American Journal of Anal yt ical Chemistry, 2011, 2, 37-45
doi:10.4236/ajac.2011.228122 Published Online December 2011 (http://www.SciRP.org/journal/ajac)
Biosorption of Malathion from Aqueous Solutions Using
Herbal Leaves Powder
Tharakeswar Yadamari, Kalyan Yakkala, Gangadhar Battala, Ramakrishna Naidu Gurijala*
Department of Envi ron mental Sciences, Sri Venkateswara Universit y , Tirupati, India
Received October 2, 2011; revised November 8, 2011; accepted November 16, 2011
Abstract
Commonly available herbal leaves powder namely Achyranthes aspera (uthareni) and Phyllanthus niruri
(Nela usiri) are used as biosorbents for the removal of malathion in the present investigation. The efficiency
of the biosorbents is tested for the determination of malathion using batch experiments under controlled con-
ditions as a function of pH, contact time, initial malation concentration and the optimization amount of bio-
sorbents. The quantification of malathion in aqueous samples, before and after equilibration with biosorbents
is carried out by existing spectrophotometric method based on the oxidation of malathion with excess
N-bromosuccinimide (NBS) and Rhodamine B at ( 
max = 550 nm) is used for the unconsumed NBS. The
biosorption capacities are found to be pH dependent. The maximum adsorption is noticed at pH = 6 with a
contact time of 120 minutes. Biosorption equilibrium isotherms are plotted for malathion uptake capacity (Qe)
against residual malathion concentration (Ce) in solution. The Qe versus Ce sorption isotherms relationship is
expressed mathematically by Langmuir and Freundlich models. The removal of malathion using biosorbents
Achyranthes aspera (uthareni) and Phyllanthus niruri (Nela usiri) from spiked river water samples are found
to be 94% and 96% respectively. The developed eco-friendly potential biosorbents indicate that the present
method can be successfully applied for the quantitative determination and removal of malathion from real
water samples.
Keywords: Biosorption, Malathion, Achyranthes aspera (Uthareni) and Phyllanthus niruri (Nela usiri),
Isotherm Models
1. Introduction
Natural water is contaminated with various pesticides
and their transformation products. Pesticides are poten-
tial contaminants of natural water because they are di-
rectly applied to the soil and are transported into ground
water or leached to the surface water [1-5]. The rapid use
of pesticides fo r high yielding of crops has unfor tunately
generated many environmental problems. As a result,
human beings are exposed indirectly to pesticides in
trace amounts through various foodstuffs [6]. Patients of
acute organophosphorus poisoning have been reported to
suffer from problems like vomiting, nausea, excessive
salivation, blurred vision, headache, giddiness etc. [7].
Malathion shown in Scheme 1 is one of the widely used
organophou sphours p esticid e wh ich is us ed to kill in sects
on agricultural crops, on stored products, in home gar-
dens and in outdoor sites. The various effects observed
by malathion exposure are due to its active metabolite
malaxon on various organs of organisms [8]. Numerous
malathion poisoning incidents have taken place among
pesticides workers and small children through accidental
exposure. Wide range of toxic effects of malathion is
observed in various organisms [9]. Malathion is rapidly
and effectively absorbed practically by all routs, includ-
ing the gastrointestinal tract, skin, mucous membranes
and lungs. Removal of malathion from natural water has
been important concern due to its toxic and hazardous
OPS
S
O
O
O
O
O
Scheme 1. Chemical structure of malathion.

