REMOVAL OF CADMIUM CD (II) AND SILVER AG (I) FROM AQUEOUS SOLUTIONS BY NANO ACTIVATED ALUMINA PART II: CONTINUOUS FLOW EXPERIMENTS

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 6, Issue 12, Dec 2015, pp. 48-57, Article ID: IJCIET_06_12_005
Available online at
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=12
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
REMOVAL OF CADMIUM CD (II) AND
SILVER AG (I) FROM AQUEOUS
SOLUTIONS BY NANO ACTIVATED
ALUMINA
PART II: CONTINUOUS FLOW
EXPERIMENTS
Eng. Enas Sameer AL-Khawaja and Prof. Dr. Alaa Hussein Al-Fatlawi
College of Engineering / Babylon University, Iraq
ABSTRACT
The extent of removal of heavy metal ions (cadmium and silver) in single
and binary system by adsorption on alumina has been investigated.
Adsorption experiments were performed in continues flow technique (fixed
bed) from synthetic solutions using alumina as adsorbent. Several
experimental parameters that affect the extent of adsorption of the metal ions
of interest have been investigated such as adsorbent bed depth and
concentration of the adsorbate with different contact time. The percent of
removal efficiency was also been studied. pH of the system used equal =6.5,
temperature =25ºC. This work proposes a cost-effective method for the
efficient removal of Cd (II) and Ag (I) from aqueous solutions.
Keywords: Continues Flow, Adsorption, Alumina, Heavy Metal Ions.
Cite this Article: Eng. Enas Sameer AL-Khawaja and Prof. Dr. Alaa Hussein
Al-Fatlawi, Removal of Cadmium CD (II) and Silver AG (I) From Aqueous
Solutions by Nano Activated Alumina Part II: Continuous Flow Experiments.
International Journal of Civil Engineering and Technology, 6(12), 2015, pp.
48-57.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=6&IType=12
1. INTRODUCTION
Adsorption is considered as one of the suitable water treatment methods due to its
ease of operation and the availability of a wide range of adsorbents. Besides,
adsorption can also be applied for the removal of soluble and insoluble organic,
inorganic, and biological pollutants. Additionally, adsorption can also be used for
source reduction and reclamation for potable, industrial, and other water purposes. In

Removal Of Cadmium CD (II) and Silver AG (I) From Aqueous Solutions by Nano Activated
Alumina Part II: Continuous Flow Experiments
spite of these facts, adsorption has certain limitations such as it could not achieve a
good status at commercial levels. Probably, it is due to the lack of suitable adsorbents
of high adsorption capacity and commercial scale columns. Besides, a single
adsorbent cannot be used for all kind of pollutants. The different adsorbents are used
for different pollutants. Initially, activated carbon was used for the removal of
pollutants from water, which has been replaced by some cost-effective adsorbents. In
the last two decades, nanotechnology has developed with its applications in almost all
branches of science and technology. In this series, water treatment is not deprived of
nanotechnology. Nanosize adsorbents have been prepared and used for the removal of
water pollutants. In view of the importance of water quality and emerging utilities of
nanotechnology, attempts have been made to discuss various aspects of water
treatment by adsorption using nano-adsorbents, [Imran, 2011].
Some nanoparticles have been prepared and used for water treatment.
Nanoparticles have proven themselves as excellent adsorbents due to their unique
features. The most important characteristics of these particles; which made them ideal
adsorbents, are small size, catalytic potential, high reactivity, large surface area, ease
of separation, and large number of active sites for interaction with different
contaminants. These properties are responsible for high adsorption capacities by
increasing the surface area, free active valences, and surface energies of nanoparticles.
The commonly used nanoparticles for water treatment are made of alumina, anatase,
akaganeite, cadmium sulphide, cobalt ferrite, copper oxide, gold, maghemite, iron,
iron oxide, iron hydroxide, nickel oxide, silica, stannous oxide, titanium oxide,
titanium oxide, zinc sulfide, zinc oxide, zirconia, and some alloys, [Imran, 2011].
Alumina can be used as an alternative for activated carbon .Alumina is a fine
weight material similar in appearance to common salt and it is highly porous and
exhibits tremendous surface area, resulting in superior adsorbent capabilities. It is
more preferable than activated carbon especially for removing inorganic compounds,
[Jenan, et al., 2014] .
Adsorption offers high efficiency, cost-effectiveness and easy handling. Recovery
of the metals and other adsorbed species is also possible. A number of adsorbents, e.g.
activated carbon, flyash, chitosan, zeolite, montmorillonite, sphagnum moss peat,
kaolinite, wollastonite, bentonite, sawdust, sea weeds, alumina, soya cake and
redmud have been reported for the removal of metallic pollutant from aqueous
solutions and wastewaters, [Sharma, et al., 2008].
2. REMOVAL OF INORGANIC POLLUTANTS
Heavy metals are generally considered to be those whose density exceeds 5gm/ .
Removal of heavy metals from wastewater is of primary importance because they are
not only causing contamination of water bodies and are also toxic to many life forms.
Industrial processes generate wastewater containing heavy metal contaminants. Since
most of heavy metals are non degradable into nontoxic end products, their
concentrations must be reduced to acceptable levels before discharging them into
environment. Otherwise these could pose threats to public health and/or affect the
aesthetic quality of potable water. According to World Health Organization (WHO)
the metals of most immediate concern are nickel, cadmium, chromium, copper, zinc,
iron, mercury and lead, [Ahmed and Farah, 2014].

