Research Journal of Recent Sciences ________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci.

Adsorption Studies of Zn (II) ions from Wastewater using
Calotropis procera as an Adsorbent
Vaishnav Vinod, Daga Kailash, Chandra Suresh and Lal Madan
Department of Chemistry, Jai Narain Vyas University, Jodhpur, Rajasthan, INDIA

Available online at: www.isca.in
(Received 11th October 2011, revised 27th February 2012, accepted 10th March 2012)

Abstract
Increased industrialization and human activities have impacted on the environment through disposal waste containing heavy
metals. The presence of heavy metals in the environment can be detrimental to a variety of living species. Metals can be
distinguished from other toxic pollutants, because these are non biodegradable, may undergo transformation, and can have a large
environmental, public health, and economic impact. The presence of toxic heavy metal contaminants in aqueous streams, arising
from the discharge of untreated metal containing effluents into water bodies, is one of the most important environmental issues.
Zinc is an essential mineral, but too much is not beneficial. Symptoms of zinc toxicity include nausea/vomiting, fever, cough,
diarrhea, fatigue, neuropathy and dehydration. Adsorption technique is one of the most important technologies for the treatment of
polluted water from zinc, but seeking for the low-cost adsorbent is the target of this study. Removal of zinc studied using adsorbent
prepared from poly vinyl activated charcoal of calotropis procera leaves (PVAC-CP). Batch adsorption experiments performed by
varying adsorbent dose, pH of the metal ion solution and contact time. Adsorption of zinc is highly pH dependent and the results
indicate that the maximum removal (85.8%) took place at dose 15gm/l in the pH range of 6 and initial concentration of 60 ppm.
Kinetic experiments reveal that the dilute zinc solution reached equilibrium within 105 min. the adsorbent capacity was also
studied the zinc adsorption followed both the Langmuir and Freundlich equation isotherms. Comprehensive characterization of
parameters indicates that PVAC-CP to be an excellent material for adsorption of zinc ion to treat wastewater containing low
concentration of the metal.
Keywords: Wastewaters, adsorption isotherms, calotropis procera.

Introduction
Industrial activities and mining operations have exposed man
to the toxic effects of metals1. Heavy metals are present in
the soil, natural water and air, in various forms and may
become contaminants in food and drinking water 2. Heavymetal adsorption reactions, in a competitive system, are
important to determine heavy-metal availability to plants and
their mobility throughout the soil. It is now well established
that the free metal ion concentration, which is of relevance in
metal bioavailability and toxicity studies, often controlled by
metal ion binding to natural organic matter3,4. Although zinc
compounds have been use for at least 2,500 years in the
production of brass, zinc wasn't recognized as a distinct
element until much later. Metallic zinc first produced in India
sometime in the 1400s by heating the mineral calamine
(ZnCO3) with wool.
Andreas Sigismund Marggraf rediscovered zinc in 1746 by
heating calamine with charcoal. Today, most zinc is
produced through the electrolysis of aqueous zinc sulfate
(ZnSO4 ). Treatment processes for heavy metal removal from
wastewater include precipitation, membrane filtration, ion
exchange, adsorption and co precipitation adsorption. Studies
on the treatment of effluent bearing heavy metal have

International Science Congress Association

revealed adsorption to be a highly effective technique for the
removal of heavy metal from waste stream and activated
carbon has been widely used as an adsorbent5,6,7. Heavy
metals are not biodegradable and tend to accumulate in living
organisms, causing various diseases and disorders. Removal
of heavy metals from industrial wastewater is of primary
importance because they are not only causing contamination
of water bodies and are also toxic to many life forms8.
Exposure of Zn in large amounts is extremely toxic to living
organisms. In humans, it can cause a range of serious
ailments including anemia, damage to pancreas, lungs, metal
fume fever, decreased immune functions, ranging from
impaired neuropsychological functions, growth retardation
and stunting, impaired reproduction, immune disorders,
dermatitis, impaired wound healing, lethargy, loss of appetite
and loss of hair9,10.
The aim of this research is to develop an inexpensive and
effective metals ion adsorbent from plentiful natural waste
sources, such as PVAC-CP, and to explain the adsorption
mechanism taking place.