T. YADAMARI ET AL. 38
behavior. The various adsorbents are used for the re-
moval of pesticides in water samples includes-Activated
carbon [10-15], straw [16], Lignocellulosic substrate
from agro industry [17], baggasse fly ash [18], coal fly
ash [19], Charcoal from agro waste [20] and bark [21].
Biosorption is one of the effective alternative methods
for the removal of pesticides in contaminated water sam-
ples. Biosorption has been used as an alternative tech-
nology for removing toxic pollutants in water samples
[22]. In addition to scientific preference, economic con-
siderations also play crucial role in the selection of ap-
propriate biomass for pollution abatement. Thus intense
research attention is now focused on cost effective, eco-
friendly and easily available adsorbent particularly of
biological origin [23]. However, the performance of a
biosorbent depends on the characteristic properties of the
biomass as well as the microenvironment of the target
toxicant. The search for an appropriate and inexpensive
biomass is a continuing process. The most effective and
optimized utilization of a biomass demands a detailed
understanding of th e binding mechan ism. The adsorp tion
of malathion is monitored by various researchers using
biomaterials such as Rhizopus oryzae biomass by Sub-
hankar Chatterjee et al. [23], bagasse fly ash by Gupta et
al. [24], thermally treated egg shell by Khalid Z. El-
wakeel et al. [25] and Waste Jute Fiber Carbon by Sen-
thilkumaar et al. [26]. In the present study, commonly
available herbal leaves powder namely Achyranthes as-
pera (uthareni) and Phyllanthus niruri (Nela usiri) is
used as a biosorbents for the removal of malathion from
real water samples.
2. Experimental
2.1. Apparatus
Measurements are performed with a UV-visible spectro-
photometer model UV-1800 from Shimadzu, (Japan) for
recording the absorbance spectra. A LI-120 digital pH
meter (Elico, India) is used for the pH measurement,
weighing of the reagents and chemicals are carried with
Shimadzu AUX 320 digital electronic balance. IR spec-
trometer (Thermo-Nicolet FT-IR, Nicolet IR-200, USA)
is used for functional groups analysis of the biomass.
2.2. Reagents and Solution
All the reagents used in this stud y are of an alytical gr ade,
malathion is obtained from Hyderabad Chemicals Ltd,
India. Double distilled water is used through o ut the pre-
sent work. N-Bromosuccinimide is obtained from Sigma
Aldrich, USA. Rhodamine B is obtained from Sd. Fine.
Chem. Pvt. Ltd., India. Hydrochloric acid and Glacial
acetic acid are obtained from Merck., India.
Malathion stock solution 1000 µg·mL–1 is prepared by
using 0.813 µL of technical grade malathion (95 .5%) and
dissolved in a little amount of glacial acetic acid and
made up to the mark with deionised double distilled wa-
ter to a 100 mL volumetric flask. N-Bromosuccinimide
w/v (0.01%), an d Rhodamine B w/v (0 .02% ) are used fo r
the present studies.
2.3. Preparation of Biosorbent Materials
Leaves of Achyranthes aspera (uthareni) and Phyllan-
thus niruri (Nela usiri) are collected and washed several
times and dried in shadow. Dried leaves are grounded
and sieved to 50 µ cm size mesh. Sieved leaves powder
is washed with deionised double distilled water and then
dried. To avoid the release of colour from the leaves
powder in to the aqueous solution during adsorption it is
treated with formaldehyde. For this 5 mL of aqueous
formaldehyde is added to 100 mL 0.1 M H2SO4 and then
10 g of washed leaves powder is added to this solution.
The final mixture is stirred and heated at 50˚C for 24 - 48
hours till the mixture became thick slurry. The slurry is
washed with deionised distilled water and then dried.
The prepared biomass was then stored in air tight glass
bottles to be protected from moisture. The prepared bio-
sorbent is used in th e further studies.
2.4. Malathion Measurement Procedure
An aliquot of sample solution containing 0.3 - 1.8
µg·mL–1 is transferred into a series of 25 mL calibrated
flask. To this 1.5 mL of NBS, 1 mL of glacial acetic acid
and 0.5 mL of hydrochloric acid are added successively.
The solution is kept aside with occasional shaking for
about 10 min at ~30˚C. Then 0.7 mL of rhodamine B
solution is added and mixed thoroughly. The absorbance
is measured against distilled water at 558 nm. The de-
crease in absorbance corresponding to consumed oxidant
by subtracting the decrease in absorbance of the test so-
lution (dye minus test) from that of the blank solution
(dye minus blank). Calibration graph is prepared by plot-
ting the decrease in absorbance of dye against amount of
the pesticide [27].
2.5. Fourier Transformed Infrared
Spectroscopic (FTIR) Analysis
FTIR spectra of powdered Achyranthes aspera (uthareni)
and Phyllanthus niruri (Nela usiri) biomass have been
recorded on IR spectrometer (Thermo-Nicolet FT-IR,
Nicolet IR-200, USA). Pressed pellets are prepared by
grinding the samples with KBr in a mortar and immedi-

