Bulletin of

Trends in

Chemical Sciences

Scibay Publications

S. Radjarejesri*, V. Parimala

Department of Science, Sona college of Technology, Salem, Tamilnadu, India- 636005

Department of chemistry, Sri Sarada college, Salem, Tamilnadu, India-636003

Vol. 1 (1) 2016, 22-26

Introduction

Mangifera indica is a species of mango of the

Anacardiaceae family. It is found in India and many

varieties of mango have been cultivated varieties in other

warm regions of the world. It is the largest fruit-tree in

the world, capable of a height of one-hundred feet and an

average circumference of twelve to fourteen feet,

sometimes reaching twenty [1]. Here we report on the

porous texture and characteristics of activated carbon

prepared from activation of mango seed kernel by H3PO4.

These constitute a by-product from mango processing,

with few practical applications and whose uncontrolled

spill (e.g. in rivers) causes some environmental concern.

In fact, applications of seeds are limited to use as fuel or

feedstock as food for animal. We will show that carbon

adsorbents with high surface areas and pore volumes can

be obtained from this material, and that development of

the porous structure can be modulated by the use of

hydroxides for chemical activation. Prior to the use, the

seed of mango was repeatedly washed with distilled

water in order to remove fibres and other inorganic

impurities, then oven-dried for 24 h at 750o C to reduce

the moisture content.

Activated carbon can be produced from all carbon

containing ligno cellulosic materials i.e. lignin, macro-algal

defective coffee, press cake, palm shell, rice husk, wastes

of vegetable origin (e.g. nutshells, fruit stones) There are

two processes for preparation of activated carbon:

chemical activation and physical activation. Chemical

activation is known as a single step method of preparation

of activated carbon in the presence of chemical agents.

Physical activation involves carbonization of a

carbonaceous materials followed by activation of the

resulting char in the presence of activating agents such as

CO2 or steam. The chemical activation usually takes place

at a temperature lower than that used in physical

activation; therefore it can improve the pore development

in the carbon structure because of the effect of chemicals.

Paper Open access

Preparation and characterization of activated carbon derived from mango seed kernel

(mangifera indica) in presence of ortho phosphoric acid

ABSTRACT

The study reports the use of Mango seed kernel as precursor for the preparation of activated carbon by

pyrolysis in presence of ortho phosphoric acid (Chemical activity) at different impregnation ratio. The prepared

adsorbents were characterized for its surface properties such as pH, bulk density, pHpzc, porosity and iodine number

was conducted and compared to a commercial activated carbon. A significant difference in the properties of

moisture, pH, porosity, ash content, iodine number, carboxylic acid content, lactones, pHpzc and basic sites content

were observed on the activated carbons. Activated carbon of high surface area and high degree of porosity was

characterized using SEM and FT-IR. Materials with a well developed pore structure and excellent adsorption

capacities with pore size 20-60µm were obtained.

Key words – Ortho Phosphoric acid; activated carbon; mango seed kernel;

Radjarejesri and Parimala / Bulletin of Trends in Chemical Sciences 1 (1) (2016) 22-26

23 Scibay Publications

The carbon yields of chemical activation are higher than

physical activation.

Materials and methods

Sample collection, preparation and carbonization

Mangifera indica plant seeds were collected from

agricultural land in Salem, Tamilnadu in India. They were

sun dried and stored in air tight plastic container for

chemical activation. In the preparation of the mango

seeds, the procedure described hence was followed. First,

the dried mango nuts collected were cracked using

hammer and the kernel was then removed from the nuts.

It was dried under sun light at room temperature for two

weeks after which they were crushed using laboratory

mortar and pestle. The resulting particles were again sun-

dried for 5 h to remove any residual moisture left in them.

The particles were then sieved using sieve size of 6 mm.

The activation was at different impregnated ratio

(1:1, 1:1.5, 1:2, 1:2.5), the prepared adsorbents were

designated as I, II, III, and IV. All the adsorbents were

stirred well for 30 min to get homogenous slurry. Later,

place the mixture in furnace and heat up to carbonization

temperature at 7500C for 30 min. The temperature is

raised from room temperature to carbonization

temperature with increase of 100 C/min. After heating, the

mixture is cooled to room temperature and washed with

distilled water until the activated carbon’s pH comes to 7.

Later the powder is dried in oven for 24 h and used for

further characterization.

Results and discussion

Characterisation of activated carbon SEM (Scanning Electron Microscope)

The surface morphology of the prepared activated

carbon was analyzed using scanning electron microscope.

The SEM image exhibits the carbon is highly porous in

nature and also it is uniform, because porosity is one of

the key factors to access the quality of carbon for specific

applications. High porous material is highly useful for the

adsorption and filtration application.

