Synthesis of palm oil empty fruit bunch magnetic pyrolytic char impregnating with FeCl3 by microwave heating technique

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Synthesis of palm oil empty fruit bunch magneticpyrolytic char impregnating with FeCl3 bymicrowave heating technique

N.M. Mubarak a,b,*, A. Kundu c, J.N. Sahu a,d,*, E.C. Abdullah e,N.S. Jayakumar a

aDepartment of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, MalaysiabDepartment of Chemical and Petroleum Engineering, Faculty of Engineering, UCSI University, Kuala Lumpur 56000,

Malaysiac Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur, MalaysiadDepartment of Petroleum and Chemical Engineering, Faculty of Engineering, Institut Teknologi Brunei, Tungku

Gadong, P.O. Box 2909, Brunei DarussalameMalaysia e Japan International Institute of Technology (MJIIT), Universiti Teknologi Malaysia, Jalan Semarak,

54100 Kuala Lumpur, Malaysia

a r t i c l e i n f o

Article history:

Received 26 July 2013

Received in revised form

9 December 2013

Accepted 22 December 2013

Available online 28 January 2014

Keywords:

Magnetic bio-char

Methylene blue

Adsorption

EFB

Microwave heating

* Corresponding authors. Department of ChMalaysia. Tel.: þ60 3 79675295; fax: þ60 3 79

E-mail addresses: mubarak.yaseen@gma0961-9534/$ e see front matter ª 2013 Elsevhttp://dx.doi.org/10.1016/j.biombioe.2013.12.

a b s t r a c t

Empty fruit bunch (EFB) is one of the most abundant residues of the Palm oil mill industry

in Malaysia. The novel magnetic bio-char was synthesized by single stage microwave

heating technique, using EFB in the presence of ferric chloride hexahydrate. The effect of

microwave powers, radiation time and impregnation ratio (IR) of ferric chloride hexahy-

drate to biomass were studied. Also the process parameters such as microwave powers,

radiation times and IR were optimized using response surface method. The statistical

analysis revealed that the optimum conditions for the high porosity magnetic bio-char

production were at 900 W microwave power, 20 min radiation time and 0.5 (FeCl3:

biomass) impregnation ratio. These newly produced magnetic bio-char have a high surface

area of 890 m2 g�1 and that leads to highly efficient in the removal of methylene blue (MB)

with an efficiency of 99.9% from aqueous solution with a maximum adsorption capacity of

265 mg g�1.

ª 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Malaysia is famous for production of oil Palm as the agricul-

tural industry. About 90 million metric ton of renewable

biomass such as empty fruit bunch (EFB), kernel shell, and

emical Engineering, Facu675319.il.com (N.M. Mubarak), jaier Ltd. All rights reserved021

trunks are produced in approximately three million hectares

of oil Palm plantations currently [1]. Among these, EFB

12.4 million tonnes [1] and Palm shell 2.4 million tonnes [2]

waste are produced. The burning of biomass caused emis-

sion of hazardous and toxic chemicals such as dioxins. Limi-

tation of land fill sites and additional cost due to the treatment

lty of Engineering, University of Malaya, 50603 Kuala Lumpur,

[email protected] (J.N. Sahu)..

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5266

of the leachates from the sites has grown interest among the

researchers for effective and commercially valuable utiliza-

tion of the EFB. One of the options the EFB can convert to good

quality bio-char.

Bio-char is carbon a rich material produced from pyrolysis

carbonaceous biomass [3]. Bio-char is highly recognized for its

effective agricultural and environmental applications such as

improving soil fertility and effective host of the microor-

ganism [4]. Bio-char can also contribute to the reduction of

greenhouse gas reductionwith its carbon storage capacity and

reducing CO2, CH4 and N2O production in soil [5]. Bio-char is a

soil enhancer which stores carbon and makes fertile soils,

reduction of nitrogen leaching into groundwater, reduction of

nitrous oxide emission, increasing cation-exchange capacity

for enhanced soil fertility, soil acid moderation, high rate of

water retention and high amount of soil microbes that are

beneficial [6,7]. Furthermore, bio-char in recent year has been

recognized as low cost suitable material for various environ-

mental applications [8e12]. Recently, activated carbon (AC) is

one of the good adsorbents used in the industrial sector;

however regeneration and desperation problem occur in in-

dustrial application. Powdered bio-char, like powdered AC, is

difficult to be separated from the aqueous solution [13]. To

overcome the shortcomings, an innovative technology has

been developed to remove pollutants like heavy metals,

phosphate, and organic compounds, from aqueous solutions

[14,15]. To remove these sorbent effectively, magnetic bio-

char is introduced to the commercially available sorbents

[16,17], so that magnetic separation technique can be applied

to separate organic arsenic [18] with magnetic iron oxide, se-

lenium [19] and phosphate [20]. However, the cost of the

traditional loading-process of magnetic medium is high [21].

