed over a long period by the
polymerization of various biological remnants, is
the principal component of natural organic matter
(NOM) [1]. The complex chemical composition of
humic acid and the presence of numerous organic
functional groups, including hydroxyl(-OH),
carboxyl(-COOH), carbonyl(C=O), methoxy(-
O-CH3), and quinone groups (–(C(=O)–), make
it able to chemically adsorb, exchange ions, and
physical chelation with contaminants in bodies
of water that are both organic and inorganic. This
compromises the water quality and endangers the
ecosystem and public health [2]. Environmental
studies now have one goal guring out how to
eliminate humic acid from water properly and
effectively. Physical and chemical oxidation
techniques are the primary means of regulating
humic acid in water. The coagulation method [3],
occulation method [4], and adsorption method [5]
are physical techniques for removing humic acid.
However, these techniques transport humic acid
into the solid phase; further solid waste processing
is still necessary. Due to the rapid degradation and
mineralization of humic acid, chemical oxidation
is of major interest [6]. Commonly used chemical
------------------------
6Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
oxidation processes for treating organic wastewater
include the photocatalysis method [7-9], The Fenton
oxidation method [10], and the electrochemical
oxidation method [11]. Despite this, each of these
processes has drawbacks, including difcult
reaction conditions and complicated operations.
The in situ oxidizing agent sodium perborate
(SPB, NaBO3) is frequently employed. In contrast
to sodium percarbonate, cyclic perborate ions
(B2O8H4
-2), which are made up of two peroxide
chains lacking BO3
- anions, are present in
sodium perborate instead of being associated
with inorganic salt and hydrogen peroxide [12].
After being dissolved in water, sodium perborate
creates hydrogen peroxide steadily, making it an
effective hydrogen peroxide alternative [13]. Solid
sodium perborate is safer, simpler to carry, and
easier to store than liquid hydrogen peroxide. The
formation of hydroxyl radicals (.OH) can occur
during sodium perborate activation across a broad
range, which is crucial. The primary methods for
sodium perborate activating are ultraviolet light
[14] and transitional metal ions [15]. Scientists
have utilized UV-activated perborate to remove
organic pollutants [13]. Furthermore, the perborate
is often used as an oxidant in homogeneous photo-
Fenton and heterogeneous Fenton-like reactions to
remove colorant and phenolic compounds [12,16].
Of these, the UV-activated process is simple to
use, secure, and free of other pollutants, allowing
it to effectively stimulate hydrogen peroxide to
break down organics in sewage [17,18]. Though
UV-activated peroxide as well as the UV-activated
sodium perborate (UV/SPB) approach has been
used to eliminate organics from water, reports
of the elimination of HA using UV-activated
SPB are infrequent. To reduce humic acid in an
aqueous solution, it was important for this research
to construct a UV/SPB symbiotic system (UV/
SPB). The inuences of the primary humic acid
concentration, sodium perborate concentration,
and starting pH value on humic acid cleansing
were investigated using the practical and effective
spectrophotometric approach [19]. Using a free
radical masking test, the primary compounds
produced in the symbiotic system for removing
humic acid were identied. The degradation process
was carefully investigated using UV spectrum,
total organic carbon, and 3-dimensional excitation-
emission matrix spectroscopic (3D-EEM).
2. Material and Methods
2.1. Chemicals
Every chemical was obtained with the highest level
of purity, including humic acid (M.wt 2485 dalton,
CAS1415-93-6, Merck Millipore Co., USA),
Sodium perborate (NaBO3, SPB, CAS10486-00-7,
Weifang Haizhiyuan Chemistry and Industry Co.,
China), Sodium sulfate (Na2SO4, CAS7757-82-
6, Tokyo Chemical Industry Co., Japan), Sodium
hydroxide (NaOH, CAS1310-73-2, Weifang
Haizhiyuan Chemistry and Industry Co., China),
Sulfuric acid (H2SO4, CAS7664-93-9, Merck
Millipore Co., USA), Sodium carbonate (Na2CO3,
CAS497-19-8, Merck Millipore Co., USA), Sodium
dihydrogen phosphate (NaH2PO4, CAS7558-80-
7, Tokyo Chemical Industry Co., Japan), Sodium
nitrate (NaNO3, CAS7631-99-4, Merck Millipore
Co., USA), Sodium bicarbonate (NaHCO3, CAS144-
55-8, Weifang Haizhiyuan Chemistry and Industry
Co., China), Sodium chloride (NaCl, CAS7440-23-
5, Weifang Haizhiyuan Chemistry and Industry Co.,
China), and Tertiary butanol (TBA, CAS75-65-0,
Merck Millipore Co., USA).
