Utilization of Coal Fly Ash as CO Gas Adsorbent

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Internat. J. of Waste Resources, Vol. 2(2)2012:13-15, Dyah Sawitri and Ayu Lasryza

ISSN: 2252-5211

Utilization of Coal Fly Ash as CO Gas Adsorbent Dyah Sawitri#1, Ayu Lasryza#2 #

Department of Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Sepuluh Nopember Kampus Keputih ITS Sukolilo Surabaya 60111, INDONESIA 1

[email protected] [email protected]

2

Abstract — This research focused on coal fly ash fabricated as CO adsorbent. Coal fly ash having grain size of 325 mesh was characterized by XRF, XRD and SEM-EDX. Physical activation was done at temperatures of 5000C, 5200C, 5400C, 5600C, 5800C and 6000C. Chemical activation was undertaken by mixing between fly ash and NaOH with mass ratio of 1: 1.2 with subsequent heating at 7500C for 1 h and followed by washing the specimens until pH=7. The samples were dried at 1000C for 1 h. The major constituents of unactivated coal fly ash are Fe, Ca, K, Si and Al in the form of quatz and anorthite. The chemical activation led to reduce the amount of quartz or increase the amount of anorthite. Physical activation does not affect the amount of minerals. Surface area of coal fly ash with physical activation at temperature 5400C and chemical activation is 32.444 m²/g (BET). Keywords— fly ash; adsorbent; activation; characterization Submitted: September 9, 2012

I. INTRODUCTION This document is a template. An electronic copy can be downloaded from the conference website. For questions on paper guidelines, please contact the conference publications committee as indicated on the conference website. Information about final paper submission is available from the conference website. Coal is one of alternative energy resources. In term of price coal is cheaper than natural oil. Indonesia has a lot of coal resources, and the utilization of coal in Indonesia increases every years. It attains 14,1% from total of other energy resources. It is expected that coal usage will increase until 34,6% at 2025[1]. Utilization of coal produces waste that can contaminate environment such as CO2, NOX, CO, SO2, hydrocarbon dan solid waste. The solid waste is in the form of ash, i.e fly ash and bottom ash. According to data of Ministry of Environment in 2006, fly ash production reaches 52,2 ton per day, whereas bottom ash waste production reaches 5,8 ton per day[1]. Coal fly ash is exhaust waste was usually released to air without control. Actually fly ash waste is a kind of hazardous waste. Generally, fly ash can be temporary saved at coal power plant and further thrown in landfill. Accumulation of this coal fly ash may raise environment al problem[2]. Coal fly ash can be used for raw material of cement and construction material[2]. Another utilization of coal is as adsorbent[3]. As adsorbent, fly ash has advantage in term of economical prices and good for gas and liquid waste management[4]. Physical and chemical activation is required to allow coal fly ash for being use as adsorbent. Physical activation is done by heating at high temperature, whereas chemical activation is done by mixing of fly ash and acid liquid or alkali. II. MATERIALS AND METHODS A. Materials Coal fly ash is exhaust result of kiln I process in PT. Semen Gresik. It has grain size of 325 mesh. Coal fly ash have dark brown colour. This colour depend on type of coal, too. In

Accepted: October 23, 2012

this research the type of coal is lignite whose quality is the lowest among other type of coals. B. Methods Two activations were used in this research, namely physical and chemical activations. The physical activation was done by heating the sample at temperatures of 500°C, 520°C, 540°C, 560°C, 580°C, and 600°C for 1 hour. Chemical activation was done by mixing fly ash and NaOH with the mass fractions of fly ash and NaOH are 1 : 1.2. The mixtures were heated at temperature of 7500C for 1 hour followed by grinding process. Then, the samples were mixed with distilled water with L/S of 1/5 in a constant stirring of 400 rpm for 30 minutes. Finally leaching was done until pH = 7, the samples were then subsequently dried at temperature of 1000C for 1 hour. Raw material coal fly ash was characterized by X-Ray Fluorescence (Minipal4 PanAlytical), X-Ray Diffraction (Brücker AXS D8 Focus) Cu K-α with λ = 1,5418 Å, Scanning Electron Microscopy (SEM) Zeiss-EVO MA 10 equipped with Electron Diffraction-X (EDX) of Brücker, and BET analysis with Quantachrome Autosorb iQ. III. RESULTS AND DISCUSSION A. Unactivated Coal Fly Ash Characterization Table 1 shows composition in unactivated fly ash. From Table 1 it is known that the highest contents in the fly ash are Fe, Ca, K, Si and Al, and the highest oxide are Fe2O3, CaO, SiO2, Al2O3 and K2O. The important substance for adsorbent are Si and Al, while Ca is the substance that has to be remove. Ca can disturb the adsorption process because it may lead the reaction to become unstable. Table 2 is mineral composition of unactivated coal fly ash from XRD analysis. XRD analysis shows that the most dominant minerals are amorphous structure and crystalline phase of quartz (SiO2). Fly ash samples consist mainly amorphous aluminosilicate with a less number of iron-rich part. It is likely that the iron oxide bounds with aluminosilicate to form amorphous phase. While aluminum 13

Internat. J. of Waste Resources, Vol. 2(2)2012:13-15, Dyah Sawitri and Ayu Lasryza

and silicon form either as sillimanite, quartz, or binds with Ca to form anorthite. Calcium was associated with oxygen, sulfur or with silicon or aluminum. The calcium-rich material is different in elemental composition from the amorphous alumino-silicate parts. It is clearly a non-silicate mineral possibly calcite, lime, gypsum or anhydrite[5]. TABLE I XRF ANALYSIS OF UNACTIVATED COAL FLY ASH

No.

