Environ Sci Pollut Res
DOI 10.1007/s11356-014-2974-9

ENVIRONMENTAL SCIENCE AND POLLUTION SENSING, MONITORING, MODELING AND REMEDIATION

Determination of lead(II) sorption capacity of hazelnut shell and activated carbon obtained from hazelnut shell activated with ZnCl2
Aziz Şencan & Mustafa Karaboyacı & Mehmet Kılıç

Received: 26 November 2013 / Accepted: 23 April 2014
# Springer-Verlag Berlin Heidelberg 2014

Abstract This study aimed to determine the Pb+2 adsorption capacities of hazelnut shell and activated carbon obtained from hazelnut shell. It also aimed to determine the effect of
ZnCl2 in the activation process. The hazelnut was pyrolyzed at
250 and 700 °C. For determining the capture speed of the adsorbents, the pseudo-first- and second-order kinetic studies were performed. The Freundlich and Langmuir isotherm models were used to determine adsorption equilibrium. The surface characterization of hazelnut shell and activated carbon was determined by Brunauer-Emmett-Teller (BET) analysis and FTIR spectrum. Pb+2 adsorption capacity of obtaining activated carbon was determined by ICP-OES analysis. The raw hazelnut shell’s BET surface area is 5.92 m2/g and the surface area of activated carbons which is pyrolyzed at 250 and 700 °C were determined (270.2 and 686.7 m2/g, respectively. The surface area of hazelnut shell, which pyrolyzed at
700 °C after being activated with ZnCl2, was determined to be
736.49 m2/g. Results show that physical adsorption process is dominant for the activated carbon pyrolysis at 700 °C but the chemical adsorption is dominant for the activated carbon pyrolysis at lower degrees and for raw hazelnut shell.

Keywords Activated carbon . Heavy metals . Lead(II) .
Kinetic . Isotherm . Hazelnut

Responsible editor: Philippe Garrigues
A. Şencan (*) : M. Karaboyacı
Department of Chemical Engineering, Süleyman Demirel University,
32260 Isparta, Turkey e-mail: azizsencan@sdu.edu.tr
M. Kılıç
Department of Environmental Engineering, Süleyman Demirel
University, Isparta, Turkey

Introduction
In the last two centuries, along with the mankind’s increasing industrial activities, elements and metals have been used intensively. Therefore, it can be said that the heavy metal contamination is also known for this period of time. Because of the increasing industrial development and the usage of metals for various activities of humanity, the environmental health is being seriously threatened. In terms of the environment, the metals especially like Cd, Cr, Pb, and Hg, because of their tendency to accumulate, have toxic and inhibition effects on living organisms (Forster and Wase 1997). Lead has acute and chronic effects on people. Especially, it damages the liver and the stomach in a short time and the brain and the kidney in a long period of time (Tchobannoglous et al. 2002). That is why developing new methods to control the environmental metal contamination and sending the heavy metals out of water supplies is needed.
One ion’s or molecule’s accumulation in another phase’s surface or its gaps is called adsorption. The material that accumulates is called as adsorbate, and the solid that adsorbs is called adsorbent. The liquid’s concentration in one solid’s micro cracks on its surface or pores is called as capillary adsorption. Adsorption phenomena depend on the materials which will be adsorbed, concentration in the solution. Beside this, the agents like temperature, pH, amount of adsorbent material, and mixing speed are the factors that effect the adsorption (Öztürk 2006).
Activated carbons are composites which have an outstanding inner surface area and volume of pores, and generally contain 87–97 % of carbon which has nonuniformed surface form. And the rest of it may contain hydrogen, oxygen, sulfur, and nitrogen. There may be useless materials in activated carbon at the rate of 5 to 20, but these materials should be abducted before usage. This process is called as decreasing the content of ash and in usage as adsorbents and this content