2.2. Experiment
The humic acid removal studies were carried
out at 25oC. The UV led (16 W, 254 nm) was
positioned above the beaker at a length of 3.5 cm.
The magnetic stirrer held the beaker, which served
as the chemical reactor. In this study, the UV
irradiation was estimated to be 35.2 Jm cm-2 for an
hour. A certain amount of the humic acid solution
was diluted to 100 mL before the experiment.
The sodium perborate was then added to the HA-
imitated wastewater, and light irradiation started
the reaction. 2.5 mL aliquots were taken out at
predetermined intervals to measure the absorbance.
Every experiment was run at least twice. Tertiary
butanol was utilized as the scavenger to conrm the
7
UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim
creation of hydroxyl radicals.
2.3. Analysis and Procedure
To determine the effectiveness of the humic acid
removal process, the solution’s absorbance was
measured using a UV-vis spectrophotometer and
an external reference technique at a wavelength
of 254 nm [20]. The mathematics formula read in
Equation 1 as follows:
HA elimination efciency = (C0 – Ct / C0)×100 %
(Eq.1)
where Ct represents the humic acid quantity at the
time of treatment t, and C0 represents the initial
humic acid quantity.
A variety of distinct UV-vis adsorption patterns
were used to determine the change in the humic
acid molecule structure. absorbance values were
determined by spectrophotometer at wavelengths
(nm) at 203, 250, 253, 254, 365, 436, 465, and
665, respectively [21]. To characterize the changes
in the humic acid molecule structure, continuous
variations in the solution’s absorbance range (200-
800 nm) were also examined (Schema 1). A TOC
tester was used to measure total organic carbon
(TOC). Ax (sample absorbance at x nm) and TOC
were used to determine specic UV absorbance
(SUVAx) which was shown in (Equation 2) [22].
(SUVAx) = (Ax / TOC) × 100%
(Eq.2)
The mechanism of the humic acid degradation
was investigated using the 3D-EEM spectrum.
The corresponding apertures were 10 and 5 nm,
respectively, while the wavelength limits for the
emission and stimulation ranges were (280-550
nm) and (200-400 nm), respectively.
Schema 1. Removal procedure for the humic acid and determined
by the UV-Vis spectrophotometer
8
3. Results and discussion
3.1. Study of the humic acid elimination by UV/
SPB process
3.1.1.Performance comparison of the humic acid
elimination in various systems
First, three processes—UV, SPB, and UV/SPB—
were examined for their ability to remove the humic
acid, as shown in Figure 1 The following were the
experimental parameters: starting pH 3, 10 mg L-1
of the humic acid, 1 mmol L-1 of Sodium perborate,
and 10 mg L-1 of the humic acid.
The single UV treatment took 1 hour to remove
0.5 % of the humic acid, which was barely
eliminated. The single sodium perborate treatment
had a negligible effect on the removal of the
humic acid, with a decolorization ratio of 1.5%
after an hour. The UV/SPB process had a higher
decontamination efciency of 88.83 % than the
other two processes, which rose by a smaller
amount. In addition, when the humic acid was
removed using UV light and hydrogen peroxide
with the same molecular weight, the elimination
ratio was only 40.2 % after 1 hour (60 min). It
has the same effect as hydrogen peroxide when
Sodium perborate is dissolved in water (Equation
3) [12], which is why it is frequently employed
for in situ chemical oxidation. Hydrogen peroxide
was produced in the only Sodium perborate
system, but because it cannot be activated to
produce hydroxyl radicals, very little humic acid
was eliminated. In the UV/SPB system, hydrogen
peroxide produced from Sodium perborate can
generate hydroxyl radicals after being exposed
to UV (Equation 4) [14], This might oxidize and
damage the functional groups in the structure of
the molecule of the humic acid.
