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© Applied Science Innovations Pvt. Ltd., India Carbon – Sci. Tech. 6 / 3 (2014) 30 – 42

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ARTICLE Received : 02/09/2014, Accepted:08/10/2014

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Physico-Chemical Characterization Studies of Activated Carbon Derived from

Sterculia Quadrifida Seed Shell Waste

P. Shanthi (A), K. Jothi Venkatachalam

(B), S. Karthikeyan

(C*)

(A) Department of Chemistry, Kongunadu College of Engineering and Technology, Thottiam, Tamil

Nadu, India.

(B) Department of Chemistry,Anna University of Technology, Tiruchirappalli, Tamil Nadu, India.

(C) Department of Chemistry, Chikkanna Government Arts College, Tirupur, Tamil Nadu, India.

A carbonaceous adsorbent prepared from the Sterculia Quadrifida shell by various activation process,

viz., Acid process, Chloride process, Carbonate process and Sulphate process are successfully reported.

It shows excellent improvement in the surface characteristics. Their physico-chemical characterization

studies such as bulk density, moisture content, ash content, fixed carbon content, matter, soluble in

water, matter soluble in acid, pH, decolourizing power, porosity and specific gravity have been carried

out to assess the suitability of these carbons as potential adsorbent for waste water treatment. The

present study undertaken to evaluate the efficiency of a carbon adsorbent prepared from Sterculia

Quadrifida seed shell waste for removal of dyes in aqueous solution.

Keywords: Sterculia Quadrifida seed shell waste; Activated Carbon; Dye Adsorption Characteristics ------------------------------------------------------------------------------------------------------------------------------------------------

1. Introduction :

The textile industry produces large quantities of highly colored effluents, which were generally toxic and

resistant to destruction by biological treatment methods. Most of the dyestuffs used are complexly

structured large organometallic compounds with low biodegradability. This was one of the most

important reasons for the water pollution. Water is essential for survival is suffering from persistent

demand of safe drinking water. Dye industries are the largest sector of chemical industries in India, since

they are used in textile, paint and paper industries. The use of charcoal extends far back into history.

Ancient Hindus in India used charcoal for drinking water purification whereas Egyptians used it for

medical adsorbent and purifying agent as early as 1500 BC [1]. Activated carbon was first introduced

industrially in the first part of the 20th century, when activated carbon from vegetable material was

produced for use in sugar refining [2]. Powdered activated carbon was first produced commercially in

Europe in the 19th century, using wood as a raw material, which found wide use in the sugar industry.

First production of activated carbon used black ash as the source, after it was accidentally discovered

that the ash was very effective in decolorizing liquids [3]. Activated carbon has been used extensively

for this purpose in many industries. In particular, it has been commonly used for the removal of organic

dyes from textile waste waster [4].

Many investigators have the feasibility of using inexpensive alternative materials like Jatropha Curcus

seed shell, Delomix regia seed shell, Ipomea Carnia stem, turmeric waste [4], Fly-ash [5], Wollastonite

[6], Olive stones [7], almond shells [8], apricot and peach stones [9], maize cob [10], linseed straw, saw

dust [11], rice hulls [12], cashew nut hull, cashew nut sheath [13], coconut shells and husks [14],

ASI

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eucalyptus bark [15], linseed cake, tea waste ash [16]. Beside these other source of activated carbon is

sulfonated coal [17], tyre coal dust [18], activated bauxite, cement kiln dust [19], Share oil ash [20] and

ground sunflower stalk [21], Feronia limonia swingle Shell [22], Moringa oleifera fruit shell waste [23],

Balsamodendron caudatum [24], Leucama Leucocephlam [25] etc., as the carbonaceous precursors for

the removal of dyes from waste water.

In the present investigation the adsorption of dyes on activated carbon prepared from Sterculia

Quadrifida seed shell waste by carbonization with various activation process. Their physico-chemical

characterization studies haven been carried out to assess the suitability of these carbons as adsorbent in

the wastewater and their capacity to remove commonly used synthetic dyes such as Acid Blue 92,

Rhodamine B, Reactive Red 4 and Direct Red 28 has been evaluated.

2. Experimental:

Adsorbent: Sterculia Quadrifida seed shell wastes were collected from various places in Erode city,

Tamil Nadu, India. They were cut into small pieces, dried in sunlight until all the moisture was

evaporated. The dried Material was used for the preparation of activated carbons using physical and

chemical activation methods and used for adsorption studies. Table (1) shows the list of various

activated carbons and their preparation methods.

Photograph of the Sterculia Quadrifida seed shell

Table (1): List of Activated Carbons prepared from Sterculia Quadrifida seed

shell wastes and their preparation methods.