Therefore, a new invention of microwave technology is

introduced to defeat the problems. Microwave irradiations

have capability of molecular level heating, which leads to

homogeneous and quick thermal reactions [22e24]. It also

gives a better control [25], energy efficiency [26] and cost

effectiveness [27] over conventional heating. Hence micro-

wave heating offers a potentially attractive alternative to

conventional pyrolysis systems. The thermal conversion of

the bio material requires a uniform heating to maintain the

overall quality of the bio-char. Heating rate should also be fast

to reduce the production cost. Microwave heating can be used

to heat the bio-materials faster and uniformly throughout the

bulk. The microwave penetrates the material and the micro-

wave energy is converted to heat energy. In this way, heat is

generated throughout the bulk of the material. Microwave

heating improved the quality with a less processing time

[28,29]. Till date, study with magnetic bio-char production via

microwave heating using agricultural waste biomass into a

valuable product has not yet been conducted.

In this study, novel magnetic bio-char was produced using

discarded material i.e. EFB by pyrolysis with impregnated

FeCl3. The pyrolysis of the impregnated EFB was carried out

with the help of single stage microwave heating technique.

The details of process parameter were studied such as: mi-

crowave powers, radiation time and impregnation ration

ferric chloride hexahydrate to biomass. The performance of

the produced magnetic bio-char was applied to remove

methylene blue (MB) from aqueous solution. The preparation

conditions were statistically optimized to produce high sur-

face area, high yield of magnetic bio-char and high adsorption

of MB.

2. Materials and methods

2.1. Raw materials

The EFB sample was collected from the Seri Ulu Langat Palm

Oil Mill in Dengkil, Selangor, Malaysia. The EFB was collected

in plastic bags and preserved in a cooling room at 4 �C.Analytical grade Ferric chloride hexahydrate (FeCl3.6H2O) was

purchased from Merck and used as received.

2.2. Experimental procedure for magnetic bio-char

The EFB was first thoroughly washed with distilled water to

remove water soluble impurities and surface adhered parti-

cles and dried at 105 �C for 24 h until a constant weight of the

material was obtained. The dry biomasswas then crushed and

sieved into a particle size of less than 150 mm. The impreg-

nation ratio (IR) of ferric chloride hexahydrate to biomass for

different amount of sample was prepared. The mixing was

performed in a thermal shaker at controlled temperature

(30 �C) for a period of 3 h at 2.5 Hz using 500 mL beaker. After

mixing, the slurry was subjected to vacuum drying at 100 �Cfor 24 h. The pyrolysis of the biomass was carried out in a

HAMiab-C1500 microwave muffle system oven as shown in

Fig. 1. About 30 g of impregnated biomass sample was placed

in a quartz tube of 35mmOD, 28mm ID and 500mm length. In

all experiments, nitrogen flow 200 cm3 min�1 was kept con-

stant. After the reaction finished, the sample was allowed to

cool at room temperature. Then it was collected from quartz

tube and weighted to determine the yield of the product.

These producedmagnetic bio-char then washedwith distilled

water until the pH becomes neutral. Finally the sample was

stored in tightly closed bottles.

2.3. Statistical approach of magnetic bio-charproduction

Response surface methodology (RSM) is a well known

approach to optimizing the effect of multiple process vari-

ables on the properties of prepared products using a combi-

nation of mathematical and statistical techniques [30,31]. A

standard RSM design called central composite design (CCD)

was applied with three central points and two replicate was

selected for the optimization of magnetic bio-char sample

production. The factors and their levels are described in Table

1. Twenty five experiments were suggested by design of

experiment for magnetic bio-char production. The responses

for each run based on the surface area were further statisti-

cally analyzed by the statistical software to determine the

optimum reaction condition. This method was chosen for

fitting a quadratic model with a minimum number of experi-

ments. It also helps analyze the interaction between the

effective process parameters and identify the factor setting

that optimizes the response [32].

Fig. 1 e Schematic of microwave reactor for production of magnetic bio-char.

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2.4. Characterizations of the magnetic bio-char

The physical morphology of the EFB derived novel magnetic

bio-char was studied by using (Brand: Zeiss Model: Auriga)

field emission scanning electron microscope (FESEM). The

optimum novel magnetic bio-char sample then was charac-

terized using FESEM (Brand: Zeiss Model: Auriga). Fourier

Transform Infrared (FTIR) spectroscope (Brand: Bruker, Model:

IFS66v/S) was used to analyze the novel magnetic bio-char for

determination of the surface functional groups. Besides

porosity, adsorption behavior of magnetic bio-char is also

influenced by the chemical reactivity of the surface especially

in the form of chemisorbed oxygen in various forms of func-

tional group. These surface oxides have acidic as well as basic

properties [33]. Physical characterization of magnetic bio-char

produced at the optimum condition was analyzed with

Autosorb 1 surface area analyzer by nitrogen adsorption at

�77 K. Prior to analysis, the samples were degassed at 200 �Cfor 3 h. The Brunauer, Emmett, and Teller (BET) surface area

was determined by using “Quanta Chrome Autosorb 6B” BET

analyzer.

