INDUSTRIAL APPLICATION SUITABILITY OF INDIGENOUS BENTONITE CLAY IN PHARMACEUTICAL SECTOR

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- vi 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.