S.No Activated carbon Preparation method

1 SQAC1 Sulphuric Acid process

2 SQAC2 Phosphoric Acid process

3 SQAC3 Zinc chloride impregnation

4 SQAC4 Potassium carbonate impregnation

5 SQAC5 Sodium sulphate impregnation


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Carbonization Procedure:

Chemical activation with sulphuric acid Carbonization: The dried material was kept in the muffle

furnace at 250 °C and then it was soaked with excess of sulphuric acid for a period of 24 hours. During

the addition of sulphuric acid charring occurs immediately, accompanied by evolution of heat and fumes.

At the end of this period, the product was washed with large volume of water to remove the free acid,

dried at 160 °C for 2 hours by using air oven finally activated at 800 °C and powdered.

Chemical activation with phosphoric acid Carbonization: The materials to be carbonized were

soaked with excess of phosphoric acid for a period of 24 hours. After impregnation, the product was

washed with large volume of water to remove the free acid, dried at 160 °C for 2 hours by using air oven

finally activated at 800 °C and powdered.

Chemical activation with zinc chloride Carbonization: The materials to be carbonized were soaked in

10 % solution of zinc chloride for a period of 24 hours. After impregnation, the product was washed

with large volume of water, and then treated with 10 % solution of HCl to remove the cations. Then the

materials were washed with plenty of water to remove excess of acid, dried at 160 °C for 2 hours by

using air oven finally activated at 800 °C and powdered well.

Chemical activation with potassium carbonate Carbonization: The dried materials to be carbonized

were soaked in 10 % solution of potassium carbonate for a period of 24 hours. After impregnation, the

product was washed with plenty of water, and then it was dried at 160 °C for 2 hours by using air oven

finally activated at 800 °C and powdered well.

Chemical activation with sodium sulphate Carbonization: In this method the dried materials to be

carbonized were soaked in 10 % solution of sodium sulphate for a period of 24 hours. At end of this

period, the product was washed with large volume of water, and then it was dried at 160 °C for 2 hours

by using air oven finally activated at 800 °C and powdered well.

The materials treated with concentrated H2SO4, H3PO4, ZnCl2, K2CO3 and Na2SO4 which are named as

SQAC1, SQAC2, SQAC3, SQAC4 and SQAC5 respectively. The physico-chemical properties of treated

activated carbon were measured by suitable standard methods. The pH and conductivity were analyzed

using Elico pH meter (LI-120) and conductivity meter (M-180) respectively. Moisture content (%) by

mass, Ash content (%) by mass, volatile content (%), Bulk Density (g/L), Specific gravity, Porosity (%),

Matter soluble in water, Matter soluble in acid, Surface Area (m2/g), Fixed carbon (%), Yield (%) were

analyzed as per standard procedures [27]. The zero point charge of the carbon were measured by using

the pH drift method [28]. The decolourizing power of the different activated carbons were carried out

using Basic Methylene Blue solution of known concentration dispersed with known quantity of

activated carbon and stirred for pre-determined duration as per the standard techniques [29].

Batch adsorption studies: The batch adsorption studies were performed at 30 °C. A pre-determined

amount of adsorbent is mixed with known initial concentration of individual dye solution such as Acid

Blue 92, Rhodamine B, Reactive Red 4 and Direct Red 28 agitated for desired time. The adsorbent and

the adsorbate were separated by filtration and the filtrate was analyzed for residual dye concentration

spectrophotometrically.


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The different concentration of individual dye solution such as Acid Blue 92, Rhodamine B, Reactive

Red 4 and Direct Red 28 was estimated spectrophotometrically using Elico UV visible

spectrophotometer. The amount of dyes adsorbed in mg/L at time t was computed by using the following

equation.

tq = V

m

CC

s

o t×

_

where, Co and Ct are the dye concentration in mg/L initially and a given time t, respectively, V is the

volume of the dye solution in ml and ms is the weight of the activated carbon. The percentage of

removed dye ions (R %) in solution was calculated using equation.

% Removal = 100_

×

m

CC

s

to

The initial concentration of dye, pH and temperature was investigated by varying any one parameters and

keeping the other parameters constant.

3. Result and Discussion: The characteristics of the activated carbon prepared from Sterculia

Quadrifida seed shell waste in various methods were listed in Table (2).