Environ Sci Pollut Res

should be taken in 0.1–0.2 % rate (Choma et al. 1987).
Activated carbons are used in various industries for different goals. Because it is a good adsorbent, it is used in wide areas like purification and refinement of the activated carbon gases, treatment of water and wastewater, carbon contribution to metal industry, making protective wearing in the defense industry, making bombs for silencing the explosive and electronic systems in weapon industry, and also in the health sector. As a result, the activated carbon that we use for different goals in our daily life is an indispensable material (Stoeckli and Kraehenbuehl 1984). Activated carbon in liquid or gas phase is used for the adsorption of various materials. It can adsorb a lot of different molecules in it is inner surface
(Jaroniec and Choma 1986). In an ideal formed activated carbon, the pores are almost 0.2–1.0 cm3/g. The surface area is 400–1,000 m2/g, and this value may be exceeded in production for special goals (Morgan and Fink 1997; Küçükgül
2004). Activated carbons are porous adsorbents and are used in several industrial processes. These carbons have often been used in the adsorption of pollutants present in gas or liquid phases in order to control environmental pollution, to remove organic compounds, or to remove toxic metallic species (AlOthman et al. 2012).
In this study, heavy metal adsorption capacities of the hazelnut shell’s and activated carbon’s, which is obtained from hazelnut shell, were firstly determined. And then, by making studies about increasing the activated carbon surface area, changes of the adsorption capacity were observed. For extension of the surface area, the thermal procedures are applied first. For this extension, chemical activation is achieved with zinc chloride and made some studies on determining the obtained sorbents’ potential of adsorbing the Pb+2 ion. In the literature, different activated carbons were obtained from different biomasses and the contaminant adsorption capacities were determined for the obtained activated carbons
(Imamoglu and Tekir 2008; Acharya et al. 2009; Demirbas et al. 2009). In addition to this, Pb+2 ion adsorption studies are not too much for the activated carbon derived from hazelnut shells. The dominant mechanism for the adsorption phenomena was determined by utilizing the FTIR spectra. Also, there is no study in the literature about the raw hazelnut shell and activated carbon, which was obtained from hazelnut shell, by different methods, surface bonds and the effects of carbonization on the surface bonds, and contribution of that bond in the adsorption process.

contaminations on them by being washed with a great amount of distilled water before being used in the study. Then they were incubated for 48 h in 60 °C. After the drying process, by being treated in the grinder robot; these hazelnut shell is minimized to the required piece size. For the homogenization of this piece sizes, the material which is sieved in a sieve that has biomass 300 and 180-μm pore size and stayed together between two sieves. Hazelnut shells were waited in desiccator before being used in the study and therefore, it is ensured that it is not effected by the moisture of the occasion in a possible way. All the chemicals used in the study are in analytical purity.
As a stock in a concentration of 1,000 mg/L, Pb+2 solution is arranged by using Pb(NO3)2, and the Pb+2 solution which is used in adsorption experiments is used by being diluted from this stock solution. For arranging the solution pH values to the desired value, the NaOH and HCl solutions which have molarities between 0.1 and 3.0 M are used. For determining the biomass, heavy metal adsorption capacity, the filtrate’s heavy metal concentration was determined by using spectrophotometric methods with ICP-OES device. For chemical activation process, 20 % of ZnCl2 solution was used.
Converting hazelnut shells to the activated carbon
Thermal activation
The hazelnut shell is transformed into activated carbon by pyrolysis in two different temperatures, 250 and 700 °C. The hazelnut shell which is brought for the certain piece size is placed into a steel capsule. For sending away the oxygen from the stage, a great deal of azote gas is given into the capsule.
The capsule, which is cooked immediately, was left in the ash oven for pyrolysis. During the activated carbon’s pyrolysis, three different rates of temperature enhancement are determined and provided the ash oven to be in 250 and 700 °C
(beginning temperature is 100 °C). These rates are 1, 2.5, and
5 °C/min. These rate, which gives the highest adsorption efficiency used in activated carbon’s Pb+2 adsorption in three speeds, is used in other studies. The obtained activated carbon samples, to remove the remnants from its structure, are washed with a great amount of distilled water and left to be dry in 60 °C in the oven for 24 h. The samples were especially left in the desiccator in the adsorption studies to avoid being effected by the stage moisture.
Chemical activation

Materials and method
Adsorbent
The hazelnut shell which is used in the study is obtained from
Ünye in Turkey. These hazelnut shells purified from

