article chicken feather as sequestrant for lead ions in

Copyright © 2014 by Modern Scientific Press Company, Florida, USA

International Journal of Modern Analytical and Separation Sciences, 2014, 3(1): 51-66

International Journal of Modern Analytical and Separation Science

Journal homepage: www.ModernScientificPress.com/Journals/IJMAS.aspx

ISSN: 2167-7778

Florida, USA

Article

Chicken Feather as Sequestrant for Lead Ions in Aqueous

Solution

Egwuatu C. I.*, Umedum, N. L., Anarado C. J. O., A. N. Eboatu

Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, P. M. B. 5025 Awka, Anambra

State, South Eastern Nigeria

*Author to whom correspondence should be addressed to; Email: [email protected]; Tel.:

+2348063620152

Article history: Received 7 July 2014, Received in revised form 5 October 2014, Accepted 15 October

2014, Published 22 October 2014.

Abstract: Chicken feather was investigated as a possible biosorbent for the removal of lead

ions in aqueous solutions. The effects of contact time, pH, concentration and temperature

were investigated. Results showed that equilibrium data were best described by the Langmuir

isotherm with R2 value of 0.9782. Maximum adsorption capacity was 1.149954mg/g and

0.951134mg/g from Langmuir and Dubinin-Radushkevic respectively. Adsorption was

best described by the second order kinetic model with R2 value of 0.9687. Thermodynamic

studies showed that adsorption was endothermic, spontaneous with increased degree of

randomness. Optimum sorption was also observed at pH 4.

Keywords: Metal, Adsorption, Isotherm, Thermodynamics, FTIR.

1. Introduction

Lead is one of the most common heavy metals that have drawn the attention of environmentalists

because of its toxic nature. Others include arsenic, mercury, cadmium etc. It is essentially of no nutritive

importance to human life. It however bioaccumulates in living organs up to a level it becomes

detrimental to the health of that organism. It can damage nervous connections (especially in young

children) and cause brain disorders. Lead poisoning typically results from ingestion of food or water

contaminated with lead; but may also occur after accidental ingestion of contaminated soil, dust, or lead

mailto:[email protected]

Int. J. Modern Anal. Sep. Sci. 2014, 3(1): 51-66


52

based paint[ http://en.wikipedia.org/wiki/Lead#cite_note-44] . Lead that is emitted into the atmosphere

can be inhaled, or it can be ingested after it settles out of the air. It is rapidly absorbed into the

bloodstream and is believed to have adverse effects on the cardiovascular system, kidneys, and the

immune system[Bergeson, 2008]. In pregnant women, high levels of exposure to lead may cause

miscarriage. Chronic, high-level exposure have been shown to reduce fertility in males[Golub, 2005].

More recently cases of lead poisoning leading to deaths of people and animals were reported in Zamfara

State, Nigeria[Sadeeq, 2010 and Isah, 2010]. Sources of lead pollution include exhaust fumes from

automobiles, waste water from battery manufacturing, metallurgical, metal-finishing and chemical

industries. The need therefore arises for its immobilization to prevent it from reaching mankind through

the food chain. Searching for low-cost alternative methods for metal removal has become a challenge

worldwide [AjayKumar et al, 2009]. Methods exist for the removal of toxic metal ions from aqueous

solutions, such as ion exchange, chemical precipitation, and adsorption, etc.[Sari and Tuzen, 2009; F

Krika et al, 2012]. Among these methods, adsorption is by far the most versatile and widely used

process[Ghodbane et al, 2008; Vimala and Das, 2009; Pehlivan et al, 2008].

