Abstract
The present work aimed at assessing the pharmaceutical tableting properties of some Egyptian kaolin samples belong to the Abu Zenima kaolin deposits (estimated at 120 million tons). Four representative samples were selected based on kaolinite richness and their structural order-disorder degree, and after purification, they were dried at 70 °C and heated from room temperature up to 400 °C (10 °C/min). Mineralogy, micromorphology, microtexture, granulometry, porosimetry, moisture content, bulk and tapped density, direct and indirect flowability, and tableting characteristics are studied. Results indicated that purified kaolin samples were made up of 95–99% kaolinite, <3% illite, 1% quartz and 1% anatase. The powder showed mesoporous character (pore diameters from 2 to 38 nm and total pore volume from 0.064 to 0.136 cm3/g) with dominance of fine nanosized particles (<1 μm–10 nm). The powder flow characteristics of both the ordered (Hinckley Index HI > 0.7, crystallite size D001 > 30 nm) and disordered (HI < 0.7, D001 < 30 nm) kaolinite-rich samples have been improved (Hausner ratio between 1.24 and 1.09) as their densities were influenced by thermal treatment (with some observed changes in the kaolinite XRD reflection profiles) and by moisture content (variable between 2.98% and 5.82%). The obtained tablets exhibited hardness between 33 and 44 N only from the dehydrated powders at 400 °C, with elastic recovery (ER) between 21.74% and 25.61%, ejection stress (ES) between 7.85 and 11.45 MPa and tensile fracture stress (TFS) between 1.85 and 2.32 MPa, which are strongly correlated with crystallinity (HI) and flowability (HR) parameters. These findings on quality indicators showed the promising pharmaceutical tabletability of the studied Egyptian kaolin powders and the optimization factors for their manufacturability and compactability.
Highlights
Tablets represent about 75% of all the common orally administered solid dosage forms
Developmental studies by Tan et al [18] and Dey et al [19] on the kaolinite functionality as pharmaceutical carrier reported that the drug loading capacities and controlled release by this clay mineral can be improved by means of physical and chemical modifications, as well as by hybridation with biopolymers [20,21,22]
The Al2 O3 /SiO2 ratios of the bulk kaolin samples were found very close to the stoichiometric ratio (0.85) of the theoretical kaolinite, except in sample K-3 which was slightly influenced by the illite content [38]
Summary
Tablets represent about 75% of all the common orally administered solid dosage forms. Kaolinite is a generally inexpensive, ubiquitous and biologically safe raw geomaterial to be used in pharmaceutical formulations at specific high purity grades This phyllosilicate mineral exhibits a simple pseudohexagonal platy-form of stacking layered structure, with excellent physical and chemical properties that make it suitable as excipient (e.g., diluent, binder, disintegrant, pelletizing, granulating, amorphizing and film coating, emulsifying and suspending agents and drug carrier) in solid and semi-solid dosage formulations, besides its therapeutic activity in many biomedicinal applications [2,3,4,5,6,7,8,9,10,11,12,13]. Some important natural and modified microporous aluminosilicate minerals (e.g., zeolite and phillipsite) have been proved excellent functionalities in the drug loading and controlled release as pharmaceutical carrier and they are compatible with kaolin minerals for solid dosage formulations [23,24,25,26,27,28,29]
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