Characteristic studies of some activated carbons from agricultural wastes

JAMBULINGAM et al.: PROPERTIES OF ACTIVATED CARBONS FROM AGRICULTURAL WASTES 495

Characteristic studies of some activated carbons from agricultural wastes

M Jambulingam1,*, S Karthikeyan2, P Sivakumar2, J Kiruthika3 and T Maiyalagan4

1PG & Research Department of Chemistry, PSG CAS, Coimbatore2Department of Chemistry, Erode Sengunthar Engineering College, Thudupathi, Erode 638 057

3Department of Biotechnology, Government College of Technology, Coimbatore4Department of Chemistry, IIT Madras, Chennai

Received 07 September 2005; revised 17 November 2006; accepted 20 February 2007

Agricultural wastes like tobacco stem, bulrush Scirpus acutus stem, Leucaena leucocephala shell, Ceiba pentandra

shell, Pongamia pinnata shell have been explored for the preparation of activated carbon. Characterization studies such as

bulk density, moisture, ash, fixed carbon, matter soluble in water, matter soluble in acid, pH, decolourising power, phenol

number, ion exchange capacity, iron content and surface area have been carried out to assess the suitability of these carbons as

absorbents in water and wastewater. The results obtained show them to be good adsorbents for both organics and inorganics.

Present study reveals the recovery of valuable adsorbents from readily and cheaply available agriculture wastes.

Keywords: Activated carbon, Adsorption, Agricultural wastes, Surface area

IPC Code: C01B31/08

Introduction

Ancient Hindus in India used charcoal for

drinking water filtration and Egyptians used carbonized

wood as a medical adsorbent and purifying agent as early

as 1500 BC1. Activated carbon from vegetable material

was introduced industrially in the first part of the 20th

century, and used in sugar refining2. In the US, activated

carbon from black ash was found very effective in

decolorizing liquids3. Agricultural by-products and waste

materials used for the production of activated carbons

include olive stones4, almond shells5, apricot and peach

stones6, maize cob7, linseed straw8, saw dust9, rice hulls10,

cashew nut hull11, cashew nut sheath12, coconut shells

and jusks13, eucalyptus bark14, linseed cake15 and tea

waste ash16. Besides these, other sources of activated

carbon are sulfonated coal17, tyre coal dust, activated

bauxite, cement kiln dust18, ground sunflower stalk, shale

oil ash, rubber seed coat, palm seed coat19, de-oiled

soya20 , baggase fly ash21, Red mud22 etc. This study

explores new activated carbon from biological waste

materials through various processes.

Materials and Methods

Agricultural wastes (tobacco stem, bulrush

Scirpus acutus stem, Leucaena leucocephala shell, Ceiba

pentandra shell and Pongamia pinnata shell), collected

from fallow lands in and around Erode District, Tamil

Nadu, India, were cut into small pieces (3 cm), dried in

sunlight and used for the preparation of activated

carbons.

The material to be carbonized was impregnated

with respective salt solutions (ZnCl2, CaCl

2, Na

2SO

4,

Na2CO

3) for varying periods. Accordingly, sufficient

quantities were soaked well with 10% salt solution

(5 l capacity) respectively so that the solution gets well

adsorbed for a period of 24 h. At the end of 24 h, excess

solution was decanted off and air-dried. Then the

materials were placed in muffle furnace carbonized at

400°C for 60 min. The dried materials were powdered

and activated in a muffle furnace kept at 800°C for

60 min. After activation, the carbons obtained were

washed sufficiently with 4N HCI. Then the materials

were washed with plenty of water to remove excess acid,

dried and powdered.