Substance

1. 2. 3. 4. 5. 6. 7. 8. 9.

Al Si P K Ca Ti Mn Fe Ba

Concentrate (%) 1,8 9,3 0,64 2,19 30,0 1,79 0,60 51,23 0,76

Oxide Al2O3 SiO2 P2O5 K2O CaO TiO2 MnO Fe2O3 BaO

Concentration (%) 2,9 14 1,0 1,84 29,2 2,9 0,49 46,51 0,61

B. Activation Coal Fly Ash Characterization From Table 3 and 4 one can observe that amorphous phase and quartz crystalline still dominate in fly ash after physical activation. There is little changes of mineral composition after physical activation. On the other hand, the chemical activation changed the amount of minerals in fly ash. For example, after chemical activation the amount of quartz decreases while the amount of anorthite increases. Figure 2 exemplifies the change in the amount of mineral of fly ash after physical and chemical activation. From figure 2 it is known that chemical activation plays an important in changing the amount of minerals, while the physical activation does not affect significantly. TABLE III XRD QUANTITATIVE DATA OF COAL FLY ASH WITH PHYSICAL ACTIVATION Crystal/ Mineral

Physical Activation Formula

Unit 500

520

540

560

580

600

Quartz

SiO2

%

20,0

21,1

22,0

22,2

22,3

21,0

Sillimanite

Al2SiO5

%

4,2

2,8

3,2

2,5

3,1

2,8

Anhydrite

CaSO4

%

0,4

0,6

0,4

0,8

1,0

0,4

XRD ANALYSIS OF UNACTIVATED COAL FLY ASH

Magnetite

Fe3O4

%

2,9

3,2

3,6

3,9

3,2

3,5

Mineral Quartz Sillimanite Anhydrite Magnetite Anorthite Siderite Arcanite Periclase Hematite Maghemite Wuestite Amorphous

Anorthite

Ca3SiO5

%

1,6

2,1

2,3

2,7

1,4

1,7

Siderite

FeCO3

%

1,1

0,9

1,4

1,1

1,2

1,3

Arcanite

K2SO4

%

2,7

2,8

2,4

2,1

2,8

3,1

TABLE III

No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

ISSN: 2252-5211

Formula SiO2 Al2SiO5 CaSO4 Fe3O4 Ca3SiO5 FeCO3 K2SO4 MgO Fe2O3 Fe2O3 FeO -

Consentration (%) 21,1 1,6 0,7 3,3 1,7 1,1 2,4 6,2 0,5 3,9 1,2 54,9

Figure 1 shows elemental mapping of unactivated fly ash. EDX analysis indicates that the big particle contains a lot of Si while Fe and Al distribute evenly in all particles. This evidence indicates intermixing of Fe and Si-Al mineral phases while Ca may in form non-silicate minerals[5]. These results are supported with XRD data.

Periclase

MgO

%

6,7

6,3

5,9

7,4

6,6

6,4

Hematite

Fe2O3

%

0,5

0,6

0,5

0,6

0,6

0,6

Maghemite

Fe2O3

%

3,5

3,4

2,7

2,8

3,4

3,0

Wuestite

FeO

%

0,5

1,2

0,8

0,6

0,9

0,9

Amorphous

-

%

54,0

53,7

54,1

52,5

52,7

54,3

R_wp

-

%

2,9

2,9

2,9

2,9

2,9

2,9

TABLE IV XRD QUANTITATIVE DATA OF COAL FLY ASH WITH CHEMICAL ACTIVATION Crystal/ Mineral

Formula

Unit

Quartz

SiO2

Sillimanite Anhydrite

Chemical Activation 500

520

540

560

580

600

%

13,2

1,0

0,5

5,1

0,2

3,3

Al2SiO5

%

0,0

2,6

4,0

2,5

4,3

8,4

CaSO4

%

0,0

0,0

0,1

1,2

0,3

0,0

Magnetite

Fe3O4

%

3,1

3,4

0,1

0,0

4,3

3,5

Anorthite

Ca3SiO5

%

35,6

14,2

7,1

20,8

17,1

24,0

Siderite

FeCO3

%

1,3

0,0

0,0

0,2

0,2

0,2

Arcanite

K2SO4

%

14,1

18,0

16,9

18,6

15,3

14,8

Periclase

MgO

%

11,9

15,3

22,5

12,2

9,9

6,5

Hematite

Fe2O3

%

0,2

0,0

1,4

0,1

0,1

0,1

Maghemite

Fe2O3

%

0,0

0,0

3,0

0,0

0,0

0,0

Wuestite

FeO

%

1,0

2,8

6,2

2,7

4,6

2,0

Amorphous

-

%

15,2

41,1

38,3

34,5

42,7

35,4

R_wp

-

%

5,1

9,6

8,5

7,2

8,5

6,9

Fig. 1 Result SEM of unactivation coal fly ash

14

Internat. J. of Waste Resources, Vol. 2(2)2012:13-15, Dyah Sawitri and Ayu Lasryza