NaBO3+H2O NaBO2 +H2O2
(Eq.3)
H2O2+hv 2.OH
(Eq.4)
Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
Fig. 1. Performance comparative of humic acid elimination in various systems
9
3.1.2.Humic acid concentration effect
Figure 2a illustrates the impact of the humic acid
concentration on the humic acid elimination by the
UV/SPB system. The optimized parameters were
the sodium perborate concentration of 1 mmol L-1
and primary pH of 3. The elimination ratio dropped
as the humic acid primary concentration raised.
After 1 hour, the elimination ratio dropped from
89.81% to 70.81% when the humic acid content
increased from 5 to 15 mg L-1.
Because there weren’t enough oxygen radicals
generated by the system to completely oxidize
all of the pollutants in the solution, it proved that
the oxygen radicals generated during the UV/
SPB system were continually used. Additionally,
as humic acid concentration gradually increased,
the competition between humic acid molecules
and oxygen radicals grew more intense. Further,
the increased humic acid content would absorb
more UV rays [23], preventing hydrogen peroxide
activation and the subsequent generation of
hydroxyl radicals (.OH), which resulted in a
decrease in the elimination of the humic acid.
3.1.3.Effect of sodium perborate concentration
Reactive radicals are produced by the Sodium
perborate (SPB), which is important for the
symbiotic mechanism. Investigations were done
on the effect of Sodium perborate concentration on
humic acid removal (Figure 2b). A concentration
of humic acid of 10 mg L-1 and a pH of 3 was used
in the test. After 1 hour, the Sodium perborate
concentration was increased from 0.25 to 1.0 mmol
L-1, and the humic acid elimination ratio increased
from 53.0 to 88.83 %. The number of active
oxygen radicals in the system was increased with
an increase in Sodium perborate concentration,
which aided in the elimination of humic acid.
Nevertheless, In excess, Sodium perborate would
hunt the hydroxyl radical and produce the peroxy
hydroxyl radical (HO2
.) (Equation 5) [24]. peroxy
hydroxyl radical has a weaker redox potential than
hydroxyl radical. Consequently, the reduction in
humic acid elimination was caused by the excess
Sodium perborate (2 mmol L-1).
.OH +H2O2 H2O + HO2
.
(Eq.5)
3.1.4.Primary pH effect
Figure 2c illustrates the impact of various initial pH
levels on the elimination of humic acid following UV/
SPB processing. The Sodium perborate concentration
was 1 mmol L-1 and the humic acid concentration
was 10 mg L-1 during the experiment. After 1 hour,
the pH value increased from 3 to 11, while the humic
acid elimination fell from 88.83% to 58.4%. Strongly
acidic conditions render the humic acid molecule
neutral, resulting in more photochemical activity
than under neutral or basic conditions. The pH has an
impact on the redox potential Energy(OH, H2O ) as well.
The redox of Energy(OH, H2O ) decreases from 2.61 V to
2.14 V as pH rises from 3 to 11 [25]. The alkaline state
would cause the hydroxyl radical to undergo a reaction
(Equation 6-8) that would change it into O.- (E = 1.78
V), which had a lower oxidation capability than the
hydroxyl radical. When the pH reaches 11, the main
form of hydrogen peroxide changes to HO2
-, which
reacts with hydroxyl radical (.OH) at a faster rate than
hydrogen peroxide does [27], therefore going to lead
using more hydroxyl radical in the process.