ZnCl2 is used to acquire activated carbon with chemical activation. At the beginning, raw hazelnut shell is poured into
ZnCl2 solution (20 %). The mixing rate is 60 g hazelnut shell/
1 l solution. This mixing is stirred for 24 h at room temperature and filtered through filter paper to remove its water then

Environ Sci Pollut Res

left to be dry. The sample was pyrolyzed in two different temperatures after it is dried. Pyrolyzed samples are washed with 5 % (w/w) HCl solution. To remove the acid residue from the stage, it is washed with distilled water until its pH value was 7. Washed samples were dried and ground, and then put in desiccator until its usage.
The surface characterization of activated carbon

Kinetic studies

For the surface characterization of hazelnut shell and the activated carbon obtained from hazelnut shell, BrunauerEmmett-Teller (BET) surface area measurements and IR spectrums have been made. BET surface area is made by
Micromeritics device. IR spectrums were made with Fourier
Rotative Pelkin Elmer BX spectrometer.
Adsorption studies
To determine the raw hazelnut shell and its adsorption performance, optimum pH, kinetic, and isotherm determination studies were made for every single activated carbon sample. There were some adsorption tests done in different pH values to determine the pH value’s effect on adsorption capacity. For the Pb+2 adsorption experiments, pH values were taken between 1 and 6. The reason why these values were taken is that after the pH is 6, lead hydroxide occurs in solution (there is a
0.5 unit difference between the values). After arranging the beginning pH value of the heavy metal solution which has
100 mg/L beginning concentration to the stated values, 50mg-weighting sorbent was added to the solutions and this mixture was shaken in orbital incubator for 1 h under the conditions of 150 rpm and 20 °C. To see if there is settling in terms of metal ions during adsorption process, other control samples, which do not have sorbent in it but with pH values rearranged to the intended value, were shaken in the same time with the other mixings. There are two grains of all samples, and all the adsorption experiments were retaken when the samples are not close to each other. This situation is taken into consideration in all adsorption experiments. After the shaking process, sorbents left the solution by floating and the metal morality in this filtrate was determined by using the ICP device.
After calculating the pH value which obtains the maximum sorption capacity, the heavy metal concentration in the filtrate was determined. By calculating their adsorption capacities, we tried to determine the optimum pH value with the following equation: qe ¼

ðC o −C e Þ
ÃV
m

L), Ce represents the metal ion concentration left on the permeate (mg/L), m represents the dry weight of the biomass in the mix (g), and the V represents the volume of the mixing (L).
Adsorption capacities were calculated with the adaptation of the equation used in the adsorption experiments in this study. ð1Þ

In this equation; qe represents the amount of metal ions which adsorbed on biomass on equilibrium time (mg/g), C0 represent the solution’s beginning metal ion concentration (mg/

After a certain time in adsorption process, the amount of heavy metal which is adsorbed by the sorbent will not change.
So the adsorption process will reach to the dynamical equilibrium. This period of time which passes over when the metal concentration’s decreasing pattern stops is determined at the equilibrium time. To determine this period of time, by rearranging the beginning pH value of the heavy metal solution which has 100 mg/L of concentration to the optimum pH value which is determined in the former process, they are placed into the vials with the volume of 50 mL. These mixings, which are made by adding 50-mg-weighting biomass into them, were exposed to be shaken in the orbital incubator under conditions of 150 rpm and 20 °C in the following period of time: 5, 10, 15, 30, 60, 90, and 120 min.
At the end of these periods of time, the mix is filtered to remove the sorbent from the suspension, by using sieve paper with 1 μm pore size. The metal concentrations were calculated in obtaining the filtrate.
Experimental data were adapted to the pseudo-first-order kinetic model in the way as follows: qt ¼ qe ð1−expð−k 1 t ÞÞ

ð2Þ

In this equation, qt represents the amount of metal ion adsorbed in any t time (mg/g), qe represents the amount of metal ion adsorbed during the equilibrium time (mg/g), and k1 represents the pseudo-first-order kinetic constant (min−1).
Pseudo-second-order kinetic model is as follows: qt ¼

qe 2 k 2 t
1 þ qe k 2 t

ð3Þ

In this equation, qt represents the amount of metal ion adsorbed in any t time (mg/g), qe represents the amount of metal ion adsorbed during the equilibrium time (mg/g) k2
(g/mg.min.) and the pseudo-second-order kinetic constant
(min−1), and t represents the time (min). Nonlinear regression method is used in solving the equations with the aid of the
Microsoft Office Excel program. The same solution is used in determining the isotherm model constants.