T. YADAMARI ET AL.39
ately analyzed in the region of 4000 - 400 cm–1.
2.6. Batch Adsorption Studies
The affinity of biomass to adsorb malathion is studied in
batch experiments. In all sets of experiments, fixed vol-
ume of malathion solution (25 mL) is stirred with desired
biosorbent dose (50 - 125 mg) for the period of two
hours. Different conditions of pH (3 - 8), initial concen-
trations (0.3 - 1.8 µg·mL–1) and contact time (30 - 150
minutes) are evaluated during study. In order to regulate
pH of the medium 0.1 N of HCI and NaOH are used. The
solutions are separated from biomass by filtration through
whatman 40 filter paper. Malathion concentration in the
filtrate is estimated using UV spectrophometer at 558 nm
wave length by following t he procedure prescribed above.
The amount of malathion adsorbed in mg·g–1 at time is
computed by using the following equation.

i
ee
CV
m
QC 
where:
Qe is the malathion concentration adsorbed (mg
malathion concentration/g bioso rb ent) at equilidrium,
V is the volume of the solution (L),
Ci and Ce are the initial and equilibrium concentration
of malathion (mg/L) and m is the dry weight of the bio-
sorbent (g).
the percentage of the removal of malathion concentra-
tion (Rem%) in solution was calculated usi ng the equati on:


100%ie
i
em
CC
C
R
where Ci and Ce are the initial and the equilibrium con-
centration of malathion (µg·mL–1).
2.7. Adsorption Isotherm Models
An adsorption is a quantitative relationship describing
the equilibrium between the concentrations of absorbate
in solution (mass/volume) and their concentration (mass
adsorbate/mass adsorbent).
An adsorption isotherms relate to the concentration of
solute on the surface of the adsorbent to the concentra-
tion of the solute in the fluid where the adsorbent is in
contact. These values are usually determined experimen-
tally. In order to describe the equilibrium isotherm of
biosorption process, Langmuir and Freundlich isotherm
models are discussed in the present experiment.
2.7.1. Langmuir Isotherm Model
The Langmuir isotherm model is based on the following
assumptions:
 Each active site interact with only one adsorbate
molecule,
 Sorbate molecules are adsorbed on well localized
sites,
 There is no interaction between adjacent adsorbed
molecules, and
 The adsorption sites are all energetically equivalent.
Langmuir isotherm is given by the following equation:
max
1
L
e
L
ee
KQ
C
QC
K

where Qe is the equilibrium malathion concentration on
the adsorbent (mg/g),
Ce is the equilibrium malathion concentration in the
solution (mg/g),
Qmax is the maximum biosorption capacity of adsorb-
ent (mg/g) and
KL is the Langmuir biosorption constant (L/mg).
Langmuir isotherm equation can be represented by the
following linear form;
max max
1
ee
eL
CC
QKQ Q

The values of Langmuir constant Qmax and KL are cal-
culated from the slope and intercept of the linear plot
Ce/Qe versus Ce. The essential feature of Langmuir iso-
therm model can be expressed by means of a separation
factor of equilibrium parameter (RL), which is calculated
according to the following equation;
1
1
L
L
i
R
K
C

The values of RL indicates the type of biosorption iso-
therm to be:
 Linear (RL = 1),
 Favorable (0 < RL < 1),
 Unfavorable ( RL > 1) and
 Irreversible (RL = 0).
2.7.2. Freundl i c h Isotherm Model
The Freundlich isotherm model is derived from Gibbs
adsorption combined with a mathematical description of
the free energy of the surface. Freundlich proposed an
empirical isotherm equation assuming a heterogeneous
adsorption surface and active sites with different energy.
The Freundlich equation is as follows:
1n
efe
QKC
The Freundlich isotherm can be derived from Lang-
muir isotherm by assuming that there exists a distribution
of sites on the adsorbent which have different affinities