OH- + .OH H2O + O-
(Eq.6)
HO2
-+ .OH OH- + HO2
. (k= 7.5 × 109)
(Eq.7)
.OH + H2O H2O + HO2
. (k= 2.7 × 107)
(Eq.8)
3.1.5.Elimination of humic acid in various water
bodies
Figure 2d shows how the UV/SPB system removes
humic acid from various water bodies. Following
a one-hour reaction, the amounts of humic acid
removed from tap water, lake water, and DI
(deionized water) were 88.83%, 59.63%, and 47.53
%, respectively. It shows that both tap water and lake
water prevented humic acid from being eliminated.
These were the underlying causes. First, the hydroxyl
UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim
10
radical produced by the UV/SPB process would face
competition from other naturally occurring organic
substances in the lake. Second, the attendance of
several anions in both tap water and lake water may
limit the action of the oxidizing agents, decreasing
the effectiveness of removing humic acid.
3.1.6.Common anions’ inuence on water
Figure 3a illustrates how common anions including
HCO3
-, CO3
-2, NO3
-, SO4
-2, Cl-, and H2PO4
- affect
the removal of humic acid by the UV/SPB process.
When the Carbonate anion (CO3
-2) concentration
was dropped from 1 to 10 mmol L-1, as shown in
Figure 3a, the elimination efciency dropped from
63.7 to 44.9 %. The cause of the decline in humic
acid elimination was that the hydroxyl radical
produced by the process was used by Carbonate
anion (CO3
-2) to create CO3
.- with a low oxidation
capability (Equation 9) [28].
.OH + CO3
-2 CO3
.- + OH- (k= 4.2× 108) (Eq.9)
According to Figure 3b, the humic acid elimination
efciency rapidly declined from 74.2 to 53.5
% during 1 hour when the HCO3
- concentration
rose from 1 to1 to 10 mmol L-1. The system also
converted hydroxyl radicals into HCO3
- (Equation
10). In addition, the HCO3
- addition would result in
a rise in the pH of the solution [29].
.OH + HCO3
- CO3
.- + H2O (k= 4.2×108)
(Eq.10)
In Figure 3c, the elimination of humic acid reduced
from 84.1 % to 79.9 % as the chlorine anion (Cl-)
was increased from 1 to 30 mmol L-1. more excess
chlorine anion would use more hydroxyl radicals
and create more chlorine radicals (Equation 11,12).
Therefore, the decrease in humic acid elimination
was caused by the loss in oxidation capability [30].
.OH + Cl- ClOH.- (k= 4.3×109)
(Eq.11)
Cl- + Cl- Cl2
.- (k= 8×109)
(Eq.12)
Figure 3d shows that the humic acid elimination
ratio decreased with increasing Nitrate anion
(NO3
-) addition. The humic acid elimination was
reduced to 33.4 % when 20 mmol L-1 of Nitrate
anion was introduced. Reactive nitrogen species
(NO2
.) (E0 = 0.867 V), can be produced when UV
ray activated Nitrate anion which has reduced
oxidation capability and also would be damaged
through the UV/SPB process (Equation 13-15)
[31]. Additionally, Nitrate anion could use hydroxyl
radical immediately (Equation 16) [32].
NO3
- + hv NO2
. + O.-
(Eq.13)
NO3
- + hv NO2
- + O
(Eq.14)
2NO2
. + H2O NO3
- + NO2
- + 2H+
(Eq.15)
NO3
- + .OH NO3
. + OH- (k= 4×105)
(Eq.16)
Figure 3e demonstrates that the humic acid elimination
activity was unaffected by the rise in sulfate anion
(SO4-2) quantity. The sulfate anion concentration was
increased to 20 mmol L-1, which resulted in an 88.0 %
increase in humic acid elimination effectiveness. The
literature claims that sulfate anion does not interact
with the reactive species produced in the system
[33,34]; hence it has no impact on eliminating humic
acid. As shown in Figure 3f, the increase of H2PO4
-
anion little affected the humic acid elimination. The
humic acid removal efciency decreased from 86.3 %
to 82.4 % as the Dihydrogenphosphate anion (H2PO4
-
) level increased from 10 to 30 mmol L-1. Although
Dihydrogenphosphate anion and hydroxyl radical
can combine to generate the hydrogen phosphate
radical (HPO4
.) (Equation 17) [35], The elimination
of humic acid wouldn’t be impacted because of the
highly sluggish reaction rate.
