Synthesis and Characterization of Carbon Conditioned with Iron Nanoparticles Using Pineapple-Peel

doi:10.4236/anp.2013.24053

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Advances in Nanoparticles, 2013, 2, 384-390

Published Online November 2013 (http://www.scirp.org/journal/anp)

http://dx.doi.org/10.4236/anp.2013.24053

Open Access ANP

Synthesis and Characterization of Carbon Conditioned

with Iron Nanoparticles Using Pineapple-Peel

G. García-Rosales1*, L. C. Longoria-Gándara2, S. Martínez-Gallegos1, J. González-Juárez1

1Posgrade Department, Instituto Tecnologico de Toluca, Metepec, México

2Scientific Reseach and Reactor, Instituto Nacional de Investigaciones Nucleares,

Ocoyoacac, México

Email: *[email protected]

Received September 3, 2013; revised October 30, 2013; accepted November 9, 2013

cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

ABSTRACT

This paper presents the preparation of carbon conditioned with iron nanoparticles (CI) using a pineapple peel treated

with iron salts, carboxymethylcellulose sodium and hexamine. First, the pineapple peel was analyzed by thermo gra-

vimetric analysis (TGA) to determine the optimal temperature for pyrolysis. The formation of carbon conditioned by

iron nanoparticles was studied as a function of time at 30 min, 60 min, 90 min, 120 min, 150 min and 180 min. Scan-

ning electron microscopy (SEM) was used to identify changes in the morphology of the materials. The specific area of

each material was obtained by the BET method. The elemental composition of pineapple-peel (PP), washed pineap-

ple-peel (WPP) and carbon iron (CI), was determined by neutron activation analysis (NAA). The results show that the

optimal time for obtaining spherical iron nanoparticles with a diameter between 10 nm and 30 nm is 180 min on the

carbonaceous material with a specific surface area of 167 m2/g.

Keywords: Pineapple; Carbon; Iron-Nanoparticles; Synthesis; Neutron Activation Analysis

1. Introduction

Iron nanoparticles are used in environmental applications,

such as the removal of toxic metals from polluted water

[1-3]; however, a major drawback is that their size limits

direct application because handling is difficult unless

they are recovered through an ultrafiltration system [4].

Therefore, a material that can function as a support is

recommended for using iron nanoparticles [5-8]. Carbo-

naceous materials that are obtained from organic cellu-

losic waste and then conditioned with iron nanoparticles

can be a good choice for environmental applications,

such as the removal of metals in water [9-13]. The ad-

vantage of using carbon obtained from biomass and con-

ditioned with iron nanoparticles is that synthesis of both

the carbonaceous material and the nanoparticles can be

performed simultaneously during pyrolysis, if the bio-

mass has been previously chemically conditioned. In this

work, pineapple peel conditioned with iron salts, hexa-

mine and sodium carboxymethylcellulose was used to

obtain carbonaceous material containing iron nanoparti-

cles via pyrolysis. First, the pineapple peel was analyzed

by thermo gravimetric analysis (TGA) to determine the

optimal pyrolysis temperature. Pyrolysis is performed at

different reaction times: 30 min, 60 min, 90 min, 120 min,

150 min and 180 min. To determine the effect of pyroly-

sis time on both the morphology and the size of nanopar-

ticles in the carbon matrix, characterization via scanning

electron microscopy (SEM) and calculation of the spe-

cific surface area via the BET method were performed.

Finally, the neutron activation analysis (NAA) was used

to determine the elemental composition.

2. Materials and Methods

2.1. Washing and Drying of Pineapple Peel

For this study, pineapples obtained from Mexico were

used. In the laboratory experiments, the peel was sepa-

rated from the pineapple, then ground and sieved to ob-

tain a size of 0.85 mm. The material was washed several

times with double-distilled water to remove surface im-

purities and then dried at 25˚C for 24 h. The pineapple

peels were then repeatedly washed with water at 120˚C

for 15 min to remove the brown discoloration completely,

and finally dried at 25˚C for 24 h.

*Corresponding author.

G. GARCÍA-ROSALES ET AL. 385

2.2. Thermogravimetric Analysis

To determine the optimal temperature for pyrolysis, a

small amount of sample was placed directly onto a plati-

num crucible, and TGA was performed using a calo-

rimetric SDT Q600 (TA Instruments-Waters) under N2 at

a heating rate of 10˚C min−1 with a temperature range of

25˚C - 800˚C.