In Dolomite process, sufficient quantities of

dried agricultural wastes were taken over a calcium

*Author for correspondence

Tel: 0422-5397901-902

E-mail: [email protected]

Journal of Scientific & Industrial Research

Vol. 66, June 2007, pp.495-500

496 J SCI IND RES VOL 66 JUNE 2007

Table 1 — Activated carbon from Tobacco stem

Sl. No Properties HCl H2SO

4ZnCl

2Na

2SO

4Na

2CO

3CaCO

3CaCl

2H

2SO

4 + H

2SO

4 +

NH4S

2O

8H

2O

2

1 pH 6.71 5.50 6.20 8.63 8.15 9.03 7.19 7.80 6.98

2 Moisture content, % 9.2 10.2 26.8 11.8 11.8 4.4 19.2 10.8 8.8

3 Ash content, % 10.69 14.46 10.16 13.89 10.68 8.78 14.20 8.36 8.86

4 Volatile matter, % 12.20 9.30 9.81 14.40 11.40 16.80 14.90 11.20 10.50

5 Fixed carbon 74.6 73.5 59.8 73.1 68.8 75.2 68.8 81.0 83.1

6 Conductivity, ms/cm 0.23 0.20 0.41 0.19 0.42 0.31 0.26 0.59 0.92

7 Specific gravity, S 1.10 1.33 1.49 0.89 1.25 1.48 1.32 1.88 1.37

8 Bulk density, D 0.63 0.69 0.51 0.44 0.56 0.42 0.36 0.66 0.49

9 Porosity 24.55 33.08 72.48 50.56 39.20 64.86 65.15 54.26 42.34

10 Matter soluble in water, % 0.60 0.58 0.78 1.03 2.42 1.88 2.66 1.81 1.84

11 Matter soluble in acid, % 0.81 0.13 1.14 1.59 1.24 1.50 1.03 0.61 1.44

12 Surface area, m2/g 385 351 1250 342 760 271 1204 858 723

13 Sodium, w/w % 1.1 5.1 8.0 5.0 6.1 8.0 12.0 1.5 6.0

14 Potassium, w/w % 4.1 5.1 8.6 6.7 3.6 4.1 3.0 4.0 1.0

15 Yield, % 40 50 46 32 31 60 47 50 65

carbonate bed and the upper layer of waste was also

covered with a layer of calcium carbonate. The whole

material was carbonized at 400°C for 60 min, powdered

well and followed by the thermal activation at 800°C

for 60 min. In Acid process, dried material was treated

with excess of H2SO

4. Charring of the material occurred

immediately accompanied by evolution of heat in fumes.

When the reaction subsided, mixture was left in an air

oven maintained at 140-160°C for 24 h. In chemical

activation process, 1 part of the material and 1.5 parts

of H2SO

4 were mixed with 0.4 parts of NH

4S

2O

8 and

kept in muffle furnace at 120°C for 14 h. At the end of

this period, the product was washed with large volume

of water to remove free acid, dried at 110°C and finally

activated at 800°C for 60 min.

pH and conductivity were analyzed using Elico

pH meter (model L1-120) and conductivity meter (model

M-180), respectively. Moisture content (%) by mass, ash

(on dry basis) % by mass, bulk density, specific gravity,

porosity, matter soluble in water, matter soluble in acid,

phenol adsorption capacity, carbon tetrachloride activity,

iron content were analyzed as per standard procedures.

Estimation of Na and K was done using Elico Model

Flame Photometer. BET surface area was measured at

liquid N2 temperature using Quantachrome Analyzer.

Results and Discussion

Bulk density of carbons obtained from all the

materials shows that Bulrush S. acutus carbon has the

higher bulk density due to its high fibre content and P.

pinnata carbon has the lower bulk density, which can

be attributed to the material hardness (Tables 1-5). Ash

content for all the varieties of carbons is very low

thereby increasing the fixed carbon content except for

the carbon obtained from P. pinnata and Bulrush S.

acutus carbon by H2SO

4+NH

4S

2O

8. Except carbons

prepared by Acid process, carbon obtained from all other

processes exhibit small amount of leaching property.

Characterization studies on porosity, surface

area. Iodine number, CCl4 activity and phenol adsorption

capacity clearly indicate that the carbons obtained by

various processes will depend only on the composition

of raw agricultural waste surface area properties of

Na2SO

4 process for Bulrush Scirpus acutus carbon, HCl

process for Leucaena and C. pentandra shell waste

carbon, chloride process for tobacco waste and

Dolomite process for Pongamia carbon.

