RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 598
Removal of Murexide (Dye) from Aqueous Media using Rice Husk as an Adsorbent
RABIA REHMAN, JAMIL ANWAR, TARIQ MAHMUD*, MUHAMMAD SALMAN,
UMER SHAFIQUE AND WAHEED-UZ-ZAMAN
Institute of Chemistry, University of the Punjab, Lahore-54590, Pakistan.
(Received on 9th September 2010, accepted in revised form 24th November 2010)
Summary: The use of low-cost and ecofriendly adsorbent was investigated as an ideal alternative to
the current expensive methods of removing dyes from wastewater. Rice husk was used as an
adsorbent for the removal of Murexide from aqueous solutions. The rate of adsorption was
investigated under various parameters such as size of adsorbent, contact time of solution with
adsorbent, temperature, pH, adsorbent dose and stirring speed for the removal of this dye. Langmuir
isotherm was also applied to evaluate maximum adsorption capacity of rice husk for Murexide. On
the basis of results obtained, it is proposed that rice husk can be effectively used for the elimination
of Murexide from waste water.
Dyes are common constituents of effluents
discharged by various industries, particularly the
textile industry. Many industries such as dyestuff,
textiles, leather, and paper use dyes to color their
products and also consume significant volumes of
water. Various kinds of dyes and their break down
products are toxic for the living organisms.
Discharging dyes into the hydrosphere can cause
environmental damage as the dyes give water
undesirable color and reduce sunlight penetration,
with some dyes also being toxic in nature .
Recently, an increasing interest has been focalized on
removing dyes from water due to its refractory
biodegradation and poisonous nature . Despite a
wide range of wastewater treatment techniques
available, there is no single process capable of
adequate treatment for these effluents. Various
techniques have been utilized for the removal of dyes
from waste water [3-6]. Formal physical and
chemical methods are either costly, e.g., activated
carbon, or produce concentrated sludge, e.g., Fenton's
reagent, or may not capable of treating large volumes
of effluent without the risk of clogging, e.g.,
membrane filtration [7, 8]. Among several chemical
and physical methods, the adsorption has been found
to be superior compared to other techniques for
wastewater treatment in terms of its capability for
efficiently adsorbing a broad range of adsorbates and
its simplicity of design.
Adsorption technique is quite popular due to
the availability of a wide range of adsorbents and it is
proved to be an effective and appealing process for
removal of non-biodegradable pollutants [9-12] like
dyes from wastewater . The common adsorbent
i.e. activated carbon, has good capacity for removal
of pollutants . However, commercially available
activated carbons are still considered as expensive
materials for many countries due to the use of non-
renewable and relatively expensive starting material
such as coal, which is unjustified in pollution control
applications. Thus, there is a demand for other
adsorbents, which are of inexpensive material and
does not require any costly additional pretreatment
step, so the adsorption process will become
economically practicable. A successful adsorption
process not only depends on dye adsorption
performance of the adsorbents, but also on the
constant supply of the adsorbent materials for the
process. So it is preferable to use low cost adsorbents,
such as industrial wastes, natural ores or agricultural
byproducts. Therefore, in recent years, this has
prompted a growing research interest in the
production of activated carbons from renewable and
cheaper precursors which are mainly industrial and
agricultural by-products . This has resulted in a
search for developing other adsorbents based on solid
wastes. Such low cost adsorbents have given
satisfactory performance at the laboratory scale for
treatment of colored effluents .
In the present work, rice husk obtained
from the food process was tested as an adsorbent for
dyes with a model system of aqueous Murexide
solutions. Murexide (NH4C8H4N5O6,
purpurate or MX, is the ammonium salt of purpuric
acid. Its structural formula is shown in Fig. 1. It can
be prepared by heating alloxantin in ammonia gasat
100°C or by boiling uramil (5-aminobarbituric acid)
with mercury oxide. Murexide in its dry state has the
appearance of a reddish purple powder which is
J.Chem.Soc.Pak., Vol. 33, No. 4 2011
*To whom all correspondence should be addressed.
RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 599
slightly soluble in water. In solution, its color ranges
from yellow in strong acidic pH through reddish-
purple in weakly acidic solutions to blue-purple in
alkaline solutions . It is used in analytical
chemistry as a complexometric
complexometric titrations. The pH for titration of
calcium is 11.3. It
a colorimetric reagent for measurement of calcium,
strontium cobalt, nickel, copper, zinc and cadmium
[18-21]. As Murexide is used in various studies, so
during its use, a considerable amount of Murexide
goes with wastewater to the rivers and oceans and
make hazardous for the aquatic lives. Therefore,
removal of dye is important aspect of wastewater
treatment before discharge.