2.3. Synthesis

A mixture of 12 mL C28H30Na8O27 (2% w/w; Sigma-

Aldrich®), 18 mL Fe(NO3)3·9H2O (0.06 M; Sigma-Al-

drich®, 98%) and 6 mL (CH2)6N4 (0.5 M; Sigma-Al-

drich®, 99.9%) was combined in a reactor under Ar with

constant agitation. Once the mixture was homogenized, 3

g pineapple peel (mesh 20) was added to the mixture and

agitated in an ultrasonic bath for 45 min prior to being

placed in a fused alumina crucible, which was then sub-

sequently introduced into a quartz tube under argon

within a furnace (Lindberg®/Blue Model CC58114A-1).

To determine the effect of synthesis time on the mor-

phology of the nanoparticles, six samples were prepared

using pyrolysis times of 30 min, 60 min, 90 min, 120 min,

150 min and 180 min; the products obtained were labeled

CFe30, CFe60, CFe90, CFe120, CFe150 and CFe180,

respectively.

2.4. Scanning Electron Microscopy and Specific

Surface Areas

The morphology of the material was analyzed with a

scanning electron microscope (Model JEOL® JSM-6610

LV) at 25 kV. The samples were mounted on an alumi-

num holder with aluminum conductive tape and were

then covered with a layer of gold approximately 150 Å

thick using a sputter coater (Desk II model, Denton

Vacuum). In all cases, micrographs were obtained using

a backscattered electron detector. The elemental compo-

sitions of the samples were then determined by energy

dispersive spectroscopy (EDS) using an OXFORD spec-

trometer. The diameters of the particles obtained were

measured using MeasureIt software (Olympus Soft Im-

aging Solutions). The specific surface area, pore volume

and pore diameter of the carbonaceous materials were

determined by the Brunauer-Emmett-Teller (BET) nitro-

gen adsorption method in a BELPREP-flow II surface

area analyzer (BEL JAPAN Inc.). The dried and de-

gassed samples were then analyzed by a multipoint N2

adsorption-desorption method at room temperature.

2.5. Elemental Composition

The NAA was performed using the comparator method.

Approximately 30 mg of each sample, PP (prewashed

pineapple), PPL (pineapple washed) and CFe180 (carbon

with iron), was encapsulated in polyethylene containers

for the shorter irradiation times (30 s and 5 min) and in

quartz vials for irradiation of 20 h. Lichen BCR-482 and

IAEA-Soil 7 were used as reference materials. The en-

capsulated samples were irradiated for 30 s to 5 min with

a thermal neutron flux·s of 1.3 × 1013 n/cm2 in an Irradia-

tion System tire (SINCA) in a TRIGA Mark III reactor

(ININ, Mexico) and for irradiation of 20 h in the Fixed

Irradiation System (SIFCA) with a flow of 9 × 1012

n/cm2·s. The activity of the samples was measured in a

gamma spectrometer equipped with an ORTEC® hyper-

pure Ge detector.

3. Results and Discussion

3.1. Thermogravimetric Analysis

Figure 1 shows the relative mass loss (TGA) and differ-

ential thermal analysis (DTA) curves corresponding to the

dried pineapple-peel.

The endothermic mass loss (8.3 wt%) observed for

temperatures lower than 120˚C can be attributed to water

desorption [14,15]. The second mass loss (30.56 wt%)

between 120˚C and 190˚C is associated with the decom-

position of organic substances. Beyond this temperature,

thermal degradation of the main components of the bio-

mass begins: from 190˚C - 320˚C, hemicellulose de-

grades, followed by cellulose from 320˚C - 400˚C, and

then lignin above 400˚C (59.94 wt%) [16]. In agreement

with Gutierrez et al. [17], a pineapple-peel has an average

fiber content of 67.88% (including cellulose, hemicellu-

lose, lignin and silica), which renders this waste biomass

suitable for obtaining carbonaceous material [18]. Stabi-

lization of the material was observed above 625˚C, and

the total weight loss calculated until 650˚C was 77.47

wt%. Based on this result, the selected pyrolysis tem-

perature was 650˚C to obtain carbonaceous material.

3.2. Effect of the Pyrolysis Time on Nanoparticle

Morphology and Specific Surface Area

To characterize the textural properties of the carbona-

Figure 1. Thermogravimetric and DTA curves of pineapple

peel powder.

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G. GARCÍA-ROSALES ET AL.

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386

ceous materials obtained at 30 min, 60 min, 90 min, 120

min, 150 min and 180 min, these materials were chemi-

cally and morphologically analyzed. Figure 2(a) shows

that the material synthesized at 30 minutes does not possess

(a)

(b)

(c)

(d)

(e)

(f)

Figure 2. Micrographs, mapping and size distribution particle of iron carbon samples obtained at different synthesis times. a)

CFe30 min; b) CFe60 min; c) CFe 90 min; d) CFe 120; e) CFe 150 min; f) CFe 180 min.

