XRD, FTIR and Microstructure Studies of Calcined Sugarcane Bagasse Ash

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1 Available online at Advances in Applied Science Research, 2011, 2 (3): ISSN: CODEN (USA): AASRFC XRD, FTIR and Microstructure Studies of Calcined Sugarcane Bagasse Ash D. Govindarajan * and G. Jayalakshmi Department of Physics, Annamalai University, Annamalai Nagar ABSTRACT Sugarcane Bagasse Ash (SCBA) is generated as a combustion by-product from boilers of sugar and ethanol factories. It is mainly composed of silica and carbon materials. In this paper, as received SCBA were calcined at different temperatures ranging from 500 C to 1000 C for 4 hours in furnace and characterized by XRD, FTIR and SEM techniques. Keywords: SCBA, calcination, unburned carbon, crystallanity. INTRODUCTION Sugarcane bagasse ash is an important by-product of the sugarcane industry and most of it is burned to produce steam and electricity in a co-generation plant at the ethanol factory. The sugarcane bagasse ash is the result from the bagasse combustion and mainly consists of high amount of silica (SiO 2 ) and unburned carbon. It s utilization as an adsorbent as well as mineral admixture in cement and concrete has been examined [1]. Recently, the use of agriculture solid waste materials as pozzolans in the manufacture of blended mortars and concrete has been the focus of research [2,3,4]. SCBA has proved to be a viable by-product for admixture in cement, with its intrinsic characteristic such as high content of silica in the form of quartz [5]. However, the high carbon content is an obstacle for its use in cement/mortars. Therefore it would be valuable if the unburned carbon in SCBA could be removed and used for other applications. In the present study, the obtained SCBA is fired at different temperatures and the calcined SCBA are characterized through XRD, FTIR and SEM techniques. MATERIALS AND METHODS SCBA was collected from E.I.D. Parry Sugar Mill, Nellikuppam, Tamil Nadu, India. As received SCBA was black in colour due to carbon content (Fig.1). The SCBA was fired in controlled 544

2 conditions at 500 C, 600 C, 700 C, 800 C, 900 C and 1000 C for 4 hours in rectangular silica trays. At the end of each process, the furnace was cooled down to 200 C and the ash was taken out of the furnace and cooled to room temperature. After cooling, the ash was ground and screened to 75 µm sizes and stored in a desiccators for characterization. In this condition the grey and white colour (Fig.2) of the SCBA indicated as complete burning. 500 C 600 C 700 C 800 C 900 C 1000 C Fig.1. Uncalcined SCBA Fig.2. Calcined SCBA at different temperatures X-ray diffraction patterns of SCBA samples were taken using a XRDML Gonio X-ray diffractometer with Cu-Kα radiation operated at 40 kv and 30 ma. The scan rates are 0.1 to 120 degrees with 2 /m in the Bragg s angle (2θ) range from 10 to 70. FTIR measurements were carried out using a Avator Nicolet 360 spectrophotometer. The microstructure of SCBA samples were performed with JEOL make SEM (Model JSM 5610). RESULTS AND DISCUSSION The XRD patterns (Fig.3) show a remarkable difference between calcined and uncalcined SCBA, which suggests that phase transformation has take place. In SCBA (Fig. 3.(a)), silica is the primary component with small amounts of calcium and other compounds. The intense broad peak observed from the uncalcined SCBA and 500 C, 600 C, 700 C calcined SCBA samples between 2θ 18 and 30 indicates the amorphous nature of silica. According to Corderio et al [6] states that carbon and volatile compounds present in the SCBA are considerably removed at higher calcinations temperature. For the SCBA 800 C and 900 C (Fig.3.(e-f)), some reasonably sharp and intense peak starts to show up on the top of the amorphous background. This may be due to the recrystallisation of amorphous silica to crystalline with temperature and this implies that the crystallanity increases as temperature increases. At 1000 C, the SCBA becomes highly crystalline as evident from sharp reflection peaks. Minor compounds also present in the SCBA calcined at 1000 C were calcium and iron oxides. The progress in the evolution of its crystallinity with temperature can be conveniently monitorded by FTIR spectroscopy. The FTIR spectra of calcined and uncalcined SCBA were shown in Fig.4. From the FTIR spectrum of uncalcined SCBA (Fig. 4.(a)), four main bands are seen, a broad band centered at 3400 cm -1, a strong broad band at 1098 cm -1, a sharp medium band at 796 cm -1 accompained with a hump at 620 cm -1 and a strong band at 469 cm -1. The broad band centered at 3400 cm -1 is attributed to symmetric and asymmetric stretching vibrations of O-H absorbed water molecules. 545