is also used as
Rice husk was used as an adsorbent in this
study. It is a low-value agricultural by-product used
in heavy metal and dye removal. It has been
investigated as a replacement for currently expensive
methods of dye removal from solutions. Rice husk is
also being used to treat textile dyes such as like
malachite green, [22, 23] congo red,  methylene
blue  and acid yellow 36 . The treatment and
preparation of rice husk activated carbon are of
importance and became a subject of study [27, 28]. It
was used to remove various dyes and metal ions from
The main objective of this work is to study
the adsorption potential of low cost biosorbent, i.e.
rice husk for the removal of hazardous dye Murexide
from the water and to evaluate the effect of dye
temperature, and pH of the medium, on the
adsorption characteristic of rice husk. This paper also
discusses the Langmuir adsorption isotherm model as
applied to the adsorption of Murexide onto the rice
dose, contact time,
Results and Discussion
Adsorbent Size or Mesh Size
The effect of particle size on adsorption was
studied by using different mesh sizes of rice husk.
The particle size decreases and surface area exposed
for adsorption of dye increases as mesh size
increases. The results are shown in Fig. 2. Adsorption
was 1.2 % for the mesh size of 80-100 microns to
maximum adsorption value 6.9 % for the mesh size
of 40-60 microns. It was observed that smaller the
adsorbent size results in more surface area which
enhanced the adsorption capacity of adsorbent. The
adsorption capacity of rice husk depends on the
surface activities, i.e. specific surface area available
for solute surface interaction which is accessible to
the solute. It is expected that adsorption capacity will
be increased with a larger surface area. In other
words, smaller particle size increases the adsorption
capacity. It is also supported by the literature.
Adsorption being a surface phenomenon, the smaller
adsorption size will offer comparatively larger
surface areas and higher adsorption will occur at
Mesh size vs % age adsorption
Mesh Size (microns)
% Age Adsorption
Fig. 2: Effect of mesh size of rice husk on
percentage adsorption of Murexide.
The effect of variation in the adsorbent dose
on the adsorption of Murexide was studied. The
results are shown in Fig. 3. It was observed that the
adsorption yield increased as the adsorbent dose
decreases. The maximum adsorption value was
11.8% for the dose 0.2 g. This increase in adsorption
with decrease in adsorbent dose was due to the
availability of more adsorption sites. Another reason
may be due to the particle interactive behavior such
as aggregation, resulted from high adsorbent dose.
Such aggregation would lead to decrease in total
RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 600
surface area of the adsorbent and hence the
Adsorbent dose vs %age adsorption
Adsorbent dsoe (g)
Fig. 3:Effect of adsorbent dose on percentage
adsorption of Murexide.
The effect of various contact intervals on
adsorption was studied. The results are shown in Fig.
4. The minimum adsorption was 2% for 5 minutes
and maximum value was 6% for 15 minutes. The
adsorption characteristic indicated a rapid uptake of
the adsorbate. The adsorption rate decreased to a
constant value with increase in contact time because
of all available sites was covered and no active site
available for binding.
Initial dye concentration vs % age adsorption
5 10 15202530
Initial dye concentration (ppm)
Fig. 4: Effect of initial concentration of dye on
Effect of Dye Concentration
The effect of initial dye concentration on
adsorption was studied. The results are shown in Fig.
5. It was observed that adsorption increased with
increase in initial concentration of the dye. The
minimum adsorption was 12.04 % for 5.0 ppm to
maximum adsorption value 78.48 % for 25 ppm
concentration of dye solution. This may be due to
available active sites and increase in the driving force
of the concentration gradient, as an increase in the
initial concentration of the dye.
Contact Time Vs % age adsorption
5 15 3045 60
Contact Time (minutes)
% age adsorption
Fig. 5: Effect of contact time of rice husk with
Murexide solution on percentage adsorption.
Effect of pH
The pH of the aqueous solution is clearly an
important parameter that control the adsorption
process. The percentage of adsorption was studied as
a function of pH in the range of 2-10. The results are
shown in Fig. 6. The minimum adsorption was 1.6%
at pH= 8 and maximum adsorption value was 95.7 %
at pH= 2. The maximum adsorption occurred in the
acidic media. This indicated that rice husk is an
efficient adsorbent for Murexide in acidic conditions.
This might be due to the force of attraction like
hydrogen bonding between the oxygen atoms of
adsorbate and hydroxyl groups of adsorbent that
ultimately lead to the increase in percentage
Effect of Agitation Rate
The effect of variation in the agitation rate
on the adsorption process was studied. The results are
shown in Fig. 7. It was observed that adsorption yield
increased with decrease in stirring speed. The
minimum adsorption was 49 % for a speed of 500
rpm and maximum adsorption was 73 % at a speed of
300 rpm. By increasing the speed further, there was
no further increase in adsorption. This may be
because all binding sites have been used and no
binding sites were available for further adsorption.
