Removal of 17-methyltestosterone from aqueous solution
through active plant based reactor
Fahrizal Adnan and Sudtida Pliankarom Thanasupsin*
* Department of Chemistry, Faculty of Science, King Mongkut’s University of Technology Thonburi, 126
Bangmod, Thung Khru, Bangkok 10140, Thailand
INTRODUCTION
17α-methyltestosterone (MT) is a synthetic anabolic androgenic steroids hormone
which has endocrine disrupting property at part per billion levels that can interfere with
normal functions of the reproductive systems of humans and animals. [1] MT is
commonly used to induce sex reversal of Nile Tilapia (Oreochromis niloticus). To
obtain monosex-male cultures with economically viable mean, mixing fry feed with 60
mg of MT per one kilogram of feed was conducted. The tilapia fry will be fed with this
feed for 21 days in the nursing pond. The uneaten feed containing MT remains in the
water and deposits as sediments at the bottom of the pond. Improper discharge of this
wastewater may lead to surface water contaminations, which bring about environmental
concerns for its toxicity and biodiversity deterioration. [2] Numbers of research have
reported the effect of MT on reproductive system in various kinds of animal. [3] [4] [5]
[6] A range of conventional biological treatment technologies, such as activated sludge
and its modification, can achieve relatively high removal of endocrine disrupting
compounds (EDCs) from municipal and domestic wastewater, however this technology
has limited applications for treating discharge water from tilapia farming. Advanced
Oxidation Processes (AOPs) is one of the recent technologies providing high removal
efficiency for treatment of recalcitrant and persistent organic contaminants. [7] [8] [9]
Major drawback of this technology lie about the complicate reactions and specific
operating conditions. Moreover, the intermediate substances produced during the
oxidation process become one of the major environmental concerns. Phytoremediation
has been developed rapidly as a technology for the remediation of organic contaminants
in soil and water because it can achieve the goal of complete mineralizing the
contaminants into relatively non-toxic substances (e.g. carbon dioxide, nitrate) and
offers potential advantages in low cost and minimum landscape disruption. Active plant
processes, such as duckweed species, are expected to contribute to aqueous removal of
organic compounds. [10] [11] [12] [13] [14] Nevertheless, harvesting of overgrown
duckweed can be an operational problem. In Thailand, Salvinia cucullata Roxb.ex Bory
is an indigenous floating-type aquatic plant, having complex root system. The aim of
this study was to investigate the potential ability of Salvinia cucullata Roxb.ex Bory to
remove MT from aqueous solution.
MATERIALS AND METHODS
Material
Batch test. Active plants reactors were used in this study. Batch tests were carried out to
investigate the potential ability of Salvinia cucullata Roxb.ex Bory to remove MT from
aqueous solution. Plants at the same growth stage were selected to start of the
experiments. Synthetic wastewater of MT solutions was used in all tests.
Chemicals. All reagents used during the extraction and analysis were analytical reagent
grade. 17α-methyltestosterone (17β-Hydroxy-17α-methyl-4-androsten-3-one, CAS n:
58-18-4, purity 97.7%) was purchased from Sigma-Aldrich (St. Louis, MO, USA).
Methanol and acetonitrile were all HPLC-grade and purchased from Merck (Darmstadt,
Germany). Deionized (DI) water was obtained in the laboratory. The cartridges used
for, SPE were OASIS HLB C-18 3 mL, 60 mg (Waters, USA). Some physical and
chemical properties of MT are given in Table 1.
Table 1. Properties of 17 α -Methyltesterone
Name
17α-methyltestosterone
Structure
R1
R2
R3
Formula
Molecular Weight (MW)
CAS.No.
Melting point
Water solubility
pKa
log kow (log P)
Solubility
-CH3
-CH3
C20H30O2
302.45
58-18-4
162 – 168 oC
3.39 mg/lat 25 oC
15.13
3.559
Soluble in methanol, ethanol, ether and
other organic solvents
Determination of MT. All water samples were collected in 60 mL PET bottles from
different reactors. The water samples were stored at 4 ̊C. The liquid samples of synthetic
solution from the active plant reactors were filtered through 0.45μm membrane filter
(Schleicher & Schuell) and then extracted by solid phase extraction (SPE). The SPE
condition was conducted as follows; Conditioning – with 10 mL MeOH : 10 mL DI
water, Loading – with 10 mL sample volume, Washing – with 5 mL DI water and
Eluting – with 5 mL acetonitrile.