T. YADAMARI ET AL. 40
mg of biosorbent and with a continuous stirring for 120
minutes. After adsorption, malathion is determined in
filtrate by UV-Vis Spectrophotometer followed by the
procedure prescribed above.
for different adsorbetes with each site behaving accord-
ing to Langmuir isotherm. Here, Kf is a measure of the
capacity of the adsorbent and “n” is a measure of how
affinity for the adsorbate changes with the change in ad-
sorption density. 3. Results and Discussion
when n = 1, the Freundlich isotherm becomes linear
isotherm and indicates that all sites on the adsorbent have
equal affinity for th e adsorbates. Values of n > 1 indicate
the affinities decrease with increasing adsorptio n density.
The linear form of Freundlich isotherm equation can be
shown as;
Efficiency of the biosorbents (herbal leaves powder) is
tested for the removal of malath ion in natural water. The
rate of adsorption is a function of the initial concentra-
tion of malathion which makes it an important factor to
be considered for effective biosorption. The factors like
effect of pH, contact time, dosage of biosorbent etc., on
malathion sorption capacity of herbal leaves powder are
investigated. All the experiments are repeated thrice to
confirm the results and average values are presented.
1
log loglog
ef
CK
n
 e C
The Freundlich isotherm constants 1/n and Kf are cal-
culated from the slopes and intercepts of the linear plot
of log Qe versus log Ce. 3.1. Fourier Transformed Infrared
Spectroscopic (FTIR) Analysis
2.8. Application to Real Water Samples
FTIR spectra of powdered Achyranthes aspera (uthareni)
and Phyllanthus niruri (Nela usiri) biomass for mala-
thion adso rp tion are sh own in Figures 1 and 2. As can be
seen from the [Figure 1], the vibration bands at 3288.82
cm–1, 1635.92 cm–1, 2922.3 cm–1, 1518.17 cm–1 are due
The developed biosorbents are used for the removal of
malathion in the river water samples which are collected
in and around Tirupati. To 20 mL of sample, a known
amount of malathion (1.2 µg·mL–1) is spiked and the
aqueous samples are adjusted to pH = 6 by adding 100
Wavenumbers (cm
–
1
)
Figure 1. FTIR spectrum of Achyranthes aspera (uthareni) leaves powder.

T. YADAMARI ET AL.41
to the presence of hydroxyl group, Carbonyl (C=O), and
presence of vinyl stretch C-H, C-N stretching vibrations.
As in the [Figure 2], the vibrations are due to the pres-
ence of stretch C-H, C-N stretching vibrations.
3.2. Effect of pH
pH is an important parameter that influences the adsorp-
tion process by way of modifying the functional groups
of the biomass. The effect of pH on adsorption of ma-
lathion is conducted in the pH r ang e of 3.0 - 8 .0. Adsorp -
tion of malathion by two biosorbents Achyranthes aspera
(uthareni) and Phyllanthus niruri (Nela usiri) is found to
increase only to a small extent with increase in pH values
from 3.0 - 6.0 and then decreased with increase in pH i.e.
from 6.0 - 8.0. After tests with both biosorbents Phyl-
lanthus niruri is removing the malathion effectively at a
percentage of 96, where as Achyranthes aspera is re-
moving the malathion at a percentage of 94 at pH 6.0.
the pH studies for both the sorbents is shown in the
[Figure 3].
3.3. Effect of Contact Time
The equilibrium time required for the adsorption of
malathion on both the biosorbents with 1.2 µg·mL–1of
malathion is tested at different time intervals are also
studied [Figure 4]. It is shown that adsorption capacity
sharply increased with the increased in time and attained
equilibrium in 120 minutes for both the biosorbents
Phyllanthus niruri leaves powder (Nela usiri) and Achy-
ranthes aspera (uthareni) leaves powder. The removal
rate of malathion increases with the increase of the ad-
sorption time. However, it remains constant after an
equilibrium time of 120 minutes, which indicates that the
adsorption tends towards saturation. Therefore, the ad-
sorption time is set 120 minutes in each of the experi-
ment. The rate of adsorption is higher in the beginning
due to large surface area available of the biosorbent. Af-
ter the capacity of the adsorbent gets exhausted, i.e. at
equilibrium, the rate of uptake is controlled by the rate at
which the absorbate is transported from the exterior to
the interior sites of the biosorbent particles [28].
Wavenumbers (cm
–
1
)
Figure 2. FTIR spectrum of Phyllanthus niruri (Nela usiri) leaves powder.

