Bhuiyan, A H

Chowdhury, F U Z

English

IACS Institutional Repository

Indian J. Phys. 71A (5), 569-577 (1997)IJP A- an international journalStudy of the structural modification on heat treatment of Bijoypur white clay (BWC) of BangladeshF U Z  Chowdhury and A H BhuiyanDepartment of Physics, Bangladesh University of Engineering & Technology,Dhaka-1000, BangladeshR e c e iv e d  1 9  F e b r u a r y  1 9 9 7 , a c c e p te d  3  M a r c h  1 9 9 7Abstract : Different samples were prepared from as collected, washed and heat treated Bijoypur White Clay (BWC) of Bangladesh. The X-ray diffractometric analysis of BWC reveals that it is possible to remove a major part of silica by washing the as-collected clay. On heat treatment of washed BWC at 1273 K, it is observed that kaolinitic BWC transforms to a compound containing mullitic phase. The infrared (1R) spectroscopic analysis indicates the presence of OH stretching (hydroxyl absorption of kaoiinite) in washed BWC. Moreover, IR spectra indicate that the clay mineral in this study is mostly kaolinitic in nature. The OH stretching is not observed in heal treated (773 and 1273 K) BWC. From the Differential Thermal Analysis (DTA) it is evident that metakaolimte is formed after evolution of water of crystallization at 853 K. A high temperature phase (mullite) transformation is observed at about 1273 K for BWC The photomicrographs manifest the formation of clusters of different sizes on heat treatment. It is also seen that the porosity is inversely proportional to the pressure of pellet preparation.Keywords : White clay. XRD, DTA PACS Nos. : 6l.lO.Nz, 81 70 Pg. 78.30-j1. IntroductionThe engineering properties of clay depend on the compositional and environmental factors. It is important to know the different types of clay minerals for designing and analyzing different geotechnical problems. In Bangladesh, BWC is being utilized for the manufacture of various ceramic products, low tension insulators and in processing rubber by many industrial units. The mottel variety of white clay (kaolin) which is slightly sandy is used for making fire bricks. Structure, lithology, mode of occurrence and texture of the BWC indicate that it has been transported and deposited and its source is not far away [1 ]. And it seems that the source materials of BWC are in the Indian side and that is of sedimentary© 19971ACS570 F U Z Chowdhury and A H Bhuiyanorigin. BWC is light gray to gray and turns pale white on exposure to Sun. Near the surface it is pinkies with yellow patches. It is mostly soapy to feel but at places gritty.The IR study on as-collected BWC was made by M A Biswas et al [2]. M Q I Khuda et al 13] have done the quantitative chemical analysis of raw and washed BWC. The X-ray diffractometric (XRD) study of the as-collccted BWC was done by M N Islam [4]. The result of the above investigations identified the main mineral of BWC as kaolinite. So far, no detailed work has yet been appeared in the literature on the effect of heat treatment on BWC.In this paper, the results of XRD, IR, DTA and optical investigations of BWC are presented. The clay mineral composition of the raw BWC, washed BWCUnd heat treated (773 K and 1273 K) BWC was studied qualitatively by XRD. IR has widely been used in both qualitative and quantitative characterizations of clay minerals, co^ls ere. In this investigation, qualitative identification of different characteristic groups in washed and heat treated BWC was carried out. Under heat treatment, a substance may undergo structural changes, e.g., physical as well as chemical. This changes occurring due to dehydration, transition from one crystalline variety to another, destruction of crystalline lattice, oxidation and decomposition etc. DTA is used to see the phase changes of BWC on heal treatment. Microphotographs of different pellets prepared at different pressures and heat treated were also studied to see the changes of surface structure. *2. Experimental details2. /. Method o f BWC washing and sample preparation :The BWC was collected in the form of hard lumps from the mine at Bijoypur area in the district of Netrokona, Bangladesh. The method of washing of as-collected BWC as adopted in the laboratory scale