Table 1 e Novel magnetic bio-char preparation variations with

Factor Name Unit L

A Radiation time min 10

B Microwave power (temperature

inside microwave)

W 600 (

C Impregnation ratio e 0.25

2.5. Batch equilibrium study

MB was chosen in this study due to its wide applications and

toxicity. MB has a chemical formula of C16H18N3SCI, with a

molecular weight of 319.85 g mol�1. Fixed weight (1 g L�1) of

magnetic bio-char was used in all the batch experiments for

MB adsorption. MB concentration was 200 mg L�1. 100 mL of

the solutionwas taken in a conical flask and agitated at 2 Hz at

30 �C until equilibrium is reached. MB concentrations in the

supernatant solutions were measured by a double beam

UVevisible spectrophotometer (Shimadzu, ModeU V 1601,

Japan) at 668 nm after filtering the adsorbent with Whatman

filter paper to make it carbon free. MB uptake at equilibrium,

qe (mg g�1), is determined by Eq. (1):

qe ¼ ðC0 � CeÞVW

(1)

where Co and Ce are the initial and equilibrium concentrations

(mg L�1) of MB solution, respectively; V is the volume (L); and

W is the weight (g) of the adsorbent.

three levels.

ow High Low coded High coded

30 �1 1

390 �C) 1200 (650 �C) �1 1

0.75 �1 1

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2.6. Magnetic bio-char yield

Themagnetic bio-char yieldwas defined as theweight of dried

produced magnetic bio-char to the weight of dry rawmaterial

as shown in Eq. (2):

Yieldð%Þ ¼ W1

Wo� 100 (2)

where W1 and Wo are the dry weight (g) of final magnetic bio-

char produced after chemical pyrolysis and dry weight (g) of

bio-char of precursor as a feed for pyrolysis respectively.

3. Results and discussion

3.1. Effect of process parameters on synthesis ofmagnetic bio-char

Synthesis of magnetic bio-char requires the knowledge on the

effect of process parameters such as: microwave power, ra-

diation time and IR. The produced magnetic bio-char was

studied to find out the best level of performance to enhance

the yield with high porosity and adsorption capacity. The ef-

fects of each process parameter were further discussed in the

following section.

3.1.1. Effect of microwave powerThe effect of microwave power on yield and adsorption of MB

is illustrated in Fig. 2. It was found that the higher microwave

power has decreased the yield of magnetic bio-char. Higher

microwave power is less effective than lower microwave

power due to the fact that at high microwave power devel-

opment of the pore structure and active sites are insufficient

[34,35]. The reaction between the agent and precursor at high

microwave power [35] do not promotes the development of

the pore structures and active sites [34], possibly was themain

reason for this observation [36,37]. At high microwave power

of 1000 W and above (temperature inside microwave of 600 �Cand above), over gasification might occur with detrimental

impact of reducing porosity and surface area, hence the car-

bon yield and adsorption uptakewere progressively decreased

Fig. 2 e Effect of microwave power on adsorption uptake of

MB and yield.

[38]. Furthermore, the yield was found to decrease contrari-

wise to the microwave power level, mainly attributed to the

ferric reaction at higher thermal radiation which intensified a

rapid volatilization, dehydration and decomposition. There is

a maximum MB adsorption at 900 W (temperature of 550 �C).At this point, the microwave energy was calculated 54 MJ g�1.

On the other hand, the graph shows the adsorption rate of MB

increased when the microwave power increases. Enhancing

microwave power to 900 W exhibited a drastic increase of

adsorption uptake of MB, possibly related to the combined

effect of internal and volumetric heating responsible for the

expansion of carbon structure [39]. At power levels higher

than the optimum level, the MB adsorption capacity of mag-

netic bio-char progressively decreased because (i) increased

gasification showed the detrimental effect of reducing

porosity and surface area and (ii) microwave energy above the

optimum level resulted in the burning of carbon and

destruction of the pore structures.

3.1.2. Effect of radiation timeFig. 3 shows the effect of microwave radiation time on yield

and adsorption uptake capacity of MB. It was observed that as

the radiation time increased, the yield of magnetic bio-char

decreased. Possibly sintering effect is responsible for this.

Because of the sintering effect the wall between two adjacent

pores were destroyed and micro and mesopores are widened

which in turn destroyed the carbon framework [39]. Moreover

due to higher radiation time CeFeCl3 and CeCO2 reactions are

facilitated and that leads to destruction of the CeOeC and

CeC bonds and in turn the yield of carbon [40,41]. While,

extending microwave radiation duration from 5 to 20 min

exhibited a drastic enhancement of adsorption from 55 to

265 mg g�1. The condition implied that increasing the expo-

sure supplies energy, which in turn increases the reaction

rates, thus developed the rudiments of the pore structure [39].

It is also observed that the increase in radiation duration

intensified the formation of active sites inside the AC [42].

However, by increasing the microwave radiation period from

25 to 40 min, MB adsorption capacity decreased from 265 to

80 mg g�1. Some pores of carbon would be burnt by increasing

the microwave radiation time beyond the optimum radiation

Fig. 3 e Effect of radiation time on adsorption uptake of MB

and yield.

Fig. 5 e Effect of a) BET surface area and b) Pore volume on

microwave power.

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5 269

duration [42]. TheMB adsorption capacity decreasedwhen the

activation time increased in the activation stage [34].

3.1.3. Effect of chemical impregnation ratioMicrowave radiations are adsorbed by the activation agents at

the initial stage of activation. Fig. 4 shows the effect of

chemical IR on yield and adsorption uptake capacity of MB. It

was clearly observed that as the IR increased, the yield of

magnetic bio-char decreased. As IR increased from 0.25 to 0.5,

an enhancement of carbon yield occurred from 70 to 89%.

