Activated carbon/hydrogen peroxide (AC/H 2 O 2 )

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Dec 5, 2012 (4 years and 11 months ago)

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________________________________________

*

:
Corresponding Author


Activated carbon/hydrogen peroxide (
AC/H
2
O
2
) treatment of
amoxicillin and cloxacillin antibiotics in aqueous solution


Augustine Chioma Affam
*

Department of Civil Engineering,
Universiti Teknologi PETRONAS,

Bandar Seri Iskandar, 31750 Tronoh, Perak, Darul Ridzuan, Malaysia


Email:
a
ffamskii@yahoo.com
1




Malay Chaudhuri


Department of Civil Engineering
,
Universiti Teknologi PETRONAS,

Bandar Seri Iskandar, 31750 Tronoh, Perak,
Darul Ridzuan, Malaysia


Email
:
m_chaudhuri
@petronas.com.my




Abstrac
t

-

The study examined
AC/H
2
O
2

treatment
of amoxicillin and cloxacillin antibiotics

aqueous solution. The treatment
was optimized

by the central composite design (CCD) of response surface methodology (RSM).
The optimum

operating
conditions at pH 3 were
H
2
O
2
/COD molar ratio 2.0, AC 3.5 g/L and reaction time 90 min for
78.03% removal of
COD,
78.36% removal of
TOC and
97.16%

removal of
NH
3
-
N
.
Experimental removal efficiency and model prediction were in close
agreement
(<1.0% error).
Biodegradability (BOD
5
/COD ratio) improved from
zero to 0.32, indicating that the effluent was
amenable to biological treatment. FTIR spectra ind
icated degradation
of the antibiotics.

The study has shown that
AC/H
2
O
2

process is effective in pretreatment of amoxicillin and cloxacillin antibiotics aqueous solution for biological treatment
.

Keywords:


AC/H
2
O
2
,
antibiotic
, amoxicillin, cloxacillin,
response surface methodology (
RSM).

.



1. INTRODUCTION




Increasing use of pharmaceuticals including antibiotics
and their consequent discharge into the
aquatic
environment constitute an important environmental
contamination. Pharmaceuticals are most probably excreted
by patients through urine and faeces, either as parent
compounds, conjugates or metabolites (Langford and
Thomas, 2009)
.

The concern about a
ntibiotic residues in
the environment is the development and inducement of
resistant bacterial strains (
Walter and Vennes, 198
5
)
.
Removal of the antibiotics is a current challenge especially
as the conventional wastewater treatment plants are not
designed
to remove recalcitrant organics (Gulkowska
et al
.,
2008). Advanced oxidation process (Fenton or photo
-
Fenton) pretreatment of recalcitrant wastewater (cf.
antibiotics in aqueous solution) enhances the
biodegradability and produce
s

a new effluent that is
am
enable to biological treatment. Fenton and photo
-
Fenton pretreatment of antibiotic aqueous solution have
been reported (Elmolla and Chaudhuri, 2009a and 2009b).



Activated carbon (AC) is known to decompose
hydrogen peroxide (H
2
O
2
). Presumably, the process
involves the exchange of a surface hydroxyl group with a
H
2
O
2

anion (Eq. 1), according to Bansal
et al
.

(1998) as



cited in
Khalil
et al
. (
2001). The formed surface peroxide is
regarded as having an increased oxidation potential w
hich
enables the decomposition of another H
2
O
2

molecule with
release of oxygen (O
2
) and regeneration of the AC


surface

(Eq. 2)




AC


OH + H
+

OOH
¯

AC


OOH

+ H
2
O

(1)




AC


OOH + H
2
O
2



AC


OH + H
2
O + O
2


(2
)





Beside this decomposition reaction,
H
2
O
2

can
obviously be activated on the AC s
urface involving the
formation of hydroxyl radicals (OH

). AC is considered to
function as an electron
-
transfer catalyst similar to the
Haber

Weiss mechanism known from the Fenton reaction
,

with AC and AC
+

as the oxidized and reduced catalyst
states (Kimura and Miyamoto, 1994)
.


AC + H
2
O
2



AC
+

+ HO
¯

+
OH




(3)







AC
+

+ H
2
O
2



AC + HO
2

+ H
+


(4)







Studies have shown that the AC/ H
2
O
2

process can
lead to

decay of organic contaminants

in aqueous solution
(Lücking
et al
., 199
8; Huang
et al
., 2003; Georgi
and

Kopinke,

2005)
.


