dc.description.abstract |
In this PhD thesis the pharmaceutical suitability study of bentonite, the most
important clay with wide spread industrial applications, is carried out. Bentonite is an
exciting and truly amazing natural material varies in composition and texture from
place to place. Hence, not equally well in performance for its specific industrial uses.
They are mainly composed of a montmorillonite and other minor impurities that give
them a unique ―fingerprint‖. The amount of pure montmorillonite in bentonite is key
to its purity and performance. Bentonite can be considered as raw pharmaceutical
materials that once properly identified, evaluated and/or modified to fulfil regulatory
pharmacopoeial requirements and mineral purity. No such work has been done on
Pakistani bentonite and no published data is available. In this work, the mineralogical,
microbiological, geochemical and physicochemical studies of raw samples collected
from three Pakistani mining sites located at Shagai (district Karak), Dag Ismial Khel
(district Nowshera) and Chandan Garhi (district Peshawar) is carried out.
The bentonites sample collected were purified by three different methods i.e.
simple sedimentation using sodium hexametaphosphate as a dispersing agent in
Method-I, classical NaCl treatment followed by sedimentation in method-II and
activation by Na2CO3 at various ratio (2, 3, 5, 8 g Na2 CO3/100 g bentonite) followed
by sedimentation technique in Method-III.
The raw samples and the samples purified by three methods mentioned above,
were characterized by X-ray diffraction (XRD), Scanning Electron Microscope
(SEM), X-ray Fluorescence (XRF), Inductively Coupled Plasma-Atomic Emission
Spectrometry (ICP-AES), N2 Adsorption-desorption Isotherm at Temperature 77.35K,
Microbial test, CEC measurements, Pharmacopeial tests (i.e. pH, swelling capacity,
gel formation) and laser granulometry. The test results obtained for raw and purified
bentonite from each site were compared among them as well as with others.
The mineralogical and chemical composition study revealed that all the samples
from the three sites were of high quality bentonite, containing mainly Ca +2-
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montmorillonite with minor contents of illite and quartz. In addition, kaolinite was
found in Karak, albite in Peshawar and Nowshera bentonite in small quantity. The
swelling volume (apperent volume of 2g clay/100ml of distilled water) of all the three
raw bentonite were in the range of 5mL to 7mL which is less than pharmacopeias
requirements i.e. ≥ 20 mL. The gel formation value (4mL) of Peshawar bentonite also
failed to comply with the pharmacopeias requirement (2mL).
All the purified samples were found free of quartz impurities as confirmed by
XRD. The swelling, gelling and other properties were also improved by the
purification process. The XRD and CEC tests confirmed the conversion of raw
bentonite to sodium bentonite by 5% Na2CO3 for Karak and Nowshera while that of
Peshawar by 3% Na2CO3. Moreover, XRD, XRF and TGA studies also testify the
conversion of calcium bentonite to Sodium form by method-II. The results for purified
samples from the three sites are in conformity with major pharmacopeial requirement
of advanced countries for bentonite, hence Pakistani bentonite in purified can be
designated as value added pharmaceutical raw material.
The comparative study of purified samples revealed its variation in properties
quantitatively, which make them important for specific pharmaceutical uses. The
results of samples purified by three different methods are also varying from each
other. All the studied bentonites in purified form could be used as suspending agent
for both oral and topical application but the sample obtained by Method II and III
could be preferred because of its excellent swelling capacity and sedimentation
volume. The high CEC, high surface area, small particle size and pore size distribution
suggesting their use as a good adsorbent of drugs and a drug carrier in control release
of medicine. |
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