Environ Sci Pollut Res
Fig. 1 The change of sorbent’s sorption capacity with pH
(conditions: 100 mg L−1 initial concentration, 300–180 μm particle size, 1 g L−1 adsorbent dosage, 150 rpm, 60 min agitation time, and 20 °C)

Isotherm study
There were isotherm experiments made to determine the equilibrium situation of sorbent’s process of adsorbing the heavy metal. For this particular purpose, 25, 50, 75, 100, 125, and
150 mg dry weight biomass was added to 50 mL of the solution which has 100 mg/L heavy metal concentration; the formed mixing was shaken off in the orbital incubator under
20 °C until the equilibrium time which is determined after the kinetic studies. After adsorption was done, mixtures were filtered and their Pb+2 concentrations were determined. These obtained experimental data were analyzed due to the nonlinear regression analyses; the Freundlich and Langmuir isotherms parameters were calculated, and the isotherm model which

Fig. 2 Distribution of the lead ions in aqueous solution according to pH value

shows compliance to the adsorption phenomenon is determined. Parameters that belong to the nonlinear Freundlich isotherm model are determined through Eq. 4: qe ¼ K F C e ð1=nÞ

ð4Þ

In this equation, qe represents the amount of metal ion adsorbed in the equilibrium time (mg/g); KF represents the proportional adsorption capacity, a parameter that belongs to the isotherm; n represents the adsorption density; and Ce represents the materials concentration which stays in the solution in equilibrium time (mg/L).

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Fig. 3 Pseudo-first- and secondorder kinetical graphics of the sorption process made with nutshell (conditions: 100 mg L−1 initial concentration, pH 5, 300–
180 μm particle size, 1 g L−1 adsorbent dosage, 150 rpm, and
20 °C)

Parameters that belong to nonlinear Langmuir isotherm are as follows: qe ¼

qm a L C e
1 þ aL C e

ð5Þ

In this equation, qe represents the amount of metal ion adsorbed in the equilibrium time (mg/g), qm represents the maximum monolayer adsorption capacity (mg/g), aL represents the isotherm fix which states the adsorption energy
(L/mg), and Ce represents the materials concentration which stays in the solution in equilibrium time (mg/L).

Results and discussion
The effect of pH value on the adsorption
In the sorption studies, the crucial parameter is the pH. pH has an important effect on metal ion’s resolution and ionizing of the functional groups on the activated carbon’s surface. This
Table 1 Sorbents’ first- and second-order kinetic model constants and regression numbers qe Raw
250 °C
700 °C
Zn+700 °C

