Available online at http://ijcpe.uobaghdad.edu.iq and www.iasj.net 

Iraqi Journal of Chemical and Petroleum 
 Engineering  

Vol.20 No.3 (September 2019) 1 – 6 
EISSN: 2618-0707, PISSN: 1997-4884 

 

Corresponding Authors:  Name:
 
 Hala N. Abdulkareem,  Email: halan1988@yahoo.com , Name: Abeer I. Alwared, Email: 

dr.Abeer.wared@coeng.uobadghdad.edu.iq  
IJCPE is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. 

 

Performance of Immobilized Chlorella Algae for Removing pb(II) 

Ions from Aqueous Solution 

 
Hala N. Abdulkareem

 
and  Abeer I. Alwared 

 
Environmental Eng. Department, University of Baghdad 

 

Abstract 

 
   This study aims to show the  effectiveness of immobilization of Chlorella green algae biomass in the form of bead for the removal 

of lead ions from synthetic polluted water  at various operational parameters such as pH (2–6), biosorbent dosage (0.5–20 g/L) and 

initial concentration (10–100 mg/L). More than 90 % removal efficiency was achieved. FTIR and SEM-EDX analysis of the 

biosorbent before and after sorption show differences in the functional groups on the adsorbent surface. Langmuir and Freundlich 

equilibrium isotherm, pseudo-first-order and pseudo-second-order kinetic models were applied to the experimental and results and 

show good conformity with Langmuir isotherm model and pseudo-second-order kinetic model with correlation coefficient (0.994) 

and (0.998) respectively. 
       
Keywords: Lead ions, Chlorella green algae, Biosorption, Immobilization, Isotherm, and kinetic models.  
 
Received on 17/02/2019-, Accepted on 03/04-/2019, published on 30/09/1029 
 

https://doi.org/10.31699/IJCPE.2019.3.1  

 
1- Introduction 
 

   Toxic metal ions removal from wastewater is important 

in economic and environmental problems. Heavy metals 

and other metal ions contaminants are aqueous waste 

streams of many industries, such as mining and tanneries.  

   Some metals associated or released with these activities 

are Pb, Hg, Cr, and Cd. Some of these metals accumulate 

in living organisms and cause various diseases and 

disorders. Metals such as lead, mercury, arsenic, zinc, 

copper, and cadmium are highly toxic when adsorbed into 

the body causing accumulative poisoning, brain damage, 

cancer, and so forth.  

   Lead is an enzyme inhibitor and general metabolic 

poison that has the ability to replace calcium in the bone 

to form sites for long-term release, hence, the need to 

remove these toxic metals from water and wastewater is a 

point of interest. Lead permissible limit in wastewater as 

set by the Environment Protection Agency is 0.1 mg/L, 

and in drinking water, it is 0.05 mg/L ‎[1].  

   The conventional methods for heavy metals removal 

include chemical precipitation, electrodialysis, ion 

exchange, membrane separations, reverse osmosis, and 

solvent extraction which maybe not effective at low metal 

concentration and costly so the search for new, effective 

and economical technique for metal removal from 

wastewaters has directed attention to biosorption that uses 

various biological materials at little or no cost to remove 

heavy metal ‎[2].  

   Biosorption, describes the removal of heavy metals 

from aqueous solution by using nonliving biomass.  

   Biosorption is favorable as an alternative to 

conventional methods of metal recovery from solutions 

due to availability and low-cost raw material.  

Freely suspended biomass may have better contact with 

adsorbate during the removal process, suspended biomass 

maybe not the practical form to the direct use because of 

many problems, and one of them is the separation of the 

biomass from the treated water. Immobilization suggested 

as an easy handling of the biomass, enhance its stability, 

reusability, mechanical strength, and the ease of 

separation and regeneration ‎[1]. 

   This study aims to investigate the feasibility of using 

immobilized chlorella biomass for the removal of lead 

ions from aqueous solutions. The effects of different 

experimental parameters, such as initial pH, removal time, 

dose of sorbent and initial lead concentration on the 

sorption capacity were studied. 

 

2- Materials and Methods 
 

2.1. Sorbents and Contaminant 

 

   The algae used in the experiment were purchased from 

the buy algae web site (https://www.buyalgae.com/) as a 

pure dried sample of chlorella in a powdered form. The 

selected amount of the algal biomass mixed with 2% 

sodium alginate solution before that the algae wetted with 

a specific amount of distilled water, the mixture then 

dropped in a 5 % CaCl2 solution left there in the solution 

for 2 hr to full solidification. The formed beads of 

diameter 4 ± 0.1 mm were washed with distilled water 

before using in the experiments.  

https://doi.org/10.31699/IJCPE.2019.3.1


H. N. Abdulkareem
 
and  A. I. Alwared / Iraqi Journal of Chemical and Petroleum Engineering 20,3 (2019) 1 - 6 

 

 

2 
 

   Lead ions stock solution was prepared by dissolving the 

known amount of Pb(NO3)2 powder, in a known volume 

of distilled water different concentrations were prepared 

by dilution from the stock solution. 

