MINERALOGICAL STUDY OF CLAY SAMPLES FROM NORTH-WEST PENINSULAR MALAYSIA USING X-RAY DIFFRACTION METHOD[1]

Ahmad Saat, and Zaini Hamzah1
International Education Centre (INTEC), UiTM Kampus Seksyen 17,
40200 Shah Alam, Malaysia.
1Faculty of Applied Sciences, Universiti Teknologi MARA
40450 Shah Alam, Malaysia.
Tel: 603-55227070, E-mail: ahmad183@salam.uitm.edu.my

ABSTRACT
Clay has been regarded as very important natural industrial materials. All these industries exploit the properties that clay can be molded into any shape and fired to dry without losing its form. A study was carried out on clay samples from eight sites in the north-eastern part of Peninsular Malaysia. The study was accomplished by using X-ray diffraction (XRD) technique. The x-ray diffraction spectra obtained enable the determination of the lattice spacing associated with the types of clay and non-clay minerals present in the samples. The major components of clay minerals present in all samples studied are kaolinite and illite. Non-clay minerals such as quartz, mica, feldspar, goethite and chlorite are also present in small quantities in the samples studied.
Keywords:Clay minerals, XRD, Kaolinite, Illite

INTRODUCTION
Clay has been used in a wide range of areas, ranging from building materials industry and pottery up to agricultural and ceramic industries. All these industries exploit the properties that clay can be molded into any shape and fired to dry without losing its form. In the present study, qualitative mineralogical study of clay samples from north-western of Peninsular Malaysia was carried out by using x-ray diffraction. Thus, for the analysis only the values of lattice spacing (d) as well as the corresponding relative intensities (I) of the particular diffraction peaks were the only variables determined.

X-ray diffraction technique (XRD) is one of the very popular analytical methods used by mineral and soil scientists for mineralogical study [1, 2 ,3 ,4, 5, 6] as well as geochemical or elemental analysis [7,8] of soil and sediments. Sometimes in the study XRD is coupled with other methods such as x-ray fluorescence [9], analytical electron microscopy (AEM) [10] or modified with internal standard or spiking [11] for quantitative mineralogical determination. The popularity of this method is partly due to the simple sample preparation, uncomplicated data analysis and moreover the results are reasonably reliable.

Experimental Method
Sampling and sample preparation
Samples were obtained from various factories in the north-western region of Peninsular Malaysia. The samples were collected in such a way that contamination was minimized. In the laboratory, foreign organic matter and coarse sands particles in the clay samples were removed and oven-dried overnight at 50 oC. Then samples were crush into powdery form, and then sieved to remove finer sand particles. Slurries were prepared by adding adequate amount of distilled water to the powdery clay samples. The clay from the top portion of the slurries was removed and dried for the subsequent XRD study.

Instrumentation
The x-ray diffraction (XRD) of the samples was carried out using a Phillips horizontal diffractometer Model PW1380, with horizontal goniometer. The samples’ spectra were obtained using CuKa x-ray (l = 1.542 Å) with a nickel filter and tube ratings of 40 kV 30 mA. The detector used was a proportional counter. The scanning rate of the spectra was 1o/cm/min. This scanning rate was found to give a reasonably good peak resolution with satisfactory width of peaks.

Results and Discussions
The XRD spectra obtained were analyzed to determine the lattice spacing by using Bragg’s formula, and the corresponding peak relative intensity. The lattice spacing values (d) and relative intensities (I) are compared with those for kaolinite and illite as described by Jasmund and Mering [12]. The peak of the spectra of the samples can be divided into two groups; one group due to the clay minerals present in the samples while the other due to non-clay minerals such as mica, quartz, feldspar and goethite. It was found that the peaks of the samples match very closely with the diffraction peaks for kaolinite and illite combined. This observation shows that kaolinite and illite are the two main minerals found in clay samples.

The existence of kaolinite in the samples is made certain by the presence of peaks at around 7.20 Å correspond to the d(001) spacing of kaolinite, as well as latticing spacing of 3.75 Å and 1.98 Å [4, 10, 13, 14, 15]. Although the spacing of 7.20 Å and 3.75 Å could be attributed to chlorite as well, the absence of 14.2 Å lattice spacing from all samples except two, confirm the absence of chlorite [13, 14]. The presence of relatively small intensity peak correspond to 14.2 Å lattice spacing in two samples showed that chlorite present in small amount in these samples.

On heating at 600 oC, the mineralogical structure of kaolinite will collapse and turn into amorphous. This will results in the disappearance of major kaolinite 7.20 Å, 3.75 Å and 1.98 Å spacing [13, 14, 15]. A study on the effect of heating was also carried out on all the samples, where the samples were heated at 600 oC for one hour before being scanned in the diffractometer. Results of the study showed that the kaolinite diffraction peaks disappeared in the spectra of the heated samples.

Illite in the clay samples can be confirmed by the presence of d(001) lattice spacing at about 10.0 Å, as well as major diffraction peaks corresponds to lattice spacing of 5.05 Å and 3.34 Å. Unfortunately, the 3.34 Å lattice spacing which corresponds to the most intense peak in every sample diffraction spectrum obtained, is also shared by quartz [13], while the 5.05 Å spacing is interfered by the 5.02 Å lattice spacing peak of mica [12]. Nevertheless, the spacing obtained by XRD in the present study coincides well with the combination of kaolinite and illite lattice spacing obtained by Jasmund and Mering [12].

The effect of heating up to 600 oC is not very significant on illite, because illite will only loses hydroxyl water from the lattice, and still retains its essential crystal character although assuming the form of anhydrous modification (Carroll, 1974). This phenomenon was also observed on the heated samples studied.

The clay samples studied also contained non-clay minerals. The main non-clay minerals present in the sample is mica. However the presence of quartz cannot be ignored as shown by the presence of the 4.25 Å and 2.13 Å lattice spacing apart from the 3.34 Å spacing that is common to illite as well. Feldspar was also detected in most of the samples.

Finally, it is worthwhile to mention that the experimental procedure was repeated for moist samples. The spectra obtained show no significant different between the dry (powder) and moist samples, except that there are occasionally small non-significant shift in the diffraction peaks position.

CONCLUSION
From the results of the study it may be concluded that the major clay minerals present in the samples studied are kaolinite and illite. Non-clay minerals such as mica, quartz and feldspar are also present in small quantity in the samples.

ACKNOWLEDGEMENTS
The first author would like to thank INTEC for the financial support to present the paper at ICXRI 2006.

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[1] Presented at ICXRI 2007, Kota Kinabalu, Sabah