K1.ad

R2

K2.ad

qe

R2

39.21
60.95
97.54
142.5

0.0719
0.0554
0.05484
0.04315

0.987
0.975
0.991
0.995

0.00242
0.00103
0.00063
0.00031

42.534
68.1046
109.147
163.314

0.991
0.987
0.988
0.997

effect has a great place on the sorption phenomenon
(Nomanbhay and Palanisamy 2005). The change in pH and sorbent, sorption capacity in the study is given in Fig. 1.
It is clearly seen that the occasion pH is an active parameter on sorption incident. pH studies were made between the pH values of 1 and 6, and because there is a residue in the solution when the pH is over 6, there was no study over this value
(Fig. 2). It is observed that between pH values 1 and 3, sorption capacity is comparatively too low and over pH 4, the capacity gets much better. When comparing the hazelnut shell pyrolysis at 250 °C and the values at 700 °C, it is seen that the sorption capacity of the activated carbon has increased
40 %. Towards these data, we can say that especially the raw hazelnut shell is positively charged in low pH values. In low pH values, hydrogen ions protonate activated carbon grains and make them positively charged. The intense existence of the H+ ions in occasion makes a competition with the positively charged heavy metal ions and that makes the adsorption of the heavy metal with the electrostatic forces impossible
(Nomanbhay and Palanisamy 2005; Al-Qodah 2006). The reason why sorption is powerful, especially after pH 4, may be the ionization of the carboxyl groups in the activated carbon. Carboxylic acid’s pKa is about 4.2. Carboxylic acid, above these pH values ionizes. Therefore the carboxyl which has conjugation becomes a negatively charged ion. That is how it generates a familiarity through the positively charged ions in the water. When looking at the activated carbon’s IR spectrum (Fig. 5), the existence of the carboxyl groups is seen.
Strains seen in 1,100 and 1,000 cm−1 show the existence of carboxyl (Dikman 1985). Also, when the pH increases, H+ concentrations will be neutralized with the OH− ions in the solution and concentration will be decreased, so the heavy

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Fig. 4 Langmuir and Freundlich isotherm constants (conditions:
100 mg L−1 initial concentration, pH 5, 300–180 μm particle size,
150 rpm, 90 min agitation time, and 20 °C)

metal ions will not be compatible and the electrostatic forces and sorption will come forward. As a result of the studies, the ideal pH value for sorbents is determined as 5 and that is the basis for the next studies. Özcan et al. (2009) with the
Phaseolus vulgaris L. biomass determined the ideal pH value as 5 in lead adsorption studies. They also state that the hydrogen ion competes with the adsorbent at low pH values. Beside this, they emphasize that there are metal pellets in the solution when there is pH value over than intended.

Kinetic studies
Adsorption kinetics expresses the capture speed of the pollutant in the solution by activated carbon. Determination of this speed level is needed for the design of processes based on adsorption. In this process, hydraulic retention time depends on kinetical data. There are some tests need to be done to determine the kinetical data in a good way (Ho and McKay
1999). Obtained results after the experimental studies are shown in Fig. 3 with a graphic.
When the graphic is examined, it is seen that the sorption process is made quickly. In the first 15 min, 62 % of the sorption were done. At the end of 90 min, it is seen that sorption is done. Pehlivan et al. (2009) studied on lead
Table 2 Pb(II) adsorption’s Langmuir and Freundlich constants
Freundlich

Raw
250 °C
700 °C
Zn+700 °C

Langmuir n 0.11
0.16
0.18
0.21

KF
24.34
32.35
48.88
60.26

R2
0.848
0.951
0.93
0.99

aL
0.27
0.54
0.19
0.29

qm
41.9
62.0
116.2
151.9

R2
0.966
0.959
0.86
0.88

outgoing Pb+2 in aqueous solutions with their hazelnut shell and established that the hazelnut shell removes the 90 % of the
Pb+2 away the aqueous solution.
For the kinetical analyses of the obtained data, by investigating pseudo-first- and pseudo-second-order equations to see if they are good for this or not, we determined kinetic constants. In this calculation process, nonlinear regression method is used. Data obtained through calculation is shown in Table 1.
In Table 1, when looking at the R2 values by pyrolysis raw sorbent at 250 °C, it is expressed as second-order kinetic, sorbents which were pyrolyzed at 700 °C and activated with
ZnCl2 sorption process is more compliable with pseudo-first order-kinetic model. Ho and McKay (1999), stated that the pseudo-second-order kinetic mechanism which gives high regression in all time periods may be the chemisorption which includes electron change and share between the adsorbate and the adsorbent. Data obtained through the study are the indicators that in the sorption process, chemical incidents are not dominant because of incompliance. When looking at the IR spectrums of both sorbents, sorbents could not make a C≡C adsorption as a result of combustion. That is why it may be said that the physical capture is more dominant is sorption process. Isotherm studies
Adsorption isotherm is an essential data source for practical design and fundamental understanding of the carbonaceous adsorbents. The parameters obtained from different isotherm models are important for the optimization of the adsorption mechanism pathways and expression of the surface properties of adsorbents (Foo and Hameed 2012). An adsorption process depends on the surface area, pore size distribution, and surface chemistry of the adsorbents (Mahapatra et al. 2012). In this study, adsorption capacities of activated carbons obtained at

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Fig. 5 Raw nutshell’s IR spectrums taken before and after the adsorption (above is raw, bottom is the Pb(II) adsorbed sorbent’s spectrum)

different activation temperatures and activated with ZnCl2 sorbents were investigated. Several adsorption isotherm equations are available, and two important isotherms are selected in this study.