   Then the pH of the aqueous solution was controlled 

using 0.1 M HCl and 0.1 M NaOH to the required value. 

Fig. 1 shows the algae before and after immobilization. 

 

 
(a) 

 
(b) 

Fig. 1. Chlorella algae (a) before (b) after immobilization 

 

 

 

 

 

2.3. Experimental Work 

 

   250 mL conical-flasks were used in the experiments, 

each flask washed with HNO3 diluted solution then 

washed with distilled water before starting the 

experiments. The flasks filled with 100 mL of Pb(II) ion 

solution and selected sorbent amount. In order to do the 

experimental work, several parameters were studied to 

examine their effect on the removal process such as pH, 

contact time, initial metal concentration, agitation speed, 

and sorbent dose. The agitation of flasks in the form of 

shaking was done for a defined time using orbital shaker 

(Edmund Buhler SM25, German). (10 mL) volume of the 

contaminated solution collected from each flask, without 

the need for further filtration, solutions analyzed to 

measure the remaining metal concentration. The 

measurements of metal ions carried out using atomic 

absorption spectrophotometer (AAS, Sens AA, 

Australian) Duplicate measurements of the samples were 

done for more accurate results. The removal efficiency of 

contaminants calculated from eq. (1): 

 

  
(     )

  
                                                                                    (1) 

 

Where Co and Ce are the initial and equilibrium lead 

concentrations (mg/L).  

   The amount of sorbate adsorbed on the sorbent material, 

qe (mg/g), can be determined by: 

 

   (     )
 

 
                                                                                  (2) 

 

Where m is the amount of sorbent on the flask (g) and V 

is the volume of contaminant solution (L) 

 

3- Results and discussion 
 

3.1. Characteristic of Immobilized Beads 

 

a. FTIR Analysis 
 

   Fourier Transform Infrared (FTIR) spectroscopy was 

used to identify the functional groups present in the 

biosorbent. The biomass samples were examined using 

the FTIR spectrometer (model: FT/IR-4100typeA) within 

range of 400-4000 cm
-1

.  

   Analysis as can be seen in Fig. 2 indicated the broad 

and strong bands at 3500 to 3000cm
-1

which can be 

attributed to the overlapping of –OH and –NH stretching. 

The band at 2900 attributed to the C-H, at 1620 to 

1590cm
-1 

due to the C=O, and amide groups, at 1400 cm
-1

 

N-H bending in the amine groups, and at 1025 cm
-1

 to CO 

stretching of alcohols and carboxylic acids.  

   As compared to simple biosorbent, biosorbent loaded 

with chromium (VI) the broadening of -OH peak at 3440 

cm
-1

 and carbonyl group peak at 1628 cm
-1

 was observed. 

This indicates the involvement of hydroxyl and carbonyl 

groups in the biosorption of metal ions ‎[3]. 

 

 

 



H. N. Abdulkareem
 
and  A. I. Alwared / Iraqi Journal of Chemical and Petroleum Engineering 20,3 (2019) 1 - 6 

 

 

3 
 

 
Fig. 2. FTIR of immobilized chlorella black before lead 

removal red after lead removal 

 

b. SEM-EDX Results 
 

   SEM-EDX result of chlorella algae bead before and 

after pb (II) ion deposit on the surface of beads as shown 

in Fig.3. The EDX also shows the composition of the 

surface of the alginate bead before and after sorption 

which indicate that change in light metal on alginate 

surface which support the theory of ion exchange during 

the removal process. 

 

 
(a) 

 

 
(b) 

 

 

 
(c) 

 

 
(d) 

 

Fig. 3. SEM-EDX analysis of immobilized chlorella algae 

A SEM before and B after lead removal C and D EDX 

before and after lead removal respectively 

 

3.2. Effect of Different Parameter 

 

a. pH of the solution 
 

   In the biosorption the initial pH of the solution is a very 

important parameter. The effect of this parameter was 

studied in a pH range, 2-6, and not exceeded 6 to avoid 

precipitation of heavy metal. Fig. 4 shows removal 

efficiency variation with the variation of pH value. At pH 

value 2, the removal efficiency was low due to solution 

protonation that lower lead ion passing and compete with 

it.  

   The removal efficiency starts to increase because 

functional groups such as carboxyl, phosphate, imidazole 

and amino groups, would be exposed due to 

deprotonation and carried negative charges, thus 

facilitating the biosorption of metal.  