The present study examined the application of the
AC/H
2
O
2

process in the pretreatment of amoxicillin and
cloxacillin antibiotics aqueous solution for biological
treatment. The process was optimized by response surface
methodology (RSM) for the removal of chemical oxygen
demand (COD), total organic carbon (TOC) a
nd ammonia
-
nitrogen (NH
3
-
N). Ant
ibiotic degradation was estimated

by
Fourier transform infrared (FTIR) spectroscopy.


2

MATERIALS AND METHODS

2.1

Chemicals and antibiotics


Hydrogen peroxide (35%, w/w) was purchased from
R&M Marketing, Essex, U.K.
Amoxicillin (AMX) and
cloxacillin (CLX) used were obtained from a commercial

source (Farmaniaga Company). The commercial products
were used

as purchased without any additional
reformulation. Sodium hydroxide and

sulphuric acid were
purchased from HACH Com
pany, USA. Figure 1 shows the
chemical structure of the antibiotics.


(a
)




(b
)


Fig.1. Chemic
al structure of (a) AMX

and (b) (CLX)





Activated carbon (F400
-
GLY) was obtained from the
Calgon Corporation, Pittsburgh, PA, USA. Activated
carbon (AC)

characteristics are shown in
Table 1. The AC
was ground to a size of 425 µm.


2.2 Analytical methods


Chemical oxygen demand (COD) was measured

according to the Standard Methods (APHA, 1992). When
the sample contained hydrogen peroxide (
H
2
O
2
), to reduce
interference in COD determination pH was increased to
above 10 to decompose H
2
O
2

to oxygen and water (Talinli
and Anderson, 1992; Kang
et al
., 19
99). A TOC analyzer
(Model 1010; O & I Analytical) was used for determining
total organic carbon (TOC). NH
3
-
N was measured
according
to Water Analysis Handbook (HACH
, 2002).
Five
-
day biochemical oxygen demand (BOD
5
) was
measured according to the Standard
Methods (APHA,
1992).

The bacterial seed for BOD
5

test was obtained from
a municipal wastewater treatment plant. DO was measured
using YSI 5000 dissolved oxygen meter.
FTIR spectra of



the antibiotic aqueous solution were taken by a Shimadzu
FTIR
-
8400S
.




2.3

Antibiotic

aqueous solution




Antibiotic aqueous solution was prepared weekly by
dissolving 150 mg each of AMX and CLX in 1000 mL
distilled water and stored at 4
ºC. The characteristics of the
antibiotic aqueous solution were COD 390 mg/L, TOC
168.8
mg/L, NH
3
-
N 20.6 mg/L and biodegradability
(BOD
5
/COD ratio) zero.



2.4

Experimental p
rocedure






Batch AC/
H
2
O
2

treatment was conducted in 250
-
mL
conical flasks. The a
ntibiotic aqueous solution (200
mL)
was dosed with AC and the pH was adjusted to 3.0, the
optimum pH for Fenton treatment of antibiotic aqueous
solution
(Elmolla and Chaudhuri, 2009a).
Thereafter,
H
2
O
2

was added according to the selected

H
2
O
2
/COD molar ratio
and the flasks were immediate
ly placed on an orbital shaker.
The
H
2
O
2
/COD molar ratio, AC dose and reaction time
were determined by the design expert software and central
composite design (CCD) for variable optimization. At
selected reaction time, a flask was removed from the shaker,
the pH adjusted to above 10 to decompose hydrogen
peroxide and an aliquot of the supernatant was filtered
through 0.45 µm membrane filter for measurement of
chemical oxygen demand (COD),

5
-
day
biochemical
oxygen demand (BOD
5
), ammonia nitrogen (NH
3
-
N)

and
total organic carbon (TOC)
,

and filtered through 0.20 µm
membrane filter for FTIR spectra.



Table 1.