2.1. Cadmium
Cadmium is consider one of the most toxic metals affecting the environment, the
source of cadmium are mining and metallurgy of cadmium, cadmium electroplating,
is widely used in pigments, as heat stabilizers for plastics, for corrosion resistance of
steel and cast iron, metal plating, phosphate fertilizer, mining, pigments, alloy
industries, in soldering and brazing and in the battery industry (Ni - Cd batteries), and
ceramic industries waste waters contain undesired amounts of ions is highly
toxic and there is some evidence that it is carcinogenic, [Ahmed and Farah, 2014].
According to the Agency for Toxic Substances and Disease Registry (ATSDR) of
the U.S. Department of Health and Human Services, the permissible limits of in
drinking water are 0.04 , [Jie, et al., 2015].
2.2. Silver
Silver is one of the basic elements that make up our planet. Silver is rare, but occurs
naturally in the environment as a soft, "silver" colored metal. Because silver is an
element, there are no man-made sources of silver. People make jewelry, silverware,
electronic equipment, and dental fillings with silver in its metallic form. It also occurs
in powdery white (silver nitrate and silver chloride) or dark-gray to black compounds
(silver sulfide and silver oxide). Silver could be found at hazardous waste sites in the
form of these compounds mixed with soil and/or water. Therefore, these silver
compounds will be the main topic of this profile. Throughout the profile the various
silver compounds will at times be referred to simply as silver. Photographers use
silver compounds to make photographs. Photographic materials are the major source
of the silver that is released into the environment. Another source is mines that
produce silver and other metals, [U.S. Public Health Service, 1990].
Silver is a very useful raw material in various industries due to its excellent
malleability, ductility, electrical and thermal conductivity, photosensitivity and
antimicrobial properties. Significant amounts of silver are lost in the effluents
discharged from such industries and due to the toxicity of silver to living organisms,
the removal of this metal from wastewaters is an important concern. The presently
available technologies for the removal of silver include precipitation, electrolysis,
solvent extraction, use of ion-exchange resins, chelating agents, etc. These processes
can be profitably used on a large scale when the metal concentrations in effluents are
sufficiently high, i.e., above 100 ppm, [Murat, et al., 2006].
Silver levels of less than 0.000001 mg silver per cubic meter of air ( ), 0.2-
2 parts silver per billion parts water (ppb) in surface waters, such as lakes and rivers,
and 0.2-0.3 parts silver per million parts soil (ppm) in soils are found from naturally
occurring sources, [U.S. Public Health Service, 1990].
3. MATERIALS
Cadmium nitrate ( ) and silver nitrate were used for preparing
synthetic solutions of heavy metal ions in the required concentration. Add a drop of
0.1M (NaOH and ) to adjust pH of the solution. Nano activated alumina ( )
used as the adsorbent for the study was prepared by sol-gel method in laboratory by
using aluminum nitrate ( with 50/50 mix of ethanol alcohol with
water and adding drops of ammonium hydroxide. Alumina was activated by heating
at 700°C for 2 hours before being used.