Similarly, increasing IR from 0.25 to 0.5 indicated an incre-

ment of adsorption uptake from 95 to 265 mg g�1, and then

steadily decreased. By increasing the IR of char/FeCl3, the

activation process would play a key role in pore development,

giving a sustaining increase in the BET surface area and pore

volume. Correspondingly, the adsorption uptake was further

enhanced. Beyond this optimum value, the excessive FeCl3would promote a vigorous gasification reaction, which de-

stroys the carbon framework leading to a dramatic decrease of

accessible area widening and burning of pores could be the

reason for decreasing adsorption capacity [39].

3.1.4. Effect of microwave power on the BET surface area andpore volumeFig. 5 shows the influence of microwave heating on the BET

surfaceareaandporevolumeof themagneticbio-charwith the

activation of ferric chloride. At low microwave power, it was

observed that lowBETsurfaceareaandvery small pore volume

was developed on the surface of magnetic bio-char. Sharp in-

creases in BET surface area from250 to 890m2 g�1 and increase

in pore volume from 0.25 to 0.68 cm3 g�1 was observed when

power increased from 600 to 900 W. Higher microwave power

enhanced the development of porosity of the magnetic bio-

char in this research. Furthermore, increase in microwave

power caused decreases of the BET surface area and pore vol-

ume.This isdue to thereductionofporesizeathighmicrowave

power (>900W), the surface areas ofmicropore are also lower.

The reduction of micropore sizes and surface area could be

caused by the shrinkage or carbon deposition. Extensive mi-

cropores narrowing could also lead to pores closings.

Shrinkage effects occurred as a function of the bond breaking

processes that facilitate alignment of the structural units.

Fig. 4 e Effect of IR on adsorption uptake of MB and yield.

Subsequent bond formation or cross-linking would result in a

furtherdecrease inmicroporesvolumeandsurfacearea.These

structural alignments will reduce the interspaces among char

particles, and will promote more compact bulk and more or-

dered structure of the chars [43]. Another reason could be the

polymerization between volatile and non-volatile radical

components in the formation of carbon depositions. The de-

positions could occur in both pore mouth and passages that

lead to pore narrowing [44]. Additionally, microwave heating

hadaneffecton thedevelopmentofmicroporeandmesopores,

the micropore surface area of magnetic bio-char decreased

with the increase ofmicrowave power probably because of the

increased interaction between activation agent and pre-

cursors, resulting in the more intensive pyrolysis of starting

materials. Thus, some microspores were enlarged into meso-

pore. The total pore volume rose as microwave power

increased and the maximum value was obtained at 900 W.

3.2. Statistical analysis of magnetic bio-char production

The CCD is a statistical technique useful for modeling and

analysis during complex optimization [45e47]. The method

used permits reduction of the number of experimental trials

required, and parameters interactions in three dimensional

also be evaluated. The results from the experiments were

Table 2 e ANOVA for production of magnetic bio-char.

Source Sum of squares DF Mean square F value Prob > F Status

Model 7.653E þ 0.005 9 85027.6 87.57 0.0001 Significant

A 2898.8 1 2898.8 24.43 0.003

B 4798.73 1 4798.73 47 0.002

C 31,239 1 31,239 45.53 0.0001

D 3164 1 3164 32.2 0.0005

A2 81020.9 1 81020.9 14.68 0.001

B2 1945.30 1 1945.3 0.35 0.004

C2 2251.2 1 2251.2 4.08 0.006

AB 59,109 1 59,109 10.17 0.005

AC 24,798 1 24,798 4.49 0.052

BC 1145 1 1145 0.26 0.006

BC 623 1 623 5.06 0.06

Residual 77,287 14 5520

Lack of fit 76,953 5 15,390 414.62 0.0002 Not-significant

Pure Error 334.09 9 37.12

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5270

analyzed using analysis of variance (ANOVA) using DOE. The

variables such as microwave power, radiation time and IR

were employed for the analysis in the design to obtain the

high BET surface area of magnetic bio-char. The estimated

regression coefficient and the significance tests on the coef-

ficient are shown in Table 2. The significant of the model is

indicated by the F test value which is 87.57. In addition, the

ANOVA shows the Prob > F value of less than 0.05 indicating

the model is significant. The relationship of the variable was

tested for adequacy of fit by ANOVA. The adequacy of the

model developed was demonstrated by the high coefficient

value (R2 ¼ 0.997) and adjusted coefficient (R2 Adj ¼ 0.987) is

near to one, representing a significance of the model. The

model Eq. (3) is as follows:

BET surface area¼692:38þ 86:56Aþ 16:33B� 118:17C

� 172:77A2 � 26:77B2 � 1:07C2

þ 60:78AB� 39:37AC� 9:51BC

(3)

where, the responsewas the BET surface area ofmagnetic bio-

char, A is the coded value of reaction time, B is the coded value

of microwave power and C is the coded value of impregnation

ratio. The coefficient of a single factor indicates a single

interaction for the specific factor. On the other hand, the co-

efficients with two factors represent the interaction between

the two different parameters. The positive sign in the equa-

tion indicates a synergistic effect whereas negative sign in-

dicates antagonistic effect.