Chicken feathers are one of the epidermal growths that form the distinctive outer covering, or

plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex

integumentary structures found in vertebrates and indeed a premier example of a complex evolutionary

novelty[Prom, R.O, 2002]. The poultry industry produces a large amount of feathers as waste, and like

other forms of keratin, these are slow in their decomposition. Feathers have a number of utilitarian,

cultural and religious uses. They are both soft and excellent at trapping heat; thus, they are sometimes

used in high-class bedding, especially pillows, blankets, and mattresses. They are also used as filling for

winter clothing, such as quilted coats and sleeping bags; goose and eider down have great loft, the ability

to expand from a compressed, stored state to trap large amounts of compartmentalized, insulating

air.[Bosner R.H., 2004]. Bird feathers have long been used for fletching arrows. Colorful feathers such

as those belonging to pheasants have been used to decorate fishing lures. Feathers of large birds (most

often geese) have been and are used to make quill pens.

The present study investigated the sorption capacity, kinetics, equilibrium and thermodynamics

studies of lead adsorption onto chicken feathers.

2. Materials and Methods

2.1. Materials

Chicken feathers were obtained from the poultry farm section of Eke Awka Market in Anambra

State of Eastern Nigeria. These were washed with distilled water and sun-dried for 24hrs. They were

http://en.wikipedia.org/wiki/Lead#cite_note-44



http://en.wikipedia.org/wiki/Epidermis_(zoology)

http://en.wikipedia.org/wiki/Plumage

http://en.wikipedia.org/wiki/Bird

http://en.wikipedia.org/wiki/Integumentary

http://en.wikipedia.org/wiki/Heat

http://en.wikipedia.org/wiki/Bedding

http://en.wikipedia.org/wiki/Pillow

http://en.wikipedia.org/wiki/Blanket

http://en.wikipedia.org/wiki/Mattress

http://en.wikipedia.org/wiki/Clothing

http://en.wikipedia.org/wiki/Coat_(clothing)

http://en.wikipedia.org/wiki/Sleeping_bag

http://en.wikipedia.org/wiki/Goose

http://en.wikipedia.org/wiki/Eider

http://en.wikipedia.org/wiki/Feather#cite_note-37

http://en.wikipedia.org/wiki/Fletching

http://en.wikipedia.org/wiki/Arrow_(weapon)

http://en.wikipedia.org/wiki/Pheasant

http://en.wikipedia.org/wiki/Fishing_lure

http://en.wikipedia.org/wiki/Goose

http://en.wikipedia.org/wiki/Quill



53

later ground to powder in a mill and sieved using a Particle Size Distribution analyzer (Model 117.08,

MALVERN instruments, USA), to obtain particle size of 350µm prior to use. For all the adsorption

experiments, 3g of ground chicken feathers sample was used in each case.

All the chemicals used in the study were of analytical grade and obtained from E. Merck Limited,

Mumbai, India.

2.2. Characterization

Characterization of the adsorbents was carried out by FT-IR studies. FT-IR (FTIR RX-1,

PerkinElmer, USA) spectrometer was employed to determine the functional groups in chicken feathers

responsible for metal adsorption. Fourier Transform Infrared Spectroscopic (FT-IR) studies identify the

functional groups in the 4000–400 nm range. Atomic adsorption spectrophotometer(VARIAN

SPECTRAAA55) was used for the determination of Pb2+ content in standard and used solutions. The

pH of the solutions was measured with a 5500 EUTECH pH Meter using solid electrode calibrated with

standard buffer solutions.

2.3. Preparation of Pb2+ Standard

A stock solution containing 1000 mg/l of standard Pb2+ was prepared by dissolving 1.598g of

Pb(NO3)2 in 200ml of deionized water. The solution was then made up to 1000ml. Batch adsorption

experiments were performed after proper dilution of the stock solution.

2.4. pH Studies Experiment

The uptake of Pb2+ as a function of H+ ion concentration was determined in the pH range of 2–

8. The adjustment of initial pH of solutions was carried out by adding required amount of dilute 0.1 M

NaOH and 0.1 M HCl solutions.