4. METHODS OF CONTINUOUS EXPERIMENTS (COLUMN
TESTS)
Fig. 1 showed a schematic and experimental set up used in the present study which is
constructed of Pyrex glass tube of (60 cm) height, and (1cm) internal diameter, with
upward flow. In order to avoid the exiting adsorbent from column, glass wool at the
top and bottom of the column was applied. The column dimensions were defined to
minimize the occurrence of channeling by making the column diameter at least 30
times the maximum particle size found in the material used. The column dimensions
also met the minimum length-to-diameter requirement, [Relyea, 1982]. This means
the column length (60 cm) must be four times greater than its diameter (1cm).
In order to investigate the effect of bed depth on the behavior of the adsorbent
column, bed depths (5, 10, and 15 cm) equivalent with (3, 5.8, and 8.5 gm) weight of
alumina with concentrations (25, 50 and 100 mg/l) for cadmium and silver
respectively and constant flow rate of 8 mL/min were used. Effluent samples from the
column were collected at specified time intervals, and remaining cadmium and silver
concentrations in the solution were measured by Atomic Absorption technique. In all
experiments, the pH values were adjusted to 6.5.
Maximum adsorption capacity of the adsorbent in a fixed-bed column is
calculated by Eqs. 1 and 2:
(1)
(2)
Figure 1 Schematic set up
4.1. Column Experiments
The adsorption experiments were carried out in columns that were equipped with a
flow meter for controlling the column flow rate. This experiment is useful in
understanding and predicting the behavior of the process. The sample solution was
passed through the adsorption column with a different amount of alumina bed depth
(5, 10, and 15) cm for and (1, 5, and 10) cm for , with a flow rate of
8mL/min. The flow rate was kept constant by controlling the flow meter. The
concentration of ( and ) residual in the sorption medium was determined
using atomic adsorption instrument (AAS).
The results of ( and ) adsorption onto different adsorption fixed beds
using a continuous system were presented in the form of breakthrough curves which

showed the loading behaviors of ( and ) to be adsorbed from the solution
expressed in terms of relative concentration defined as the ratio of the outlet (
and ) concentration to the inlet ( and ) concentration as a function of
time ( Ce/C₀ vs. time).
4.1.1. Effect of Adsorbent Bed Height in Single System:
The effect of bed height was investigated for ( and ) adsorption onto
(alumina); the experimental breakthrough curves are presented in Figs. (1 and 2).
These Figs. show the breakthrough curves obtained for adsorption on the
alumina for three different bed heights of (5, 10, and 15) cm and for (1, 5, and
10) cm with a constant flow rate of 8 mL/min, initial concentration of 50 mg/L, and
solution pH of 6.5. It is clear that the increase in bed depth increases the breakthrough
time and the residence time of the solute in the column.
Both the breakthrough and exhaustion time increased with increasing the bed
height. A higher ( and ) uptake was also expected at a higher bed height due
to the increase in the specific surface of the alumina which provides more fixation
binding sites for the metals to adsorb. The increase in the adsorbent mass in a higher
bed provided a greater service area which would lead to an increase in the volume of
the solution treated.
The effect of bed depth on the removal efficiency capacity of alumina was shown
in Figs.(3 and 4), by plotting the removal efficiency versus different bed time. These
Figs. show that the increasing in bed depth would increase the removal capacity
because additional spaces will be available for the wastewater molecules to be
adsorbed on these unoccupied areas. Furthermore, increasing bed depth will give a
sufficient contact time for these molecules to be adsorbed on the alumina surface.
Figure 1 Experimental breakthrough
curves for adsorption of at
different bed depth of alumina (
=50 mg/L, Q=8 mL/min, pH=6.5).
different bed depth of alumina (
=50 mg/L, Q=8 mL/min, pH=6.5).