Fig.1 SEM image of adsorbent I

Fig.2 FTIR image of adsorbent I

Fourier Transform Infrared (FTIR) Analysis

FTIR analysis was carried out in order to identify the

different functional groups present in mango seeds which

are responsible for adsorption process. The peaks

appearing in the FTIR spectrum were assigned to various

functional groups according to their respective wave

numbers as reported in literatures. It was observed that

the different wave numbers of peaks at 3606, 3012, 1708,

904,and 875 2925, cm-1. FTIR studies of precursor ratio

1:1(Adsorbent I) was performed. The studies showed the

50010001500200030004000

1/cm

96

97.5

99

100.5

%T

36

06

.89

32

21

.12 3

01

2.8

1

17

08

.93

15

25

.69

14

75

.54

14

44

.68

13

63

.67

12

20

.94

10

16

.49

90

4.6

1

87

5.6

8

47

0.6

3

45

9.0

6

ACT CARBON1:1 H3PO4

Radjarejesri and Parimala / Bulletin of Trends in Chemical Sciences 1 (1) (2016) 22-26

24 Scibay Publications

presence of various functional groups. The spectrum

obtained has been shown in the Fig. 2 with various

absorptions at the corresponding wave numbers.

Determination of mesh size

The physical size, (or) mesh size, of a carbon must

be considered in relation to the flow rate in the system it

is to be used. Naturally, the smaller the carbon’s mesh size

the greater its resistance to flow. Thus it is usual to select

the smallest mesh size carbon that will satisfy. The

pressure drop limitations of the system. The effect of

mesh size was studied by using four different

concentrations of mango seeds. 0.1g of mango seed

powder was sieved into desired material.

Determination of bulk density

A 10ml measuring cylinder was weighed

accurately. Sufficient amount of carbon samples were

transferred with constant tapping and filled up to 7ml

mark. After filling the measuring cylinder was weighed

and the bulk density was calculated by using mass/

volume ratio. The different values are interpreted in the

table 1.

Calculation and expression of results- bulk density.

DB = (m4-m3)/v1

Where,

m3=is the gram of the measuring cylinder.

m4=is the mass in gram of the measuring cylinder and

its content.

V1=is the volume in liters of measuring cylinder [2]

Determination of moisture content

Thermal drying was used in the determination of

moisture content of the samples. 1.0g of the dried

activated carbon was weighed in triplicates and placed in

washed, dried and weighed crucible .The crucible was

placed in an oven and dried at 1050C to constant weight

for 4 hours according to the method of Renagaraj [3]. The

values are summarized in Table-1

Determination of ash content

A standard test method for ash content was

carried out crucible was pre-heated in muffle furnace to

about 5000 C. cooled in a desiccator and 1.0g of activated

carbon samples were weighed and transferred into the

crucibles and reweighed. The crucibles containing the

samples were then placed in a cold muffle furnace and the

temperature was allowed to rise to 5000C. It was removed

and allowed to cool in desiccators to room temperature

(300C) and reweighed again. The values are summarized

in Table-1

Determination of volatile matter

About 1.0gm of the carbon sample was weighed

accurately and transferred into a closed silica crucible.

The closed silica crucible along with the carbon

samples were placed in an air oven and maintained at

1000C±50C temperature for about 7mins. The silica

crucible was removed from the oven and the carbon

samples were ignited in an electric furnace at a room

temperature of 1000C±100C for about 1hour. The

process of igniting and cooling was repeated until

difference between the last two successive weighing

was less than 1 mg. The values are summarized in Table-

1

Determination of fixed carbon

The fixed carbon content of a coal is determined

by subtracting the percentage of moisture, volatile

matter, and ash from a sample. The values are

summarized in Table-1

Fixed Carbon = 100% Sample - (%Moisture-%Ash-

%Volatile Matter)

Determination of iodine number

0.01g of activated carbon from each precursor

was weighed and taken in a beaker and 10 ml of standard

iodine solution (0.01M) was added and the mixture was

swirled vigorously for 10mins. The solution was filtered

by using funnel impregnated with clean filter paper. 8ml

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25 Scibay Publications

of the clear filtrate was titrated with the standard sodium

thiosulphate solution (0.001M) to obtain a persistence

pale yellow color. 5ml of freshly prepared starch indicator

solution was added and titrated until a colorless solution

appeared. The procedure was repeated until a

consecutive concordant end point is obtained. Blank

titration of 8ml standard iodine solution was carried out

without the addition of the precursor sample. This gave

this number of iodine molecules adsorbed by the

precursor. The values are summarized in Table-1

Determination of oxygen containing functional groups

The method proposed by Boehm was used to estimate

the acid base properties of commercial activated carbon

and agricultural activated carbon samples [4]. It is well

known that surface chemical groups are more complex

than by Boehm’s titrations, but this method gives a semi-

quantitative measure of surface functionalities. Boehm’s

method is based on acid base titration of carbon acidic or

basic centers. Consequently selective neutralization of

surface groups by equilibrations with a series of bases

with increasing strength was conducted as follows:

NaHCO3 neutralizes carboxylic groups: Na2CO3 neutralizes

carboxylic groups and also allows lactonic groups to open

and form carboxylic groups, which are then neutralized;

NaOH neutralizes carboxylic, lactonic, and phenolic

groups [4].