C
haracteristics
of AC

Surface area (m
2
/g)

626

Micropore area (m
2
/g)

509

Micropore volume (mL/g)

0.23

Average pore diameter (Å)

15.35

Bulk
density (g/mL)

0.52

Conductivity (
µS
/cm)

4.00

pH

5.65

pH
ZPC

6.2

Bulk density (g/mL)

0.52


2.5

Optimization

and response surface
modeling





Design expert software (version 6.0.7) was used for
statistical design of experiment and data analysis.
Central
composite design (CCD) of the response surface
methodology (RSM) was used to optimize the operating
conditions (variables) of the AC/
H
2
O
2

treatment. The
variables were simultaneously changed in a central
composite circumscribed design. The coded values of the
variables
H
2
O
2
/COD molar ratio,
AC dose and reaction
time were set at five levels:
-

α (minimum),
-
1

(low),

0
(central), +1

(high)

and +α (maximum) and 20
experiments were performed to give statistical consistency
to the mathematical model. The variables,
H
2
O
2
/COD
molar ratio and AC dose and reaction time were studied in
the range of 1.0

3.0, 0.4

1.0 g/200 mL, and 60

120 min,
respect
ively. Optimum
H
2
O
2
/COD molar ratio 3 and
reaction time 60 min for Fenton treatment of antibiotic
aqueous solution have been reported (Elmolla and
Chaudhuri, 2009a). Chosen response parameters for the
AC/
H
2
O
2

process were removal of COD, TOC and NH
3
-
N.
Reg
ression analysis, graphical analysis and analysis of
variance (ANOVA) were carried out using the design
expert software. The optimum operating conditions were
identified from the response surface plots and the response
equation simultaneously.


The followi
ng response equation


Y

=

β
o

+ β
1
A +β
2
B + β
3
C + β
11
A
2

+ β
22

B
2

+ β
33
C
2

+ β
12
AB


+
β
13
AC+
β
23
BC

(5)




was used to assess the predicted result (Y) as a function of
the variables
H
2
O
2
/COD molar ratio (A), AC dose

(B) and
reaction time (C), and calculated as the sum of a constant
(
β
o
), three first
-
order effects (
A, B and
C), three second
-
order effects (
A
2
, B
2

and C
2
) and three

interaction effect
(AB, AC and BC).


3.
RESULTS AND
DISCUSSION


3.1
Statistical

a
nalysis






T
he results obtained were analyzed by ANOVA to
assess the “goodness of fit”. The models for COD, TOC



and NH
3
-
N removal

(Y
1
, Y
2

and Y
3
) were significant by the
F
-
test at 95% confidence level if prob
.
>F
<
0.05.
The
following fitted regression model (equations in terms of
coded values) was obtained to quantitatively investigate the
effects of
H
2
O
2
/COD molar ratio (A), AC dose (B) and
reaction time (C) on COD, TOC and NH
3
-
N removal.


COD removal

Y
1
=78.03 +
0.23A + 2.08B + 4.83C


0.0068A
2
-

7.25B
2



+ 3.71C
2
+ 3.12AB


3.38AC + 7.62BC



(6)




TOC removal


Y
2
= 78.36
-

7.15A + 5.44B + 1.93C


6.87A
2
-

10.09B
2



-

6.65C
2

+ 3.30AB


4.79AC + 5.
85BC


(7)


NH
3
-
N removal



Y
3
= 97.16 + 0.64A


1.67B + 0.27C + 0.15A
2
-

2.32B
2




+ 0.33C
2

+
1.12AB + 0.12AC


0.13BC

(8)




In Eq.

6, 7 and 8, the values of the sum of a constant (βo),
78.03, 78.36 and 97.16 represent the percentage removal of
COD, TOC and NH
3
-
N, respectively. The positive sign
indicates that the variable is directly proportional to the
response (COD, TOC and NH
3
-
N
r
emoval), and the
negative sign indicates that the variable is inversely
proportional to the response.

Table 2 shows the
experimental design, real and codified values (in
parentheses) of the variables, and responses (observed
removal of COD, TOC and NH
3
-
N).