Table (2): Physico-chemical Characteristics Sterculia Quadrifida seed shell activated carbon

S.No. Parameters SQAC1 SQAC2 SQAC3 SQAC4 SQAC5

1 pH 6.8 6.3 7.2 6.4 6.7

2 conductivity, ms cm-2 0.427 0.325 0.488 0,592 0.199

3 Moisture content, % 13 14 5 5 5

4 Ash content, % 5.7 5.8 2.1 5.26 3.15

5 Volatile content, (%) 10 12.2 32.6 38.8 38.2

6 Bulk Density, g/L 0.44 0.53 0.615 0.33 0.395

7 Specific gravity 0.5 0.57 0.97 0.5 0.5

8 Matter soluble in water, % 2.29 2.32 6.13 6.13 10.52

9 Matter soluble in acid, % 4.59 6.97 10.5 10.5 16.8

10 Zero point charge in pH Units 5.2 5.5 4.9 6.2 5.9

11 Surface Area, m2/g 665 855.1 550.6 390.8 280.2

12 Decolourizing power, mg/g 133.5 117 189 178.5 243

13 Porosity, % 12 6.1 36.5 34 21

14 Iodine Number, mg/g 521 571 199 655 728

15 Fixed Carbon, % 7.3 68 60.3 50.9 53.6

16 Yield, % 44.2 56.5 42.1 39.6 41.2


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The evolution of characteristics of five types of activated carbon derived from Sterculia Quadrifida seed

shell waste indicates that the carbon obtained by SQAC2 & SQAC3 process has higher bulk density than

the carbon prepared by other process. It was observed that carbon prepared by SQAC4 process has lower

bulk density. As reported, the observed decrease in the bulk density may be due to increase in the pore

system with SQAC4 impregnation.

The moisture content was found to be higher in the case of carbons by SQAC1, SQAC3 &SQAC5

process compared with SQAC2 & SQAC4 moisture content of the carbon has no effect on its adsorptive

power, it dilutes the carbon which necessitates the use of additional weight of carbon during treatment

process.

Ash content generally gives an idea about inorganic constituents associated with carbon obtained by

different carbonization methods. The ash content value indicates that the overall ash content for all the

varieties of carbon prepared shows comparable lesser values. This may be attributed to lower inorganic

content & higher fixed carbon. Solubility studies of carbon in acid and water were performed to evaluate

the amount of impurities present in the carbon prepared by different carbonization process. The

solubility studies were performed since the presence of impurities in the carbon may affect the expected

quality of the treated water during treatment. The carbon prepared by all other process exhibits moderate

level of impurities. The high value of water & acid soluble matter is prepared by SQAC5 process which

indicated that a large amount of sulphate salt would have been incorporated into the carbon structure.

The high pH (i.e. alkalinity) can be related to the introduction of some basic groups and removal of

acidic function groups. All the carbon obtained from the various process shows alkaline nature.

Adsorptive properties are directly related to the porosity of activated carbon, the highly porous carbon

can adsorb relatively large amount of organic compounds. SQAC3 is one of the highly porous carbons

among the five varieties. Decolorizing power is an indication of ability of a carbon to adsorb high

molecular weight substance like dye molecules. SQAC3, SQAC4 & SQAC5 shows decolorizing power

of greater than 150, indicates that the carbon is good for dye adsorption.

The zero point charge implies that the prepared carbon is free from surface charge nearly neutral pH.

Hence the carbon samples are suitable for the treatment of water even at the neutral medium. High

charring nature of H2SO4 & H3PO4 produces less ash and ultimately results more fixed carbon. High

yield obtained in the H3PO4 process followed by H2SO4 impregnation process. The results of

characterization studies indicate that Sterculia Quadrifida seed shell waste is a good precursor material

for the production of activated carbon of high efficiency.

Fourier Transform-Infra Red (FT-IR) Characteristics: FT-IR measurements of Sterculia Quadrifida

seed shell waste activated carbon (Fig.1a to 1e) showed the presence of the following groups. A sharp

peak at 1000 cm-1 found in SQAC2. This is due to the introduction of surface hydrogen bonded strong –

OH groups by H3PO4. Absence of most of the –CH and -NH peaks proves that the solid surface of

carbon homogeneous and does not have any specific functional –OH groups. In case of SQAC2 surface

area and porosity plays a major role in adsorption rather than surface functional groups. In case of

SQAC1, SQAC2 & SQAC4 broad peak around 1500 cm-1 due to –OH str vibration. This is attributable

to the surface hydroxyl groups and chemisorbed water [30, 31].


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Scanning Electron Microscope: The morphology of the prepared activated carbon samples surface was

examined using Scanning Electron Microscope. The micrographs (Figure 2a to 2e) of the clean activated

carbon particles showed smooth areas with long ridges and rough area with micropores and more

number of edges. Small cavities, pores and rough surfaces on the carbon sample indicate the presence

interconnected porous network. Tubular pores and cavities will increase the surface area of the adsorbent

be many fold.