is based on the principle of washing in a slow stream of water as describe in a previous literature [5].The washed BWC was dried in an electric oven at 378 K for 24 hours. The dried BWC sample was then ground and was allowed to pass through 200 mesh sieve Then pellets (dia. 0.005 m) were obtained by a die punch at 2000, 3000 and 3500 psi by using a hydraulic pressure unit. The thickness of the pellet sample depends on the applied pressure and amount of BWC. After removing the sample from die punch its edges were then polished by a metallographic polisher (MSP-2 of Shimadzu Scientific Instrument Company Ltd., Japan) and using CAMBIMENT special silicon carbide grinding paper with gritnumber 320, 400 and 420. Finally, the samples are heat treated at 773 and 1273 K for 5hours. These samples are used for polarizing microscopy. For the other investigations, the washed BWC powder and washed BWC powder heat treated at 773 and 1273 K are used These samples are represented as follows .Sample A : As-collected BWC,Sample B : Washed BWC,Sample C : Washed BWC heat treated at 773 K andSample D : Washed BWC heat treated at 1273 K.Study of the structural modification on heat treatment etc 5712.2. Experimental techniques:An X-ray difractometer (model JDX-8P) of JEOL LTD., Tokyo, Japan was used. The target is CuKtf and the wavelength of X-ray radiation is 1.5418 A. Fine BWC powder, sieved through 200 mesh, was used. XRD patterns were recorded for 20  from 5° to 81° for samples A, B, C and D.The IR spectra of samples B, C and D were recorded at room temperature using an IR spectrophotometer (IR-470 Shimadzu Corporation, Japan).A Shimadzu Micro DTA system (model DT-30) manufactured by Shimadzu Corporation, Kyoto, Japan is used in the present investigation.A Reichert Metaverl reflected polarized light microscope of C. Reichert Optische Wcrke AG, Austria was used. Different areas arc chosen to see the variation of the surface structures.3. Results and Discussion3. /. XRD analysis :The XRD patterns of samples A, B, C and D are presented in Figure l. The XRD patterns are represented respectively by diffractograms 1, 2, 3 and 4. The 2ft dhkJ and the possibleFigure 1. XRD patterns of different samples of BWCconstituent compounds identified, are depicted in Tables 1, 2, 3 and 4 for samples A, B, C and D respectively. The XRD analysis of sample A (diffractogram 1) shows the presence of kaolinite (7.03, 3.56 and 1.49 A), silicon oxide (4.15, 3.32 and 1.82 A), aluminium oxide (4.44, 2.44 and 1.45 A), iron oxide (1.67, 1.38 and 1.28 A), potassium aluminium silicate hydroxide (4.93, 3.56, 2.53 and 2.37 A), aluminium silicate (9.61 and 4.44 A) etc. Very small amount of oxides of potassium, calcium, sodium etc. may also be present as reported by Alim Biswas and Basak [2]. In diffractogram 2 (washed BWC) it is seen that the percentage composition of the main ingredient, i.e., kaolinite increases and that of silicon oxide decreases due to washing of as-collected BWC. There is not much change in other compositional compounds in the washed clay. The XRD pattern of sample C572 F U Z  Chowdhury and A H  Bhuiyan(diffractogram 3), gives the signature of the presence o f all the constituent compounds those are present in the washed BWC with some variations. It is observed that there is muchTable 1. 20. <fhk| and the plane of reflections of different constituents of sample A (diffractogram 1).20 in degree4ikJ in A Kaolinite SiliconoxideAluminiumoxideAluminiumsilicatePotassiumaluminiumsilicatehydroxideIronoxide9.2 9.61 00112.6 7.03 00118.0 4 93 00420.0 4.44 110 20l TlO21.2 4.15 100 012 \25.0 3 56 002 172 113,20426.8 3.32 101 022 00635.2 2.53 130 111 131 311, 11636.8 2.44 110 111 210 11738.0 2.37 003 117,208 40040.0 2.26 102 22040.3 2.24 111 40242.8 2.11 200 733 20846.0 1.96 221 201 601 231 225, 119 33250.2 1.82 112 510 Il5 43155.0 1.67 204 202 601 105 44060.0 1.54 114 211 313 61162.4 1.49 060 113, 80164.2 1.45 330 113 020 62267.8 1.38 062 212 712 63168.4 1.36 30173.6 1.28 402 104 72175.8 1.24 220Table 2. 