physical activation chemical activation

25 20,0

22,3

22,2

22,0

21,1

21,0

activation may active the unactivated substances, Else, activation process causes surface area changing of coal fly ash than unactivated coal fly ash, and finally aids the adsorption process.

20

IV. CONCLUSIONS 20,0

15 % Quatrz

ISSN: 2252-5211

Unactivated coal fly ash consist mainly of Fe, ca, K, Si, and Al, in the form of quartz and amorphous. The mineral contents were found to change after chemical activation e.g. quartz was reduced, anorthite was increased. Physical activation does not affect it. Surface area of coal fly ash is 32.444 m²/g (BET) that is known to change after activation proccess with phisical activation at temperature 5400C and also chemical activation.

10 5,1 5

1,0

3,3

0,5

0,2

0 500

520

540

560

580

600

0

Temperature ( C)

Fig. 2 Comparison of quartz contents after physical and chemical activation

There is also supported by BET analysis. The surface area of activated coal fly ash there is physical activation at temperature 5400C is 32.444 m²/g whereas unactivated coal fly ash is can not measured (BET). That is included mesopore material and supported by isoterm graphic on figure 3. Figure 3 shows that curve of activated fly ash is included type IV because between desorption line is not coincide with adsorption line and also indicated mesopore adsorbent[7].

ACKNOWLEDGMENT The authors would like to thank to DITJEN DIKTI as organizer of Program Kreativitas Mahasiswa for funding this research, Mr. Heri Purnomo, ST from PT. Semen Gresik for his assistanship in XRD analysis, Ninit Martianingsih, S.Si who helps the SEM-EDX characterization, Nurul Faradillah Said, S.Si who helps the XRF characterization, and Endah Yuliyanti, S.Si who helps the BET characterization. REFERENCES [1]

Volume @ STP (cc/g)

16 14

[2]

12 10

[3]

8

[4]

6 4

[5]

2

[6]

0 0,0

0,2

0,4

0,6

0,8

1,0

Relative Pressure (P/Po)

Fig. 3 Isoterm linear graphic of activated coal fly ash

Physical activation causes losing water content (intercrystalline water) in fly ash as indicated by thermogravimetry experiments [6]. Whereas chemical

[7]

Setiaka, Juniawan, Ita Ulfin, Nurul Widiastuti, Adsorpsi Ion Logam Cu(ii) dalam Larutan pada Abu Dasar Batubara Menggunakan Metode Kolom. Prosiding Tugas Akhir. Jurusan Kimia, Institut Teknologi Sepuluh Nopember. Surabaya, 2011. Jumaeri,dkk, “Preparasi dan Karakterisasi Zeolit dari Abu Layang Batubara secara Alkali Hidrotermal,” Reaktor, Vol. 11 No.1, Juni 2007, Hal. : 38-44, 2007. Ahmaruzzaman M, “A review on the utilization of fly ash. Progress in Energy and Combustion Science,” 36: 327–363, 2010. Mohan S, Gandhimathi R, “Removal of heavy metal ions from municipal solid waste leachate using coal fly ash as an adsorbent,” Sience Direct. Journal of Hazardous Materials, 169: 351-359, 2009. Barbara G, Kutcko, Ann G. Kim, “Fly Ash Characterization by SEMEDS,” Fuel, 85: 2537-2544, 2006. Lasryza, Ayu, “Pemanfaatan Fly Ash Batubara sebagai Adsorben Emisi Gas Buang CO pada Kendaraan Bermotor,” Tugas Akhir. Jurusan Teknik Fisika, Institut Teknologi Sepuluh Nopember. Surabaya, 2012. Anonim. (2012). Physisortion Methods and Techniques. [Online]. Available : http://www.google.co.id/url?sa=t&rct=j&q=mesopore&source=web&c d=4&cad=rja&ved=0CDQQFjAD&url=http://www.sklc.dicp.ac.cn/yiqi /Seminar%2520JSD%2520%2520II.ppt&ei=6K1_UP6LKJHwwRrQe3ooDIDQ&usg=AFQjCNG hp5Ms2PcV9I1B2oB0viTxC1VPow

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Utilization of Coal Fly Ash as CO Gas Adsorbent

Internat. J. of Waste Resources, Vol. 2(2)2012:13-15, Dyah Sawitri and Ayu Lasryza ISSN: 2252-5211 Utilization of Coal Fly Ash as CO Gas Adsorbent D...

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