Fig. 6 represents the 3-dimensional plot for magnetic bio-

char prepared surface area affect by variables are microwave

power, reaction time and impregnation ratio. The 3-D plot of

the interaction between time and power as depicted in Fig. 6

(a) shows that initially with increasing time BET surface area

increases but after 20 min the BET surface area decrease

which may be due to the fact that if the FeCl3 impregnated

material is exposed to microwave radiation for longer periods

it becomes ash and the material is damaged. When the ma-

terial is exposed to microwave for a shorter period of time the

power has no effect on the BET surface area, but at the higher

exposure time of more than 15min BET surface area increases

as the power increases. The plot suggests that there is sig-

nificant interaction between time and power. The interaction

between IR and power is shown in Fig. 6 (b). It shows

significant interaction between the two variables mentioned

with power was the actual factor. It can be inferred that lower

IR is more suitable for producing a magnetic bio-char with the

high BET surface area. However at exposuremore than 20min

to microwave again the BET surface area reduces due to

damage to the material. So there exists an optimum point in

between the highest and the lowest level of the two variables

via IR and time. The interaction of IR and time is shown in

Fig. 6 (c). It can be seen that the BET surface area slightly in-

creases as the IR increase at the beginning however at a higher

IR 0.63, BET surface area gradually decrease. Power and IR do

not have a significant interaction.

3.3. Characterization of novel magnetic bio-char

3.3.1. Analysis of BET surface areaPhysical characterizationofhighest adsorptionperformanceof

the magnetic bio-char produced was analyzed using BET

(Brand: Quanta Chrome Model: Autosorb 6B). Results proved

that higher surface areawith higher pore size distribution. The

specific BET surface area of the EFB based magnetic bio-char

prepared was found to be 890 m2 g�1. The results obtained

agreedwithpreviousstudy [48]which reported thatBETsurface

area is higher than 350 m2 g�1 after carbonization of lignin at

900 �C. In addition, macropores are produced during the acti-

vation stage while carbonization forms only micropores and

mesopores. This developmentwas reportedpreviously inother

studies and explained that the activation not only widens the

sizeof theexistingporesbut also formsanewpores [49,50]. The

median pore size for EFB based magnetic bio-char was almost

2 nm, which is in the range of microporous size [45] thus, cor-

robating that the prepared magnetic bio-char is mainly

microporous. Since the diameter of molecules of MB has a

minimummolecularcross-sectionof0.8nm,andtheminimum

porediameter that theMBmolecule canenterwasestimated to

be 1.3 nm. In contrast, the iodine molecule is significantly

adsorbedbecauseof its smallersize, permitting thepenetration

of iodine into micropores larger than 1 nm [51,52].

3.3.2. Field emission scanning electron microscopeThe FESEM technique was employed to observe the surface

physical morphology of the selected magnetic bio-char. Fig. 7

Fig. 6 e 3-D plots of BET surface area of magnetic bio-char, (a) interaction of reaction power and reaction time, (b) interaction

of IR and reaction power, (c) interaction of IR and reaction time.

Fig. 7 e (a, b) FESEM image of raw EFB at different magnification, (c, d) FESEM image of magnetic Bio-char produced at

different magnification.

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5 271

Fig. 8 e FTIR absorption spectra, a) Raw EFB b) Magnetic bio-char.

Table 3 e EDX analysis of the magnetic bio-char.

Element Element mass fraction of dry material

Non-magnetic bio-char Magnetic bio-char

C 76.42 10.26

O 23.3 4.43

F 0.05 1.04

Fe 0.23 84.28

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5272

shows images of raw EFB and the prepared novel magnetic

bio-char with different magnification scale (1 mm and 10 mm).

In Fig. 7 (a, b), it can be clearly seen that the surface texture of

raw EFB is intense, slender, and compressed covered by

depositing tarry substances, with a small amount of pores

observed on the surface of the precursor. On the other hand,

after a chemical activation process with the optimum condi-

tions of 900 Wmicrowave power, 20 min radiation time, 0.5 IR

and nitrogen gasification at 200 cm3 min�1, large pores of

different sizes and shapes were well developed porosity, a

distribution of a series of asymmetrical cavities around the

surface of magnetic bio-char as shown in Fig. 7 (c, d). The

microporosity is opened and broadened with a shift to meso-

and micropore as the removal of the exterior of the particle is

significant at high burn-offs [53]. This reflects that N2 is effi-

cient in developing pores on the surfaces of the precursor,

therefore enhancing a novel magnetic bio-char with porous

structure, large surface area and the compactness of the shell

structure is seen to have high adsorption capacity for the

removal of MB from aqueous solution.

3.3.3. Fourier transform infrared spectroscopyFTIR spectroscope (Bruker, IFS66v/S) was used to analyze the

novel magnetic bio-char for determination of the surface

functional groups. Fig. 8 (a, b) shows the FTIR results for the

surface functional groups of the raw EFB and magnetic bio-

char respectively. Fig. 8 (a) shows raw EFB has no functional

group attachment was observed. On the other hand Fig. 8 (b)

shows that the functional groups have been successfully

impregnated on the surface of magnetic bio-char. The band

located at 3436-3247 cm�1 is related to the NeH groups, while

the region between 2361 and 2270 cm�1 is grouped as C^C

stretch of alkynes. Vibration of C^N is ascribed at intensity

1995 cm�1. The transmittance at 1652e1498 cm�1 is similar to

the OeH (hydroxyl) group, and CH2 and CeOeC (ether, ester

and phenol) functionalities are shownwith intensive peaks at

1425 and 1276 cm�1. Similarly, the sharp peaks found at 1053

and 808 cm�1 are corresponds to the CeO (anhydrides) and

CeH derivatives. These results agreed with the surface

chemistry of other agricultural by products [54e56].