The amounts of various acidic functional

groups were measured by selectively neutralized using

NaHCO3, Na2CO3 and NaOH solution respectively. The

basicity was determined by the reaction of carbon with

HCl. About 0.01g of carbon was placed in 20ml of 0.1N of

each solution and the mixtures were allowed to stand for

48h at room temperature. The mixtures were separated

by filtering. The amount of each base neutralized by the

carbon was determined by back titration using 0.1 HCl

solutions [5], whereas the amount of HCl consumed by

basic groups in carbon was determined by back titration

using 0.1 NaOH. The values are summarized in Table-1

Point zero charge measurements (pHpzc)

To a series of 250ml conical flasks add 50ml of

0.1M KCl and adjust initial pHi of the solution from 2-10

Table.1 Physio-chemical characterization of prepared activated

carbons

S No.

Description

I

II

III

IV

CC*

1 Mesh size (Mic) 100 100 100 100 100

2 Bulk density 0.56 0.50 0.44 0.40 0.50

3 Moisture content

4.3 6.8 6.9 6.8 8.9

4 Ash content 38.0 26.7 30.9 19.8 38.7

5 Point zero charge

7.4 6.53 6.8 6.0 7.5

6 Volatile matter 25.32 36.24

23.13

15.17

27

7 Fixed carbon 32.77 30.51

39.01

58.16

26.09

8 Iodine adsorption

246.5 171.5

248 249.5

-

9 Acidic functional groups Phenolic- Lactones-

0.01 0.3

0.15 0.35

0.03 0.24

0.03 0.24

- 0.31

10 Basic functional group

- 0.05 0.08 0.1 0.02

11 Yield 52.94 48.66

46.62

39.40

-

by 0.1M HCl or 0.1M NaOH .To the solution add

0.1g of adsorbent (for ex 1:1 prepared material ) to each

of the flask. The suspensions were then shaken manually

and allowed to equilibrate for 48h. After 48h the

suspension was filtered and the final pHf values of

supernatant liquid were noted. The difference between

initial and pHf values (∆H) was plotted against pH. Now

you will get pHpzc for one of the material prepared.

Similarly repeat the same procedure for different ratio of

activated carbon prepared from Ortho Phosphoric acid.

The values are summarized in Table-1

Conclusion

The present work features the utilization of

commonly available waste material. The investigation

comprises of the pyrolysis of mango seed kernel

impregnated with ortho phosphoric acid and converted

into the activated carbon. Materials with a well developed

Radjarejesri and Parimala / Bulletin of Trends in Chemical Sciences 1 (1) (2016) 22-26

26 Scibay Publications

pore structures and excellent adsorption capacities with

pore size 20 - 60µm were obtained. Using Response

Surface Methodology, the activated carbons from mango

kernel with high surface area, high carbon yield, low ash

content, low moisture content, bulk density, low volatile

matter, etc. suitable for adsorption studies were obtained.

Further the acid – base functional groups, iodine value,

carbon yield, mesh size were analysed and found

satisfactory as a good adsorbent. The activated carbon

was characterized by using FTIR and SEM to study the

structure. It is concluded that the prepared activated

carbon of different impregnation ratios can be effectively

used to adsorb coloured solute and impurities from

industrial effluents. Industrial low cost effective

adsorbents have tremendous potential in the process of

adsorption. This pilot study of production of activated

carbon will for sure contribute to the measures of abating

the environmental degradation caused by dumping of

agricultural wastes.

References

[1] Palaniswamy, K. P., Muthukrishna, C. R.,

Shanmugavelu, K. G., Indian Food Packer, , 28 (1974) 12 –

18.

[2]Rengaraj, S., Agri. Solid Waste Removal Org., 22 (2002)

543 – 548.

[3]Boehm, H. P., In Chemical Identification of Functional

Groups, Eley, D. D. Ed., 16 (1966) 179.

[4] Mesquita, J., Particia, P., Martelli, B., Fatima Gorgulho.

H., Braz. Chem. Soc., 17 (2006) 1133 – 1143.

[5]Toles, C., Rimmera, S., Hower, J. C., Production of

Activated Carbons from a Washington Lignite using

Phosphoric Acid Activation, 34 (1996) 1419 – 1426.