Table 2
.
Experimental design and observed removal


A:
H
2
O
2
/COD

(code)


B:

AC


( c o d e )

C:
R e a c t i o n
T i me


( c o d e )


R e m o v a l ( % )


C O D


T O C




NH
3
-
N


2.00 (0.0)

1.20(1.68)

90.0(0.0)

59

67.1

87

3.68 (1.68)

0.70(0.0)

90.0(0.0)

72

48.26

98

3.00 (1.0)

0.40(
-
1.0)

120.0(1.0)

66

24.71

96

2.00 (0.0)

0.70(0.0)

90.0(0.0)

74

85.68

97

2.00 (0.0)

0.70(0.0)

39.55

(
-
1.68)

78

51.76

96


0.3 2


(
-
1.6 8 )

0.7 0 ( 0.0 )

9 0.0 ( 0.0 )

85

71.95

97

2.00 (0.0)

0.20

(
-
1.68)

90.0(0.0)

57

34.88

94

3.00 (1.0)

0.40(1.0)

60.0(
-
1.0)

76

57.07

97

1.00 (
-
1.0)

1.00(
-
1.0)

60.0(1.0)

54

55.24

93

1.00 (
-
1.0)

0.40(
-
1.0)

120.0

(
-
1.0)

68

65.45

97

2.00 (0.0)

0.70(0.0)

90.0(0.0)

97

79.72

95

2.00 (0.0)

0.70(0.0)

90.0(0.0)

74

72.22

98


0.70(0.0)

90.0(0.0)

73

64.14

99

2.00(0.0)

0.70(0.0)

140.45

(1.68)

100

69.72

100

3.00(1.0)

1.00(1.0)

60.0(
-
1.0)

78

46.84

96

1.00(
-
1.0)

0.40(
-
1.0)

60.0(
-
1.0)

74

58.39

97

3.00(1.0)

1.00(1.0)

120.0(1.0)

89

58.15

96

2.00(0.0)

0.70(0.0)

90.0(0.0)

77

66.5

97

1.00(
-
1.0)

1.00(1.0)

120.0(1.0)

88

65.45

91

2.00(0.0)

0.70(0.0)

90.0(0.0)

73

96.47

97


Table 3 shows the ANOVA of the response parameters
using the results of all experiments performed from the

design. Adequate precision (A.
P.) compares the range of the
predicted values at the design points to the average
pr
ediction error. Ratios greater than 4 indicate adequate
model discrimination and can be used to navigate the
design space defined by the CCD (Ghafari
et al.,

2009).
The A.
P. for all the responses was greater than 4. The
probability of lack of fit (PLOF)
describes the variation of
the data around the fitted model. This will be significant
when PLOF<0.05. The PLOF for all the responses was
<0.05.The coefficient of variance (C.V.) is the ratio of the
standard error of estimate to the mean value of the observ
ed
response and defines reproducibility of the model. A model
normally can be considered reproducible if its C. V. i
s not
greater than 10% (Design expert s
oftware, 2009; Beg
et al
.
2003). The C.
V. of
NH
3
-
N

(1.15%)

was <
10%, whereas
that of

COD (11.09%) and

TOC (17.18%) were >
10%,

and
thus fell short of reproducibility. The R
2

values, COD (R
2

=
0.7454) and TOC (R
2

= 0.7798) were observed to be lower,
except for NH
3
-
N (R
2

= 0.8692
)
.





Table 3
.

ANOVA of the response parameters



Parameter


A.P.


PLOF


C.V
.


R
2


COD


7.190


0.0400


11.09


0.7454


TOC


6.373


0.0219


17.18


0.7798


NH
3
-
N


10.637


0.0022


1.51


0.8692



3.2


Process

analysis




Figures
2, 3, and 4

show the response surface plots for
COD, TOC and NH
3
-
N removal. Maximum COD, TOC
and NH
3
-
N
removal were 78.03, 78.36 and 97.16%
respectively at H
2
O
2
/COD molar ratio 2.0, AC dose


0.70 g/200mL (3.5
g/L) and reaction time 90
min.




Three confirmatory experiments were conducted
under the optimum operating conditions to verify the model
respon
se. As shown in Table 4, experimental removal
efficiency and model prediction were in close agreement
with less than 1.0% error.


DESIGN-EXPERT Plot
COD Remov al
Design Points
X = A: H2O2/COD
Y = B: FeGAC
Actual Factor
C: Time = 90.00
COD Removal
A: H2O2/COD
B: FeGAC
1.00
1.50
2.00
2.50
3.00
0.40
0.55
0.70
0.85
1.00
73.4476
73.4476
76.2898
76.2898
77.4767
77.4767
77.8202
78.0325
6
6
6
6
6
6

Fig. 2
.