H2PO4
-+ .OH HPO4
. + H2O (k= 2×104)
(Eq.17)
Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
11
UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim
Fig. 2. Effect of several factors during UV/SPB system on Humic acid elimination:
a) Humic acid concentration, b) Sodium perborate concentration,
c) primary pH, d) UV/SPB elimination of Humic acid in various waterbodies
12
3.2. Mechanism of UV/SPB humic acid
elimination
3.2.1.Examining Scavenging
Tertiary butanol (TBA) had the ability to remove
hydroxyl radical from the process of oxidation
(kTBA,
.
OH = 3.8-7.6×108) [36]. The effect of Tertiary
butanol adding on the elimination of humic acid
in the UV/SPB process is shown in Figure 4. The
empirical parameters were starting pH 3, humic acid
concentration of 10 mg L-1, and Sodium perborate
dosage of 1.0 mmol L-1. The humic acid elimination
was constrained by the addition of Tertiary butanol,
as shown in the gure, which decreased from 16.5
to 11.5 % with the addition of Tertiary butanol and
increased from 0.05 to 0.5 mol L-1.
According to its testimony, hydroxyl radical may
Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
Fig. 3. Common anions’ effects on the elimination of humic acid in UV/SPB process
13
be the primary oxidizing agent in the symbiotic
system. After the addition of Tertiary butanol, the
removal of humic acid was not entirely inhibited,
which may be because the HO2 generated by
the breakdown of hydrogen peroxide (H2O2)
could likewise produce other activated particles,
including superoxide anion radicals (O2
.-) and
singlet oxygen (1O2) (Equation 18-22) [37,38],
which also have some oxidation ability and cannot
be entirely repressed by Tertiary butanol.
H2O2 2.OH
(Eq.18)
OH + H2O2 HO2
. + H2O
(Eq.19)
HO2
. O2
.- + H+
(Eq.20)
OH + O2
.- 1O2 + OH-
(Eq.21)
2H+ + O2
.- H2O2 + 1O2
(Eq.22)
3.2.2.Mechanism of humic acid degradation
The humic acid molecule structure changes may
be reected in the absorbance ratios [39]. Figure
5a depicts the development of these ratios in the
UV/SPB mechanism. The value of absorbance
ratio (253/203) declined from 0.98 to 0.44 with
a rise in reaction time, showing the durability of
functional groups (such as carboxyl [-COOH] and
carbonyl groups [-C=O]) in humic acid aromatic
structure gradually decreased. The absorbance
ratio (250/365) increased from 2.42 to 3.20, which
indicated that the humic acid molecular weight had
been reduced. The humic acid chromophore was
damaged by the absorbance ratio (254/436) rising
from 4.63 to 5.60. The absorbance ratio (465/665)
dropped from 3.5 to 1.0, demonstrating the loss of
aromaticity in humic acid.
The humic acid molecule’s structural differences
can also be seen in the UV-visible absorption
spectra. Figure 5b depicts the evolution of the
humic acid absorption spectrum in the UV/SPB
process over time. Implies that hydroxyl radical
produced in the UV/SPB process damaged the
chromophore groups and double bond structure
(C=C) of humic acid, as well as oxidizing the
UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim
Fig. 4. Tertiary butanol addition’s effect on humic acid removal
14
unsaturated ketone, the absorption edge of humic
acid at 200-250 nm, becomes weaker with time.
Additionally, the absorption edge shifted to the
region of short wavelengths, a phenomenon known
as blue shift. This proved that the carbon atom
substitution process took place in the carbonylic
group (C=O) of the humic acid chromophore [40].