This is also supported by literature. An increasing
RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 601
agitation rate may reduce the film boundary layer,
surrounding the sorbent particles, thus increasing the
external film diffusion rate and the uptake rate .
pH vs % age adsorption
% age adsorption
Fig. 6:Effect of pH on percentage adsorption of
Agitation rate vs % age adsorption
Agitation rate (rpm)
% age adsorption
Fig. 7: Effect of agitation rate on percentage
adsorption of Murexide.
Effect of Temperature
Temperature has important effect on the
adsorption. The percentage adsorption was studied at
various temperatures. The results were shown in Fig.
8. It was observed that adsorption yield decreased
with increase in temperature. The minimum
adsorption was 52 % at 50 °C and maximum
adsorption was 74 % at 30°C. The decrease in
adsorption may occur because at high temperature,
molecules move with greater speed and less time of
interaction was available for adsorption with
Temperature vs % age adsorption
2030 40 50
% age adsorption
adsorption of Murexide.
of temperature on percentage
The Langmuir isotherm was shown in Fig. 9
and the corresponding parameters are given in Table-
1. ‘Qmax’ value was 15.06. Value of ‘R2’ showed
correlation or linear relationship. R2 (correlation
coefficient) value approaching to one, clearly
suggested that Langmuir isotherm holds good to
explain adsorption of Murexide on rice husk. ‘b’ (an
adsorption equilibrium constant related to apparent
energy of sorption) for Murexide is 0.011 L g–1.
Table-1: Langmuir Isotherm parameters.
Langmuir Isotherm for Murexide
y = 5.9419x + 0.0664
R2 = 0.9896
Fig. 9:Langmuir isotherm for adsorption of
Murexide on rice husk.
RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 602
The adsorption mechanism for the removal
of dyes may be supposed to involve the following
Diffusion of the dye through the boundary layer,
Intra-particle diffusion, and
Adsorption of the dye on the adsorbent surface.
The boundary layer resistance will be
affected by the rate of adsorption and increase in
contact time, which will reduce the resistance and
increase the mobility of dye during adsorption. Since
the uptake of dye at the active sites of rice husk is a
rapid process due to less contact time between
adsorbate and adsorbent requirement (15 minutes) at
normal local temperature (30
adsorption is mainly governed by liquid phase mass
transfer rate, diffusion through the boundary layer or
intra-particle mass transfer rate .
0C), the rate of
All chemicals used during experimental
work were of AnalR and were used as such without
purification. Murexide (Fluka, λmax = 520 nm,
Mol.wt = 284.19 g/mol, reddish purple), HCl (Merk,
11.6M), NaOH (Merck, Mol. wt = 40 g). Double
distilled water was used for the preparation of all
types of solutions and dilutions when required.
Balance ER-120A (AND), Electric grinder
(Ken Wood), pH meter HANNA pH 211(with glass
electrode), UV/VIS spectrophotometer (Labomed,
Inc. Spectro UV-Vis double beam UVD= 3500).
1.0 g of Murexide was taken in 1000 mL
measuring flask and dissolved in double distilled
water, making volume up to the mark. This was 1000
ppm Stock solution of the dye. Standard solutions of
dye were prepared by successive dilution of the Stock
The adsorption studies were carried out at
25 ± 1 °C. pH of the solution was adjusted with 0.1 N
HCl and 0.1 N NaOH. Rice husk i.e adsorbent was
ground to fine powder and dried in oven at 70 oC for
45 minutes. A known amount of adsorbent was added
to sample and allowed sufficient time for adsorption
equilibrium. The mixtures were then filtered and dye
concentration weas determined in the filtrate using
(Spectro UV-Vis Double
Labomed spectrophotometer at 520 nm (λmax).
The effects of various parameters on the rate
of biosorption process was observed by varying mesh
size (20-100 microns) to study particle size of
adsorbent (20-100 microns), contact time, t (15-60
min), initial concentration of dye Co (5-30 ppm),
adsorbent amount (0.1-0.6 g) , initial pH of the
solution (2-10), agitation speed (100-500 rpm) and
temperature (20-50 °C). The solution volume (V) was
kept constant (25 mL). The dye adsorption
(percentage) at any instant of time was determined by
the following equation:
where Co and Ce are the concentrations of the dye, at
initial and at any instant time respectively. To
increase the accuracy of the data, each experiment
was repeated three times and average values were
Study of Adsorption Isotherm
Six solutions with concentrations 30, 40, 50,
60, 70 and 80 ppm were made by proper dilution of
Stock solution of Murexide. pH was adjusted to 2.