4.1.2. Effect of Adsorbent Concentration in Single System:
The effect of changing of ( and ) concentrations (25, 50, and 100) mg/L
with constant bed height of alumina of 10 cm for and 5cm for , flow rate
of 8 mL/min, and solution pH of 6.5 were shown by the breakthrough curves
presented in Figs. (5 and 6). At the highest cadmium concentration of 100 mg/L,
the alumina bed was exhausted in the shortest time of less than 1 hour, leading to the
earliest breakthrough. The breakpoint time decreased with an increase in the initial
concentration as the binding sites became more quickly saturated in the column. This
indicated that an increase in the concentration could modify the adsorption rate
through the bed. A decrease in the cadmium concentration to 50 mg/L gave an
extended breakthrough curve, indicating that a higher volume of the solution could be
treated. This was due to the fact that a lower concentration gradient caused a slower
transport due to a decrease in the diffusion coefficient or mass transfer coefficient.
Figure 3 Effect of different bed
depth on the removal efficiency of
(Q=8 mL/min, =50mg/L,
pH=6.5).
Figure 4 Effect of different bed
depth on the removal efficiency of
(Q=8 mL/min, =50mg/L,
pH=6.5).
different concentration ( =10cm,
Q=8 mL/min, pH=6.5).
different concentration ( =5cm, Q=8
mL/min, pH=6.5).

The effect of initial cadmium concentration onto alumina are shown in Figs. 7 and
8. It could be seen that the percent of cadmium removal decreased with the increase in
initial concentration to 100 mg/L. This means that the amount of cadmium sorbed per
unit mass of sorbent increased with the increase in initial concentration to 50 mg/L.
This plateau represents saturation of the active sites available on alumina samples for
interaction with contaminants, indicating that less favorable sites became involved in
the process with the increase in concentration.
4.1.3. Effect of Adsorbent Bed Height in Binary System:
The effect of bed height was investigated in binary system for ( and )
adsorption onto alumina; the experimental breakthrough curves are presented in Figs.
(9 and 10). These Figs. show the breakthrough curves obtained for ( and )
adsorption on the alumina for two different bed heights of (5 and 10) cm, at a constant
flow rate of 8 mL/min, initial concentration of 50 mg/L, and solution pH of 6.5. It is
clear that the increase in bed depth increases the breakthrough time and the residence
time of the solute in the column.
Both the breakthrough and exhaustion time increased with increasing the bed
height. A higher ( and ) uptake was also expected at a higher bed height due
to the increase in the specific surface of the alumina which provides more fixation
binding sites for the metals to adsorb. The increase in the adsorbent mass in a higher
bed provided a greater service area which would lead to an increase in the volume of
the solution treated.
Figure 7 Effect of different
concentration on the removal
efficiency of Cd (Q=8 mL/min,
=10cm, pH=6.5).
efficiency of Ag (Q=8 mL/min,
=5cm, pH=6.5).

The effect of bed depth on the removal efficiency capacity of alumina was shown
in Figs.(11 and 12), by plotting the removal versus different bed time. This Figs. show
that increasing bed depth would increase the removal capacity because additional
spaces will be available for the wastewater molecules to be adsorbed on these
unoccupied areas. Furthermore, increasing bed depth will give a sufficient contact
time for these molecules to be adsorbed on the alumina surface.
4.1.4. Effect of Adsorbent Concentration in Binary System:
The effect of changing of ( and ) concentration (25, 50, and 100) mg/L
with constant bed height of alumina of 10 cm, flow rate of 8 mL/min, and solution
pH of 6.5 was shown by the breakthrough curves presented in Fig. 13. At the highest
cadmium concentration of 100 mg/L, the alumina bed was exhausted in the
shortest time of less than 1 hour, leading to the earliest breakthrough. The breakpoint
time decreased with an increase in the initial concentration as the binding sites
became more quickly saturated in the column. This indicated that an increase in the
concentration could modify the adsorption rate through the bed. A decrease in the
Figure 10 Experimental
breakthrough curves for adsorption
of binary at bed depth of
alumina=10 cm, =50 mg/L, Q=8
ml/min, pH=6.5).
curves for adsorption of binary at bed
depth of alumina=5 cm, =50 mg/L,
Q=8 ml/min, pH=6.5.
Figure 11 Effect of removal efficiency
of binary at bed depth of alumina=5
cm, Q=8 mL/min, =50mg/L,
pH=6.5).
Figure 12 Effect of removal
efficiency of binary at bed depth of
alumina=10 cm, Q=8 mL/min,
=50mg/L, pH=6.5).