Linearly expanded quinone groups and unsaturated
carbons make up humic acid and fulvic acid. When
specic substituent groups were used to replace the
carbon atom of a chromophore, such as a carbonyl
group (C=O), the absorption edge would shift to
a low amplitude. In general, specic ultraviolet
absorbances (SUVA) (254, 280, 365, and 436)
were chosen to describe the mineralization and
decomposition of natural organic matter. Where
SUVA-365 nm denotes the molecular volume,
SUVA-436 nm denotes the chromophore situation
in natural organic matter, SUVA-280 nm denotes
the stability of the aromatic system, and SUVA-254
nm denotes the molar mass [39].
After one hour of UV/SPB treatment, Figure 5c
demonstrates that the SUVA-254 and SUVA-
280 values decreased with time, indicating that
the molar mass of organic compounds decreased
and the basic aromatic framework was destroyed.
The decrease in SUVA-365 showed that as
the process developed, the volume of organic
molecules dropped. The lowering value of SUVA-
436 demonstrated that different oxidizing agents
destroyed the functional groups and chromophores.
Additionally, the total organic carbon (TOC) in the
process decreased from 7.139 to 2.440 mg L-1 and
the mineralization efciency increased to 65.81 %,
showing that the majority of humic acid had been
converted into water (H2O) and carbon dioxide
(CO2). UV spectrum and total organic carbon
ndings demonstrated that the UV/SPB symbiotic
therapy could successfully break down the intricate
chemical composition of humic acid.
Figure 6 displays the outcomes of further
investigating the humic acid degradation process
in the UV/SPB process using 3D-EEM. The
intricacy of the spectral reaction and the scanning
sample led to the division of the scanning spectrum
into ve sections. According to the structure
of heterocyclic amino acids in natural organic
matter, the I and II range can indicate aromatic
proteins in organic molecules [40]. The III region
in the humus structure denotes fulminate-like
compounds connected to hydroxyl (-OH) and
carboxyl (-COOH) groups. Region IV’s coverage
area reects the tiny molecular structure of organic
materials [35]. A humic-like uorescence is shown
by the V area. The uorescence density of the ve
locations whole decreased and slowly vanished
from 0 to 15 minutes (Fig. 6a and 6b) and 1 hour
(Fig. 6c), moreover demonstrating that the humic
acid molecular formula was broken down and
mineralized in this cooperative system.
Anal. Methods Environ. Chem. J. 5 (3) (2022) 5-18
Fig. 5. (a)Ultraviolet absorption level, (b) Ultraviolet-visible spectrum,
(c) SUVAx and TOC content for humic acid degradation
15
UV/SPB process for removing humic acid in water Ahmed Jaber Ibrahim
4. Conclusions
The UV/SPB synergistic technique was developed
in this work to eliminate humic acid from water,
and the experimental ndings showed that the
procedure could efciently degrade humic acid.
The humic acid elimination effectiveness was 88.83
% after 1 hour of therapy under the experimental
parameters of 10 mg L-1 humic acid concentration,
1 mmol L-1 Sodium perborate dose, and initial
pH 3. When compared to DI (deionized water),
the humic acid was eliminated far less effectively
In tap and lakes water. The anion effect studies
proved that, aside from SO4
-2, Cl-, and H2PO4
-. the
carbonate anion (CO3
-2), bicarbonate anion (HCO3
-
), and nitrate anion (NO3
-) exhibited varying
degrees of humic acid elimination inhibition.
By using masking tests, it was determined that
the primary chemical responsible for removing
humic acid was the hydroxyl radical produced
by Sodium perborate activation. Results from
the UV-vis spectrum, absorbance ratio, specic
UV absorbance (SUVA), and 3D-EEM together
demonstrated that the symbiotic mechanism could
decompose and mineralize humic acid in water
effectively.
5. Acknowledgements
This research is supported by the Physical Chemistry
Lab., Chemist Department, College of Education
for Pure Science (Ibn-al Haitham), University of
Baghdad.
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