3.3.4. EDX analysis of magnetic bio-charFor the confirmation of oxidation reaction, elemental com-

positions of the magnetic bio-char before and after function-

alization were examined by Electron Dispersive X-ray (EDX)

analysis. Table 3 shows a listed of the elemental composition

of the non-magnetic bio-char and magnetic bio-char. The

composition of carbon (C) in non-magnetic and magnetic bio-

char was 76.42% and 10.26% respectively. There was a reduc-

tion of 66.16% from non-magnetic bio-char to magnetic bio-

char, which related to the attachment of iron oxide mag-

netic composite on carbon. Thus, iron oxide functionalization

was successfully achieved by EDX analysis.

3.3.5. Thermogravimetric analysisRodriguez-Reinoso and Molina-Sabio [53] stated that three

stages could be identified during the thermal decomposition

of lignocellulosic materials, i.e., (i) evaporation of adsorbed

water in the range of 27e300 �C, (ii) primary pyrolysis in the

range of 300e500 �C with the release of most gases and early

development of the basic structure of the char; and (iii) further

consolidation of cross-linked product structure between 500

and 850 �Cwith a small weight loss. Fig. 9 shows the variations

of the magnetic bio-char mass with respect to reaction

Fig. 9 e TGA and DTG analysis of the magnetic bio-char produced at optimal conditions.

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5 273

temperatures at specific time. TGA (Brand; Mettler Toledo

model; Mettler Toledo TGA/STDA 85e) analysis shows one

peak at 360 �C indicating weight loss of themagnetic bio-char.

In addition, the peak corresponds to the decomposition of one

element only (carbon), since no other peaks were observed. A

slight loss of weight between 70 and 120 �C was observed,

which correspond to the release of adsorbed water. As the

temperature continued to rise from 350 to 650 �C, the com-

pound decomposed at a faster rate caused the weight loss due

to the oxidation of magnetic bio-char. There is a steep and

steady weight loss of powdered magnetic bio-char at

400e600 �C. The flat profile between 650 �C and 850 �C showed

that the metal ferric ions were not volatile and thus remain as

residue. These observations revealed themechanism involved

in the activation progress. Some chemical components might

join to form with bond in the aromatic nucleus of precursors,

followed by recombination and formation of new polymeric

structures with more thermal stability.

4. Conclusion

Theaimof thestudy toproduceanovelmagneticbio-char from

a discarded material particularly EFB was successfully ach-

ieved by a single stage microwave heating. The high yield and

high surface area of magnetic bio-char were effectively pro-

duced at microwave power of 900 W, radiation time of 20 min

and IR of 0.5. This optimum condition contributed to a high

surface area of 890m2 g�1 and that leads to removal ofMBwith

high efficiency of 99.9% from aqueous solution with a

maximumadsorptioncapacityof 265mgg�1.On thewhole, the

high performance of the developed novel magnetic bio-char

could replace AC, due its high surface area, high porosity and

high adsorption capacity. Therefore, this novel study innovate

new dimension to the various applications of AC.

Acknowledgment

This work was supported by University of Malaya for fully

funding under HIR-MOHE (UM/MOHE HIR, Grant No. D000020-

16001).

r e f e r e n c e s

[1] Tanaka R, Rosli W, Magara K, Ikeda T, Hosoya S. Chlorine-free bleaching of kraft pulp from oil palm empty fruitbunches. JARQ 2004;38(4):275e9.

[2] Rahman SHA, Choudhury JP, Ahmad AL. Production of xylosefrom oil palm empty fruit bunch fiber using sulfuric acid.Biochem Eng J 2006;30(1):97e103.

[3] Chen B, Chen Z, Lv S. A novel magnetic bio-char efficientlysorbs organic pollutants and phosphate. Bioresour Technol2011;102(2):716e23.

[4] Warnock DD, Lehmann J, Kuyper TW, Rilig MC. Mycorrhizalresponses to bio-char in soil-concepts and mechanisms.Plant Soil 2007;300(1e2):9e20.

[5] Yanai Y, Toyota K, Okazaki M. Effects of charcoal addition onN2O emissions from soil resulting from rewetting air-driedsoil in short-term laboratory experiments. Soil Sci Plant Nutr2007;53(2):181e8.

[6] Kookana RS, Sarmah AK, Zwieten L Van, Krull E, Singh B.Biochar application to soil: agronomic and environmentalbenefits and unintended consequences. In: Sparks DL, editor.Advances in agronomy San Diego. South Australia: Elsevieracademic press inc; 2011. pp. 103e43.

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5274

[7] Lin YF, Chen HW, Chien PS, Chiou CS, Liu CC. Application ofbifunctional magnetic adsorbent to adsorb metal cations andanionic dyes in aqueous solution. J Hazard Mater2010;185(2e3):1124e30.