Accurately weighed sorbent (0.2 g) of particle size
60-80 microns was added to 50 mL of each dye
solution and was agitated for 15 minutes. At the end,
suspensions were filtered off and supernatants were
analyzed for remaining dye concentration by using
Langmuir isotherm was plotted by using
standard straight-line equation and corresponding two
parameters for Murexide were calculated from its
qe (mg g-1) is the amount of dye adsorbed and Ce
(ppm) is concentration at equilibrium. qm (mg g-1) (or
Qmax) and b (Lg-1) are Langmuir isotherm parameters
RABIA REHMAN et al., J.Chem.Soc.Pak., Vol. 33, No. 4, 2011 603 Download full-text
From the present study, it is concluded that
rice husk is a proficient adsorbent for the removal of
dyes from aqueous media. Optimum conditions for
removal of Murexide with rice husk were: 0.2 g of
adsorbent, dye concentration 25 ppm, temperature 30
oC, 15 minutes contact time, 300 rpm stirring speed
and pH 2.0. Qmax value was 15.06 which pointed out
that rice husk can effectively be used for the removal
of Murexide from water.
A. R. Gregory, S. Elliot and P. Kluge, Journal of
Applied Toxicology. 1, 308 (1991).
K.K.H. Choy, G. MeKay and J. F. Porter,
Resources, Conservation and Recycling, 27, 57
S.D. Khattri and M.K. Singh, Water Air and
Soil Pollution, 120, 283 (2000).
A.K. Mittal and S.K. Gupta, Water Science and
Technology, 34, 81-87 (1996).
F. Perineau, J. Molinier and A. Gaset, Journal
of Chemical Technology & Biotechnology, 32,
T. Robinson, G. McMuUan, R. Marchant and P.
Nigam, Bioresource Technology, 77, 247 (2001).
C. I. Pearce, J. R. Lloyd and J.T. Guthrie, Dyes
Pigments, 58, 179 (2003).
M. J. Iqbal and M. N. Ashiq, Journal of the
Chemical Society of Pakistan, 32, 419 (2010).
10. N. Zahra, Journal of the Chemical Society of
Pakistan, 32, 259 (2010).
11. C. H. Xiong, Journal of the Chemical Society of
Pakistan, 32, 429 (2010).
12. A. Qayoom, S. A. Kazmi,
Chemical Society of Pakistan, 32, 582 (2010).
13. Z. Aksu, Process Biochem. 40, 997 (2005).
14. G. M. Walker and L. R. Weatherley, Water
Research, 31, 2093 (1997).
Crini, Bioresource Technology, 97,
Journal of the
15. I. A. W. Tan, A. L. Ahmad, B. H. Hameed,
Journal of Hazardous Materials, 154 337
16. K.G. Bhattacharyya, A. Sharma, Dyes Pigments.
57, 211 (2003).
17. N. M. Winslow, Journal of the American
Chemical Society, 61 (8), 2089 (1939).
18. E. S. Reynolds and R. E. Linde, Analytical
Biochemistry, 5 (3), 246 (1963).
19. H. Gordon and G. Norwitz, Talanta, 19 (1) 1
20. D.S. Russell, J.H. Campbell and S.S. Bermaban,
Analytica Chimica Acta, 25 (1), 81 (1961).
21. M. Shamsipur and N. Alizadeh, Talanta, 39 (9)
22. Y. Guo, S. Yang, W. Fu, J. Qi, R. Li, Z. Wang
and H. Xu, Dyes Pigments, 56, 219(2003).
23. Y. Guo, H. Zhang, N. Tao, Y. Liu, J. Qi, Z.
Wang and H. Xu, Materials Chemistry and
Physics, 82,107 (2003).
24. R. Han, D. Ding, Y. Xu, W. Zou, Y. Wang, Y.
Li and L. Zou, Bioresource Technology, 99,
25. P. Sharma, R. Kaur, C. Baskar and W. J. Chung,
Desalination, 259, 249 (2010).
26. P. K. Malik, Dyes Pigments, 56, 239 (2003).
27. N. Yalcin and V. Sevinc, Carbon, 38, 1943
28. Y. Guo, J. Qi, S. Yang, K. Yu, J. Zhao, Z. Wang
and H. Xu, Materials Chemistry and Physics,74,
29. T.G. Chuah, A. Jumasiah, I. Azni, S. Katayon
and S.Y. T. Choong , Desalination, 175, 305
30. S. S. Nawar and H.S. Doma, Science of the
Total Environment, 79, 271(1989).
31. M. Dogan, Y. Ozdemir, M. Alkan, Dyes and
Pigments, 75 701 (2007).
32.J. Anwar, U. Shafique, M. Salman, W. Zaman,
S. Anwar, J. M. Anzano, Journal of Hazardous
Materials, 171, 797 (2009).