 

 

 

500750100012501500175020002500300035004000

1/cm

40

50

60

70

80

90

100

%T

3
8

5
3

.9
4

3
7

3
1

.4
5

3
4

3
6

.3
3

2
9

2
8

.0
7

2
8

7
2

.1
3

2
1

8
5

.4
4

1
6

4
9

.2
1

1
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9

1
4

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1
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1
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.2
8

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4

6
4

6
.1

8

5
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.8

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.7
9

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.4
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1
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2

Smooth
Smooth 1



H. N. Abdulkareem
 
and  A. I. Alwared / Iraqi Journal of Chemical and Petroleum Engineering 20,3 (2019) 1 - 6 

 

 

4 
 

   At higher pH in basic conditions, the amount of OH- 

ions is increased in the solution, so metal ions react with it 

and precipitated as a metal hydroxide ‎[4], ‎[5]. 

 

 
Fig. 4. Effect of pH on removal process 

 

b. Sorbent Dose 

 

   Doses of (0.05, 0.2, 0.6, 1 and, 2 gm) were used in 

different flasks with the same conditions to study their 

effect on the sorption process and the results are 

represented in Fig.5 .The uptake capacity of the sorbent 

increased when decreasing biosorbent dosage because of 

interference between the binding sites on the surface, 

while increasing sorbent dose more than 1 gm/100,  ml 

the quantity of metal ions uptake decreases because of the 

sites on the biosorbent surface remain unsaturated during 

the removal process ‎[6], ‎[7], ‎[8]. 

 

 
Fig. 5. effect of dose on the removal process 

 

c. Sorption Time 
 

   Fig. 6 presents the removal efficiency of pb(II) ions 

during different time periods. It can be seen from this 

figure that biosorption rate was increased rapidly at the 

initial stage of time from 0 to 30 and thereafter become 

nearly constant at around 90% then gradually the 

biosorption retarded due to the decrease in biosorption 

sites on the sorbent surface ‎[9]. 

 

 
Fig. 6. Effect contact time on the removal process 

 

d. Initial lead Concentration 

 

   With increasing initial metal ions concentration the 

biosorption capacity also increased, high metal ions 

concentration provides a driving force that overcomes the 

resistance of the mass transfer layer between the beads 

and the metal in the solution. Also, the biosorption 

process enhanced because of the number of collisions 

between metal ions and biosorbent increases when 

increasing initial metal concentration. The reduction in 

metal removal efficiency might be attributed to the 

insufficient binding sites for adsorption associated with 

increasing metal concentration, and that the binding was 

saturated ‎[9],  ‎[10] as showed in Fig. 7 

 

 
Fig. 7. Effect of initial concentration on the removal 

efficiency of lead ions 

 

4- Isotherm and kinetic studies 
 

4.1. Isotherm 

 

   Desorption isotherm which is the equilibrium 

relationship at a given temperature were studied by. 

Langmuir, and Freundlich, Equations are used widely to 

describe sorption process. The importance of these 

models is finding the relationship between the sorbed 

amount of sorbate onto adsorbent (qe) and the 

concentration of sorbate remaining at equilibrium (Ce) in 

the aqueous solution ‎[11].   

 

0

20

40

60

80

100

0 2 4 6 8

%
 R

e
m

o
v

a
l 

 

pH 

0
10
20
30
40
50
60
70
80
90

100

0 1 2 3

%
 R

e
m

o
v

a
l 

 

Dose (gm) 

0

20

40

60

80

100

0 50 100 150 200

%
 R

e
m

o
v

a
l 

 

Time (min) 



H. N. Abdulkareem
 
and  A. I. Alwared / Iraqi Journal of Chemical and Petroleum Engineering 20,3 (2019) 1 - 6 

 

 

5 
 

a. Langmuir model 

 

This model, suggests that sorption process occurs 

uniformly on the active sites of the sorbent at the surface, 

and once a sorbate occupies a site, no further sorption can 

take place at that site, Langmuir model can be represented 

as ‎[12] 

 

   
       

     
                                                                                          (3) 

 

Where b and qmax, are the Langmuir constants, represent 

the saturated monolayer sorption capacity (mg/g), and the 

sorption equilibrium constant, and refer to the slope of the 

model. 

 

b. Freundlich model 

 

      
   

                                                                                            (4) 

 

   Is an empirical Model which suggests that sorption 

based on multilayer heterogeneous surface given by eq. 

(4) where 1/n is the intensity of sorption and k is a 

constant related to the maximum adsorption 

capacity ‎[13],  ‎[14]. 

 

4.2. Sorption Kinetics 

 

   The transformation rate of pollutant from aqueous 

solution to solid phase [6] and the kinetic in the present 

study were represented using two models: 

 

a. Pseudo-first order kinetic model 

 

     (    
    )                                                                              (5) 

 

   The qe and qt are the equilibrium and the amount of 

sorbate removed from the solution at time t respectively 

in (mg/g), and k1 is the pseudo first order rate constant 

(1/min) [15] 

 

b. Pseudo-second order kinetic model 
 

This model can be described as: 

 

    
 

(
 

    
  

 

  
)
                                                                                        (6) 

 

Where k2 is the pseudo second order rate constant (g/mg 

min) [16]. 