[8] Chen B, Zhou D, Zhu L. Transitional adsorption and partitionof nonpolar and polar aromatic contaminants by bio-char sof pine needles with different pyrolytic temperatures.Environ Sci Technol 2008;42(14):5137e43.

[9] Kołodynska D, Wnetrzak R, Leahy JJ, Hayes MHB,Kwapinski W, Hubicki Z. Kinetic and adsorptivecharacterization of bio-char in metal ions removal. ChemEng J 2012;197:295e305.

[10] Sourja C, Sirshendu D, Jayanta KB. Adsorption study for theremoval of basic dye: experimental and modeling.Chemosphere 2005;58(8):1079e86.

[11] Qiu Y, Zheng Z, Zhou Z, Sheng GD. Effectiveness andmechanisms of dye adsorption on a straw-based bio-char.Bioresour Technol 2009;100(21):5348e51.

[12] Cao X, Ma L, Gao B, Harris W. Dairy-manure derived bio-chareffectively sorbs lead and atrazine. Environ Sci Technol2009;43(9):3285e91.

[13] Lata H, Garg VK, Gupta RK. Adsorptive removal of basic dyeby chemically activated parthenium biomass. Desalination2008;219:250e61.

[14] Yao Y, Gao B, Inyang M, Zimmerman AR, Cao XD,Pullammanappallil P, et al. Bio-char derived fromanaerobically digested sugar beet tailings: characterizationand phosphate removal potential. Bioresour Technol2011;102(10):6273e8.

[15] Yao Y, Gao B, Inyang M, Zimmerman AR, Cao XD,Pullammanappallil P, et al. Removal of phosphate fromaqueous solution by bio-char derived from anaerobicallydigested sugar beet tailings. J Hazard Mater2011;190(1e3):501e7.

[16] Zhang G, Qu J, Liu H, Cooper AT, Wu R. CuFe2O4/activatedcarbon composite: a novel magnetic adsorbent for theremoval of acid orange II and catalytic regeneration.Chemosphere 2007;68(6):1058e66.

[17] Wiatrowski HA, Das S, Kukkadapu R, Llton ES, Barky T,Yee N. Reduction of Hg(II) to Hg(0) by magnetite. Environ SciTechnol 2009;43(14):5307e13.

[18] Lim SF, Zheng YM, Chen JP. Organic arsenic adsorption ontoa magnetic sorbent. Langmuir 2009;25(9):4973e8.

[19] Loyo RL dA, Nikitenko SI, Scheinost AC, Simonoff M.Immobilization of selenite on Fe3O4 and Fe/Fe3C ultrasmallparticles. Environ Sci Technol 2008;42(7):2451e6.

[20] Zeng L, Li X, Liu J. Adsorptive removal of phosphate fromaqueous solutions using iron oxide tailings. Water Res2004;38(5):1318e26.

[21] Zhang H, Xiao R, Huang H, Xiao G. Comparison of non-catalytic and catalytic fast pyrolysis of corncob in a fluidizedbed reactor. Bioresour Technol 2009;100(3):1428e34.

[22] Ania CO, Parra JB, Menendez JA, Pis JJ. Microwave-assistedregeneration of activated carbon loaded withpharmaceuticals. Water Res 2007;41(15):3299e306.

[23] Liu X, Yu G. Combined effect of microwave and activatedcarbon on the remediation of polychlorinated biphenyl-contaminated soil. Chemosphere 2006;63(2):228e35.

[24] Steenwinkel YZ, Zande LMV d, Castricum HL, Bliek A,Brink RWV d, Elzinga GD. Microwave-assisted in-situregeneration of a perovskite coated diesel soot filter. ChemEng Sci 2005;60(3):797e804.

[25] Kappe CO. Controlled microwave heating in modern organicsynthesis. Angew Chem Int Ed 2004;43(46):6250e84.

[26] Gronnow MJ, White RJ, Clark JH, Macquarrie DJ. Energyefficiency in chemical reactions: a comparative study ofdifferent reaction techniques. Org Process Res Dev2005;9(4):516e8.

[27] Masek O, Budarin V, Gronnow M, Crombie K, Brownsort P,Fitzpatrick E, et al. Microwave and slow pyrolysis bio-charecomparison of physical and functional properties. JAnal Appl Pyrol 2013;100:41e8.

[28] Guo J, Lua AC. Preparation of activated carbons from oil-palm-stone chars by microwave-induced carbon dioxideactivation. Carbon 2000;38:1985e93.

[29] Thostenson ET, Chou TW. Microwave processing:fundamentals and applications. Compos Part A Appl SciManuf 1999;30(9):1055e71.

[30] Alam MZ, Muyibi SA, Toramae J. Statistical optimization ofadsorption processes for removal of 2,4-dichlorophenol byactivated carbon derived from oil palm empty fruit bunches.J Environ Sci 2007;19(6):674e7.

[31] Xinehui D, Srinivasakannan C, Jin-hui P, Li-bo Z, Zheng-yong Z. Preparation of activated carbon from jatropha hullwith microwave heating: optimization using responsessurface methodology. Fuel Process Technol2011;92(3):394e400.