Response surface plot for COD removal

DESIGN-EXPERT Plot
TOC Remov al
Design Points
X = A: H2O2/COD
Y = B: FeGAC
Actual Factor
C: Time = 90.00
TOC Removal
A: H2O2/COD
B: FeGAC
1.00
1.50
2.00
2.50
3.00
0.40
0.55
0.70
0.85
1.00
51.3565
57.1984
63.0402
68.8821
78.36
6
6
6
6
6
6




Fig. 3
.

Response surface plot for TOC removal

DESIGN-EXPERT Plot
NH3-N Remov al
Design Points
X = A: H2O2/COD
Y = B: FeGAC
Actual Factor
C: Time = 90.00
NH3-N Removal
A: H2O2/COD
B: FeGAC
1.00
1.50
2.00
2.50
3.00
0.40
0.55
0.70
0.85
1.00
93.1199
94.4741
95.681
96.6096
96.6096
97.158
97.158
6
6
6
6
6
6

Fig. 4
.

Response surface plot for NH
3
-
N removal










Table
4
.

Experimental removal efficiency and model


prediction
.


Parameter

Model
prediction

Experimental
removal

Error
(%)

COD

removal (%)

78.03

78.54,78.1,78.25
Av.(78.29)

0.27

TOC

removal (%)

78.36

78.45,78.7,78.57
Av.(78.57)

0.21

NH
3
-
N

r
emoval

(%)

97.16

98.98,97.0,97.92
Av.(97.97)


0.80






3.3
Antibiotic degradation and biodegradability



The antibiotic aqueous solution and the solution treated
under the optimum
operating conditions were analyzed by
FTIR spectroscopy to ascertain the extent of antibiotic
degradation. On interaction of infrared light with matter,
chemical bonds will stretch, contract and bend. As a result,
chemical functional group tends to absorb
infrared
radiation in a specific wavelength range regardless of the
structure of the rest of the molecule. Infrared spectra of
organic b
onds consisting of beta
-
lactam

carbonyl group an
d
aromatic ring could shift

to specific bands due to
degradation (Anacon
a and Figueroa,
1999; Rozas

et al
.,
2010
).
IR features of penicillins are reported in the
range of
1550
cm
-
1

and 1880 cm
-
1
,
but usually occur at about

1770 cm
-
1

as a result of vibration of strong bands of the
beta
-
lactam carbonyl group (Kupka, 1997
)
.
The
characteristic band which occurred at 1637.45 cm
-
1

for the
untreated antibio
tic aqueous solution in Figure 5

(a) shifted
and modified to 1622.02 cm
-
1

for
the treated solution in
Figure 5

(b). This can be attributed to pairing up of the
organic group

de
gradation

interme
diates (Rozas
et al
.,
2010)
.




Biodegradability (BOD
5
/COD ratio) of the antibiotic
aqueous solution improved from zero (untreated) to 0.32
(treated). Similar biodegradability improvemen
t was
observed in Fenton treatment of an aqueous
solution of
amoxicillin, ampicillin and cloxacillin and considered
amenable to biological treatme
nt (Elmolla and Chaudhuri,
2009a
).



(a)


(
b)


Fig
.
5
.
FTIR

spectra of (a) untreated and (b) treated




antibiotic aqueous solution





4. CONCLUSIONS




The optimum operating conditions of AC/
H
2
O
2

treatment of amoxicillin and cloxacillin antibiotics
aqueous solution at pH 3 were
H
2
O
2
/COD molar ratio
2.0, AC 3.5 g/L and reaction time 90 min for 78.03%
removal of COD, 78.36% removal of TOC and 97.16%
removal of NH
3
-
N. Experimental removal efficiency
and model prediction were in close agreement (<1.0%
error).



Biodegradability improved from zero to 0.32,
indicating the pretreated antibiotic aqueous solution
was amenable to biological treatment



FTIR spec
tra indicated degradation of the antibiotics.



AC/H
2
O
2

process is effective in pretreatment of
amoxicillin and cloxacillin antibiotics aqueous solution
for biological treatment.





ACKNOWLEDGEMENT


The authors are thankful to the management and authorities
of

the Universiti Teknologi PETRONAS for providing
facilities for this research.



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