cadmium concentration to 50 mg/L gave an extended breakthrough curve, indicating
that a higher volume of the solution could be treated. This was due to the fact that a
lower concentration gradient caused a slower transport due to a decrease in the
diffusion coefficient or mass transfer coefficient.
The effect of initial cadmium concentration onto alumina are shown in Fig. 14. It
could be seen that the percent of cadmium removal decreased with the increase in
initial concentration to 100 mg/L. This means that the amount of cadmium sorbed per
unit mass of sorbent increased with the increase in initial concentration to 50 mg/L.
This plateau represents saturation of the active sites available on alumina samples for
interaction with contaminants, indicating that less favorable sites became involved in
the process with the increase in concentration.
5. REFERENCES
[1] Ahmed A., Farah Q., 2014, "Removal of Nickel and Cadmium Ions from
Wastewater by Sorptive Flotation: Single and Binary systems", College of
Engineering-University of Baghdad, Journal of Engineering, Number 11 Volume
20.
[2] Imran A., 2011, "New Generation Adsorbents for Water Treatment", Department
of Chemistry, Jamia Millia Islamia (Central University), New Delhi-110025,
India.
[3] Jenan A., Asawer A., Ramzi H., Abbas H., 2014, "Study the Feasibility of
Alumina for the Adsorption of Metal Ions from Water ", Chemical Engineering
Department, College of Engineering, University of Baghdad, Baghdad, Iraqi
Journal of Chemical and Petroleum Engineering, Vol.15 No.3, 37-50, ISSN:
1997-4884.
[4] Jie L., Junfeng L., Xingzhong Y., Haoran D., Guangming Z., Haipeng W., Hou
W., Jiayu L., Shanshan H., Shuqu Z., Zhigang Y., Xiaoxiao H., Yan H., 2015,
"Facile synthesis of alumina-decorated multi-walled carbon nanotubes for
simultaneous adsorption of cadmium ion and trichloroethylene", College of
Environmental Science and Engineering, Hunan University, Changsha, China,
Chemical Engineering Journal 273 -101–110.
Figure 13 Experimental
breakthrough curves for adsorption
of binary at different concentration
(bed depth of alumina=10cm, Q=8
mL/min, pH=6.5).
efficiency of binary (Q=8 mL/min,
=10cm, pH=6.5).

[5] Murat A., Abdulkerim K., Orhan A., Yuda Y., 2006, "Removal of silver (I) from
aqueous solutions with clinoptilolite", Faculty of Engineering and Natural
Sciences, Sabancı University, Tuzla, 34956 Istanbul, Turkey.
[6] Praful Kakde and S N Paul Effect of Alumina Nanoparticle Addition on the
Mechanical and Wear Behaviour of Reinforced Acrylonitrile Butadiene Styrene
Polymer. International Journal of Advanced Research in Engineering and
Technology, 5(6), 2014, pp. 185 - 192.
[7] Relyea, 1982, "Theoretical and experimental considerations for the use of the
column method for determining retardation factors", Radioactive Waste
Management and the Nuclear Fuel Cycle 3, No. 2: 151–166.
[8] Sharma Y.C., V. Srivastava, V.K. Singh, S.N. Kaul and C.H. Weng, 2008,
"Nano-adsorbents for the removal of metallic pollutants from water and
wastewater", MIT College of Engineering, Kothrud, Pune, India.
[9] U.S. Public Health Service, 1990, "Toxicological Profile for silver ", Agency for
Toxic Substances and Disease Registry.
[10] Prof. Dr. Alaa Hussein Al-Fatlawi and Mena Muwafaq Neamah, Column Study
of The Adsorption of Phosphate by Using Drinking Water Treatment Sludge and
Red Mud. International Journal of Civil Engineering and Technology, 6(9),
2015, pp. 08-19.

REMOVAL OF CADMIUM CD (II) AND SILVER AG (I) FROM AQUEOUS SOLUTIONS BY NANO ACTIVATED ALUMINA PART II: CONTINUOUS FLOW EXPERIMENTS

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