[32] Tan IAW, Ahmad AL, Hameed BH. Optimization ofpreparation conditions for activated carbons from coconuthusk using response surface methodology. Chem Eng J2008;137(3):462e70.

[33] Boehm HP. Surface oxides on carbon and their analysis: acritical assessment. Carbon 2002;40:145e9.

[34] Deng H, Yang L, Tao G, Dai J. Preparation andcharacterization of activated carbon from cotton stalk bymicrowave assisted chemical activation: application inmethylene blue adsorption from aqueous solution. J HazardMater 2009;166(2e3):1514e21.

[35] Liu QS, Zheng T, Li N, Wang P, Abulikemu G. Modification ofbamboo-based activated carbon using microwave radiationand its effects on the adsorption of methylene blue. ApplSurf Sci 2010;256(10):3309e15.

[36] Hejazifar M, Azizian S, Sarikhani H, Li Q, Zhao D.Microwave assisted preparation of efficient activatedcarbon from grapevine rhytidome for the removal ofmethyl violet from aqueous solution. J Anal Appl Pyrol2011;92(1):258e66.

[37] Oghbaei M, Mirzaee O. Microwave versus conventionalsintering: a review of fundamentals, advantages andapplications. J Alloys Compd 2010;494(1e2):175e89.

[38] Upadhyaya A, Tiwari SK, Mishra P. Microwave sintering ofWeNieFe alloy. Scr Mater 2007;56(1):5e8.

[39] Sun K, Ro K, Guo M, Novak J, Mashayekhi H, Xing B. Sorptionof bisphenol A, 17a-ethinyl estradiol and phenanthrene onthermally and hydrothermally produced bio-chars. BioresourTechnol 2011;102(10):5757e63.

[40] Foo KY, Hameed BH. Coconut husk derived activated carbonvia microwave induced activation: effects of activationagents, preparation parameters and adsorptionperformance. Chem Eng J 2012;184:57e65.

[41] Adinata D, Daud WMAW, Aroua MK. Preparation andcharacterization of activated carbon from palm shell bychemical activation with K2CO3. Bioresour Technol2007;98(1):145e9.

[42] Li W, Zhang LB, Peng JH, Li N, Zhu XY. Preparation of highsurface area activated carbons from tobacco stems withK2CO3 activation using microwave radiation. Ind Crops Prod2008;27(3):341e7.

[43] Wu Y, Wu S, Huang S, Gao J. Physicochemical properties andstructural evolutions of gas-phase caarbonization char athigh temperatures. Fuel Process Technol 2010;91(11):1662e9.

[44] Demirbas A. Carbonization ranking of selected biomass forcharcoal, liquid and gaseous products. Energy ConversManage 2001;42(10):1229e38.

[45] Lee J, Ye L, Landen WO, Eitenmiller RR. Optimization of anextraction procedure for the quantification of vitamin E in

b i om a s s a n d b i o e n e r g y 6 1 ( 2 0 1 4 ) 2 6 5e2 7 5 275

tomato and broccoli using response surface methodology. JFood Compos Anal 2000;13(1):45e57.

[46] Sahu JN, Jyotikusum A, Meikap BC. Optimization ofproduction conditions for activated carbons from tamarindwood by zinc chloride using response surface methodology.Bioresour Technol 2010;101(6):1974e82.

[47] Benaddi H, Bandosz TJ, Jagiello J, Schwarz JA, Rouzaud JN,Legras D, et al. Surface functionality and porosity ofactivated carbons obtained from chemical activation ofwood. Carbon 2000;38(5):669e74.

[48] Huidobro A, Pastor AC, Reinoso FR. Preparation of activatedcarbon cloth from viscous rayon part IV chemical activation.Carbon 2001;39(3):389e98.

[49] Bansal RC, Goyal M. Activated carbon adsorption. USA: CRCpress; 2005. pp. 351e3.

[50] Mcdougall GJ. The physical nature and manufacturing ofactivated carbon. J S Afr Inst Min Met 1991;91(4):109e20.

[51] Hu Z, Srinivasan MP. Mesoporous high-surface-areaactivated carbon. Microporous Mesoporous Mat2001;43(3):267e75.

[52] Wartelle LH, Marshall WE, Toles CA, Johns MM. Comparisonof nutshell granular activated carbons to commercialadsorbents for the purge-and-trapgas chromatographicanalysis of volatile organic compounds. J Chromatogr A2000;879(2):169e75.

[53] Rodriguez-Reinoso RF, Molina-Sabio M. Activated carbonsfrom lignocellulosic material by chemical and/or physicalactivation: an overview. Carbon 1992;30(7):1111e8.

[54] Pietrzak R, Jurewicz K, Nowicki P, Babel K, Wachowska H.Microporous activated carbons from ammoxidisedanthracite and their capacitance behaviours. Fuel2007;86(7e8):1086e92.

[55] Bouchelta C, Medjram MS, Bertrand OJP. Preparation andcharacterization of activated carbon from date stones byphysical activation with steam. J Anal Appl Pyrol2008;82(1):70e7.

[56] Sun RC, Tomkinson J. Fractional separation and physic-chemical analysis of lignin from the black liquor of oil palmtrunk fibre pulping. Sep Purif Technol 2001;24(3):529e39.