3 Fig.3. The XRD spectra of (a) uncalcined SCBA and calcined SCBA at (b) 500 C (c) 600 C (d) 700 C (e) 800 C (f) 900 C and (g) 1000 C The strongest vibration in the cm -1 region was commonly observed in (alumino) silicates and silica polymorphs due to OT O stretching modes, where T= Si, Al [7]. The signal at 1098 cm -1 is therefore assigned to the asymmetric stretching vibrations of tetrahedra SiO 4, while band at 796 cm -1 is due to symmetric stretching vibrations of the same units. The fourth signal at 469 cm -1 is assigned to the Si-O bending mode. A very weak band discern at 620 cm -1, which is characteristic of the crystalline cristobalite [8]. As temperature increases from 900 C to 1000 C (Fig.4.(f-g)), the intensity of the bands centered at around 1098, 796 and 469 cm -1 becomes a sharper, thus indicating an increase in crystallinity. These observations are in good agreement with XRD results. The SEM micrographs of the calcined SCBA samples with two different magnifications were shown in Fig.5. From the microgrphs, it can be clearly seen that SCBA samples were composed of grains with different size and shapes. They are prismatic, spherical and fibrous. Similar morphologies were observed by Batra et al [1] in SCBA. According to him, the prismatic particle consists mainly of Si and O. The spherical particles contain Si and O as well as some other minor compounds. The fibrous one consist of only carbon. At higher magnification small pores are observed on the surface of the particles. 546

4 Wave number (cm -1 ) Fig.4. The FTIR spectra of (a) uncalcined SCBA and calcined SCBA at (b) 500 C (c) 600 C (d) 700 C (e) 800 C (f) 900 C and (g) 1000 C (a) (b) 547

5 (c) (d) (e) (f) Fig.5. The SEM photographs of calcined SCBA at (a) 500 C (b) 600 C (c) 700 C (d) 800 C (e) 900 C and (f) 1000 C 548

6 CONCLUSION From the present investigations, the following conclusion can be drawn. The XRD results showed that SCBA structure have been changed from amorphous nature (500 C to 700 C) to crystalline materials (1000 C). This results also supported by the FTIR. SEM analysis reveals the presence of prismatic, spherical and fibrous structure of the SCBA particles. As temperature increases, the SCBA colour changes from black to grey and white which indicates that the carbon content present in the SCBA were reasonably reduced. REFERENCES [1] S. Batra Vidya, Sigita Urbonaite, Gunnar Svensson, Fuel, 2008, 87, [2] N.B. Singh, S.S. Das, N.P. Singh, V.N. Dwivedi, Indian J. Eng. Mater. Sci., 2009, 16, [3] L.M. Ordonez, J. Paya, A.M. Coats, F.P. Glasser, Adv. Cem. Res., 2002, 14(3), [4] N. Al-Akhras, B. Abu-Alfoul, Cem. Concr. Res., 2002, 32, [5] Almir Sales, Sofia Araujo Lima, Waste Management,2010, 30, [6] G.C. Cordeiro, R.D. Toledo Filho, E.M.R. Fairbairn, Constr. Build. Mater., 2009, 23, [7] E.M. Flanigen, H. Khatami, H.A. Szymanski, Adv. Chem. Series., 1971, 101, [8] D. Prasetyko, Z. Ramli, S. Endud, H. Hamdan, B. Sulikowski, Waste Management, 2006, 26,