2.5. Equilibrium Studies Experiment

100ml of varying concentrations(10mg/l, 20mg/l, 30mg/l, 40mg/l, and 50mg/l) of the Pb2+

solution was introduced into conical flasks containing the adsorbent. These were stirred mechanically

and allowed to stand for 1hr while other parameters such as temperature, pH and time were kept constant.

Samples were drawn out from the mixture and analyzed using AAS. The data obtained from

experiment were fitted into three different isotherm models namely; Langmuir, Freundlich, and Dubnin-



54

Radushkevich models. The correlation coefficients R2 was used to determine the best fit isotherm

model.

2.5.1. The Langmuir isotherm model

Langmuir isotherm which applies to equilibrium monolayer adsorption onto a surface with a

finite number of identical sites[Langmuir, 1918] is represented by the following linearized equation:

1

q=

1

qmax

kLCe

+1

qmax

(2a)

where q is the amount of adsorbed metal in mg/g, qmax is the maximum sorption capacity in mg/g, KL is

the Langmuir constant. A plot of 1/q v 1/Ce allows for the determination of qmax and kL.

The essential characteristics and the feasibility of the Langmuir isotherm is expressed in terms

of a dimensionless constant known as separation factor or equilibrium parameter RL, which is defined

as,

RL =1

1 + bC0

(2b)

The RLvalue indicates the shape of the isotherm as follows:

Table 1. RLvalues and significance

RL value Type of isotherm

RL> 1 Unfavorable

RL = 1 Linear

0< RL< 1 Favorable

RL = 0 Irreversible

2.5.2. The Freundlich isotherm model

The Freundlich isotherm is empirical and is best suited for adsorption on heterogeneous

surfaces[Freundlich, 2006]. The equation in linearized form is given as:

lnq = lnkF +1

nlnCe (3)

Where KF and n are Freundlich constants. A plot of lnq vs. lnC is used to determine kF and n.

2.5.3. Temkin isotherm model

The equation for the above model is given as;



55

q =RT

blnkT +

RT

bln C (4)

q is amount adsorbed per gram of the adsorbent (mg/g), C is concentration of metal ion after certain

period of time (mg/L), KT and b are Temkin constants, R is universal gas constant (8.314J/K/mol) and T

is temperature in Kelvin.

A plot of q vs. lnC will give a slope and an intercept from which b and kT are evaluated

(Mahamadi & Nharingo, 2010; Vijayaraghavan, et al., 2006).

2.5.4. Dubinin–Radushkevich isotherm(D-R) model

This isotherm assumes that the characteristics of the sorption curve are related to the porosity of

the biosorbents (Abdelwahab et al., 2007). This model was also chosen to evaluate the mean energy of

sorption. It is represented in the linear form by the equation (Igwe & Abia, 2007).

lnq = lnqm − βε2 (5)

Where

ε = RTln (1 +1

Ce) (6)

where q is amount adsorbed per gram of the adsorbent (mg/g), qm is equilibrium adsorption capacity

(mg/g) using model, β is Polanyi potential, ε is activity coefficient, Ce is concentration in mg/l of metal

ion in solution at equilibrium, R is universal gas constant (8.314J/K/mol) and T is temperature in Kelvin.

The values of β and qm are evaluated from the slope and intercept of the graph of lnq versus ε2.

The mean energy of sorption E (kJ mol−1) is calculated from the relation [Horsfall Jr. et al., (2004)]

E =1

√2β (7)

2.6. Kinetic Studies Experiment

Batch kinetic studies were performed using a mixture of 200ml of 40mg/l of Pb2+ solution and

the adsorbent. Other parameters were kept constant while samples were drawn at time intervals of 5,

10, 30, 60, 90 and 120min and analyzed. The kinetics of Pb2+ adsorption on chicken feathers was studied

using pseudo-first-order [Lagergren, 1898], pseudo-second-order [Ho et al, 2000] and intra-particle

diffusion [Weber and Morris, 1963] models. The conformity between experimental and theoretical

values was expressed by the correlation coefficient R2, chi-square χ2 and theoretical qe. The equation

for evaluating the χ2 is given as

χ2 = ∑(qexp − qth)