160

Research Journal of Recent Sciences ____________________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci

Material and Methods
Preparation of Poly Vinyl Activated Charcoal from
Calotropis Procera (PVAC-CP): The naturally dried leaves
of the plant Caltrops procera obtained locally. It cut into
small pieces. The leaves treated with concentrated sulphuric
acid (five times its volume) and kept in oven at 150C for 24
hours. It filtered and washed with distilled water repeatedly
to remove sulphuric acid (washings tested with two drops of
barium chloride solution) and finally dried. The adsorbent
sieved to 40-60-mesh size and heated at 150 C for 2 hours. 1
gm of PVA dissolved in 10ml hot water (10% solutions) as a
result gel formation occurs.
Now 2.5gm of furnace black added in it to form a thick paste.
This paste mixed with activated carbon obtained from the
leaves of the plant Caltrops procera. Now the thick paste
obtained, and then dried to form lumps. The lumps further
ground into fine powder. This powder used as an adsorbing
material. When 2.5gm furnace black used the results were
better.
Zinc sulphate solution: A stock solution of aqueous
solution of Zinc (II) obtained by dissolving 0.4404 g of AR
grade Zinc Sulphate in 1000ml of double distilled water to
give 100 ppm solution
Sorption isotherms: Equilibrium studies that give the
capacity of the adsorbent and the equilibrium relationships
between adsorbent and adsorb ate described by adsorption
isotherms which are usually the ratio between the quantity
adsorbed and the remaining in solution at fixed temperature
at equilibrium. Freundlich and Langmuir isotherms are the
earliest and simplest known relationships describing the
adsorption equation. These two isotherms model used to
assess the different isotherms and their ability to correlate
experimental data.
Langmuir Model: The Langmuir equation derived from
simple mass-action kinetic, assuming chemisorptions. This
model based on two assumptions that the forces of
interaction between adsorbed molecules are negligible, once
a molecule occupies a site, and no further sorption takes
place11. The saturation value reached beyond which no
further sorption takes place. The saturation monolayer
represented by the expression:
Ce/qe = 1/Qob +Ce/Qo
Where, Ce is equilibrium concentration (mg/I), q is the
amount at equilibrium time per unit adsorbent (mg/g) and Q
and b are Langmuir constants related to adsorption capacity
and energy of adsorption respectively.
The essential characteristics of a Langmuir isotherm
expressed in terms of a dimensionless constant separation
factor or equilibrium parameter RL. It defined by
RL = 1/ (1+bCo)

International Science Congress Association

Where Co is the initial adsorb ate concentration (mg/l) and b
is the Langmuir constant (mg/l). Values of Dimensionless
equilibrium parameter RL (0.99614) show the adsorption to
be favorable (0< RL<1). More ever the higher correlation
coefficient value (R2=0.982) confirmed the suitability of the
modal.
Freundlich Adsorption Isotherm: The Freundlich isotherm
model chooses for estimate the adsorption intensity of the
sorbent towards the adsorbent12. It is an empirical equation
employed to describe the isotherm data given by:
Qe = KF (Ce) 1/n
The linear form of the equation or the log form is
Log qe = log kf + 1/n log CeKF and n are Freundlich
constants; n gives an indication of the favorability and KF the
capacity of the adsorbent. The values of 1/n, less than unity
is an indication that significant adsorption takes place at low
concentration but the increase in the amount adsorbed with
concentration becomes less significant at higher
concentrations and vice verse. The higher KF value, then
greater adsorption intensity. The value of 1/n, less than unity
obtained mostly for the PVAC-CP. Also the Kf value, the
greater the adsorption intensity. Present study verifies value
of 1/n (0.39400) and value of Kf (1.458814) from table-1.
The equilibrium
following formula