Iron content is almost uniform for all the five

carbons. This level of iron content will not affect the

effluent water without the problem of iron leaching into


Table 2 — Activated carbon from Pongamia pinnata shell


4ZnCl

2Na

2SO

4Na

2CO

3CaCO

3CaCl

2H

2SO

4 + H

2SO

4 +

H4S

2O

8 H

2O

2

1 pH 6.42 5.02 6.54 9.60 8.22 9.11 8.25 7.18 6.05


3 Ash content, % 15.75 9.74 10.06 7.70 10.04 16.81 19.00 27.00 9.02

4 Volatile matter, % 8.8 10.2 15.8 13.6 11.5 17.6 8.0 9.1 6.8

5 Fixed carbon 87.5 82.1 73.4 76.6 85.2 70.4 81.6 81.0 84.6



8 Bulk density, D 0.33 0.40 0.32 0.37 0.39 0.39 0.34 0.38 0.43

9 Porosity 40.00 51.81 49.21 59.78 53.01 58.06 32.00 54.22 65.60



12 Surface area, m2/g 289 514 219 722 602 746 228 322 455

13 Sodium, w/w % 8.2 1.3 6.0 13.0 18.0 1.0 1.2 3.0 8.5

14 Potassium, w/w % 1.2 1.4 1.9 3.7 1.3 1.3 9.0 1.8 6.0

15 Yield, % 49 65 51 39 41 50 42 56 55

Table 3 — Activated carbon from Ceiba pentandra shell


4ZnCl

2Na

2SO

4Na

2CO

3CaCO

3CaCl

2H

2SO

4 + H

2SO

4 +

H4S

2O

8 H

2O

2

1 pH 5.55 6.41 5.35 8.57 9.60 8.30 8.13 8.09 6.71


3 Ash content, % 10.04 11.64 10.96 15.09 7.42 7.02 17.12 14.67 12.83

4 Volatile matter, % 14.5 20.2 25.0 20.8 17.3 25.2 22.2 10.5 17.4

5 Fixed carbon 69.3 69.5 62.9 68.7 74.0 63.7 73.8 76.5 72.6



8 Bulk density, D 0.43 0.37 0.30 0.34 0.53 0.30 0.43 0.38 0.41

9 Porosity 63.25 61.86 69.39 64.58 55.83 74.79 59.81 58.70 59.80



12 Surface area, m2/g 1143 424 321 430 429 750 261 309 403

13 Sodium, w/w % 4.0 1.1 7.0 1.2 6.0 4.0 3.0 5.6 1.3

14 Potassium, w/w % 2.0 4.0 7.0 5.0 3.0 9.0 1.3 5.0 4.0

15 Yield, % 60 40 32 36 36 41 32 35 44


Table 4 — Activated carbon from Scirpus acutus stem


4ZnCl

2Na

2SO

4Na

2CO

3CaCO

3CaCl

2H

2SO

4 + H

2SO

4 +

H4S

2O

8 H

2O

2

1 pH 6.13 5.22 6.42 9.04 9.51 8.02 8.64 7.54 6.04


3 Ash content, % 4.15 12.87 19.38 17.28 13.89 10.89 10.79 26.70 12.11

4 Volatile matter, % 12.8 12.9 10.0 15.8 12.5 10.2 11.0 11.6 9.1

5 Fixed carbon 82.2 79.8 81.0 82.2 82.0 79.1 83.0 81.1 80.1



8 Bulk density, D 0.46 0.75 0.36 0.35 0.42 0.28 0.32 0.70 0.48

9 Porosity 55.34 40.00 58.14 44.44 49.40 55.56 60.98 44.00 40.74



12 Surface area, m2/g 901 554 612 429 480 263 762 501 559

13 Sodium, w/w % 6.6 1.4 1.6 3.1 4.2 8.8 2.1 5.2 6.1

14 Potassium, w/w % 63 1.9 5.0 4.5 1.6 4.11 10.9 50 67

15 Yield, % 42 39 43 39 30 51 49 54 37

Table 5 — Activated carbon from Leucaena leucocephala seed shell


4ZnCl

2Na

2SO

4Na

2CO

3CaCO

3CaCl

2H

2SO

4 + H

2SO

4 +

H4S

2O

8 H

2O

2

1 pH 6.74 6.67 6.96 8.10 9.05 9.50 7.86 6.95 7.25


3 Ash content, % 14.50 10.94 15.57 17.07 7.12 1.57 16.07 5.67 16.85

4 Volatile matter, % 20.00 26.70 27.50 31.20 30.00 24.20 27.80 31.30 34.20

5 Fixed carbon 73.80 73.50 59.80 73.10 69.00 72.10 69.70 81.00 84.30



8 Bulk density, D 0.83 0.89 0.41 0.44 0.76 0.52 0.46 0.86 0.79

9 Porosity 24.55 33.08 72.48 50.56 39.20 64.86 65.15 54.26 42.34



12 Surface area, m2/g 278 341 1320 342 798 229 1204 888 713

13 Sodium, w/w % 2.2 5.8 8.4 7.4 6.4 4.0 5.0 15.5 10.0

14 Potassium, w/w % 13.1 7.9 7.6 10.7 7.0 6.6 2.9 9.0 8.0

15 Yield, % 45 51 40 31 42 52 39 50 65


treated water. The level of Na and K content is high

only in the case of tobacco waste carbon. In general, Na