G. GARCÍA-ROSALES ET AL. 387

a homogeneous morphology; there are rough spots. Nu-

cleation of spherical particles with an average diameter

of 114.8 nm (σ = 19.3) occurs, which is in agreement

with EDS analysis, having a composition of C(82 wt%),

O(14.22 wt%), Na(1.43 wt%), Si(0.64 wt%), K(0.29

wt%), Ca(0.76 wt%) and Fe(0.64 wt%).

In Figure 2(b), for the pyrolysis sample obtained at 60

min, there are chains of spheres with an average diameter

of 88.06 nm (σ = 12.22) forming filaments with a length

of 300 nm - 600 nm. The composition of the spheres is C

(77.63 wt%), O (17.50 wt%), Na (2.01 wt%), Al (0.45

wt%), Si ( 1.18 wt%), Ca (0.28 wt%) and Fe (0.95 wt%).

The sample obtained at 90 minutes (Figure 2(c)) forms a

defined group of particles apparently caused by segrega-

tion of the filaments previously observed at 30 min

(Figure 1(b)). The morphology of some of these particles

is not completely spherical; there are ovals 250 × 125 nm

in dimension and spherical particles with an average di-

ameter of 71.21 nm (σ = 11.93). Elemental analysis

shows a presence composition of C (80.92 wt%), O

(16.03 wt%), Na (1.83 wt%), Si (0.31 wt%), Ca (0.63

wt%) and Fe (0.38 wt%). Figure 2(d) shows the sample

obtained at 120 min in which spherical nanoparticles are

dispersed with an average diameter of 57.69 nm (σ =

9.02) and have an elemental composition of C (82.45

wt%), O (11.60 wt%), Na (1.36 wt%), Mg (0.34 wt%), Si

(1.10 wt%), K (0.05 wt%), Ca (0.76 wt%), and Fe (1.34

wt%). In the sample obtained at 150 minutes (Figure

2(e)), the nanoparticles are the best dispersed and have

an average diameter of 44.09 nm (σ = 17.09); their com-

position consists of C (75.02 wt%), O (18.48 wt%), Na

(2.26 wt%), Si (1.08 wt%), K (0.36 wt%), Ca (0.77 wt%)

and Fe (1.03 wt%). At 180 min (Figure 2(f)), there is a

reduction in particle size without noticeable changes in

the spherical shape, having an average diameter of 32.94

nm (σ = 6.75); the composition is C (75.57 wt%), O

(18.47 wt%), Na (1.81 wt%), Si (0.95 wt%), K (0.38

wt%), Ca (1.58 wt%) and Fe (1.24 wt%). The sample

obtained after 180 minutes of pyrolysis has a more defined

particle size as well as spherical morphology.

This effect can be attributed to the use of carboxy-

methyl cellulose sodium and hexamine, which favors the

formation of iron nanoparticles of uniform size at this time

scale [19,20].

To determine the specific area and pore size of the

materials, a carbon sample without iron (CB180) was

synthesized to determine the influence of the presence of

iron nanoparticles on the specific area. The results of this

experiment on the effect of iron nanoparticles are sum-

marized in Table 1. In general, the specific area in all

materia ls is more strongly affected by the pyrolysis time,

with larger values observed for the samples containing

iron compared to the CB sample.

The specific area of CFe180 is higher than that of CFe30

by 91.3 m2/g, thereby implying that the specific areas

increase with increased pyrolysis time due to the forma-

tion of iron nanoparticles in the carbonaceous material.

However, a difference of 23.1 m2/g between the spe-

cific areas of CFe180 and CB is attributed to the presence

of iron nanoparticles [21]. CFe60 and CFe120 possess

larger specific areas than CFe180, which can be attributed

to the presence of iron nanoparticles with different mor-

phologies and to changes in the porosity of the carbona-

ceous matrix that are associated with the pyrolysis process

[22]. However, the value of CFe180 is greater, which

could favor its use in environmental applications for the

removal of contaminants from water.

3.3. Chemical Composition

Table 2 lists the results from neutron activation analysis

of the PP, PPL, CB and CFe180 samples. Initially, PPL

contains these elements: Al, Br, Ce, Co, Cr, Cs, Eu, Fe,

Hf, K, La, Mg, Mn, Na, Rb, Sb, Sc and Zn. The majority

of these elements are present in the soil where a plant

grows and can accumulate in and be incorporated into

their structure during nutrient absorption, which is nec-

essary for plant growth [23].

Table 1. Specific area, volume and diameter of pore in carbonaceous materials.