Dye Adsorption Characteristics: Acid, reactive and direct dyes have anionic character, where as basic

dyes are cationic in nature. In this study Acid Blue 92, Rhodamine B, Reactive Red 4 and Direct Red 28

are selected for the analysis of adsorption characteristics of the activated carbon prepared by five

different preparation methods. Figure (3a to 3d) shows the structure of selected dyes and Figure (4)

shows the amount selected dyes adsorbed by the five different activated carbons prepared from Sterculia

Quadrifida seed shell waste.

0 500 1000 1500 2000 2500 3000 3500 4000 4500

0

20

40

60

80

100

T %

Wave number (cm-1)

(a)


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0 500 1000 1500 2000 2500 3000 3500 4000 4500

0

20

40

60

80

100

T %

wave number (cm-1)

(b)

0 500 1000 1500 2000 2500 3000 3500 4000 4500

0

20

40

60

80

100

T %

wave number (cm-1)

(c)


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0 500 1000 1500 2000 2500 3000 3500 4000 4500

0

20

40

60

80

100

T %

Wave number (cm-1)

(d)

0 500 1000 1500 2000 2500 3000 3500 4000 4500

0

20

40

60

80

100

T %

Wave number (cm-1)

(e)

Figure (1): FTIR spectra of a) SQAC1, b) SQAC2, C) SQAC3, d) SQAC4, and e) SQAC5.


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(a) (b)

(c) (d)

(e)

Figure (2): SEM Photograph of (a) SQAC1, (b) SQAC2, (c) SQAC3, (d) SQAC4, and (e) SQAC5.


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Figure (3a): Acid Blue 92

(M. F. C26H18N3Na3O10S3 , M. Wt.697.59)

Figure (3b): Rhodamine B

(M. F. C28H31N2O3 Cl, M. Wt. 479.01)

Figure (3c): Reactive Red 4

(M.F. C32H19ClN8Na4O14S4, M. Wt.995.21)

Figure (3d): Direct Red 28

(M.F. C32H22N6Na2O6S2, M. Wt. 696.66)


40

0

10

20

30

40

50

60

70

80

90

SQAC1 SQAC2 SQAC3 SQAC4 SQAC5

Amount of dye adsorbed, mg/g-1

Carbon dosage, mg/L

Fig. 4 Amount of various dyes adsorbed onto various activated

Acid Blue 92

Rhodamine B

Reactive Red 4

Direct Red 28

Figure (4): Amount of various dyes adsorbed onto various activated carbon

prepared from Sterculia Quadrifida seed shell waste.

The amount of Acid blue 92 adsorption is very high in all the five carbons. Especially SQAC1 &

SQAC2 shows excellent adsorption. As the carbon prepared by different preparation procedures, these

carbons are expected to have different chemical structure and Textural properties on their surface area.

Many researchers in the past have proved that the surface chemical structure of carbon can also

influence the dye adsorption. All the anionic dyes show comparatively higher adsorption than the basic

dye. Amount of Acid blue 92 adsorption is slightly greater than that reactive Red 4 and Direct Red 28.

4. Conclusions:

From the results of the present investigation, it can be calculated that

1. Activated carbon can be conveniently and economically prepared from Sterculia Quadrifida seed shell waste.

2. The extensive a characterization study of the different varieties of activated carbon reveals that the carbon obtained from all the process can be assessed as superior grade carbons.

3. Acid process was the most efficient among the chemical treatment, H2SO4 & H3PO4 process gives with higher surface area.

4. The carbon obtained by K2CO3 process has lower bulk density it observed that decrease in bulk density may be due to increase in the pore system with K2CO3 impregnation.

5. The moisture content was found to be higher in case of carbon obtained by H2SO4 & H3PO4 process, but it has no effect on its adsorptive power.


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6. The ash content value indicates that the overall ash content for all the varieties of carbon prepared shows comparable lesser value. This may be attributed to lower in organic content of

higher fixed carbon.

7. The solubility studies reveals that the carbon prepared by all other process exhibits moderate level of impurities.

8. All the carbons obtained from the various process shows the high pH value which is related to alkaline nature.

9. The surface area of carbon prepared from different process is in order of

SQAC 2 > SQAC 1 > SQAC 3 > SQAC 4 > SQAC 5

10. The prepared adsorbents have a substaintial variation in the dye removal capacity. For the four categories of dyes tested, activated carbons with different surface characteristics can remove a

maximum of 90 % of dye from its aqueous solutions.

11. Hence the activated carbons prepared from various from processes are subjected to the further detailed study on the kinetics and isotherms of the above four dyes is under progress.

5. Acknowledgements: The authors are thankful to Department of Chemistry, Chikkanna Government

Arts College, Tirupur and Institute for Environmental Nanotechnology for providing the necessary

facilities for this investigation.

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