2

qth

2.6.1. Lagergren model

The pseudo-first-order kinetic model was proposed by Lagergren. Its integral and linearized



56

forms are expressed as follows:

qt

= qe(1 − e−k1t) (8𝑎)

Ln(qe(expt) − qt) = Lnqe(theo)– k1t (8b)

Where qe(expt) and qe(theo) are the experimental and theoretical equilibrium adsorption and qt is

experimental amount of metal ion adsorbed (mg/g of adsorbent) at any time t(min)

2.6.2. Pseudo-second-order model

The kinetics of adsorption process was also described by the pseudo-second-order rate equation

expressed by [Ho and McKay, 1999] as

dq

dt= k2 (q

e(theo)− q

𝑡)

2

(9a)

Separating the variables in Equation 9a gives;

dq

(qe(theo)

− q𝑡)

2 = k2 dt (9b)

Integrating Equation 9b for the boundary conditions t0 to tt and q0 and qe(theo)

gives

t

q𝑡

=1

k2qe(theo)

2+

t

qe(theo)

(9c)

A plot of t/qt versus t gives a slope and an intercept, from which the values of qe (theo) in mg/g and

the pseudo- second order rate constant k2 in gmg-1min-1 can be calculated respectively.

At time 0, the initial rate denoted as h0 is given as

h0 = k2C02 (9d)

where C0 is the initial concentration before adsorption. h0 is then evaluated from already determined k2

2.6.3. Intra-particle diffusion model

The intra-particle diffusion model is based on the theory proposed by Weber and Morris.

According to this theory,

q𝑡

= kidt0.5 + C (10)

Where qt is adsorption capacity at time t, kid is intra-particle diffusion rate constant in mg/g/min1/2.

This model shows whether the rate determining step is by the boundary film diffusion or by intra-particle

diffusion.

2.7. Thermodynamic Studies

With all other parameter kept constant, adsorption experiments were carried out at temperatures



57

of 50, 70 and 90oC in a water bath. Thermodynamic parameters such as Gibb’s free energy changes (∆G),

enthalpy change(∆H), and entropy change(∆S) were determined. Gibb’s free energy of adsorption was

computed from the equation[Han et al, 2010]:

∆G = −RTlnKC (11)

where ∆G is standard free energy change, R is universal gas constant(8.314 J/mol/ K), T is absolute

temperature in K, and KC is the equilibrium constant. The apparent equilibrium constant, KC, is defined

as [Han et al, 2010]:

Kc =q

C (12)

Where q is the concentration of adsorbed metal in mg/l, C is concentration in mg/l of Pb2+ solution after

adsorption. The values of ∆H and ∆S were be estimated from the relationships

∆G = ∆H − T∆S (13)

The amount of metal ion adsorbed per unit mass of the adsorbent was evaluated by using the

same following mass balance equation:

q =(Co − C)V

m (14)

Where q is the amount of adsorbed metal in mg/g, Co is concentration in mg/l of Pb2+ solution before

adsorption, C is concentration in mg/l of Pb2+ solution after adsorption, V is volume of solution in litre,

m is gram mass of adsorbent.

3. Results and Discussion

3.1. Characterization of the Adsorbents

Fig. 1(a) and (b) show the IR spectra of chicken feather before and after adsorption. The spectra

indicated a number of absorption peaks showing the complex nature of chicken feather. Absorbance

peaks and their corresponding intensities of the assigned functional groups are shown on table 2. The

functional group is one of the keys to understand the mechanism of metal binding on chicken

feather[Wang et al, 2008]. The peak at 3442.4 cm-1 which shifted to 3442.34cm-1 is assigned to -NH

group of collagen protein[Lurtwitayapont and Srisatit, 2010]. An intensity change of 22.8 was observed.