Langmuir and Freundlich isotherms
Results obtained from the sorbents’ isotherm studies on raw hazelnut shell and modification of it are shown in Fig. 4.

Fig. 6 250 °C pyrolyzed nutshell and the Pb(II) adsorption, before and after IR spectrums (above is raw, bottom is Pb(II) adsorped sorbent’s spectrum)

Environ Sci Pollut Res

Fig. 7 Before and after IR spectrums of nutshell pyrolyzed at 700 °C with its adsorption with Pb(II) (above is raw, bottom is Pb(II) adsorbed sorbent’s spectrum) Fig. 8 Before Pb(II) adsorption IR spectrum of nutshell pyrolyzed at 700 °C

Environ Sci Pollut Res

Fig. 9 After Pb(II) adsorption IR spectrum of nutshell pyrolyzed at 700 °C

Langmuir and Freundlich isotherm constants and R2 values showing the compliance of sorption incident with this model obtained from nonlinear analyses of the data are also given in
Table 2.
On Table 2, when looking at the R2 values, it is seen that adsorption incidents of the raw and sorbents pyrolyzed at
250 °C show compliance with the Langmuir isotherm model, but the adsorption equilibrium of sorbents pyrolyzed at 700 °C and activated with ZnCl2 is compliable with the Freundlich isotherm model. Explanation of isotherm data with Langmuir isotherm model is the indicator that the sorption incident is monolayer and that is why chemical incidents are dominant in capturing. Therefore, it may be thought that the raw hazelnut shell and the sorbents pyrolyzed at 250 °C are the dominant chemical incidents in capturing the Pb+2 ion. Also, the capturing areas on sorbents surfaces are homogenous in terms of capturing energy. Bulut and Tez (2007), in their study of adsorption with hazelnut shell and Pb+2, stated that the sorption incident at 318 K temperature complies with the
Langmuir isotherm model. Sorption process of 700 °C pyrolyzed sorbents is compliable with Freundlich model. The compliance of the adsorption incident with Freundlich isotherm model is the indicator that there is multilayered capture at the surface of sorbent and their capturing areas are distributed heterogeneously on sorbents’ surface.

Adsorbent’s Pb+2 adsorption mechanism
To determine the surface characterization and adsorption mechanism, FTIR spectrums are used in the study. For this particular purpose, by getting the before and after spectrums of sorbent’s hazelnut shell, the changes in chemical bonds were investigated. The spectrums are shown in Figs. 4 and 5.
Tangjuank et al. (2009), made cadmium adsorptions by the activated carbons obtained from cashew. They stated that they observed (O–H) bonds belong to hydrogen protons adsorbed to oxygen in 3,200–3,600 cm−1 of raw hazelnut shell. In our
FTIR spectrum obtained from raw hazelnut shell, there is also a bond in this area. This bond belongs to O–H alcoholic groups adsorbed to alcoholic groups and cellulosic in a hazelnut shell. They stated there are bonds in between 2,800 and
2,900 cm−1 for the methyl and methylene on C–H vibrations.
We may express the bonds in these methyl and methylene groups as C–H strains. Tangjuank et al. (2009) interpreted these bonds at 1,630 cm−1 as bonds belonging to C=C vibrations. The bonds that we observed at this point are the ones belonging to C=C vibrations and C–O strains. Bonds about
1,100 cm−1 are the C–O bonds that belong to alcohol and ether. When we investigate the FTIR spectrum taken after adsorption in 3,200–3,600, 1,600, and 1,100 cm−1 areas, we may see a decrease in these bonds. This shows that the lead