concentration

was

calculated

using

Ce = C0 – (% adsorption x C0 / 100)
The amount of metals adsorbed per unit weight of an
adsorbent ‘q’ was calculated using following formula
q = (C0 – Ce) x V /m
Where Ce is the equilibrium concentration (mg/l) and qe the
amount adsorbed (mg/g) at equilibrium time; C0 is the
concentration (mg/l), m is the mass of the adsorbent (gm)
and V is the volume of the solution (L).
The correlation coefficient (R) for Freundlich and Langmuir
isotherms are merely equal. The correlation coefficient (R 2)
for Freundlich (0.997) & Langmuir (0.982) obtained from
table-2. Therefore for the present adsorption study that
Freundlich and Langmuir adsorption equations found to be
better fitted. (R2  0.999)

Results and Discussion
Effect of contact time: In adsorption system, the contact
time play a vital role irrespective of the other experimental
parameters, affecting the adsorption kinetics. Figure 1
depicts that there was an appreciable increase in percent
removal of Zinc up to 105 min. thereafter further increase in
contact time the increase in removal was very small (at 120
min). Thus the effective contact time (equilibrium time)

161

Research Journal of Recent Sciences ____________________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci
taken as 105 min. and it is independent of initial
concentration (60ppm).

was varied (3, 6, 9, 12, 15,18gm/L) and performing the
adsorption studies at pH 6. The present study indicated that
the amount of Zn (II) adsorbed on PVAC-CP increase with
increase in the PVAC-CP dose up to 15gm/l and thereafter
further increase in dose the increase in removal was very
small. Thus the effective dose taken as 15gm/l.

Effect of pH: pH is an important parameter influencing
heavy metal adsorption from aqueous solutions. It affects
both the surface charge of adsorbent and the degree of
ionization of the heavy metal in solution. The influence pH
of solution on the extent of adsorption of adsorbent material
used shown in figure-2.

Conclusion
Pollution of the aquatic environment with toxic valuable
metals is widespread. Consideration of the modes of
purifying these contaminations must be given to strategies
that designed to high thorough put methods while keeping
cost at minimum. Adsorption readily provides an efficient
alternative to traditional physiochemical means for removing
toxic metals12. In conclusion, PVAC-CP could be use as
potential adsorbent for the removal of Zn (II) from aqueous
solutions. The optimium data found from this adsorption
studies given below in table-1

The removal of metal ions from solution by adsorption is
highly dependent on the pH of the solution. It was found that
85.8 % removal of Zn (II) achieved at pH 6 and thereafter the
percent removal decreases with increases in pH as 7 and 8.
Thus the optimum adsorption pH for Zn (II) removal found
to be 6.
Effect of adsorbent dose: The effect of adsorbent dose on
percent removal of Zinc is shown in figure-3 Adsorbent dose

Time dependance(at pH 6)

%Removal of Zn(II)

100
80

150ppm
60

120ppm

40

100ppm

20

80ppm
60ppm

0
0

50

Time(min) 100

150

Figure-1
Effect of contact time on removal of Zn (II) at
different concentration by PVAC-CP at pH 6

% REmoval of Zn
(II)

100

pH dependance

150pp
m
120pp
m
100pp
m

80
60
40
20
0
0

2

4

pH

6

8

10

Figure-2
Effect of pH on removal of Zn (II) at different concentrations
by 15gm/l of PVAC-CP at constant contact time 105 min.

International Science Congress Association

162

% Removal of Zn (II)

Research Journal of Recent Sciences ____________________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci

Dose dependance at pH 6

90

60pp
m
80pp
m
100pp
m

80
70

60
50
0

5

10

15

Dose (gm/l)

20

Figure-3
Effect PVAC-CP dose on percent removal of Zn (II) at
equilibrium contact time 105 min. and effective at pH 6.