The peak at 1637.7 cm-1 assigned to C=O of amino acid of collagen protein increased to 1647.23 cm-1

with an intensity change of 7.953. The peak at 1045.62cm-1, which shifted to 1030.88cm-1 with an

intensity change of 12.221 is assigned to S=O group of cysteic acid. The presence of –NH, C=O, and

S=O groups on the surface of chicken feather makes it an active site for adsorption. The observed

changes in peaks and intensities are indications that interactions leading to adsorption actually occurred

between chicken and lead ions. Intensity changes at peaks were noticeably much higher than those of

other peaks, showing that more of the interactions and hence adsorption must have taken place in them.



58

Table 2. IR data of Chicken feather

Fig. 1a: IR spectrum of Chicken feather before adsorption

Fig. 1b: IR spectrum of Chicken feather after adsorption

3.2. Effect of pH

Fig 2 shows the effect of pH on adsorption of Pb2+. The pH for the optimum adsorption of Pb2+

on chicken feather is between 4 and 5. Adsorption was at its lowest at low pH. The effect of pH on Pb2+

Wavenumber(cm-1) ∆ in intensity Assigned functional groups

Pre-sorption Post-sorption

3379.1 3442.92 0.2286 OH, NH, groups

2919.04 2918.23 3.0066 C-C of alkyl group

1541.08 1541.31 7.953 C=O carbonyl group

1031.35 1030.88 12.221 PO43- band

870.73 871.27 19.029 CO32- band

561.79 562.71 10.315 Ca2+ band



59

removal can be explained considering the surface charge on the adsorbent material. At pH lower than 4

(low pH), the less adsorption was due to the high concentration of hydrogen ions. Hydrogen ions have

the highest mobility (36.25*108m2s-1V-1) of all the cations[Mortimer, 2008]; hence they would reach the

adsorption sites faster than other cations. It then follows that at low pH, the functional groups available

on the adsorbents surface are highly protonated resulting in repulsion between them and the positive

lead ion during uptake and hence less adsorption of the preferred cations. With increasing pH,

electrostatic repulsion decreases due to reduction of positive charge density of proton on the sorption

sites thus resulting in enhanced metal adsorption. Similar observations were reported by earlier

researchers[Arulkumara et al, 2012; Momčilović et al, 2011]. Further increase of pH above 6, led to a

decrease in percentage adsorption. At this stage, the hydroxyl ions concentration has increased

tremendously apparently leading to formation of complexes of the lead ion. This in effect resulted in

lower removal efficiency.

Fig. 2: Effect of pH on the removal of Pb2+

3.3. Effect of Time

The first five minutes saw the removal of 72% of lead ions from the solution. As time progressed,

less adsorption occurred as a result of saturation of available sorption sites with lead ion. Maximum

sorption of 80.5% occurred at 90min (Fig. 3).

0102030405060708090

100

0 2 4 6 8 10

% R

emo

val o

f P

b2

+

pH



60

Fig. 3: Effect of contact time on adsorption

3.4. Effect of Initial Concentration

Percentage adsorption increased from 92 at concentration of 10mg/l to 94 at 30mg/l. Increase in

concentration to 40 and 50mg/l gave sorption percentages almost the same with that at 30mg/l. At this

point almost all the available sorption sites had been occupied and equilibrium was being attained (Fig.4).

Fig. 4: Effect of initial metal ion concentration on adsorption

3.5. Equilibrium Studies

Table 3 shows the isotherm parameters of lead ion adsorption. Correlation coefficient R2

determines the fitness of models for experimental data. The higher the R2 value, the better the model.