20, dhk\ and the plane of reflections of different constituents of sample B (diffractogram 2).20 in degreedh|ci in A Kaolinite SiliconoxidePotassiumaluminiumsilicatehydroxideAluminiumsilicateAluminium Iron oxide oxide9.2 9.61 00112.6 7.03 00118.0 4.93 00420.0 4.44 110 111 TlO 20l21.2 4.15 100 01225.0 3.56 002 113.204 U 226.8 3.32 101 006 02235.2 2.53 130 311, 116 131 11136.8 2.44 110 117 210 111Study of the structural modification on heat treatment etc 573Table 2. (Cont'd.).20 in degreeh^kl *n ^ Kaolinite SiliconoxidePotassiumaluminiumsilicatehydroxideAluminiumsilicateAluminiumoxideIronoxide38.0 2.37 003 117,208 40040.0 2.26 102 22040.3 2.24 111 40242 8 2.11 200 208 133460 1 96 221 201 225, 119 231 601 33250.2 1 82 112 Il5 510 43155.0 1.67 204 202 105 601 44060.0 1.54 114 211 313 61162 4 1.49 060 113, 80164.2 1.45 330 113 020 62267 8 1.38 062 212 712 63168.4 1.36 30173.6 1.28 402 104 72175.8 1.20 400Table 3. 26, d^ k) and (diffractogram 3).the plane of reflections of different constituents of sample C20 indegree^hklin ^ Kaolinite SiliconoxideAluminium Aluminium Iron oxide silicate oxide9.2 9.61 00112.6 7.03 00120.0 4.44 no 201 TlO21.2 4 15 100 01226.8 3 32 101 02235 2 2.53 130 111 13136.8 2.44 110 111 21040.0 2.26 102 22040.3 2.24 111 40242.8 2 11 200 T3346.0 1 96 221 201 601 231 33250.2 1.82 112 510 T15 43155.0 1.67 204 202 601 105 44060.0 1.54 114 211 313 61164.2 145 330 113 020 62267.8 1 38 062 212 712 63168.4 1.36 30f73.6 1.28 402 104 72175 8 1.24 220decrease of peak intensities of kaolinite whereas the peak of potassium silicate hydroxide is not present in the sample C. This may be due to the transformation of kaolinite to574 F  U Z  C how dhury a n d  A  H  B huiyanmetakaolinite state and removal of hydroxyl group from potassium silicate hydroxide. The XRD patterns of sample D, diffractogram 4, reveals the appearance of a new phase (possibly mullite) corresponding to 2.24, 2.22 and 1.84 A reflections [6]. XRD reflectionsTable 4. 20, and the plane of reflections of different constituents of sample D (diffractogram 4).20 in dhk\ in A Mullite Silicon Aluminium Irondegree oxide oxide oxide21.2 4.15 10026 8 3.32 210 101 i36.8 244 111 110 m40.0 2 26 102 \4 o i'l40.3 2.24 201 11140.6 2.22 12142.8 2.11 20046 0 1.96 320 201 601 33249.5 1 84 31150.2 1.82 321 112 510 43160.0 1 54 331 211 313 61167.8 1.38 112 212 712 63168.4 1 36 341 30173.6 1.28 104 72175.8 1.24 220for silicon oxide persist whereas the XRD reflections for kaolinite are absent in sample D thereby indicating a major transformation of kaolinite in the BWC to its high temperature phase mullite. These kind of transformations around this temperature region have been reported by several authors [7-10].3.2. DTA :The DTA trace of washed BWC is shown in the Figure 2. The DTA curve shows a small initial endothermic reaction which may be due to poorly crystalline kaolinite containingTamparatura(k)373 473 S 73 673 773 $73 973 IQ73 1173 1273Figure 2. DTA of washed BWC.Study of the structural modification on heat treatment etc 575BWC [11]* The curve has an intense endothermic reaction at 853 K corresponding to the evolution of the water of crystallization, i,e.y the expulsion of water from mineral lattice and thereby forming metakaolinite. This endothermic peak is about 30 K lower than that for well crystallized kaolinite [12]. The exothermic peak at 1266 K is characteristic of the clay mineral kaolinite* This exothermic peak is also considered to be resulted from mullite formation [11].3.3. IR  spectrom etric a n a ly s is :IR absorption spectra for samples B, C and D are given in Figure 3. The major absoiption bands for these three spectra are summarized in Table 5. The spectrum 1, for sample B, shows a close similarity to a standard kaolinite [13,14] along with other absoiption bands.Wove tongth ( >im |Figures. IR spectra of various samples of BWCThe minor departure in the absoiption features of this clay with that of standard kaolinite may be attributed to the variation of kaolinitic content, degree of crystallinity, presence of other constituents etc . In spectrum 2, for sample C, it is seen that the absorption of kaolinitic OH stretch at 3600-3700 enr1 disappears which agrees well with the result of XRD of sample C (diffractogram : 3, Figure 1). In spectrum 3, for sample D, the absorptions at 3600-3700 cm'1 is also absent which again agrees with the result of XRD of sample D (diffractogram : 4, Figure 1). And thejkaolinitic absorptions decrease further and only 780,690 and 460 enr1 are observed. WhTchlndicates the transformation of kaolinite to its high temperature mullite phase. This fact corroborates with the result of XRD analysis. The number of IR bands for silicon oxide [15], those are found in spectrum 1 are reduced in spectrum 2 and 3 (samples C and D).7lA(5)-9576 F U Z  Chowdhury and A H BhuiyanTable 5. Comparison of the absoiption bands for washed and heat Heated BWC samples of major constituents.SampleabsoiptionBwave no. crn^Cwave no. cm“*Dwave no. cm' 1Kaolinite 3700, 3660, 1108. 