T. YADAMARI ET AL. 42
Figure 3. Effect of pH for adsorption of malathion on bio-
sorbents (Achyranthes aspera (uthareni) leaves powder and
Phyllanthus niruri leaves powder (Nela usiri)).
Figure 4. Effect of time for adsorption of malathion on bio-
sorbents (Achyranthes aspera (uthareni) leaves powder and
Phyllanthus niruri leaves powder (Nela usiri)).
3.4. Effect of Biomass Dosage
The effect of biosorbent dosage on the removal of
malathion is shown in [Figure 5], the amount of biosor-
bent is varied from 25 mg - 125 mg and equilibrated for
120 minutes with the concentration of 1.2 µg·mL–1. The
results indicated that the percent removal of malathion
increased with the increase in the amount of adsorbent
and the efficiency of removal for Achyranthes aspera
(uthareni) leaves powder and Phyllanthus niruri leaves
powder (Nela usiri) are 94% and 96% respectively. The
highest uptake yield is obtained at biosorbent concentra-
tion of 100 mg for the both the sorbents. The removal of
Figure 5. Effect of biomass dosage for adsorption of
malathion on biosorbents (Achyranthes aspera (uthareni)
leaves powder and Phyllanthus niruri leaves powder (Nela
usiri)).
malathion concentration increased with the increase in
biosorbent concentration and attained equilibrium after
100 mg of adsorben t dosage for malathion. This is due to
the availability of more biosorbent as well as greater
availability of surface area [29].
3.5. Adsorption Isotherms
The Langmuir and Freundlich isotherm models are used
to describe the bio sorption equilibriu m of selected herbal
leaves powder. It is also helpful in comparing different
biomaterials under the same operational conditions. To
find the relationship between aqueous concentration (Ce)
and sorbed quantity (Qe) at equilibrium, mostly iso-
therms models are used for fitting the data. The Ce and
Qe values for both the biosorbents during the study of
malathion extraction is shown in the [Tables 1 and 2].
Langmuir parameters can be determined from a lin-
earized form of equatio n g i v en below.
max max
1
ee
eL
CC
QKQ Q


The values of the Langmuir constants (KL, Qmax) and
Freundlich constants (K, n) are presented for the biosorp-
tion of malathion by Achyranthes aspera (uthareni)
leaves powder and Phyllanthus niruri leaves powder
(Nela usiri) is shown in [Table 3]. It shows that the R2
value for Langmuir isotherm and Freundlich isotherm is
similar to both the biosorbents. [Figures 6 and 7] show
that Langmuir isotherm model of malathion for Achy-
ranthes aspera (uthareni) leaves powder and Phyllanthus
niruri leaves powder (Nela usiri) with R2 of 0.9907 and
0.986. [Figures 8 and 9] show that Freundlich isotherm
model of malathion for Achyranthes aspera (uthareni)