7172737475767778798081

0 50 100 150

% r

em

ova

l of

lead

ion

s

Time (min)

91.5

92

92.5

93

93.5

94

94.5

95

0 20 40 60

% r

em

ova

l of

lead

ion

s

Concentration (mg/l)



61

Hence the fitness follows the trend: Freundlich > Langmuir > Temkin > D.R. Better fitness for

Freundlich model indicates a multilayer adsorption as a result of complexity of structure and composition

of the adsorbent. Better fitness for Langmuir model shows a monolayer adsorption indicating a

homogeneous distribution on the sorbent surface, with negligible interaction between adsorbed

molecules[Abasi, et al 2011]. Sorption intensity n, was less than 1. Dimensionless separation factor RL

obtained from the Langmuir model was less than 1. RL < 1 indicates favourable adsorption while RL > 1

adsorption indicates unfavourable adsorption. This has been observed in other works [Arulkumara et al,

2012; Momčilović et al, 2011]. Mean sorption energy Em was determined from Dubnin-Radushkevich

model. It tells whether sorption occurs through physiosorption, ion exchange or chemisorption process.

Em value below 8kJ/mol shows a physiosorption process; that between 8kJ/mol and 16kJ/mol indicates

ion exchange mechanism, while that above 16kJ/mol indicates a chemisorption process. [Momčilović,

et 2011]. Em for lead adsorption was above 40kJ/mol, indicating a chemisorption process.

Table 3: Isotherm parameters of lead ion adsorption

Fig. 5: Langmuir isotherm for lead ion adsorption Fig. 6: Freundlich isotherm for lead ion

adsorption

y = 2.9991x - 0.5074R² = 0.9968

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5

1/q

e(g/

mg)

1/Ce (l/mg)

y = 1.3259x + 6.0199R² = 0.9975

012345678

-0.5 0 0.5 1 1.5

ln q

e

ln Ce

Parameters Model

Freundlich Langmuir Temkin D-R

R2 0.9975 0.9967 0.9499 0.9458

Qm (mg/g) 1.95733 1.7287

N 0.7542

KF, KL and KT 0.411519 0.1705 1.5270

RL 0.369679

β 0.00006

E(kJ/mol) 91.287



62

Fig. 7: Temkin isotherm for lead ion adsorption Fig. 8: D-R isotherm for lead ion adsorption

3.6. Kinetic Studies

Figures 9 and 10 show the Largagren first order and pseudo – second order kinetic model plots

for lead ion adsorption. Tables 4 shows results for the kinetic parameters obtained using the models.

Experimental data fitted better into the pseudo-second order model, which gave higher R2 coefficient of

correlation values than the Lagergren first order kinetic model. The rate constants k and initial rates of

adsorption h0 were determined from the pseudo-second order kinetics. Theoretical qe obtained from the

second order model (0.9695mg.g), was closer to that obtained from experiment (0.9667mg/g) than that

obtained from first order model (0.0745mg/g). This suggests that the kinetics of lead adsorption onto

chicken feather is more suitably described by the second order model than the first order model. Chi-

square value was smaller in the second order kinetics; a further indication of adsorption being described

more suitably by the model than the first order.

Fig. 9: Langergren pseudo first order kinetic Fig. 10: Pseudo second order kinetic plot for

plot for lead ion adsorption plot for lead ion adsorption

y = 1.0035x + 0.4248R² = 0.9499

00.20.40.60.8

11.21.41.61.8

-0.5 0 0.5 1 1.5

qe

LnCe

-1.5

-1

-0.5

0

0.5

1

0 10000 20000 30000Lnq

e

ε2

-6

-5

-4

-3

-2

-1

0

0 50 100

ln(q

e-q

)

Time(min)

y = 1.0346x + 0.6785R² = 0.9999

0

20

40

60

80

100

120

140

0 50 100 150

t/q

(min

g/m

g)

Time(min)