782. 690 and 460 782,690 and 4601025, 1000,910, (weak) (very weak)782, 749, 690, 530 land 422 \Silicon oxide 1160, 1055, 790, 1108, 782,690,460 790.770 and 460690 and 450 and 440 '3.4. Optical analysis:Microphotographs of different samples are presented in Figure 4. It is obvious that the surface structure changes significantly on heat treatment and pressure of pellet preparation. It is found that porosity in the pellets decreases with the increase of pellet preparation pressure. It is clearly seen that cluster results due* to'heat treatment at higher temperature. This may be an indication of decomposition and structural change that might have taken place in the BWC owing to heat treatment.4. ConclusionsThe XRD analysis of BWC reveals that it is possible to remove a major part of silica by washing. The DTA experiment reveals that metakaolinite is formed after evolution of water of crystallization at 853 K. And a high temperature mullite phase at about 1273 K  is also observed: On heat treatment, as has been seen from the XRD and DTAt in the temperature around 1273 K, the washed BWC transforms to possible mullite phase. From the IR bands it is seen that the BWC samples under examination are identical with those of the clay mineral, kaolinite. It is also seen that the OH stretching is not present in heat treated (773-1273 K) BWC. The photomicrographs manifest the formation of clusters of different sizes on heat treatment.AcknowledgmentsThe authors thank Bangladesh Council of Scientific and Industrial Research, Dhaka authority for allowing to use DTA facility. One of the authors ( F U Z  Chowdhury) also thanks UNDP and Bangladesh University of Engineering and Technology (BUET) authority for their financial assistance. He is also indebted to Bangladesh Institute of Technology, Chittagong authority for giving him study leave.Sample A1 Sample A3Sample D1 Sample D3Figure 4. Photomicrographs (250x> of MimUe as a ■ ->000 • rll\ * - *Study of the structural modification on heat treatment etc 577References[ 1 ] Kairols Mamed Beg Ogli and M A Zahei Records of Geological Survey of Bangladesh 4 Part 3 (1985)[2] M Alim Biswas and A K Basak Pak J. Sci. Ind. Res. 4 118 (1961)[3] M Qudrat 1 Khuda, M Alim Biswas and A K Basak Pak J. Sci. Ind. Res. 143 (1964)[4] M Nazrul Islam White Clay (kaolin) Deposits of Bijoypur Area, Netrokona District, Bangladesh 4 Part 3 (1985)[5] Famque Uz Zaman Chowdhury M Phil Thesis (Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh) (1993)[6] Powder Diffraction File Sets (Joint Committee on Powder Diffraction Standards, USA) 1-32 (1980)[7] R C Mackenzie (ed.) The Differential Thermal Investigations of Clays (Mmeralogical Soc.) (London : The Central Press)r(1957)[8] Patrick S Nicolson and Richard M Fulrath J  Am. Ceram. Soc. 53 237 (1970)[9] Akshoy Kumar Chakravoity and Dilip Kumar Ghosh J. Am. Ceram. Soc. 7 978 (1988)[10] D X Li and W J Thomson J. Am. Ceram, Soc. 73 964 (1990)[ | J ] Ralph E Grim Clay Mineralogy, 2nd edn. (New York ■ Mc-Graw Hill) (1968)[12] R W Grimshaw, E Heaton and A L Roberts Trans. Brit., Ceram. Soc 44 76 (1945)[13] J G Miller J. Phys. Chem. 65 800 (1961)[14] R G Wolff Am. Mineralogist 48 390 (1963)[15] R M Silverstein, G Clayton Bassler and T C Morrill Spectrometric Identification of Organic Compounds. 4th edn. (New York: John Wiley & Sons) (1981)

Study of the Structural Modification on Heat Treatment of Bijoypur White Clay (BWC) of Bangladesh

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Study of the Structural Modification on Heat Treatment of Bijoypur White Clay (BWC) of Bangladesh

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