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adsorbed to the construct via electrons not compliable with oxygen and therefore O–H and C–O bonds seen in this territory got weak and lost their permeability. Also the hazelnut shell’s BET surface area is measured as 5.92 m2/g. This number is so low. So it may be said that in the hazelnut shell’s capture of Pb+2 ions; chemisorption are dominant.
When investigating the IR spectrum obtained in pyrolysis at 250 °C, it is seen that the hazelnut shell is not carbonized enough (Fig. 6). Because there are still bonds belonging to O–
H vibrations seen between 2,800 and 3,200 cm−1. Also, there is an IR spectrum seen on the C–O bonds that belong to strains about 1,600 cm−1, and they are all already seen in 1,100 cm−1 alcohol and ester groups. When investigating the spectrum obtained after adsorption, there is a decrease in permeability in between 3,000 and 3,300 cm−1. The O–H groups on hazelnut shell are lignocellulose materials responsible for adsorption.
Because of the metal ion on the negative sides on O (oxygen)
O–H bonds gets weakened and therefore, there will be a decrease in the permeability in this area. Obtained sorbent’s
BET surface area is determined as 270.2 m2/g. Demirbas et al.
(2009) performed a study about obtaining activated carbon from hazelnut shells and hazelnut shells carbonized by airdried method. The obtained product BET surface area were determined 441 m2/g. The reason for the difference may be caused from carbonization method.
As seen in Fig. 7, after the pyrolysis at 700 °C IR spectra, all the observation seen on functional groups are gone. And this may mean that carbonization achieves exactly in pyrolysis. There is no significant change in the IR spectrum taken after adsorption. The decrease in permeability near
2,100 cm−1 exists with the interaction by C≡C bonds metal ion. Boonamnuayvitayaa et al. (2004) established that these bonds belong to C≡C groups, in IR bonds they obtained from coffee leftover. Sorbent’s BET surface area is established as
686.7 m2/g.
The before and after the adsorption IR spectrum of the sorbent’s pyrolysis at 700 °C is quite similar to the spectrum of hazelnut shell pyrolysis at 700 °C (Figs. 8 and 9). After the pyrolysis at 700 °C, raw hazelnut shell and all the functional groups seen on sorbents which are pyrolysis at 250 °C are lost.
Hazelnut shells are composed of 30 % hemicellulose, 27 % cellulose, and 43 % lignin (Demirbas 2002). Hemicellulose is composed of amorphous chains of monosaccharides, whereas cellulose is composed of linear chains of glucose, which tend to form intermolecular hydrogen bonds and make the structure crystalline, and linens are polymers of aromatic compounds.
Researchers have defined the decomposition temperature ranges for each of these components by studying the pyrolysis products of lignocellulosic biomass and agreed on the decomposition regions of lignocellulosic biomass as follows: 200–
320 °C for hemicellulose, 200–400 °C for cellulose, and the entire pyrolysis range for lignin (Seo et al. 2010). In the view of these findings, pyrolysis of lignocellulosic biomass at

temperatures above 600 °C will probably result in the collapse of the structure due to the complete decomposition of lignin, which provides a backbone for biomass-derived carbonaceous products, and the required open network will not be attained.
Considering our FTIR spectrums, there is a collapse in the lignocellulosic backbone. Because of that, it may be said that the physical adsorption is dominant here. The sorbent’s BET surface area which is obtained with this method is calculated as 736.49 m2/g.

Conclusions
As a result of these studies, hazelnut shell’s surface area is increased from 5.92 to 736.49 m2/g by thermal and chemical treatments. Because the sorbent’s surface area increased, there is more chance to capture Pb+2 ion. When looking at the FTIR spectrums in adsorption mechanism, the captures of Pb+2 chemical adsorption in raw and sorbents pyrolyzed at
250 °C is active, and it is seen that in an adsorption incident with sorbents pyrolyzed at 700 °C, physical sorption is active.
When looking at the kinetically and isothermal data, it is seen that when pyrolysis temperature is increased, the adsorption incident is shifting from chemical adsorption to physical adsorption. Acknowledgments This project was funded by Süleyman Demirel
University Scientific Research Project Foundation Fund (project no:
2148-D-10). The financial assistance from the Research Project Foundation Fund on “Determination of lead(II) sorption capacity of hazelnut shell and activated carbon obtained from hazelnut shell with different methods” is thankfully acknowledged by the authors.

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