   From the experimental results the relationships between 

the sored quantity (qe, mg/g) and the equilibrium 

concentration (Ce) for Pb(II) ions in the solution. The 

values of the calculated parameters and the correlation 

coefficients (R2) are listed in Table 1 and the models are 

represented in Fig. 8 from the table the high correlation 

coefficients were found for the Langmuir model which 

suggested that homogeneous surface of the sorbent with 

all the sorption sites assumed to have an equal sorbate 

affinity and the sorption occurs uniformly on sorbent 

active sites ‎[15].  

   The Pseudo-second order model gave a better fit based 

on the R2 values. This indicating that sorption process 

occurred was chemisorption ‎[16]. 
 

Table 1. Constants of isotherm models for sorption of pb 

(II) ion onto alginate bead 
Isotherm 

model 
Parameter value 

Kinetic 

model 
Parameter value 

Langmuir 

     (mg/g) 30.06 

Pseudo-

first order 

qe (mg/g) 18.42 

b (L/mg) 0.245 k1 (min
−1

) 0.346 

R
2
 0.994 R

2
 0.74 

Freundlich 

 

 (     )( 

   )  
7.757 

Pseudo-

second 

order 

qe (mg/g) 
18.table 

199 

  2.762 k2 (g/mg min) 0.045 

R
2
 0.873 R

2
 0.998 

 

 
Fig. 8. Isotherms and kinetic models for sorption pb (II) 

ions onto alginate bead 

 

Conclusions 

 

   A non-conventional bio-carrier of immobilized 

Chlorella green algal is a good way for lead ions removal 

from simulated wastewater without losing their ability to 

adsorb. Different parameters studied and the isotherm 

shows that. Langmuir isotherm model gives the best fit 

model for lead ions removal than Freundlich models with 

the adsorption capacity. The monolayer adsorption 

capacity of pb(II) ions calculated from the Langmuir 

model was found 30.06mg/g, Pseudo-second order kinetic 

model gives good fitting to present the process of removal 

which indicates according to the model controlling 

mechanism in the removal process is the chemisorption 

process. 

 

References 

 

[1] Surisetty, V. R, Kozinski, J., and Nageswara, L.R., 
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 كفاءة الطحالب المقيدة في ازالة الرصاص من المحاليل المائية
 

 عبير الوردهاله نصير و 
 

 جامعة بغداد, قسم اليندسة البيئية

 الخالصة
تيدف ىذه الدراسة إلى إظيار فعالية تجميد الكتمة الحيوية )الكموريال المجففة الخضراء( في شكل حبة كروية 
الشكل إلزالة أيونات الرصاص من المحاليل المائية المحضرة مختبريا في معايير تشغيمية مختمفة مثل الرقم 

تم  .مجم / لتر  100 - 10والتركيز األولي ) (g / L (20-0.5) ( ، الجرعة البيولوجية6–2الييدروجيني )
وتحميل المجيرية واالشعة  FTIR ٪  ومن خالل عمل تحميل  00الحصول عمى كفاءة إزالة بمغت أكثر من 

ظير الفرق في المجموعات لكرات االلجنيت المقيدة فييا الطحالب قبل وبعد االمتصاص  SEM-EDXالسينية 
تم تطبيق موديالت  الوظيفية عمى سطح المادة المازة نتيجة التبادل االيوني الحاصل خالل عممية االزالة.  كما

( بمعامل الرتباط  Langmuir( وكان اكثرىا انطباقا مع النتائج موديل )Freundlich و  Langmuirالتوازن )
R2= (0.994)  ( والموديالت الحركيةpseudo-first-order  و pseudo-second-order كان اكثرىا )

 R2 = (0.998).      ( بمعامل ارتباطpseudo-second-orderتماشيا مع النتائج موديل )
 

 ، موديالت رياضية وحركية : تقييد، المعادن الثقيمة، طحالب الكموريال الميتو، االمتزاز الحيويدالةلكممات الا

https://www.academia.edu/36131792/Application_of_immobilized_banana_peels_Musa_paradisiaca_L._into_calcium_alginate_beads_for_removal_of_chromium_VI_from_aqueous_solution
https://www.academia.edu/36131792/Application_of_immobilized_banana_peels_Musa_paradisiaca_L._into_calcium_alginate_beads_for_removal_of_chromium_VI_from_aqueous_solution
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https://www.ncbi.nlm.nih.gov/pubmed/10194398
https://www.ncbi.nlm.nih.gov/pubmed/10194398
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