T. YADAMARI ET AL.43
Table 1. Aqueous concentration (Ce) and sorbed quantity
(Qe) at equilibrium for malathion by Achyranthes aspera
(uthareni).
Ci Ce Qe Ce/Qe log Ce log Qe
0.5 0.028 0.118 0.237 –1.55 –0.92
0.9 0.052 0.212 0.245 –1.28 –0.67
1.2 0.071 0.282 0.251 –1.14 –0.54
1.5 0.090 0.352 0.255 –1.04 –0.45
Table 2. Aqueous concentration (Ce) and sorbed quantity
(Qe) at equilibrium for malathion by Phyllanthus niruri
(Nela usiri).
Ci Ce Qe Ce/Qe log Ce log Qe
0.5 0.019 0.12 0.158 –1.72 –0.92
0.9 0.035 0.216 0.166 –1.45 –0.66
1.2 0.049 0.287 0.170 –1.30 –0.54
1.5 0.063 0.359 0.175 –1.20 –0.44
Table 3. Linear regression data for Langmuir and Freundlich isotherm s for malathion biosorption.
Langumuir parameters Freundlich parameters
S. No. Biomass Qmax (mg/g) KL (L/mg) R2 N Kf R
2
1 Achyranthes aspera (uthareni) 3.401 1.28 0.9907 1.1005 0.4905 0.9994
2 Phyllanthus niruri (Nela usiri) 2.644 2.4 0.986 1.0930 0.6569 0.9987
Figure 6. Langmuir isotherm model for adsorption of
malathion by Achyranthes aspera (uthareni) as biosorbent.
Figure 7. Langmuir isotherm model for adsorption of
malathion by Phyllanthus niruri (Nela usiri) as biosorbent.
Figure 8. Freundlich isotherm model for adsorption of
malathion by Achyranthes aspera (uthareni) as biosorbent.
Figure 9. Freundlich isotherm model for adsorption of
alathion by Phyllanthus niruri (Nela usiri) as biosorbent. m

T. YADAMARI ET AL. 44
Table 4. Recovery percentage of malathion by using biosorbents from the river water samples.
Achyranthes aspera (uthareni) Phyllanthus niruri (Nela usiri)
Sample Malathion spiked in
µg·mL–1
Malathion found in
µg·mL–1 Recovery %Malathion spiked in µg·mL–1
Malathion found in
µg·mL–1 Recovery %
River water-1 1.2 1.13% ± 1.3% 94 1.2 1.154% ± 1.2% 96
River water-2 1.2 1.135% ± 1.5% 95 1.2 1.153% ± 1.4% 96
leaves powder and Phyllanthus niruri leaves powder
(Nela usiri) with R2 of 0.9994 and 0.9987.
The Langmuir constants (Qmax) are found to be 3.401
& 2.644 for both the biosorbents, while KL which reflects
quantitatively the affinity between the adsorbent and
adsorbate is equal to 1.28 & 2.4 L/mg for both biosor-
bents.
The Freundlich model is expressed as:
1n
efe
QKC
The above equation can be rearranged in the following
form:
1
log loglog
ef
QK
n
e C
Qe is malation sorbed (mg/g). Ce the equilibrium con-
centration of malathion solution (mg/L), Kf and N are
Freundlich constants. The constan ts Kf and 1/n is used as
an indication of whether adsorption remains constant (at
1/n = 1) or decreases with increasing adsorbate concen-
trations. It appears from the [Figures 8 and 9] that
Freundlich model best fits the experimental results which
are similar to Langmuir [Figures 6 and 7] over the ex-
perimental range with good correlation co-efficient. The
n value and Kf values are found to be as 1.1005, 1.0930
and 0.4905, 0. 65 6 9 fo r both the biosor bents.
Finally, the developed biosorbents are used for the
analysis of river water samples which are collected in
and around Tirupati by spiking with constant amount of
malathion. As shown in Table 4, the recovery percentage
of malathion using developed biosorbents Achyranthes
aspera (uthareni) and Phyllanthus niruri (Nela usiri) is
found to be 94% and 96% respectively.
4. Conclusions
The selected biosorbents namely Achyranthes aspera
(uthareni) and Phyllanthus niruri (Nela usiri) are found
to be potential sorbents for the removal of malathion
from aqueous solutions. The adsorption of malathion is
pH dependent and its adsorption capacity increased with
increasing the pH up to 6 and it decreased with further
increase of pH > 6. The developed biosorbents used to
remove the malathion effectively from aqueous so lutions
in the concentration range of (0.3 - 1.5 µg·mL–1). Lang-
muir-Freundlich isotherm models fit for the adsorption of
malathion and its recovery > 95% indicated that the
functional groups present in the biosorbents are mainly
responsible for chemical interaction between malathion
and biosorbent cell walls. The two developed ecofriendly
biosorbents Achyranthes aspera (uthareni) and Phyllan-
thus niruri (Nela usiri) have been successfully applied
for the removal of malathion in spiked river water sam-
ples.
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