Material Specific area (m2/g) Volume of pore (cm3/g) Diameter of pore (nm)

CB 98.80 0.0598 2.42

CFe30 75.70 0.0496 2.62

CFe60 284.41 0.1668 2.34

CFe90 162.36 0.0917 2.26

CFe120 182.50 0.0931 2.04

CFe150 161.03 0.0963 2.39

CFe180 167.00 0.1053 2.52

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Table 2. Elemental compositions of PP, PPL, CB y CFe.

Isotop PP [ppm] PPL [ppm] CB [ppm] CFe [ppm]

28Al 144 ± 14 60 ± 6 D 498 ± 14

82Br 17 ± 0.87 1.46 ± 0.07 4 ± 0.25 4.6 ± 0.24

141Ce 0.122 ± 0.02 ** 0.3 ± 0.0293 0.14 ± 0.02

60Co 0.29 ± 0.01 0.1612 ± 0.007 0.24 ± 0.0116 0.29 ± 0.014

51Cr 2.21 ± 0.07 0.9382 ± 0.0395 2.95 ± 0.091 2.6 ± 0.08

134Cs 0.074 ± 0.0001 ** 0.065 ± 0.0073 0.074 ± 0.006

152Eu 0.007 ± 0.0001 0.0032 ± 0 0.0083 ± 0.0014 0.0074 ± 0.001

59Fe 4020 ± 8 36.71 ± 3 4409 ± 85 5197 ± 98

181Hf 0.018 ± 0.0001 0.0098 ± 0.002 0.08 ± 0.0056 0.020 ± 0.004

42K 28342 ± 1063 362 ± 46 ** **

140La 0.159 ± 0.01 ** ** **

27Mg 460 ± 6 193 ± 24 456 ± 105 662 ± 79

56Mn 92 ± 3 60 ± 1.7 124 ± 4 152 ± 4

24Na ** ** 32947 ± 929 30499 ± 851

86Rb 2.24 ± 0.3 0.90 ± 0.1759 2 ± 0.4 3 ± 0.4

124Sb 0.783 ± 0.03 0.03 ± 0.0045 0.58 ± 0.0263 0.8424 ± 0.04

46Sc 0.010 ± 0.0001 0.005 ± 0.0004 0.014 ± 0.0007 0.0112 ± 0.0008

65Zn 132 ± 6 42 ± 2 115 ± 5 136 ± 6

**No detected.

In the PP, PPL, CB and CFe samples, the elements that

are present at low concentrations (0 - 0.08 ppm) are Eu, Sc

and Hf, where Hf is the most abundant; this result is in

accordance with Gutiérrez et al., who considered these

elements to be attached to the plant structure because they

aregenerally present in the soil. Meanwhile, Cs, La, Co

and Ce are present at concentrations between 0.050 ppm

and 0.30 ppm; Sb, Cr and Rb have concentrations of 1

ppm to 4 ppm. Br, Mn, Zn and Al are found at high con-

centrations because they are considered to be essential

components of plant tissues, especially in the CFe sample

in which the concentration of Al is nearly 500 ppm.

Mn and Zn are present because they are essential for

plant metabolism. This analysis also confirmed the pres-

ence of Mg and Fe as natural components in the pineapple

peel (Ananas comosus) because both elements are essen-

tial for photosynthesis.

Na and K are the most abundant elements; the presence

of Na in the CFe and CB samples is mainly due to the use

of sodium carboxymethyl cellulose during the chemical

conditioning of the pineapple-peel. The increase in con-

centration of the elemental compositions in PPL, CB and

CFE can be attributed to the loss of organic matter during

pyrolysis [24]. The presence of different elements in these

samples could facilitate the formation of active sites on

the material surface, thereby favoring their effectiveness

as a sorbent in the removal of metal contaminants in an

aqueous phase [25].

4. Conclusion

In this paper, the use of a pineapple peel that was chemi-

cally conditioned with iron salts, sodium carboxymethyl

cellulose and hexamine yielded a carbonaceous material

with iron nanoparticles following pyrolysis. The synthe-

sis time had a significant effect on the morphology, parti-

cle size and specific area of the carbonaceous material

was obtained. The elemental composition determined by

Neutronic Activation Analysis of CP, CPL, and CFe

showed the presence of Al, Co, Cr, Cs, Fe, Hf, K, Mg,

Mn, Na, Rb, Sc, Zn, Ce, Eu, La, Sb and Br. The method

proposed in this study provides a simple technique for

synthesizing iron nanoparticles in a carbon matrix.

5. Acknowledgements

The authors gratefully acknowledge DGEST for partial

financial support of this work and thank Jorge Perez for

his helpful assistance with electron microscopy analysis.

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G. GARCÍA-ROSALES ET AL. 389

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