The concentrations of MT were measured GC-FID. The chromatographic separation
was achieved with a DB-1 column (size 30 m x 0.25 mm, 0.10 µm). Column
temperature was controlled between 180-280oC with increasing rate 10oC/min, and keep
stable at 280oC for 4 min. Temperature in injection port was set at 200 oC. Helium was
used as carrier gas, having carrier velocity 10 cm/second. Nitrogen was used as makeup gas. The flowrate of nitrogen was set t 30mL/min. FID detector was set at 200 oC.
Injection volume was 20 L.
RESULTS AND DISCUSSION
The 7-day batch tests show that the presence of Salvinia cucullata Roxb.ex Bory
accelerated the removal of the MT from the synthetic wastewater. In the sorption tests, a
swift sorption of the MT was observed when the MT was contacted with Salvinia
cucullata Roxb.ex Bory, while the MT concentrations in tap water kept unchanged
during the 7-days sorption tests (control).
In the 7-day batch tests, MT was sorbed by Salvinia cucullata Roxb.ex Bory during the
early stage when Salvinia were contacted with the MT in synthetic wastewater. The
persistent MT concentrations in tap water, however, implied that no sorption,
biodegradation, or photolytic degradation occurred in tap water under the specific
experimental conditions.
In the Figure 1 describes concentration of MT (Ct) against time (t), it shows also initial
concentration (10 mg.L-1) had been decreased linearly by time (day). The equilibrium of
time found at 5 days and corresponding to a removal efficiency of 72.95 %. The curves
of MT removal are characterized by a relatively fast sorption in the first of contact time,
MT concentration decreasing dramatically during 12 hours of treatment process.
12
control - without plant
initial conct = 10 ppm
MT Concentration, Ct (mg.L-1)
10
8
6
4
2
0
0
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180
t (hours)
Figure 1. The concentration of MT against time
The graph shows after 4 hours treatment, the concentration had decrease to 5.16 mg.L-1.
It can be concluded that at the beginning of this treatment, Salvinia cucullata Roxb.ex
Bory had a fast direct uptake of MT. Meanwhile, within 2 until 7 days treatment, the
ability of sorption slightly lower than previous (Figure 1).
Kinetic study provides useful information about the mechanism of sorption and
subsequently investigation of the controlling mechanism of biosorption as either mass
transfer or chemisorption. This helps in obtaining the optimum operating conditions for
industrial-scale batch processes. A good correlation of the kinetic data explains the
biosorption mechanism of the metal ion on the solid phase. In order to evaluate the
kinetic mechanism that controls the biosorption process, the pseudo-first-order and
pseudo-second-order models were applied in analysis.
0.8
0.6
log qe-qt
0.4
y = -0.0049x + 0.1113
R² = 0.4037
0.2
0
-0.2
0
20
40
60
80
-0.4
-0.6
t (hours)
Figure 2 Sorption model of pseudo-first order
100
120
t/qt
50.000
45.000
40.000
35.000
30.000
25.000
20.000
15.000
10.000
5.000
0.000
0.00
y = 0.2781x + 0.8821
R² = 0.9883
20.00
40.00
60.00
80.00 100.00
t (hours)
120.00
140.00
160.00
180.00
Figure 3 Sorption model of pseudo-second order
Based on Figure 2 and Figure 3, the sorption system follows a pseudo-second-order
kinetics, the main assumption being that the rate limiting step may be chemical sorption
involving valency forces through sharing or the exchange of electrons between the
sorbent and MT, then a plot of t/qt versus t would be linear and k2 and qe can be
determined from the intercept and gradient of the graph. One of the advantages of the
pseudo-second-order equation for estimating qe values is its small sensitivity to the
influence of random experimental errors.
CONCLUSIONS
This study shows that MT can be effectively removed from the active-plant process by
Salvinia cucullata Roxb.ex Bory even when their concentrations are at part per milion
level. The presence of Salvinia cucullata Roxb.ex Bory accelerate the removal of MT
from the synthetic wastewater because MT can be quickly sorbed on Salvinia cucullata
Roxb.ex Bory. The phenomenon in this research was followed Pseudo-second order
model. Moreover, based on the assumption that the rate-limiting step may be chemical
sorption or chemisorption involving valency forces through sharing or exchange of
electrons between sorbent and sorbate, provides the best correlation of the data.
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