and K content are high in sulphate and chloride process

when compared to other treatments. Yield of Bulrush S.

acutus carbon prepared by H2SO

4 process found high in

a vast margin when compared to other carbons. Because

of high charring power of H2SO

4, yield of carbon by

H2SO

4 process shows better result.

Surface plays a predominant role for the

adsorption of solutes from solution. Classification of

activated carbons based on their surface area is as

follows: Caron I: Tobacco stem, ZnCl2 > CaCl

2 >

H2SO

4+NH

4S

2O

8 > Na

2CO

3 > H

2SO

4+H

2O

2 > HCl>

H2SO

4 > Na

2SO

4 > Dolomite; Carbon II: P. pinnata shell,

Dolomite > Na2SO

4 > Na

2CO

3 > H

2SO

4 > H

2SO

4+ H

2O

2

> H2SO

4+NH

4 S

2O

8 > HCl > CaCl

2 > ZnCl

2 ; Carbon

III: C. pentandra shell, HCl > Dolomite > Na2SO

4 >

Na2NO

3 > H

2SO

4 >H

2SO

4+ H

2O

2 > ZnCl

2 > H

2SO

4 +

NH4 S

2O

8 > CaCl

2; Carbon IV: Bulrush S. acutus Stem,

HCl >CaCl2 > ZnCl

2 > H

2SO

4+ H

2O

2 > H

2SO

4 > H

2SO

4

+ NH4 S

2O

8 > Na

2CO

3 >Na

2SO

4 > Dolomite; and Carbon

V: L. leucocephala shell, ZnCl2 > CaCl

2 > H

2SO

4+ NH

4

S2O

8> Na

2CO

3 >H

2SO

4+H

2O

2 >H

2SO

4 >Na

2SO

4>HCl >

Dolomite. Surface area of these 5 novel carbons is far

better when compared to other carbons.

Activated carbon, prepared from L.

Leucocephala shell using ZnCl2 process, shows high

surface area and is selected for further studies to analyze

its applicability for water treatment purpose. Adsorption

of Rhodamine-B (Basic Dye) onto activated carbon

prepared from L. leucocephala shell using ZnCl2 process

showed that at low concentration (20 mg/l) of dye

solution, adsorbent can remove up to 98.00 % of the

dye molecules present in the solution (Fig. 1). Even at

the high concentrations (40 mg /l & 60 mg/l), adsorbent

was able to remove 83.5 % of the dye molecules present

in the solution.

Conclusions

Based on surface area, the following activated

carbons/processes are comparable with the commercially

available activated carbons: I) Tobacco stem / ZnCl2

process; ii) P. pinnata shell / Dolomite process; iii) C.

pentandra shell / HCl process; iv) Bulrush S. acutus stem

/ HCl process; and v) L. leucocephala shell / ZnCl2

process. These carbons can be conveniently used for

textile effluents removal. In general, all these carbons

will be efficient for the adsorption of organics as seen

from adsorption of Rhodamine-B from its solution with

L. leucocephala shell.

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20

40

60

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100

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0 50 100 150 200 250

Time, min

Perc

en

tag

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f d

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re

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20 mg/L

40 mg/L

60 mg/L

Fig. 1 — Influence of time on percentage of dye removal-

concentration variation

Dy

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Time min


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Characteristic studies of some activated carbons from agricultural wastes

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