Adsorption capacity for Zn(II) vary with dose of adsorption

Adsorption capacity q
(mg/g)

40

60
ppm
80
ppm
100
ppm

30
20
10
0
0

5

10

15

20

Dose (g/L)
Figure-4
Effect of dose of adsorbent on adsorption capacity at
equilibrium contact Time 105 min and effective pH 6.

Freundlich adsorption isotherm for Zn(II)
1.6

3 gm/l

1.4

Log q

1.2

6 gm/l

1
9 gm/l

0.8
0.6

12
gm/l

0.4
0.2
0
0.8

1

1.2

1.4

1.6

1.8

2

Log Ce
Figure-5
Freundlich Isotherm plot for Zn (II) adsorption by
PVAC-CP at optimum conditions

International Science Congress Association

163

Research Journal of Recent Sciences ____________________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci

Langmuir adsorption isotherms for Zn(II)
3 gm/l

10

6 gm/l

Ce/q

8

9 gm/l

6

12 gm/l

4

15 gm/l
18 gm/l

2
0
0

10

20

30

40

50

60

70

Ce
Figure-6
Langmuir Isotherm plot for Zn (II) adsorption by
PVAC-CP at optimum conditions.
Table-1
Sr
No.

Particular

Optimium data
(PVAC-CP)

1

Time (min.)

105 min

2

pH

6

3

Dose (gm/l)

15 gm/l

4

Max. % removal of
Metal (Zn)

85.8%

Table -2
Langmuir and Freundlich constants for adsorption of Zinc (II):Dose
gm/l)

Freundlich isotherm
(linear equation)

Langmuir isotherm
(linear equation)

R2
Freundlich

R2
Langmuir

15

y=0.394x+0.164

y=0.0114x+1.771

0.997

0.982

Table -3
Dose (gm/l)

Freundlich constants

Langmuir constants

Kf

n

1/n

Qm (mg/g)

b (l/ mg)

RL

1.458814

2.53807

0.39400

8.77193

0. 06437

0.99614

15

International Science Congress Association

164

Research Journal of Recent Sciences ____________________________________________________________ ISSN 2277 - 2502
Vol. 1(ISC-2011), 160-165 (2012)
Res.J.Recent.Sci

References

7.

APHA, AWWA Standard Methods for Examination of
water and wastewater 19th Edition Washington DC
(1994)

1.

Akporhonor E.E. and Egwaikhide P.A. Scientific
Research and Essay, 2(4), 132-134 (2000)
8.

2.

Tiwari R. P., Bala Ramudu P., Srivastava R.K., Gupta
M.K., Iran, J. Environ. Health. Sci. Eng., 2007, 4(3),
139-146 (2007)

Chand S., Aggarwal V.K. and Kumar P. Removal of
Hexavalent Chromium (1994)

9.

From the Wastewater by Adsorption. Indian J Environ.
Health, 36(3), 151-158 (2000)

Broadley M.R., White P.J., Hammond J.P., Zelko I. and
Lux A., Zinc in plants, New Phytologist, 173(4), 677
(2007)

10. World Health Organization, Geneva, Guidelines for
drinking Water Quality, (1984)

4.

Hambidge K.M. and Krebs N.F., Zinc deficiency: a
special challenge, J. Nutr. 137(4) (2007)

11. Lanouette K.H., Heavy Metals Removal, Chem. Eng.,
84(21) 73-80 (1977)

5.

Iqbal Ahmad, J.Appl. Sci. Enviorn.Mgt., 9(1), 123-126
(2005)

12. Freundlich H. Colloid Capillary Chemistry (London;
Metheun) (1926)

6.

Kadirvelu K., Thamaraiselvi K. and Namasivayam C.,
Bioresource Techn., 76, 63-65 (2001)

13. Langmuir I J, J. Amer. Chem. Society, 40, 1361 (1918)

3.

International Science Congress Association

165