63

Table 4: Kinetic parameters

Kinetic Model Pseudo1st order Pseudo 2nd order

R2 0.8882 0.9999

χ2 10.684 8.6*10-6

qe(exp) (mg/g) 0.9667

qe(theo)(mg/g) 0.0745 0.9696

Kad(g/mg/min) 0.0261 1.3119

3.7. Intra Particle Diffusion

Fig.11. represents the plot of qt versus t1/2 for intraparticle transport of lead ion. The values of kid,

and Ci obtained for the plots are 0.0088mg/g/min1/2 and 0.8771mg/g respectively. Values of Ci give an

idea about the thickness of boundary layer. The larger the intercept, the greater the boundary layer

effect[Li, et al, 2010]. If the Weber–Morris plot of qt versus 𝑡1

2 is linear and passes through the origin,

then the sorption process is controlled only by intra-particle diffusion. However, for lead adsorption onto

chicken feather, the data showed a multi-linear plot. This indicates that two or more steps were

involved in the sorption process. The first, sharp portion has a very high slope indicating a high rate of

sorption. This is attributed to the availability of active sorption sites at the initial stage. The second

section has a gradient lower than the first, because less lead ions were sorbed in a longer time than at

any other stage in the course adsorption. The second linear portion was the gradual adsorption stage

where intra-particle diffusion is the rate limiting step. Referring to Fig. 11, none of the linear lines passed

through the origin. This indicated that intraparticle diffusion was not the only rate-limiting step in the

sorption process[Wu et al, 2005].

Fig. 11: Weber-Morris plot for lead ion adsorption

y = 0.0088x + 0.8771R² = 0.7216

0.86

0.88

0.9

0.92

0.94

0.96

0.98

0 5 10 15

qt(

mg/

g)

t1/2(min1/2)



64

3.8. Thermodynamics

The van’t Hoff thermodynamic plot is shown in fig. 12. The thermodynamic parameters are given

in Table 5. Equilibrium constant Kc for the adsorption of Pb2+ on chicken feather, increased with increase

in temperature. Equilibrium in these cases shifted to the right resulting to increased adsorption.

Fig. 12: van't Hoff plot for adsorption of lead ion Fig. 13: Sticking probability plot for the adsorption

of lead ion

Table 5. Thermodynamic parameters

Parameters Temperature (K)

323 343 363

Equilibrium

constant

2.42 77 96.5

ΔG(KJ/mol) 186.13 192 197.88

ΔH(KJ) 91.237

ΔS(KJ/mol/K) -0.294

EA(KJ/mol) 82.919

∆G was found to be positive. The positive values of ∆G increased with the rise in temperature.

Positive values of ∆G indicate an endergonic process while negative values indicate an exergonic process.

Endergonic processes are non-spontaneous and less feasible while exergonic processes are spontaneous

and feasible [Nuhoglu and Malkoc, 2009].

Enthalpy change ∆H was positive. Positive values of ∆H indicate endothermicity while negative

values indicate exothermicity of adsorption process.

Entropy change ∆S was found to be negative which shows a decrease in degree of randomness[Nuhoglu

and Malkoc, 2009].

y = 10974x - 35.334R² = 0.8222

-6

-5

-4

-3

-2

-1

0

0.0027 0.0028 0.0029 0.003 0.0031 0.0032

Ln K

1/T(K-1 )

y = 9973.4x - 32.532R² = 0.826

-6

-5

-4

-3

-2

-1

0

0.0026 0.0028 0.003 0.0032

Ln(1

-θ)

1/T(K-1)



65

4. Conclusions

The present work investigated the potentials of chicken feathers as adsorbent for lead ions in

aqueous solutions as an alternative to costly adsorbents for the removal lead ions. The main advantages

include its availability, low cost (inexpensive), effectiveness and sorption capability. . This work shows

that the sorption process was affected by experimental conditions such as initial metal concentration, pH

and contact time. The pH for optimum sorption capacity is 4, sorption was endothermic, non-

spontaneous and less feasible. The second order kinetic model best described the sorption process which

was a chemisorption process

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article chicken feather as sequestrant for lead ions in

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